1 /* Global common subexpression elimination/Partial redundancy elimination
2 and global constant/copy propagation for GNU compiler.
3 Copyright (C) 1997, 1998, 1999, 2000 Free Software Foundation, Inc.
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
23 - reordering of memory allocation and freeing to be more space efficient
24 - do rough calc of how many regs are needed in each block, and a rough
25 calc of how many regs are available in each class and use that to
26 throttle back the code in cases where RTX_COST is minimal.
27 - dead store elimination
28 - a store to the same address as a load does not kill the load if the
29 source of the store is also the destination of the load. Handling this
30 allows more load motion, particularly out of loops.
31 - ability to realloc sbitmap vectors would allow one initial computation
32 of reg_set_in_block with only subsequent additions, rather than
33 recomputing it for each pass
37 /* References searched while implementing this.
39 Compilers Principles, Techniques and Tools
43 Global Optimization by Suppression of Partial Redundancies
45 communications of the acm, Vol. 22, Num. 2, Feb. 1979
47 A Portable Machine-Independent Global Optimizer - Design and Measurements
49 Stanford Ph.D. thesis, Dec. 1983
51 A Fast Algorithm for Code Movement Optimization
53 SIGPLAN Notices, Vol. 23, Num. 10, Oct. 1988
55 A Solution to a Problem with Morel and Renvoise's
56 Global Optimization by Suppression of Partial Redundancies
57 K-H Drechsler, M.P. Stadel
58 ACM TOPLAS, Vol. 10, Num. 4, Oct. 1988
60 Practical Adaptation of the Global Optimization
61 Algorithm of Morel and Renvoise
63 ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991
65 Efficiently Computing Static Single Assignment Form and the Control
67 R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck
68 ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991
71 J. Knoop, O. Ruthing, B. Steffen
72 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
74 What's In a Region? Or Computing Control Dependence Regions in Near-Linear
75 Time for Reducible Flow Control
77 ACM Letters on Programming Languages and Systems,
78 Vol. 2, Num. 1-4, Mar-Dec 1993
80 An Efficient Representation for Sparse Sets
81 Preston Briggs, Linda Torczon
82 ACM Letters on Programming Languages and Systems,
83 Vol. 2, Num. 1-4, Mar-Dec 1993
85 A Variation of Knoop, Ruthing, and Steffen's Lazy Code Motion
86 K-H Drechsler, M.P. Stadel
87 ACM SIGPLAN Notices, Vol. 28, Num. 5, May 1993
89 Partial Dead Code Elimination
90 J. Knoop, O. Ruthing, B. Steffen
91 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
93 Effective Partial Redundancy Elimination
94 P. Briggs, K.D. Cooper
95 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
97 The Program Structure Tree: Computing Control Regions in Linear Time
98 R. Johnson, D. Pearson, K. Pingali
99 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
101 Optimal Code Motion: Theory and Practice
102 J. Knoop, O. Ruthing, B. Steffen
103 ACM TOPLAS, Vol. 16, Num. 4, Jul. 1994
105 The power of assignment motion
106 J. Knoop, O. Ruthing, B. Steffen
107 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
109 Global code motion / global value numbering
111 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
113 Value Driven Redundancy Elimination
115 Rice University Ph.D. thesis, Apr. 1996
119 Massively Scalar Compiler Project, Rice University, Sep. 1996
121 High Performance Compilers for Parallel Computing
125 Advanced Compiler Design and Implementation
127 Morgan Kaufmann, 1997
129 Building an Optimizing Compiler
133 People wishing to speed up the code here should read:
134 Elimination Algorithms for Data Flow Analysis
135 B.G. Ryder, M.C. Paull
136 ACM Computing Surveys, Vol. 18, Num. 3, Sep. 1986
138 How to Analyze Large Programs Efficiently and Informatively
139 D.M. Dhamdhere, B.K. Rosen, F.K. Zadeck
140 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
142 People wishing to do something different can find various possibilities
143 in the above papers and elsewhere.
153 #include "hard-reg-set.h"
156 #include "insn-config.h"
158 #include "basic-block.h"
160 #include "function.h"
164 #define obstack_chunk_alloc gmalloc
165 #define obstack_chunk_free free
167 /* Maximum number of passes to perform. */
170 /* Propagate flow information through back edges and thus enable PRE's
171 moving loop invariant calculations out of loops.
173 Originally this tended to create worse overall code, but several
174 improvements during the development of PRE seem to have made following
175 back edges generally a win.
177 Note much of the loop invariant code motion done here would normally
178 be done by loop.c, which has more heuristics for when to move invariants
179 out of loops. At some point we might need to move some of those
180 heuristics into gcse.c. */
181 #define FOLLOW_BACK_EDGES 1
183 /* We support GCSE via Partial Redundancy Elimination. PRE optimizations
184 are a superset of those done by GCSE.
186 We perform the following steps:
188 1) Compute basic block information.
190 2) Compute table of places where registers are set.
192 3) Perform copy/constant propagation.
194 4) Perform global cse.
196 5) Perform another pass of copy/constant propagation.
198 Two passes of copy/constant propagation are done because the first one
199 enables more GCSE and the second one helps to clean up the copies that
200 GCSE creates. This is needed more for PRE than for Classic because Classic
201 GCSE will try to use an existing register containing the common
202 subexpression rather than create a new one. This is harder to do for PRE
203 because of the code motion (which Classic GCSE doesn't do).
205 Expressions we are interested in GCSE-ing are of the form
206 (set (pseudo-reg) (expression)).
207 Function want_to_gcse_p says what these are.
209 PRE handles moving invariant expressions out of loops (by treating them as
210 partially redundant).
212 Eventually it would be nice to replace cse.c/gcse.c with SSA (static single
213 assignment) based GVN (global value numbering). L. T. Simpson's paper
214 (Rice University) on value numbering is a useful reference for this.
216 **********************
218 We used to support multiple passes but there are diminishing returns in
219 doing so. The first pass usually makes 90% of the changes that are doable.
220 A second pass can make a few more changes made possible by the first pass.
221 Experiments show any further passes don't make enough changes to justify
224 A study of spec92 using an unlimited number of passes:
225 [1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83,
226 [6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2,
227 [12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1
229 It was found doing copy propagation between each pass enables further
232 PRE is quite expensive in complicated functions because the DFA can take
233 awhile to converge. Hence we only perform one pass. Macro MAX_PASSES can
234 be modified if one wants to experiment.
236 **********************
238 The steps for PRE are:
240 1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
242 2) Perform the data flow analysis for PRE.
244 3) Delete the redundant instructions
246 4) Insert the required copies [if any] that make the partially
247 redundant instructions fully redundant.
249 5) For other reaching expressions, insert an instruction to copy the value
250 to a newly created pseudo that will reach the redundant instruction.
252 The deletion is done first so that when we do insertions we
253 know which pseudo reg to use.
255 Various papers have argued that PRE DFA is expensive (O(n^2)) and others
256 argue it is not. The number of iterations for the algorithm to converge
257 is typically 2-4 so I don't view it as that expensive (relatively speaking).
259 PRE GCSE depends heavily on the second CSE pass to clean up the copies
260 we create. To make an expression reach the place where it's redundant,
261 the result of the expression is copied to a new register, and the redundant
262 expression is deleted by replacing it with this new register. Classic GCSE
263 doesn't have this problem as much as it computes the reaching defs of
264 each register in each block and thus can try to use an existing register.
266 **********************
268 A fair bit of simplicity is created by creating small functions for simple
269 tasks, even when the function is only called in one place. This may
270 measurably slow things down [or may not] by creating more function call
271 overhead than is necessary. The source is laid out so that it's trivial
272 to make the affected functions inline so that one can measure what speed
273 up, if any, can be achieved, and maybe later when things settle things can
276 Help stamp out big monolithic functions! */
278 /* GCSE global vars. */
281 static FILE *gcse_file
;
283 /* Note whether or not we should run jump optimization after gcse. We
284 want to do this for two cases.
286 * If we changed any jumps via cprop.
288 * If we added any labels via edge splitting. */
290 static int run_jump_opt_after_gcse
;
292 /* Bitmaps are normally not included in debugging dumps.
293 However it's useful to be able to print them from GDB.
294 We could create special functions for this, but it's simpler to
295 just allow passing stderr to the dump_foo fns. Since stderr can
296 be a macro, we store a copy here. */
297 static FILE *debug_stderr
;
299 /* An obstack for our working variables. */
300 static struct obstack gcse_obstack
;
302 /* Non-zero for each mode that supports (set (reg) (reg)).
303 This is trivially true for integer and floating point values.
304 It may or may not be true for condition codes. */
305 static char can_copy_p
[(int) NUM_MACHINE_MODES
];
307 /* Non-zero if can_copy_p has been initialized. */
308 static int can_copy_init_p
;
310 struct reg_use
{rtx reg_rtx
; };
312 /* Hash table of expressions. */
316 /* The expression (SET_SRC for expressions, PATTERN for assignments). */
318 /* Index in the available expression bitmaps. */
320 /* Next entry with the same hash. */
321 struct expr
*next_same_hash
;
322 /* List of anticipatable occurrences in basic blocks in the function.
323 An "anticipatable occurrence" is one that is the first occurrence in the
324 basic block, the operands are not modified in the basic block prior
325 to the occurrence and the output is not used between the start of
326 the block and the occurrence. */
327 struct occr
*antic_occr
;
328 /* List of available occurrence in basic blocks in the function.
329 An "available occurrence" is one that is the last occurrence in the
330 basic block and the operands are not modified by following statements in
331 the basic block [including this insn]. */
332 struct occr
*avail_occr
;
333 /* Non-null if the computation is PRE redundant.
334 The value is the newly created pseudo-reg to record a copy of the
335 expression in all the places that reach the redundant copy. */
339 /* Occurrence of an expression.
340 There is one per basic block. If a pattern appears more than once the
341 last appearance is used [or first for anticipatable expressions]. */
345 /* Next occurrence of this expression. */
347 /* The insn that computes the expression. */
349 /* Non-zero if this [anticipatable] occurrence has been deleted. */
351 /* Non-zero if this [available] occurrence has been copied to
353 /* ??? This is mutually exclusive with deleted_p, so they could share
358 /* Expression and copy propagation hash tables.
359 Each hash table is an array of buckets.
360 ??? It is known that if it were an array of entries, structure elements
361 `next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is
362 not clear whether in the final analysis a sufficient amount of memory would
363 be saved as the size of the available expression bitmaps would be larger
364 [one could build a mapping table without holes afterwards though].
365 Someday I'll perform the computation and figure it out. */
367 /* Total size of the expression hash table, in elements. */
368 static unsigned int expr_hash_table_size
;
371 This is an array of `expr_hash_table_size' elements. */
372 static struct expr
**expr_hash_table
;
374 /* Total size of the copy propagation hash table, in elements. */
375 static unsigned int set_hash_table_size
;
378 This is an array of `set_hash_table_size' elements. */
379 static struct expr
**set_hash_table
;
381 /* Mapping of uids to cuids.
382 Only real insns get cuids. */
383 static int *uid_cuid
;
385 /* Highest UID in UID_CUID. */
388 /* Get the cuid of an insn. */
389 #ifdef ENABLE_CHECKING
390 #define INSN_CUID(INSN) (INSN_UID (INSN) > max_uid ? (abort (), 0) : uid_cuid[INSN_UID (INSN)])
392 #define INSN_CUID(INSN) (uid_cuid[INSN_UID (INSN)])
395 /* Number of cuids. */
398 /* Mapping of cuids to insns. */
399 static rtx
*cuid_insn
;
401 /* Get insn from cuid. */
402 #define CUID_INSN(CUID) (cuid_insn[CUID])
404 /* Maximum register number in function prior to doing gcse + 1.
405 Registers created during this pass have regno >= max_gcse_regno.
406 This is named with "gcse" to not collide with global of same name. */
407 static unsigned int max_gcse_regno
;
409 /* Maximum number of cse-able expressions found. */
412 /* Maximum number of assignments for copy propagation found. */
415 /* Table of registers that are modified.
417 For each register, each element is a list of places where the pseudo-reg
420 For simplicity, GCSE is done on sets of pseudo-regs only. PRE GCSE only
421 requires knowledge of which blocks kill which regs [and thus could use
422 a bitmap instead of the lists `reg_set_table' uses].
424 `reg_set_table' and could be turned into an array of bitmaps (num-bbs x
425 num-regs) [however perhaps it may be useful to keep the data as is]. One
426 advantage of recording things this way is that `reg_set_table' is fairly
427 sparse with respect to pseudo regs but for hard regs could be fairly dense
428 [relatively speaking]. And recording sets of pseudo-regs in lists speeds
429 up functions like compute_transp since in the case of pseudo-regs we only
430 need to iterate over the number of times a pseudo-reg is set, not over the
431 number of basic blocks [clearly there is a bit of a slow down in the cases
432 where a pseudo is set more than once in a block, however it is believed
433 that the net effect is to speed things up]. This isn't done for hard-regs
434 because recording call-clobbered hard-regs in `reg_set_table' at each
435 function call can consume a fair bit of memory, and iterating over
436 hard-regs stored this way in compute_transp will be more expensive. */
438 typedef struct reg_set
440 /* The next setting of this register. */
441 struct reg_set
*next
;
442 /* The insn where it was set. */
446 static reg_set
**reg_set_table
;
448 /* Size of `reg_set_table'.
449 The table starts out at max_gcse_regno + slop, and is enlarged as
451 static int reg_set_table_size
;
453 /* Amount to grow `reg_set_table' by when it's full. */
454 #define REG_SET_TABLE_SLOP 100
456 /* Bitmap containing one bit for each register in the program.
457 Used when performing GCSE to track which registers have been set since
458 the start of the basic block. */
459 static sbitmap reg_set_bitmap
;
461 /* For each block, a bitmap of registers set in the block.
462 This is used by expr_killed_p and compute_transp.
463 It is computed during hash table computation and not by compute_sets
464 as it includes registers added since the last pass (or between cprop and
465 gcse) and it's currently not easy to realloc sbitmap vectors. */
466 static sbitmap
*reg_set_in_block
;
468 /* For each block, non-zero if memory is set in that block.
469 This is computed during hash table computation and is used by
470 expr_killed_p and compute_transp.
471 ??? Handling of memory is very simple, we don't make any attempt
472 to optimize things (later).
473 ??? This can be computed by compute_sets since the information
475 static char *mem_set_in_block
;
477 /* Various variables for statistics gathering. */
479 /* Memory used in a pass.
480 This isn't intended to be absolutely precise. Its intent is only
481 to keep an eye on memory usage. */
482 static int bytes_used
;
484 /* GCSE substitutions made. */
485 static int gcse_subst_count
;
486 /* Number of copy instructions created. */
487 static int gcse_create_count
;
488 /* Number of constants propagated. */
489 static int const_prop_count
;
490 /* Number of copys propagated. */
491 static int copy_prop_count
;
493 /* These variables are used by classic GCSE.
494 Normally they'd be defined a bit later, but `rd_gen' needs to
495 be declared sooner. */
497 /* Each block has a bitmap of each type.
498 The length of each blocks bitmap is:
500 max_cuid - for reaching definitions
501 n_exprs - for available expressions
503 Thus we view the bitmaps as 2 dimensional arrays. i.e.
504 rd_kill[block_num][cuid_num]
505 ae_kill[block_num][expr_num] */
507 /* For reaching defs */
508 static sbitmap
*rd_kill
, *rd_gen
, *reaching_defs
, *rd_out
;
510 /* for available exprs */
511 static sbitmap
*ae_kill
, *ae_gen
, *ae_in
, *ae_out
;
513 /* Objects of this type are passed around by the null-pointer check
515 struct null_pointer_info
517 /* The basic block being processed. */
519 /* The first register to be handled in this pass. */
520 unsigned int min_reg
;
521 /* One greater than the last register to be handled in this pass. */
522 unsigned int max_reg
;
523 sbitmap
*nonnull_local
;
524 sbitmap
*nonnull_killed
;
527 static void compute_can_copy
PARAMS ((void));
528 static char *gmalloc
PARAMS ((unsigned int));
529 static char *grealloc
PARAMS ((char *, unsigned int));
530 static char *gcse_alloc
PARAMS ((unsigned long));
531 static void alloc_gcse_mem
PARAMS ((rtx
));
532 static void free_gcse_mem
PARAMS ((void));
533 static void alloc_reg_set_mem
PARAMS ((int));
534 static void free_reg_set_mem
PARAMS ((void));
535 static int get_bitmap_width
PARAMS ((int, int, int));
536 static void record_one_set
PARAMS ((int, rtx
));
537 static void record_set_info
PARAMS ((rtx
, rtx
, void *));
538 static void compute_sets
PARAMS ((rtx
));
539 static void hash_scan_insn
PARAMS ((rtx
, int, int));
540 static void hash_scan_set
PARAMS ((rtx
, rtx
, int));
541 static void hash_scan_clobber
PARAMS ((rtx
, rtx
));
542 static void hash_scan_call
PARAMS ((rtx
, rtx
));
543 static int want_to_gcse_p
PARAMS ((rtx
));
544 static int oprs_unchanged_p
PARAMS ((rtx
, rtx
, int));
545 static int oprs_anticipatable_p
PARAMS ((rtx
, rtx
));
546 static int oprs_available_p
PARAMS ((rtx
, rtx
));
547 static void insert_expr_in_table
PARAMS ((rtx
, enum machine_mode
, rtx
,
549 static void insert_set_in_table
PARAMS ((rtx
, rtx
));
550 static unsigned int hash_expr
PARAMS ((rtx
, enum machine_mode
, int *, int));
551 static unsigned int hash_expr_1
PARAMS ((rtx
, enum machine_mode
, int *));
552 static unsigned int hash_string_1
PARAMS ((const char *));
553 static unsigned int hash_set
PARAMS ((int, int));
554 static int expr_equiv_p
PARAMS ((rtx
, rtx
));
555 static void record_last_reg_set_info
PARAMS ((rtx
, int));
556 static void record_last_mem_set_info
PARAMS ((rtx
));
557 static void record_last_set_info
PARAMS ((rtx
, rtx
, void *));
558 static void compute_hash_table
PARAMS ((int));
559 static void alloc_set_hash_table
PARAMS ((int));
560 static void free_set_hash_table
PARAMS ((void));
561 static void compute_set_hash_table
PARAMS ((void));
562 static void alloc_expr_hash_table
PARAMS ((unsigned int));
563 static void free_expr_hash_table
PARAMS ((void));
564 static void compute_expr_hash_table
PARAMS ((void));
565 static void dump_hash_table
PARAMS ((FILE *, const char *, struct expr
**,
567 static struct expr
*lookup_expr
PARAMS ((rtx
));
568 static struct expr
*lookup_set
PARAMS ((unsigned int, rtx
));
569 static struct expr
*next_set
PARAMS ((unsigned int, struct expr
*));
570 static void reset_opr_set_tables
PARAMS ((void));
571 static int oprs_not_set_p
PARAMS ((rtx
, rtx
));
572 static void mark_call
PARAMS ((rtx
));
573 static void mark_set
PARAMS ((rtx
, rtx
));
574 static void mark_clobber
PARAMS ((rtx
, rtx
));
575 static void mark_oprs_set
PARAMS ((rtx
));
576 static void alloc_cprop_mem
PARAMS ((int, int));
577 static void free_cprop_mem
PARAMS ((void));
578 static void compute_transp
PARAMS ((rtx
, int, sbitmap
*, int));
579 static void compute_transpout
PARAMS ((void));
580 static void compute_local_properties
PARAMS ((sbitmap
*, sbitmap
*, sbitmap
*,
582 static void compute_cprop_data
PARAMS ((void));
583 static void find_used_regs
PARAMS ((rtx
));
584 static int try_replace_reg
PARAMS ((rtx
, rtx
, rtx
));
585 static struct expr
*find_avail_set
PARAMS ((int, rtx
));
586 static int cprop_jump
PARAMS ((rtx
, rtx
, struct reg_use
*, rtx
));
588 static int cprop_cc0_jump
PARAMS ((rtx
, struct reg_use
*, rtx
));
590 static int cprop_insn
PARAMS ((rtx
, int));
591 static int cprop
PARAMS ((int));
592 static int one_cprop_pass
PARAMS ((int, int));
593 static void alloc_pre_mem
PARAMS ((int, int));
594 static void free_pre_mem
PARAMS ((void));
595 static void compute_pre_data
PARAMS ((void));
596 static int pre_expr_reaches_here_p
PARAMS ((int, struct expr
*, int));
597 static void insert_insn_end_bb
PARAMS ((struct expr
*, int, int));
598 static void pre_insert_copy_insn
PARAMS ((struct expr
*, rtx
));
599 static void pre_insert_copies
PARAMS ((void));
600 static int pre_delete
PARAMS ((void));
601 static int pre_gcse
PARAMS ((void));
602 static int one_pre_gcse_pass
PARAMS ((int));
603 static void add_label_notes
PARAMS ((rtx
, rtx
));
604 static void alloc_code_hoist_mem
PARAMS ((int, int));
605 static void free_code_hoist_mem
PARAMS ((void));
606 static void compute_code_hoist_vbeinout
PARAMS ((void));
607 static void compute_code_hoist_data
PARAMS ((void));
608 static int hoist_expr_reaches_here_p
PARAMS ((int, int, int, char *));
609 static void hoist_code
PARAMS ((void));
610 static int one_code_hoisting_pass
PARAMS ((void));
611 static void alloc_rd_mem
PARAMS ((int, int));
612 static void free_rd_mem
PARAMS ((void));
613 static void handle_rd_kill_set
PARAMS ((rtx
, int, int));
614 static void compute_kill_rd
PARAMS ((void));
615 static void compute_rd
PARAMS ((void));
616 static void alloc_avail_expr_mem
PARAMS ((int, int));
617 static void free_avail_expr_mem
PARAMS ((void));
618 static void compute_ae_gen
PARAMS ((void));
619 static int expr_killed_p
PARAMS ((rtx
, int));
620 static void compute_ae_kill
PARAMS ((sbitmap
*, sbitmap
*));
621 static int expr_reaches_here_p
PARAMS ((struct occr
*, struct expr
*,
623 static rtx computing_insn
PARAMS ((struct expr
*, rtx
));
624 static int def_reaches_here_p
PARAMS ((rtx
, rtx
));
625 static int can_disregard_other_sets
PARAMS ((struct reg_set
**, rtx
, int));
626 static int handle_avail_expr
PARAMS ((rtx
, struct expr
*));
627 static int classic_gcse
PARAMS ((void));
628 static int one_classic_gcse_pass
PARAMS ((int));
629 static void invalidate_nonnull_info
PARAMS ((rtx
, rtx
, void *));
630 static void delete_null_pointer_checks_1
PARAMS ((unsigned int *, sbitmap
*,
632 struct null_pointer_info
*));
633 static rtx process_insert_insn
PARAMS ((struct expr
*));
634 static int pre_edge_insert
PARAMS ((struct edge_list
*, struct expr
**));
635 static int expr_reaches_here_p_work
PARAMS ((struct occr
*, struct expr
*,
637 static int pre_expr_reaches_here_p_work
PARAMS ((int, struct expr
*,
640 /* Entry point for global common subexpression elimination.
641 F is the first instruction in the function. */
649 /* Bytes used at start of pass. */
650 int initial_bytes_used
;
651 /* Maximum number of bytes used by a pass. */
653 /* Point to release obstack data from for each pass. */
654 char *gcse_obstack_bottom
;
656 /* We do not construct an accurate cfg in functions which call
657 setjmp, so just punt to be safe. */
658 if (current_function_calls_setjmp
)
661 /* Assume that we do not need to run jump optimizations after gcse. */
662 run_jump_opt_after_gcse
= 0;
664 /* For calling dump_foo fns from gdb. */
665 debug_stderr
= stderr
;
668 /* Identify the basic block information for this function, including
669 successors and predecessors. */
670 max_gcse_regno
= max_reg_num ();
673 dump_flow_info (file
);
675 /* Return if there's nothing to do. */
676 if (n_basic_blocks
<= 1)
679 /* Trying to perform global optimizations on flow graphs which have
680 a high connectivity will take a long time and is unlikely to be
683 In normal circumstances a cfg should have about twice has many edges
684 as blocks. But we do not want to punish small functions which have
685 a couple switch statements. So we require a relatively large number
686 of basic blocks and the ratio of edges to blocks to be high. */
687 if (n_basic_blocks
> 1000 && n_edges
/ n_basic_blocks
>= 20)
689 if (warn_disabled_optimization
)
690 warning ("GCSE disabled: %d > 1000 basic blocks and %d >= 20 edges/basic block",
691 n_basic_blocks
, n_edges
/ n_basic_blocks
);
695 /* See what modes support reg/reg copy operations. */
696 if (! can_copy_init_p
)
702 gcc_obstack_init (&gcse_obstack
);
705 /* Record where pseudo-registers are set. This data is kept accurate
706 during each pass. ??? We could also record hard-reg information here
707 [since it's unchanging], however it is currently done during hash table
710 It may be tempting to compute MEM set information here too, but MEM sets
711 will be subject to code motion one day and thus we need to compute
712 information about memory sets when we build the hash tables. */
714 alloc_reg_set_mem (max_gcse_regno
);
718 initial_bytes_used
= bytes_used
;
720 gcse_obstack_bottom
= gcse_alloc (1);
722 while (changed
&& pass
< MAX_PASSES
)
726 fprintf (file
, "GCSE pass %d\n\n", pass
+ 1);
728 /* Initialize bytes_used to the space for the pred/succ lists,
729 and the reg_set_table data. */
730 bytes_used
= initial_bytes_used
;
732 /* Each pass may create new registers, so recalculate each time. */
733 max_gcse_regno
= max_reg_num ();
737 /* Don't allow constant propagation to modify jumps
739 changed
= one_cprop_pass (pass
+ 1, 0);
742 changed
|= one_classic_gcse_pass (pass
+ 1);
745 changed
|= one_pre_gcse_pass (pass
+ 1);
747 alloc_reg_set_mem (max_reg_num ());
749 run_jump_opt_after_gcse
= 1;
752 if (max_pass_bytes
< bytes_used
)
753 max_pass_bytes
= bytes_used
;
755 /* Free up memory, then reallocate for code hoisting. We can
756 not re-use the existing allocated memory because the tables
757 will not have info for the insns or registers created by
758 partial redundancy elimination. */
761 /* It does not make sense to run code hoisting unless we optimizing
762 for code size -- it rarely makes programs faster, and can make
763 them bigger if we did partial redundancy elimination (when optimizing
764 for space, we use a classic gcse algorithm instead of partial
765 redundancy algorithms). */
768 max_gcse_regno
= max_reg_num ();
770 changed
|= one_code_hoisting_pass ();
773 if (max_pass_bytes
< bytes_used
)
774 max_pass_bytes
= bytes_used
;
779 fprintf (file
, "\n");
783 obstack_free (&gcse_obstack
, gcse_obstack_bottom
);
787 /* Do one last pass of copy propagation, including cprop into
788 conditional jumps. */
790 max_gcse_regno
= max_reg_num ();
792 /* This time, go ahead and allow cprop to alter jumps. */
793 one_cprop_pass (pass
+ 1, 1);
798 fprintf (file
, "GCSE of %s: %d basic blocks, ",
799 current_function_name
, n_basic_blocks
);
800 fprintf (file
, "%d pass%s, %d bytes\n\n",
801 pass
, pass
> 1 ? "es" : "", max_pass_bytes
);
804 obstack_free (&gcse_obstack
, NULL_PTR
);
806 return run_jump_opt_after_gcse
;
809 /* Misc. utilities. */
811 /* Compute which modes support reg/reg copy operations. */
817 #ifndef AVOID_CCMODE_COPIES
820 bzero (can_copy_p
, NUM_MACHINE_MODES
);
823 for (i
= 0; i
< NUM_MACHINE_MODES
; i
++)
824 if (GET_MODE_CLASS (i
) == MODE_CC
)
826 #ifdef AVOID_CCMODE_COPIES
829 reg
= gen_rtx_REG ((enum machine_mode
) i
, LAST_VIRTUAL_REGISTER
+ 1);
830 insn
= emit_insn (gen_rtx_SET (VOIDmode
, reg
, reg
));
831 if (recog (PATTERN (insn
), insn
, NULL_PTR
) >= 0)
841 /* Cover function to xmalloc to record bytes allocated. */
848 return xmalloc (size
);
851 /* Cover function to xrealloc.
852 We don't record the additional size since we don't know it.
853 It won't affect memory usage stats much anyway. */
860 return xrealloc (ptr
, size
);
863 /* Cover function to obstack_alloc.
864 We don't need to record the bytes allocated here since
865 obstack_chunk_alloc is set to gmalloc. */
871 return (char *) obstack_alloc (&gcse_obstack
, size
);
874 /* Allocate memory for the cuid mapping array,
875 and reg/memory set tracking tables.
877 This is called at the start of each pass. */
886 /* Find the largest UID and create a mapping from UIDs to CUIDs.
887 CUIDs are like UIDs except they increase monotonically, have no gaps,
888 and only apply to real insns. */
890 max_uid
= get_max_uid ();
891 n
= (max_uid
+ 1) * sizeof (int);
892 uid_cuid
= (int *) gmalloc (n
);
893 bzero ((char *) uid_cuid
, n
);
894 for (insn
= f
, i
= 0; insn
; insn
= NEXT_INSN (insn
))
897 uid_cuid
[INSN_UID (insn
)] = i
++;
899 uid_cuid
[INSN_UID (insn
)] = i
;
902 /* Create a table mapping cuids to insns. */
905 n
= (max_cuid
+ 1) * sizeof (rtx
);
906 cuid_insn
= (rtx
*) gmalloc (n
);
907 bzero ((char *) cuid_insn
, n
);
908 for (insn
= f
, i
= 0; insn
; insn
= NEXT_INSN (insn
))
910 CUID_INSN (i
++) = insn
;
912 /* Allocate vars to track sets of regs. */
913 reg_set_bitmap
= (sbitmap
) sbitmap_alloc (max_gcse_regno
);
915 /* Allocate vars to track sets of regs, memory per block. */
916 reg_set_in_block
= (sbitmap
*) sbitmap_vector_alloc (n_basic_blocks
,
918 mem_set_in_block
= (char *) gmalloc (n_basic_blocks
);
921 /* Free memory allocated by alloc_gcse_mem. */
929 free (reg_set_bitmap
);
931 free (reg_set_in_block
);
932 free (mem_set_in_block
);
935 /* Many of the global optimization algorithms work by solving dataflow
936 equations for various expressions. Initially, some local value is
937 computed for each expression in each block. Then, the values across the
938 various blocks are combined (by following flow graph edges) to arrive at
939 global values. Conceptually, each set of equations is independent. We
940 may therefore solve all the equations in parallel, solve them one at a
941 time, or pick any intermediate approach.
943 When you're going to need N two-dimensional bitmaps, each X (say, the
944 number of blocks) by Y (say, the number of expressions), call this
945 function. It's not important what X and Y represent; only that Y
946 correspond to the things that can be done in parallel. This function will
947 return an appropriate chunking factor C; you should solve C sets of
948 equations in parallel. By going through this function, we can easily
949 trade space against time; by solving fewer equations in parallel we use
953 get_bitmap_width (n
, x
, y
)
958 /* It's not really worth figuring out *exactly* how much memory will
959 be used by a particular choice. The important thing is to get
960 something approximately right. */
961 size_t max_bitmap_memory
= 10 * 1024 * 1024;
963 /* The number of bytes we'd use for a single column of minimum
965 size_t column_size
= n
* x
* sizeof (SBITMAP_ELT_TYPE
);
967 /* Often, it's reasonable just to solve all the equations in
969 if (column_size
* SBITMAP_SET_SIZE (y
) <= max_bitmap_memory
)
972 /* Otherwise, pick the largest width we can, without going over the
974 return SBITMAP_ELT_BITS
* ((max_bitmap_memory
+ column_size
- 1)
978 /* Compute the local properties of each recorded expression.
980 Local properties are those that are defined by the block, irrespective of
983 An expression is transparent in a block if its operands are not modified
986 An expression is computed (locally available) in a block if it is computed
987 at least once and expression would contain the same value if the
988 computation was moved to the end of the block.
990 An expression is locally anticipatable in a block if it is computed at
991 least once and expression would contain the same value if the computation
992 was moved to the beginning of the block.
994 We call this routine for cprop, pre and code hoisting. They all compute
995 basically the same information and thus can easily share this code.
997 TRANSP, COMP, and ANTLOC are destination sbitmaps for recording local
998 properties. If NULL, then it is not necessary to compute or record that
1001 SETP controls which hash table to look at. If zero, this routine looks at
1002 the expr hash table; if nonzero this routine looks at the set hash table.
1003 Additionally, TRANSP is computed as ~TRANSP, since this is really cprop's
1007 compute_local_properties (transp
, comp
, antloc
, setp
)
1013 unsigned int i
, hash_table_size
;
1014 struct expr
**hash_table
;
1016 /* Initialize any bitmaps that were passed in. */
1020 sbitmap_vector_zero (transp
, n_basic_blocks
);
1022 sbitmap_vector_ones (transp
, n_basic_blocks
);
1026 sbitmap_vector_zero (comp
, n_basic_blocks
);
1028 sbitmap_vector_zero (antloc
, n_basic_blocks
);
1030 /* We use the same code for cprop, pre and hoisting. For cprop
1031 we care about the set hash table, for pre and hoisting we
1032 care about the expr hash table. */
1033 hash_table_size
= setp
? set_hash_table_size
: expr_hash_table_size
;
1034 hash_table
= setp
? set_hash_table
: expr_hash_table
;
1036 for (i
= 0; i
< hash_table_size
; i
++)
1040 for (expr
= hash_table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
1042 int indx
= expr
->bitmap_index
;
1045 /* The expression is transparent in this block if it is not killed.
1046 We start by assuming all are transparent [none are killed], and
1047 then reset the bits for those that are. */
1049 compute_transp (expr
->expr
, indx
, transp
, setp
);
1051 /* The occurrences recorded in antic_occr are exactly those that
1052 we want to set to non-zero in ANTLOC. */
1054 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
1056 SET_BIT (antloc
[BLOCK_NUM (occr
->insn
)], indx
);
1058 /* While we're scanning the table, this is a good place to
1060 occr
->deleted_p
= 0;
1063 /* The occurrences recorded in avail_occr are exactly those that
1064 we want to set to non-zero in COMP. */
1066 for (occr
= expr
->avail_occr
; occr
!= NULL
; occr
= occr
->next
)
1068 SET_BIT (comp
[BLOCK_NUM (occr
->insn
)], indx
);
1070 /* While we're scanning the table, this is a good place to
1075 /* While we're scanning the table, this is a good place to
1077 expr
->reaching_reg
= 0;
1082 /* Register set information.
1084 `reg_set_table' records where each register is set or otherwise
1087 static struct obstack reg_set_obstack
;
1090 alloc_reg_set_mem (n_regs
)
1095 reg_set_table_size
= n_regs
+ REG_SET_TABLE_SLOP
;
1096 n
= reg_set_table_size
* sizeof (struct reg_set
*);
1097 reg_set_table
= (struct reg_set
**) gmalloc (n
);
1098 bzero ((char *) reg_set_table
, n
);
1100 gcc_obstack_init (®_set_obstack
);
1106 free (reg_set_table
);
1107 obstack_free (®_set_obstack
, NULL_PTR
);
1110 /* Record REGNO in the reg_set table. */
1113 record_one_set (regno
, insn
)
1117 /* allocate a new reg_set element and link it onto the list */
1118 struct reg_set
*new_reg_info
;
1120 /* If the table isn't big enough, enlarge it. */
1121 if (regno
>= reg_set_table_size
)
1123 int new_size
= regno
+ REG_SET_TABLE_SLOP
;
1126 = (struct reg_set
**) grealloc ((char *) reg_set_table
,
1127 new_size
* sizeof (struct reg_set
*));
1128 bzero ((char *) (reg_set_table
+ reg_set_table_size
),
1129 (new_size
- reg_set_table_size
) * sizeof (struct reg_set
*));
1130 reg_set_table_size
= new_size
;
1133 new_reg_info
= (struct reg_set
*) obstack_alloc (®_set_obstack
,
1134 sizeof (struct reg_set
));
1135 bytes_used
+= sizeof (struct reg_set
);
1136 new_reg_info
->insn
= insn
;
1137 new_reg_info
->next
= reg_set_table
[regno
];
1138 reg_set_table
[regno
] = new_reg_info
;
1141 /* Called from compute_sets via note_stores to handle one SET or CLOBBER in
1142 an insn. The DATA is really the instruction in which the SET is
1146 record_set_info (dest
, setter
, data
)
1147 rtx dest
, setter ATTRIBUTE_UNUSED
;
1150 rtx record_set_insn
= (rtx
) data
;
1152 if (GET_CODE (dest
) == REG
&& REGNO (dest
) >= FIRST_PSEUDO_REGISTER
)
1153 record_one_set (REGNO (dest
), record_set_insn
);
1156 /* Scan the function and record each set of each pseudo-register.
1158 This is called once, at the start of the gcse pass. See the comments for
1159 `reg_set_table' for further documenation. */
1167 for (insn
= f
; insn
!= 0; insn
= NEXT_INSN (insn
))
1169 note_stores (PATTERN (insn
), record_set_info
, insn
);
1172 /* Hash table support. */
1174 /* For each register, the cuid of the first/last insn in the block to set it,
1175 or -1 if not set. */
1176 #define NEVER_SET -1
1177 static int *reg_first_set
;
1178 static int *reg_last_set
;
1180 /* While computing "first/last set" info, this is the CUID of first/last insn
1181 to set memory or -1 if not set. `mem_last_set' is also used when
1182 performing GCSE to record whether memory has been set since the beginning
1185 Note that handling of memory is very simple, we don't make any attempt
1186 to optimize things (later). */
1187 static int mem_first_set
;
1188 static int mem_last_set
;
1190 /* Perform a quick check whether X, the source of a set, is something
1191 we want to consider for GCSE. */
1197 switch (GET_CODE (x
))
1213 /* Return non-zero if the operands of expression X are unchanged from the
1214 start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
1215 or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
1218 oprs_unchanged_p (x
, insn
, avail_p
)
1229 code
= GET_CODE (x
);
1234 return (reg_last_set
[REGNO (x
)] == NEVER_SET
1235 || reg_last_set
[REGNO (x
)] < INSN_CUID (insn
));
1237 return (reg_first_set
[REGNO (x
)] == NEVER_SET
1238 || reg_first_set
[REGNO (x
)] >= INSN_CUID (insn
));
1241 if (avail_p
&& mem_last_set
!= NEVER_SET
1242 && mem_last_set
>= INSN_CUID (insn
))
1244 else if (! avail_p
&& mem_first_set
!= NEVER_SET
1245 && mem_first_set
< INSN_CUID (insn
))
1248 return oprs_unchanged_p (XEXP (x
, 0), insn
, avail_p
);
1273 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
1277 /* If we are about to do the last recursive call needed at this
1278 level, change it into iteration. This function is called enough
1281 return oprs_unchanged_p (XEXP (x
, i
), insn
, avail_p
);
1283 else if (! oprs_unchanged_p (XEXP (x
, i
), insn
, avail_p
))
1286 else if (fmt
[i
] == 'E')
1287 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1288 if (! oprs_unchanged_p (XVECEXP (x
, i
, j
), insn
, avail_p
))
1295 /* Return non-zero if the operands of expression X are unchanged from
1296 the start of INSN's basic block up to but not including INSN. */
1299 oprs_anticipatable_p (x
, insn
)
1302 return oprs_unchanged_p (x
, insn
, 0);
1305 /* Return non-zero if the operands of expression X are unchanged from
1306 INSN to the end of INSN's basic block. */
1309 oprs_available_p (x
, insn
)
1312 return oprs_unchanged_p (x
, insn
, 1);
1315 /* Hash expression X.
1317 MODE is only used if X is a CONST_INT. DO_NOT_RECORD_P is a boolean
1318 indicating if a volatile operand is found or if the expression contains
1319 something we don't want to insert in the table.
1321 ??? One might want to merge this with canon_hash. Later. */
1324 hash_expr (x
, mode
, do_not_record_p
, hash_table_size
)
1326 enum machine_mode mode
;
1327 int *do_not_record_p
;
1328 int hash_table_size
;
1332 *do_not_record_p
= 0;
1334 hash
= hash_expr_1 (x
, mode
, do_not_record_p
);
1335 return hash
% hash_table_size
;
1337 /* Hash a string. Just add its bytes up. */
1338 static inline unsigned
1343 const unsigned char *p
= (const unsigned char *)ps
;
1352 /* Subroutine of hash_expr to do the actual work. */
1355 hash_expr_1 (x
, mode
, do_not_record_p
)
1357 enum machine_mode mode
;
1358 int *do_not_record_p
;
1365 /* Used to turn recursion into iteration. We can't rely on GCC's
1366 tail-recursion eliminatio since we need to keep accumulating values
1373 code
= GET_CODE (x
);
1377 hash
+= ((unsigned int) REG
<< 7) + REGNO (x
);
1381 hash
+= (((unsigned int) CONST_INT
<< 7) + (unsigned int) mode
1382 + (unsigned int) INTVAL (x
));
1386 /* This is like the general case, except that it only counts
1387 the integers representing the constant. */
1388 hash
+= (unsigned int) code
+ (unsigned int) GET_MODE (x
);
1389 if (GET_MODE (x
) != VOIDmode
)
1390 for (i
= 2; i
< GET_RTX_LENGTH (CONST_DOUBLE
); i
++)
1391 hash
+= (unsigned int) XWINT (x
, i
);
1393 hash
+= ((unsigned int) CONST_DOUBLE_LOW (x
)
1394 + (unsigned int) CONST_DOUBLE_HIGH (x
));
1397 /* Assume there is only one rtx object for any given label. */
1399 /* We don't hash on the address of the CODE_LABEL to avoid bootstrap
1400 differences and differences between each stage's debugging dumps. */
1401 hash
+= (((unsigned int) LABEL_REF
<< 7)
1402 + CODE_LABEL_NUMBER (XEXP (x
, 0)));
1407 /* Don't hash on the symbol's address to avoid bootstrap differences.
1408 Different hash values may cause expressions to be recorded in
1409 different orders and thus different registers to be used in the
1410 final assembler. This also avoids differences in the dump files
1411 between various stages. */
1413 const unsigned char *p
= (const unsigned char *) XSTR (x
, 0);
1416 h
+= (h
<< 7) + *p
++; /* ??? revisit */
1418 hash
+= ((unsigned int) SYMBOL_REF
<< 7) + h
;
1423 if (MEM_VOLATILE_P (x
))
1425 *do_not_record_p
= 1;
1429 hash
+= (unsigned int) MEM
;
1430 hash
+= MEM_ALIAS_SET (x
);
1441 case UNSPEC_VOLATILE
:
1442 *do_not_record_p
= 1;
1446 if (MEM_VOLATILE_P (x
))
1448 *do_not_record_p
= 1;
1453 /* We don't want to take the filename and line into account. */
1454 hash
+= (unsigned) code
+ (unsigned) GET_MODE (x
)
1455 + hash_string_1 (ASM_OPERANDS_TEMPLATE (x
))
1456 + hash_string_1 (ASM_OPERANDS_OUTPUT_CONSTRAINT (x
))
1457 + (unsigned) ASM_OPERANDS_OUTPUT_IDX (x
);
1459 if (ASM_OPERANDS_INPUT_LENGTH (x
))
1461 for (i
= 1; i
< ASM_OPERANDS_INPUT_LENGTH (x
); i
++)
1463 hash
+= (hash_expr_1 (ASM_OPERANDS_INPUT (x
, i
),
1464 GET_MODE (ASM_OPERANDS_INPUT (x
, i
)),
1466 + hash_string_1 (ASM_OPERANDS_INPUT_CONSTRAINT
1470 hash
+= hash_string_1 (ASM_OPERANDS_INPUT_CONSTRAINT (x
, 0));
1471 x
= ASM_OPERANDS_INPUT (x
, 0);
1472 mode
= GET_MODE (x
);
1482 hash
+= (unsigned) code
+ (unsigned) GET_MODE (x
);
1483 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
1487 /* If we are about to do the last recursive call
1488 needed at this level, change it into iteration.
1489 This function is called enough to be worth it. */
1496 hash
+= hash_expr_1 (XEXP (x
, i
), 0, do_not_record_p
);
1497 if (*do_not_record_p
)
1501 else if (fmt
[i
] == 'E')
1502 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1504 hash
+= hash_expr_1 (XVECEXP (x
, i
, j
), 0, do_not_record_p
);
1505 if (*do_not_record_p
)
1509 else if (fmt
[i
] == 's')
1510 hash
+= hash_string_1 (XSTR (x
, i
));
1511 else if (fmt
[i
] == 'i')
1512 hash
+= (unsigned int) XINT (x
, i
);
1520 /* Hash a set of register REGNO.
1522 Sets are hashed on the register that is set. This simplifies the PRE copy
1525 ??? May need to make things more elaborate. Later, as necessary. */
1528 hash_set (regno
, hash_table_size
)
1530 int hash_table_size
;
1535 return hash
% hash_table_size
;
1538 /* Return non-zero if exp1 is equivalent to exp2.
1539 ??? Borrowed from cse.c. Might want to remerge with cse.c. Later. */
1546 register enum rtx_code code
;
1547 register const char *fmt
;
1552 if (x
== 0 || y
== 0)
1555 code
= GET_CODE (x
);
1556 if (code
!= GET_CODE (y
))
1559 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
1560 if (GET_MODE (x
) != GET_MODE (y
))
1570 return INTVAL (x
) == INTVAL (y
);
1573 return XEXP (x
, 0) == XEXP (y
, 0);
1576 return XSTR (x
, 0) == XSTR (y
, 0);
1579 return REGNO (x
) == REGNO (y
);
1582 /* Can't merge two expressions in different alias sets, since we can
1583 decide that the expression is transparent in a block when it isn't,
1584 due to it being set with the different alias set. */
1585 if (MEM_ALIAS_SET (x
) != MEM_ALIAS_SET (y
))
1589 /* For commutative operations, check both orders. */
1597 return ((expr_equiv_p (XEXP (x
, 0), XEXP (y
, 0))
1598 && expr_equiv_p (XEXP (x
, 1), XEXP (y
, 1)))
1599 || (expr_equiv_p (XEXP (x
, 0), XEXP (y
, 1))
1600 && expr_equiv_p (XEXP (x
, 1), XEXP (y
, 0))));
1603 /* We don't use the generic code below because we want to
1604 disregard filename and line numbers. */
1606 /* A volatile asm isn't equivalent to any other. */
1607 if (MEM_VOLATILE_P (x
) || MEM_VOLATILE_P (y
))
1610 if (GET_MODE (x
) != GET_MODE (y
)
1611 || strcmp (ASM_OPERANDS_TEMPLATE (x
), ASM_OPERANDS_TEMPLATE (y
))
1612 || strcmp (ASM_OPERANDS_OUTPUT_CONSTRAINT (x
),
1613 ASM_OPERANDS_OUTPUT_CONSTRAINT (y
))
1614 || ASM_OPERANDS_OUTPUT_IDX (x
) != ASM_OPERANDS_OUTPUT_IDX (y
)
1615 || ASM_OPERANDS_INPUT_LENGTH (x
) != ASM_OPERANDS_INPUT_LENGTH (y
))
1618 if (ASM_OPERANDS_INPUT_LENGTH (x
))
1620 for (i
= ASM_OPERANDS_INPUT_LENGTH (x
) - 1; i
>= 0; i
--)
1621 if (! expr_equiv_p (ASM_OPERANDS_INPUT (x
, i
),
1622 ASM_OPERANDS_INPUT (y
, i
))
1623 || strcmp (ASM_OPERANDS_INPUT_CONSTRAINT (x
, i
),
1624 ASM_OPERANDS_INPUT_CONSTRAINT (y
, i
)))
1634 /* Compare the elements. If any pair of corresponding elements
1635 fail to match, return 0 for the whole thing. */
1637 fmt
= GET_RTX_FORMAT (code
);
1638 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1643 if (! expr_equiv_p (XEXP (x
, i
), XEXP (y
, i
)))
1648 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
1650 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1651 if (! expr_equiv_p (XVECEXP (x
, i
, j
), XVECEXP (y
, i
, j
)))
1656 if (strcmp (XSTR (x
, i
), XSTR (y
, i
)))
1661 if (XINT (x
, i
) != XINT (y
, i
))
1666 if (XWINT (x
, i
) != XWINT (y
, i
))
1681 /* Insert expression X in INSN in the hash table.
1682 If it is already present, record it as the last occurrence in INSN's
1685 MODE is the mode of the value X is being stored into.
1686 It is only used if X is a CONST_INT.
1688 ANTIC_P is non-zero if X is an anticipatable expression.
1689 AVAIL_P is non-zero if X is an available expression. */
1692 insert_expr_in_table (x
, mode
, insn
, antic_p
, avail_p
)
1694 enum machine_mode mode
;
1696 int antic_p
, avail_p
;
1698 int found
, do_not_record_p
;
1700 struct expr
*cur_expr
, *last_expr
= NULL
;
1701 struct occr
*antic_occr
, *avail_occr
;
1702 struct occr
*last_occr
= NULL
;
1704 hash
= hash_expr (x
, mode
, &do_not_record_p
, expr_hash_table_size
);
1706 /* Do not insert expression in table if it contains volatile operands,
1707 or if hash_expr determines the expression is something we don't want
1708 to or can't handle. */
1709 if (do_not_record_p
)
1712 cur_expr
= expr_hash_table
[hash
];
1715 while (cur_expr
&& 0 == (found
= expr_equiv_p (cur_expr
->expr
, x
)))
1717 /* If the expression isn't found, save a pointer to the end of
1719 last_expr
= cur_expr
;
1720 cur_expr
= cur_expr
->next_same_hash
;
1725 cur_expr
= (struct expr
*) gcse_alloc (sizeof (struct expr
));
1726 bytes_used
+= sizeof (struct expr
);
1727 if (expr_hash_table
[hash
] == NULL
)
1728 /* This is the first pattern that hashed to this index. */
1729 expr_hash_table
[hash
] = cur_expr
;
1731 /* Add EXPR to end of this hash chain. */
1732 last_expr
->next_same_hash
= cur_expr
;
1734 /* Set the fields of the expr element. */
1736 cur_expr
->bitmap_index
= n_exprs
++;
1737 cur_expr
->next_same_hash
= NULL
;
1738 cur_expr
->antic_occr
= NULL
;
1739 cur_expr
->avail_occr
= NULL
;
1742 /* Now record the occurrence(s). */
1745 antic_occr
= cur_expr
->antic_occr
;
1747 /* Search for another occurrence in the same basic block. */
1748 while (antic_occr
&& BLOCK_NUM (antic_occr
->insn
) != BLOCK_NUM (insn
))
1750 /* If an occurrence isn't found, save a pointer to the end of
1752 last_occr
= antic_occr
;
1753 antic_occr
= antic_occr
->next
;
1757 /* Found another instance of the expression in the same basic block.
1758 Prefer the currently recorded one. We want the first one in the
1759 block and the block is scanned from start to end. */
1760 ; /* nothing to do */
1763 /* First occurrence of this expression in this basic block. */
1764 antic_occr
= (struct occr
*) gcse_alloc (sizeof (struct occr
));
1765 bytes_used
+= sizeof (struct occr
);
1766 /* First occurrence of this expression in any block? */
1767 if (cur_expr
->antic_occr
== NULL
)
1768 cur_expr
->antic_occr
= antic_occr
;
1770 last_occr
->next
= antic_occr
;
1772 antic_occr
->insn
= insn
;
1773 antic_occr
->next
= NULL
;
1779 avail_occr
= cur_expr
->avail_occr
;
1781 /* Search for another occurrence in the same basic block. */
1782 while (avail_occr
&& BLOCK_NUM (avail_occr
->insn
) != BLOCK_NUM (insn
))
1784 /* If an occurrence isn't found, save a pointer to the end of
1786 last_occr
= avail_occr
;
1787 avail_occr
= avail_occr
->next
;
1791 /* Found another instance of the expression in the same basic block.
1792 Prefer this occurrence to the currently recorded one. We want
1793 the last one in the block and the block is scanned from start
1795 avail_occr
->insn
= insn
;
1798 /* First occurrence of this expression in this basic block. */
1799 avail_occr
= (struct occr
*) gcse_alloc (sizeof (struct occr
));
1800 bytes_used
+= sizeof (struct occr
);
1802 /* First occurrence of this expression in any block? */
1803 if (cur_expr
->avail_occr
== NULL
)
1804 cur_expr
->avail_occr
= avail_occr
;
1806 last_occr
->next
= avail_occr
;
1808 avail_occr
->insn
= insn
;
1809 avail_occr
->next
= NULL
;
1814 /* Insert pattern X in INSN in the hash table.
1815 X is a SET of a reg to either another reg or a constant.
1816 If it is already present, record it as the last occurrence in INSN's
1820 insert_set_in_table (x
, insn
)
1826 struct expr
*cur_expr
, *last_expr
= NULL
;
1827 struct occr
*cur_occr
, *last_occr
= NULL
;
1829 if (GET_CODE (x
) != SET
1830 || GET_CODE (SET_DEST (x
)) != REG
)
1833 hash
= hash_set (REGNO (SET_DEST (x
)), set_hash_table_size
);
1835 cur_expr
= set_hash_table
[hash
];
1838 while (cur_expr
&& 0 == (found
= expr_equiv_p (cur_expr
->expr
, x
)))
1840 /* If the expression isn't found, save a pointer to the end of
1842 last_expr
= cur_expr
;
1843 cur_expr
= cur_expr
->next_same_hash
;
1848 cur_expr
= (struct expr
*) gcse_alloc (sizeof (struct expr
));
1849 bytes_used
+= sizeof (struct expr
);
1850 if (set_hash_table
[hash
] == NULL
)
1851 /* This is the first pattern that hashed to this index. */
1852 set_hash_table
[hash
] = cur_expr
;
1854 /* Add EXPR to end of this hash chain. */
1855 last_expr
->next_same_hash
= cur_expr
;
1857 /* Set the fields of the expr element.
1858 We must copy X because it can be modified when copy propagation is
1859 performed on its operands. */
1860 /* ??? Should this go in a different obstack? */
1861 cur_expr
->expr
= copy_rtx (x
);
1862 cur_expr
->bitmap_index
= n_sets
++;
1863 cur_expr
->next_same_hash
= NULL
;
1864 cur_expr
->antic_occr
= NULL
;
1865 cur_expr
->avail_occr
= NULL
;
1868 /* Now record the occurrence. */
1869 cur_occr
= cur_expr
->avail_occr
;
1871 /* Search for another occurrence in the same basic block. */
1872 while (cur_occr
&& BLOCK_NUM (cur_occr
->insn
) != BLOCK_NUM (insn
))
1874 /* If an occurrence isn't found, save a pointer to the end of
1876 last_occr
= cur_occr
;
1877 cur_occr
= cur_occr
->next
;
1881 /* Found another instance of the expression in the same basic block.
1882 Prefer this occurrence to the currently recorded one. We want the
1883 last one in the block and the block is scanned from start to end. */
1884 cur_occr
->insn
= insn
;
1887 /* First occurrence of this expression in this basic block. */
1888 cur_occr
= (struct occr
*) gcse_alloc (sizeof (struct occr
));
1889 bytes_used
+= sizeof (struct occr
);
1891 /* First occurrence of this expression in any block? */
1892 if (cur_expr
->avail_occr
== NULL
)
1893 cur_expr
->avail_occr
= cur_occr
;
1895 last_occr
->next
= cur_occr
;
1897 cur_occr
->insn
= insn
;
1898 cur_occr
->next
= NULL
;
1902 /* Scan pattern PAT of INSN and add an entry to the hash table. If SET_P is
1903 non-zero, this is for the assignment hash table, otherwise it is for the
1904 expression hash table. */
1907 hash_scan_set (pat
, insn
, set_p
)
1911 rtx src
= SET_SRC (pat
);
1912 rtx dest
= SET_DEST (pat
);
1914 if (GET_CODE (src
) == CALL
)
1915 hash_scan_call (src
, insn
);
1917 if (GET_CODE (dest
) == REG
)
1919 int regno
= REGNO (dest
);
1922 /* Only record sets of pseudo-regs in the hash table. */
1924 && regno
>= FIRST_PSEUDO_REGISTER
1925 /* Don't GCSE something if we can't do a reg/reg copy. */
1926 && can_copy_p
[GET_MODE (dest
)]
1927 /* Is SET_SRC something we want to gcse? */
1928 && want_to_gcse_p (src
))
1930 /* An expression is not anticipatable if its operands are
1931 modified before this insn. */
1932 int antic_p
= oprs_anticipatable_p (src
, insn
);
1933 /* An expression is not available if its operands are
1934 subsequently modified, including this insn. */
1935 int avail_p
= oprs_available_p (src
, insn
);
1937 insert_expr_in_table (src
, GET_MODE (dest
), insn
, antic_p
, avail_p
);
1940 /* Record sets for constant/copy propagation. */
1942 && regno
>= FIRST_PSEUDO_REGISTER
1943 && ((GET_CODE (src
) == REG
1944 && REGNO (src
) >= FIRST_PSEUDO_REGISTER
1945 && can_copy_p
[GET_MODE (dest
)])
1946 || GET_CODE (src
) == CONST_INT
1947 || GET_CODE (src
) == SYMBOL_REF
1948 || GET_CODE (src
) == CONST_DOUBLE
)
1949 /* A copy is not available if its src or dest is subsequently
1950 modified. Here we want to search from INSN+1 on, but
1951 oprs_available_p searches from INSN on. */
1952 && (insn
== BLOCK_END (BLOCK_NUM (insn
))
1953 || ((tmp
= next_nonnote_insn (insn
)) != NULL_RTX
1954 && oprs_available_p (pat
, tmp
))))
1955 insert_set_in_table (pat
, insn
);
1960 hash_scan_clobber (x
, insn
)
1961 rtx x ATTRIBUTE_UNUSED
, insn ATTRIBUTE_UNUSED
;
1963 /* Currently nothing to do. */
1967 hash_scan_call (x
, insn
)
1968 rtx x ATTRIBUTE_UNUSED
, insn ATTRIBUTE_UNUSED
;
1970 /* Currently nothing to do. */
1973 /* Process INSN and add hash table entries as appropriate.
1975 Only available expressions that set a single pseudo-reg are recorded.
1977 Single sets in a PARALLEL could be handled, but it's an extra complication
1978 that isn't dealt with right now. The trick is handling the CLOBBERs that
1979 are also in the PARALLEL. Later.
1981 If SET_P is non-zero, this is for the assignment hash table,
1982 otherwise it is for the expression hash table.
1983 If IN_LIBCALL_BLOCK nonzero, we are in a libcall block, and should
1984 not record any expressions. */
1987 hash_scan_insn (insn
, set_p
, in_libcall_block
)
1990 int in_libcall_block
;
1992 rtx pat
= PATTERN (insn
);
1995 /* Pick out the sets of INSN and for other forms of instructions record
1996 what's been modified. */
1998 if (GET_CODE (pat
) == SET
&& ! in_libcall_block
)
2000 /* Ignore obvious no-ops. */
2001 if (SET_SRC (pat
) != SET_DEST (pat
))
2002 hash_scan_set (pat
, insn
, set_p
);
2004 else if (GET_CODE (pat
) == PARALLEL
)
2005 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
2007 rtx x
= XVECEXP (pat
, 0, i
);
2009 if (GET_CODE (x
) == SET
)
2011 if (GET_CODE (SET_SRC (x
)) == CALL
)
2012 hash_scan_call (SET_SRC (x
), insn
);
2014 else if (GET_CODE (x
) == CLOBBER
)
2015 hash_scan_clobber (x
, insn
);
2016 else if (GET_CODE (x
) == CALL
)
2017 hash_scan_call (x
, insn
);
2020 else if (GET_CODE (pat
) == CLOBBER
)
2021 hash_scan_clobber (pat
, insn
);
2022 else if (GET_CODE (pat
) == CALL
)
2023 hash_scan_call (pat
, insn
);
2027 dump_hash_table (file
, name
, table
, table_size
, total_size
)
2030 struct expr
**table
;
2031 int table_size
, total_size
;
2034 /* Flattened out table, so it's printed in proper order. */
2035 struct expr
**flat_table
;
2036 unsigned int *hash_val
;
2040 = (struct expr
**) xcalloc (total_size
, sizeof (struct expr
*));
2041 hash_val
= (unsigned int *) xmalloc (total_size
* sizeof (unsigned int));
2043 for (i
= 0; i
< table_size
; i
++)
2044 for (expr
= table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
2046 flat_table
[expr
->bitmap_index
] = expr
;
2047 hash_val
[expr
->bitmap_index
] = i
;
2050 fprintf (file
, "%s hash table (%d buckets, %d entries)\n",
2051 name
, table_size
, total_size
);
2053 for (i
= 0; i
< total_size
; i
++)
2054 if (flat_table
[i
] != 0)
2056 expr
= flat_table
[i
];
2057 fprintf (file
, "Index %d (hash value %d)\n ",
2058 expr
->bitmap_index
, hash_val
[i
]);
2059 print_rtl (file
, expr
->expr
);
2060 fprintf (file
, "\n");
2063 fprintf (file
, "\n");
2069 /* Record register first/last/block set information for REGNO in INSN.
2071 reg_first_set records the first place in the block where the register
2072 is set and is used to compute "anticipatability".
2074 reg_last_set records the last place in the block where the register
2075 is set and is used to compute "availability".
2077 reg_set_in_block records whether the register is set in the block
2078 and is used to compute "transparency". */
2081 record_last_reg_set_info (insn
, regno
)
2085 if (reg_first_set
[regno
] == NEVER_SET
)
2086 reg_first_set
[regno
] = INSN_CUID (insn
);
2088 reg_last_set
[regno
] = INSN_CUID (insn
);
2089 SET_BIT (reg_set_in_block
[BLOCK_NUM (insn
)], regno
);
2092 /* Record memory first/last/block set information for INSN. */
2095 record_last_mem_set_info (insn
)
2098 if (mem_first_set
== NEVER_SET
)
2099 mem_first_set
= INSN_CUID (insn
);
2101 mem_last_set
= INSN_CUID (insn
);
2102 mem_set_in_block
[BLOCK_NUM (insn
)] = 1;
2105 /* Called from compute_hash_table via note_stores to handle one
2106 SET or CLOBBER in an insn. DATA is really the instruction in which
2107 the SET is taking place. */
2110 record_last_set_info (dest
, setter
, data
)
2111 rtx dest
, setter ATTRIBUTE_UNUSED
;
2114 rtx last_set_insn
= (rtx
) data
;
2116 if (GET_CODE (dest
) == SUBREG
)
2117 dest
= SUBREG_REG (dest
);
2119 if (GET_CODE (dest
) == REG
)
2120 record_last_reg_set_info (last_set_insn
, REGNO (dest
));
2121 else if (GET_CODE (dest
) == MEM
2122 /* Ignore pushes, they clobber nothing. */
2123 && ! push_operand (dest
, GET_MODE (dest
)))
2124 record_last_mem_set_info (last_set_insn
);
2127 /* Top level function to create an expression or assignment hash table.
2129 Expression entries are placed in the hash table if
2130 - they are of the form (set (pseudo-reg) src),
2131 - src is something we want to perform GCSE on,
2132 - none of the operands are subsequently modified in the block
2134 Assignment entries are placed in the hash table if
2135 - they are of the form (set (pseudo-reg) src),
2136 - src is something we want to perform const/copy propagation on,
2137 - none of the operands or target are subsequently modified in the block
2139 Currently src must be a pseudo-reg or a const_int.
2141 F is the first insn.
2142 SET_P is non-zero for computing the assignment hash table. */
2145 compute_hash_table (set_p
)
2150 /* While we compute the hash table we also compute a bit array of which
2151 registers are set in which blocks.
2152 We also compute which blocks set memory, in the absence of aliasing
2153 support [which is TODO].
2154 ??? This isn't needed during const/copy propagation, but it's cheap to
2156 sbitmap_vector_zero (reg_set_in_block
, n_basic_blocks
);
2157 bzero ((char *) mem_set_in_block
, n_basic_blocks
);
2159 /* Some working arrays used to track first and last set in each block. */
2160 /* ??? One could use alloca here, but at some size a threshold is crossed
2161 beyond which one should use malloc. Are we at that threshold here? */
2162 reg_first_set
= (int *) gmalloc (max_gcse_regno
* sizeof (int));
2163 reg_last_set
= (int *) gmalloc (max_gcse_regno
* sizeof (int));
2165 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
2169 int in_libcall_block
;
2172 /* First pass over the instructions records information used to
2173 determine when registers and memory are first and last set.
2174 ??? The mem_set_in_block and hard-reg reg_set_in_block computation
2175 could be moved to compute_sets since they currently don't change. */
2177 for (i
= 0; i
< max_gcse_regno
; i
++)
2178 reg_first_set
[i
] = reg_last_set
[i
] = NEVER_SET
;
2180 mem_first_set
= NEVER_SET
;
2181 mem_last_set
= NEVER_SET
;
2183 for (insn
= BLOCK_HEAD (bb
);
2184 insn
&& insn
!= NEXT_INSN (BLOCK_END (bb
));
2185 insn
= NEXT_INSN (insn
))
2187 #ifdef NON_SAVING_SETJMP
2188 if (NON_SAVING_SETJMP
&& GET_CODE (insn
) == NOTE
2189 && NOTE_LINE_NUMBER (insn
) == NOTE_INSN_SETJMP
)
2191 for (regno
= 0; regno
< FIRST_PSEUDO_REGISTER
; regno
++)
2192 record_last_reg_set_info (insn
, regno
);
2197 if (! INSN_P (insn
))
2200 if (GET_CODE (insn
) == CALL_INSN
)
2202 for (regno
= 0; regno
< FIRST_PSEUDO_REGISTER
; regno
++)
2203 if ((call_used_regs
[regno
]
2204 && regno
!= STACK_POINTER_REGNUM
2205 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2206 && regno
!= HARD_FRAME_POINTER_REGNUM
2208 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
2209 && ! (regno
== ARG_POINTER_REGNUM
&& fixed_regs
[regno
])
2211 #if defined (PIC_OFFSET_TABLE_REGNUM) && !defined (PIC_OFFSET_TABLE_REG_CALL_CLOBBERED)
2212 && ! (regno
== PIC_OFFSET_TABLE_REGNUM
&& flag_pic
)
2215 && regno
!= FRAME_POINTER_REGNUM
)
2216 || global_regs
[regno
])
2217 record_last_reg_set_info (insn
, regno
);
2219 if (! CONST_CALL_P (insn
))
2220 record_last_mem_set_info (insn
);
2223 note_stores (PATTERN (insn
), record_last_set_info
, insn
);
2226 /* The next pass builds the hash table. */
2228 for (insn
= BLOCK_HEAD (bb
), in_libcall_block
= 0;
2229 insn
&& insn
!= NEXT_INSN (BLOCK_END (bb
));
2230 insn
= NEXT_INSN (insn
))
2233 if (find_reg_note (insn
, REG_LIBCALL
, NULL_RTX
))
2234 in_libcall_block
= 1;
2235 else if (find_reg_note (insn
, REG_RETVAL
, NULL_RTX
))
2236 in_libcall_block
= 0;
2237 hash_scan_insn (insn
, set_p
, in_libcall_block
);
2241 free (reg_first_set
);
2242 free (reg_last_set
);
2244 /* Catch bugs early. */
2245 reg_first_set
= reg_last_set
= 0;
2248 /* Allocate space for the set hash table.
2249 N_INSNS is the number of instructions in the function.
2250 It is used to determine the number of buckets to use. */
2253 alloc_set_hash_table (n_insns
)
2258 set_hash_table_size
= n_insns
/ 4;
2259 if (set_hash_table_size
< 11)
2260 set_hash_table_size
= 11;
2262 /* Attempt to maintain efficient use of hash table.
2263 Making it an odd number is simplest for now.
2264 ??? Later take some measurements. */
2265 set_hash_table_size
|= 1;
2266 n
= set_hash_table_size
* sizeof (struct expr
*);
2267 set_hash_table
= (struct expr
**) gmalloc (n
);
2270 /* Free things allocated by alloc_set_hash_table. */
2273 free_set_hash_table ()
2275 free (set_hash_table
);
2278 /* Compute the hash table for doing copy/const propagation. */
2281 compute_set_hash_table ()
2283 /* Initialize count of number of entries in hash table. */
2285 bzero ((char *) set_hash_table
,
2286 set_hash_table_size
* sizeof (struct expr
*));
2288 compute_hash_table (1);
2291 /* Allocate space for the expression hash table.
2292 N_INSNS is the number of instructions in the function.
2293 It is used to determine the number of buckets to use. */
2296 alloc_expr_hash_table (n_insns
)
2297 unsigned int n_insns
;
2301 expr_hash_table_size
= n_insns
/ 2;
2302 /* Make sure the amount is usable. */
2303 if (expr_hash_table_size
< 11)
2304 expr_hash_table_size
= 11;
2306 /* Attempt to maintain efficient use of hash table.
2307 Making it an odd number is simplest for now.
2308 ??? Later take some measurements. */
2309 expr_hash_table_size
|= 1;
2310 n
= expr_hash_table_size
* sizeof (struct expr
*);
2311 expr_hash_table
= (struct expr
**) gmalloc (n
);
2314 /* Free things allocated by alloc_expr_hash_table. */
2317 free_expr_hash_table ()
2319 free (expr_hash_table
);
2322 /* Compute the hash table for doing GCSE. */
2325 compute_expr_hash_table ()
2327 /* Initialize count of number of entries in hash table. */
2329 bzero ((char *) expr_hash_table
,
2330 expr_hash_table_size
* sizeof (struct expr
*));
2332 compute_hash_table (0);
2335 /* Expression tracking support. */
2337 /* Lookup pattern PAT in the expression table.
2338 The result is a pointer to the table entry, or NULL if not found. */
2340 static struct expr
*
2344 int do_not_record_p
;
2345 unsigned int hash
= hash_expr (pat
, GET_MODE (pat
), &do_not_record_p
,
2346 expr_hash_table_size
);
2349 if (do_not_record_p
)
2352 expr
= expr_hash_table
[hash
];
2354 while (expr
&& ! expr_equiv_p (expr
->expr
, pat
))
2355 expr
= expr
->next_same_hash
;
2360 /* Lookup REGNO in the set table. If PAT is non-NULL look for the entry that
2361 matches it, otherwise return the first entry for REGNO. The result is a
2362 pointer to the table entry, or NULL if not found. */
2364 static struct expr
*
2365 lookup_set (regno
, pat
)
2369 unsigned int hash
= hash_set (regno
, set_hash_table_size
);
2372 expr
= set_hash_table
[hash
];
2376 while (expr
&& ! expr_equiv_p (expr
->expr
, pat
))
2377 expr
= expr
->next_same_hash
;
2381 while (expr
&& REGNO (SET_DEST (expr
->expr
)) != regno
)
2382 expr
= expr
->next_same_hash
;
2388 /* Return the next entry for REGNO in list EXPR. */
2390 static struct expr
*
2391 next_set (regno
, expr
)
2396 expr
= expr
->next_same_hash
;
2397 while (expr
&& REGNO (SET_DEST (expr
->expr
)) != regno
);
2402 /* Reset tables used to keep track of what's still available [since the
2403 start of the block]. */
2406 reset_opr_set_tables ()
2408 /* Maintain a bitmap of which regs have been set since beginning of
2410 sbitmap_zero (reg_set_bitmap
);
2412 /* Also keep a record of the last instruction to modify memory.
2413 For now this is very trivial, we only record whether any memory
2414 location has been modified. */
2418 /* Return non-zero if the operands of X are not set before INSN in
2419 INSN's basic block. */
2422 oprs_not_set_p (x
, insn
)
2432 code
= GET_CODE (x
);
2447 if (mem_last_set
!= 0)
2450 return oprs_not_set_p (XEXP (x
, 0), insn
);
2453 return ! TEST_BIT (reg_set_bitmap
, REGNO (x
));
2459 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
2463 /* If we are about to do the last recursive call
2464 needed at this level, change it into iteration.
2465 This function is called enough to be worth it. */
2467 return oprs_not_set_p (XEXP (x
, i
), insn
);
2469 if (! oprs_not_set_p (XEXP (x
, i
), insn
))
2472 else if (fmt
[i
] == 'E')
2473 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
2474 if (! oprs_not_set_p (XVECEXP (x
, i
, j
), insn
))
2481 /* Mark things set by a CALL. */
2487 mem_last_set
= INSN_CUID (insn
);
2490 /* Mark things set by a SET. */
2493 mark_set (pat
, insn
)
2496 rtx dest
= SET_DEST (pat
);
2498 while (GET_CODE (dest
) == SUBREG
2499 || GET_CODE (dest
) == ZERO_EXTRACT
2500 || GET_CODE (dest
) == SIGN_EXTRACT
2501 || GET_CODE (dest
) == STRICT_LOW_PART
)
2502 dest
= XEXP (dest
, 0);
2504 if (GET_CODE (dest
) == REG
)
2505 SET_BIT (reg_set_bitmap
, REGNO (dest
));
2506 else if (GET_CODE (dest
) == MEM
)
2507 mem_last_set
= INSN_CUID (insn
);
2509 if (GET_CODE (SET_SRC (pat
)) == CALL
)
2513 /* Record things set by a CLOBBER. */
2516 mark_clobber (pat
, insn
)
2519 rtx clob
= XEXP (pat
, 0);
2521 while (GET_CODE (clob
) == SUBREG
|| GET_CODE (clob
) == STRICT_LOW_PART
)
2522 clob
= XEXP (clob
, 0);
2524 if (GET_CODE (clob
) == REG
)
2525 SET_BIT (reg_set_bitmap
, REGNO (clob
));
2527 mem_last_set
= INSN_CUID (insn
);
2530 /* Record things set by INSN.
2531 This data is used by oprs_not_set_p. */
2534 mark_oprs_set (insn
)
2537 rtx pat
= PATTERN (insn
);
2540 if (GET_CODE (pat
) == SET
)
2541 mark_set (pat
, insn
);
2542 else if (GET_CODE (pat
) == PARALLEL
)
2543 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
2545 rtx x
= XVECEXP (pat
, 0, i
);
2547 if (GET_CODE (x
) == SET
)
2549 else if (GET_CODE (x
) == CLOBBER
)
2550 mark_clobber (x
, insn
);
2551 else if (GET_CODE (x
) == CALL
)
2555 else if (GET_CODE (pat
) == CLOBBER
)
2556 mark_clobber (pat
, insn
);
2557 else if (GET_CODE (pat
) == CALL
)
2562 /* Classic GCSE reaching definition support. */
2564 /* Allocate reaching def variables. */
2567 alloc_rd_mem (n_blocks
, n_insns
)
2568 int n_blocks
, n_insns
;
2570 rd_kill
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_insns
);
2571 sbitmap_vector_zero (rd_kill
, n_basic_blocks
);
2573 rd_gen
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_insns
);
2574 sbitmap_vector_zero (rd_gen
, n_basic_blocks
);
2576 reaching_defs
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_insns
);
2577 sbitmap_vector_zero (reaching_defs
, n_basic_blocks
);
2579 rd_out
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_insns
);
2580 sbitmap_vector_zero (rd_out
, n_basic_blocks
);
2583 /* Free reaching def variables. */
2590 free (reaching_defs
);
2594 /* Add INSN to the kills of BB. REGNO, set in BB, is killed by INSN. */
2597 handle_rd_kill_set (insn
, regno
, bb
)
2601 struct reg_set
*this_reg
;
2603 for (this_reg
= reg_set_table
[regno
]; this_reg
; this_reg
= this_reg
->next
)
2604 if (BLOCK_NUM (this_reg
->insn
) != BLOCK_NUM (insn
))
2605 SET_BIT (rd_kill
[bb
], INSN_CUID (this_reg
->insn
));
2608 /* Compute the set of kill's for reaching definitions. */
2617 For each set bit in `gen' of the block (i.e each insn which
2618 generates a definition in the block)
2619 Call the reg set by the insn corresponding to that bit regx
2620 Look at the linked list starting at reg_set_table[regx]
2621 For each setting of regx in the linked list, which is not in
2623 Set the bit in `kill' corresponding to that insn. */
2624 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
2625 for (cuid
= 0; cuid
< max_cuid
; cuid
++)
2626 if (TEST_BIT (rd_gen
[bb
], cuid
))
2628 rtx insn
= CUID_INSN (cuid
);
2629 rtx pat
= PATTERN (insn
);
2631 if (GET_CODE (insn
) == CALL_INSN
)
2633 for (regno
= 0; regno
< FIRST_PSEUDO_REGISTER
; regno
++)
2635 if ((call_used_regs
[regno
]
2636 && regno
!= STACK_POINTER_REGNUM
2637 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2638 && regno
!= HARD_FRAME_POINTER_REGNUM
2640 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
2641 && ! (regno
== ARG_POINTER_REGNUM
2642 && fixed_regs
[regno
])
2644 #if defined (PIC_OFFSET_TABLE_REGNUM) && !defined (PIC_OFFSET_TABLE_REG_CALL_CLOBBERED)
2645 && ! (regno
== PIC_OFFSET_TABLE_REGNUM
&& flag_pic
)
2647 && regno
!= FRAME_POINTER_REGNUM
)
2648 || global_regs
[regno
])
2649 handle_rd_kill_set (insn
, regno
, bb
);
2653 if (GET_CODE (pat
) == PARALLEL
)
2655 for (i
= XVECLEN (pat
, 0) - 1; i
>= 0; i
--)
2657 enum rtx_code code
= GET_CODE (XVECEXP (pat
, 0, i
));
2659 if ((code
== SET
|| code
== CLOBBER
)
2660 && GET_CODE (XEXP (XVECEXP (pat
, 0, i
), 0)) == REG
)
2661 handle_rd_kill_set (insn
,
2662 REGNO (XEXP (XVECEXP (pat
, 0, i
), 0)),
2666 else if (GET_CODE (pat
) == SET
&& GET_CODE (SET_DEST (pat
)) == REG
)
2667 /* Each setting of this register outside of this block
2668 must be marked in the set of kills in this block. */
2669 handle_rd_kill_set (insn
, REGNO (SET_DEST (pat
)), bb
);
2673 /* Compute the reaching definitions as in
2674 Compilers Principles, Techniques, and Tools. Aho, Sethi, Ullman,
2675 Chapter 10. It is the same algorithm as used for computing available
2676 expressions but applied to the gens and kills of reaching definitions. */
2681 int bb
, changed
, passes
;
2683 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
2684 sbitmap_copy (rd_out
[bb
] /*dst*/, rd_gen
[bb
] /*src*/);
2691 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
2693 sbitmap_union_of_preds (reaching_defs
[bb
], rd_out
, bb
);
2694 changed
|= sbitmap_union_of_diff (rd_out
[bb
], rd_gen
[bb
],
2695 reaching_defs
[bb
], rd_kill
[bb
]);
2701 fprintf (gcse_file
, "reaching def computation: %d passes\n", passes
);
2704 /* Classic GCSE available expression support. */
2706 /* Allocate memory for available expression computation. */
2709 alloc_avail_expr_mem (n_blocks
, n_exprs
)
2710 int n_blocks
, n_exprs
;
2712 ae_kill
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_exprs
);
2713 sbitmap_vector_zero (ae_kill
, n_basic_blocks
);
2715 ae_gen
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_exprs
);
2716 sbitmap_vector_zero (ae_gen
, n_basic_blocks
);
2718 ae_in
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_exprs
);
2719 sbitmap_vector_zero (ae_in
, n_basic_blocks
);
2721 ae_out
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_exprs
);
2722 sbitmap_vector_zero (ae_out
, n_basic_blocks
);
2726 free_avail_expr_mem ()
2734 /* Compute the set of available expressions generated in each basic block. */
2743 /* For each recorded occurrence of each expression, set ae_gen[bb][expr].
2744 This is all we have to do because an expression is not recorded if it
2745 is not available, and the only expressions we want to work with are the
2746 ones that are recorded. */
2747 for (i
= 0; i
< expr_hash_table_size
; i
++)
2748 for (expr
= expr_hash_table
[i
]; expr
!= 0; expr
= expr
->next_same_hash
)
2749 for (occr
= expr
->avail_occr
; occr
!= 0; occr
= occr
->next
)
2750 SET_BIT (ae_gen
[BLOCK_NUM (occr
->insn
)], expr
->bitmap_index
);
2753 /* Return non-zero if expression X is killed in BB. */
2756 expr_killed_p (x
, bb
)
2767 code
= GET_CODE (x
);
2771 return TEST_BIT (reg_set_in_block
[bb
], REGNO (x
));
2774 if (mem_set_in_block
[bb
])
2777 return expr_killed_p (XEXP (x
, 0), bb
);
2794 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
2798 /* If we are about to do the last recursive call
2799 needed at this level, change it into iteration.
2800 This function is called enough to be worth it. */
2802 return expr_killed_p (XEXP (x
, i
), bb
);
2803 else if (expr_killed_p (XEXP (x
, i
), bb
))
2806 else if (fmt
[i
] == 'E')
2807 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
2808 if (expr_killed_p (XVECEXP (x
, i
, j
), bb
))
2815 /* Compute the set of available expressions killed in each basic block. */
2818 compute_ae_kill (ae_gen
, ae_kill
)
2819 sbitmap
*ae_gen
, *ae_kill
;
2825 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
2826 for (i
= 0; i
< expr_hash_table_size
; i
++)
2827 for (expr
= expr_hash_table
[i
]; expr
; expr
= expr
->next_same_hash
)
2829 /* Skip EXPR if generated in this block. */
2830 if (TEST_BIT (ae_gen
[bb
], expr
->bitmap_index
))
2833 if (expr_killed_p (expr
->expr
, bb
))
2834 SET_BIT (ae_kill
[bb
], expr
->bitmap_index
);
2838 /* Actually perform the Classic GCSE optimizations. */
2840 /* Return non-zero if occurrence OCCR of expression EXPR reaches block BB.
2842 CHECK_SELF_LOOP is non-zero if we should consider a block reaching itself
2843 as a positive reach. We want to do this when there are two computations
2844 of the expression in the block.
2846 VISITED is a pointer to a working buffer for tracking which BB's have
2847 been visited. It is NULL for the top-level call.
2849 We treat reaching expressions that go through blocks containing the same
2850 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
2851 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
2852 2 as not reaching. The intent is to improve the probability of finding
2853 only one reaching expression and to reduce register lifetimes by picking
2854 the closest such expression. */
2857 expr_reaches_here_p_work (occr
, expr
, bb
, check_self_loop
, visited
)
2861 int check_self_loop
;
2866 for (pred
= BASIC_BLOCK(bb
)->pred
; pred
!= NULL
; pred
= pred
->pred_next
)
2868 int pred_bb
= pred
->src
->index
;
2870 if (visited
[pred_bb
])
2871 /* This predecessor has already been visited. Nothing to do. */
2873 else if (pred_bb
== bb
)
2875 /* BB loops on itself. */
2877 && TEST_BIT (ae_gen
[pred_bb
], expr
->bitmap_index
)
2878 && BLOCK_NUM (occr
->insn
) == pred_bb
)
2881 visited
[pred_bb
] = 1;
2884 /* Ignore this predecessor if it kills the expression. */
2885 else if (TEST_BIT (ae_kill
[pred_bb
], expr
->bitmap_index
))
2886 visited
[pred_bb
] = 1;
2888 /* Does this predecessor generate this expression? */
2889 else if (TEST_BIT (ae_gen
[pred_bb
], expr
->bitmap_index
))
2891 /* Is this the occurrence we're looking for?
2892 Note that there's only one generating occurrence per block
2893 so we just need to check the block number. */
2894 if (BLOCK_NUM (occr
->insn
) == pred_bb
)
2897 visited
[pred_bb
] = 1;
2900 /* Neither gen nor kill. */
2903 visited
[pred_bb
] = 1;
2904 if (expr_reaches_here_p_work (occr
, expr
, pred_bb
, check_self_loop
,
2911 /* All paths have been checked. */
2915 /* This wrapper for expr_reaches_here_p_work() is to ensure that any
2916 memory allocated for that function is returned. */
2919 expr_reaches_here_p (occr
, expr
, bb
, check_self_loop
)
2923 int check_self_loop
;
2926 char *visited
= (char *) xcalloc (n_basic_blocks
, 1);
2928 rval
= expr_reaches_here_p_work (occr
, expr
, bb
, check_self_loop
, visited
);
2934 /* Return the instruction that computes EXPR that reaches INSN's basic block.
2935 If there is more than one such instruction, return NULL.
2937 Called only by handle_avail_expr. */
2940 computing_insn (expr
, insn
)
2944 int bb
= BLOCK_NUM (insn
);
2946 if (expr
->avail_occr
->next
== NULL
)
2948 if (BLOCK_NUM (expr
->avail_occr
->insn
) == bb
)
2949 /* The available expression is actually itself
2950 (i.e. a loop in the flow graph) so do nothing. */
2953 /* (FIXME) Case that we found a pattern that was created by
2954 a substitution that took place. */
2955 return expr
->avail_occr
->insn
;
2959 /* Pattern is computed more than once.
2960 Search backwards from this insn to see how many of these
2961 computations actually reach this insn. */
2963 rtx insn_computes_expr
= NULL
;
2966 for (occr
= expr
->avail_occr
; occr
!= NULL
; occr
= occr
->next
)
2968 if (BLOCK_NUM (occr
->insn
) == bb
)
2970 /* The expression is generated in this block.
2971 The only time we care about this is when the expression
2972 is generated later in the block [and thus there's a loop].
2973 We let the normal cse pass handle the other cases. */
2974 if (INSN_CUID (insn
) < INSN_CUID (occr
->insn
)
2975 && expr_reaches_here_p (occr
, expr
, bb
, 1))
2981 insn_computes_expr
= occr
->insn
;
2984 else if (expr_reaches_here_p (occr
, expr
, bb
, 0))
2990 insn_computes_expr
= occr
->insn
;
2994 if (insn_computes_expr
== NULL
)
2997 return insn_computes_expr
;
3001 /* Return non-zero if the definition in DEF_INSN can reach INSN.
3002 Only called by can_disregard_other_sets. */
3005 def_reaches_here_p (insn
, def_insn
)
3010 if (TEST_BIT (reaching_defs
[BLOCK_NUM (insn
)], INSN_CUID (def_insn
)))
3013 if (BLOCK_NUM (insn
) == BLOCK_NUM (def_insn
))
3015 if (INSN_CUID (def_insn
) < INSN_CUID (insn
))
3017 if (GET_CODE (PATTERN (def_insn
)) == PARALLEL
)
3019 else if (GET_CODE (PATTERN (def_insn
)) == CLOBBER
)
3020 reg
= XEXP (PATTERN (def_insn
), 0);
3021 else if (GET_CODE (PATTERN (def_insn
)) == SET
)
3022 reg
= SET_DEST (PATTERN (def_insn
));
3026 return ! reg_set_between_p (reg
, NEXT_INSN (def_insn
), insn
);
3035 /* Return non-zero if *ADDR_THIS_REG can only have one value at INSN. The
3036 value returned is the number of definitions that reach INSN. Returning a
3037 value of zero means that [maybe] more than one definition reaches INSN and
3038 the caller can't perform whatever optimization it is trying. i.e. it is
3039 always safe to return zero. */
3042 can_disregard_other_sets (addr_this_reg
, insn
, for_combine
)
3043 struct reg_set
**addr_this_reg
;
3047 int number_of_reaching_defs
= 0;
3048 struct reg_set
*this_reg
;
3050 for (this_reg
= *addr_this_reg
; this_reg
!= 0; this_reg
= this_reg
->next
)
3051 if (def_reaches_here_p (insn
, this_reg
->insn
))
3053 number_of_reaching_defs
++;
3054 /* Ignore parallels for now. */
3055 if (GET_CODE (PATTERN (this_reg
->insn
)) == PARALLEL
)
3059 && (GET_CODE (PATTERN (this_reg
->insn
)) == CLOBBER
3060 || ! rtx_equal_p (SET_SRC (PATTERN (this_reg
->insn
)),
3061 SET_SRC (PATTERN (insn
)))))
3062 /* A setting of the reg to a different value reaches INSN. */
3065 if (number_of_reaching_defs
> 1)
3067 /* If in this setting the value the register is being set to is
3068 equal to the previous value the register was set to and this
3069 setting reaches the insn we are trying to do the substitution
3070 on then we are ok. */
3071 if (GET_CODE (PATTERN (this_reg
->insn
)) == CLOBBER
)
3073 else if (! rtx_equal_p (SET_SRC (PATTERN (this_reg
->insn
)),
3074 SET_SRC (PATTERN (insn
))))
3078 *addr_this_reg
= this_reg
;
3081 return number_of_reaching_defs
;
3084 /* Expression computed by insn is available and the substitution is legal,
3085 so try to perform the substitution.
3087 The result is non-zero if any changes were made. */
3090 handle_avail_expr (insn
, expr
)
3094 rtx pat
, insn_computes_expr
;
3096 struct reg_set
*this_reg
;
3097 int found_setting
, use_src
;
3100 /* We only handle the case where one computation of the expression
3101 reaches this instruction. */
3102 insn_computes_expr
= computing_insn (expr
, insn
);
3103 if (insn_computes_expr
== NULL
)
3109 /* At this point we know only one computation of EXPR outside of this
3110 block reaches this insn. Now try to find a register that the
3111 expression is computed into. */
3112 if (GET_CODE (SET_SRC (PATTERN (insn_computes_expr
))) == REG
)
3114 /* This is the case when the available expression that reaches
3115 here has already been handled as an available expression. */
3116 unsigned int regnum_for_replacing
3117 = REGNO (SET_SRC (PATTERN (insn_computes_expr
)));
3119 /* If the register was created by GCSE we can't use `reg_set_table',
3120 however we know it's set only once. */
3121 if (regnum_for_replacing
>= max_gcse_regno
3122 /* If the register the expression is computed into is set only once,
3123 or only one set reaches this insn, we can use it. */
3124 || (((this_reg
= reg_set_table
[regnum_for_replacing
]),
3125 this_reg
->next
== NULL
)
3126 || can_disregard_other_sets (&this_reg
, insn
, 0)))
3135 unsigned int regnum_for_replacing
3136 = REGNO (SET_DEST (PATTERN (insn_computes_expr
)));
3138 /* This shouldn't happen. */
3139 if (regnum_for_replacing
>= max_gcse_regno
)
3142 this_reg
= reg_set_table
[regnum_for_replacing
];
3144 /* If the register the expression is computed into is set only once,
3145 or only one set reaches this insn, use it. */
3146 if (this_reg
->next
== NULL
3147 || can_disregard_other_sets (&this_reg
, insn
, 0))
3153 pat
= PATTERN (insn
);
3155 to
= SET_SRC (PATTERN (insn_computes_expr
));
3157 to
= SET_DEST (PATTERN (insn_computes_expr
));
3158 changed
= validate_change (insn
, &SET_SRC (pat
), to
, 0);
3160 /* We should be able to ignore the return code from validate_change but
3161 to play it safe we check. */
3165 if (gcse_file
!= NULL
)
3167 fprintf (gcse_file
, "GCSE: Replacing the source in insn %d with",
3169 fprintf (gcse_file
, " reg %d %s insn %d\n",
3170 REGNO (to
), use_src
? "from" : "set in",
3171 INSN_UID (insn_computes_expr
));
3176 /* The register that the expr is computed into is set more than once. */
3177 else if (1 /*expensive_op(this_pattrn->op) && do_expensive_gcse)*/)
3179 /* Insert an insn after insnx that copies the reg set in insnx
3180 into a new pseudo register call this new register REGN.
3181 From insnb until end of basic block or until REGB is set
3182 replace all uses of REGB with REGN. */
3185 to
= gen_reg_rtx (GET_MODE (SET_DEST (PATTERN (insn_computes_expr
))));
3187 /* Generate the new insn. */
3188 /* ??? If the change fails, we return 0, even though we created
3189 an insn. I think this is ok. */
3191 = emit_insn_after (gen_rtx_SET (VOIDmode
, to
,
3193 (insn_computes_expr
))),
3194 insn_computes_expr
);
3196 /* Keep block number table up to date. */
3197 set_block_num (new_insn
, BLOCK_NUM (insn_computes_expr
));
3199 /* Keep register set table up to date. */
3200 record_one_set (REGNO (to
), new_insn
);
3202 gcse_create_count
++;
3203 if (gcse_file
!= NULL
)
3205 fprintf (gcse_file
, "GCSE: Creating insn %d to copy value of reg %d",
3206 INSN_UID (NEXT_INSN (insn_computes_expr
)),
3207 REGNO (SET_SRC (PATTERN (NEXT_INSN (insn_computes_expr
)))));
3208 fprintf (gcse_file
, ", computed in insn %d,\n",
3209 INSN_UID (insn_computes_expr
));
3210 fprintf (gcse_file
, " into newly allocated reg %d\n",
3214 pat
= PATTERN (insn
);
3216 /* Do register replacement for INSN. */
3217 changed
= validate_change (insn
, &SET_SRC (pat
),
3219 (NEXT_INSN (insn_computes_expr
))),
3222 /* We should be able to ignore the return code from validate_change but
3223 to play it safe we check. */
3227 if (gcse_file
!= NULL
)
3230 "GCSE: Replacing the source in insn %d with reg %d ",
3232 REGNO (SET_DEST (PATTERN (NEXT_INSN
3233 (insn_computes_expr
)))));
3234 fprintf (gcse_file
, "set in insn %d\n",
3235 INSN_UID (insn_computes_expr
));
3243 /* Perform classic GCSE. This is called by one_classic_gcse_pass after all
3244 the dataflow analysis has been done.
3246 The result is non-zero if a change was made. */
3254 /* Note we start at block 1. */
3257 for (bb
= 1; bb
< n_basic_blocks
; bb
++)
3259 /* Reset tables used to keep track of what's still valid [since the
3260 start of the block]. */
3261 reset_opr_set_tables ();
3263 for (insn
= BLOCK_HEAD (bb
);
3264 insn
!= NULL
&& insn
!= NEXT_INSN (BLOCK_END (bb
));
3265 insn
= NEXT_INSN (insn
))
3267 /* Is insn of form (set (pseudo-reg) ...)? */
3268 if (GET_CODE (insn
) == INSN
3269 && GET_CODE (PATTERN (insn
)) == SET
3270 && GET_CODE (SET_DEST (PATTERN (insn
))) == REG
3271 && REGNO (SET_DEST (PATTERN (insn
))) >= FIRST_PSEUDO_REGISTER
)
3273 rtx pat
= PATTERN (insn
);
3274 rtx src
= SET_SRC (pat
);
3277 if (want_to_gcse_p (src
)
3278 /* Is the expression recorded? */
3279 && ((expr
= lookup_expr (src
)) != NULL
)
3280 /* Is the expression available [at the start of the
3282 && TEST_BIT (ae_in
[bb
], expr
->bitmap_index
)
3283 /* Are the operands unchanged since the start of the
3285 && oprs_not_set_p (src
, insn
))
3286 changed
|= handle_avail_expr (insn
, expr
);
3289 /* Keep track of everything modified by this insn. */
3290 /* ??? Need to be careful w.r.t. mods done to INSN. */
3292 mark_oprs_set (insn
);
3299 /* Top level routine to perform one classic GCSE pass.
3301 Return non-zero if a change was made. */
3304 one_classic_gcse_pass (pass
)
3309 gcse_subst_count
= 0;
3310 gcse_create_count
= 0;
3312 alloc_expr_hash_table (max_cuid
);
3313 alloc_rd_mem (n_basic_blocks
, max_cuid
);
3314 compute_expr_hash_table ();
3316 dump_hash_table (gcse_file
, "Expression", expr_hash_table
,
3317 expr_hash_table_size
, n_exprs
);
3323 alloc_avail_expr_mem (n_basic_blocks
, n_exprs
);
3325 compute_ae_kill (ae_gen
, ae_kill
);
3326 compute_available (ae_gen
, ae_kill
, ae_out
, ae_in
);
3327 changed
= classic_gcse ();
3328 free_avail_expr_mem ();
3332 free_expr_hash_table ();
3336 fprintf (gcse_file
, "\n");
3337 fprintf (gcse_file
, "GCSE of %s, pass %d: %d bytes needed, %d substs,",
3338 current_function_name
, pass
, bytes_used
, gcse_subst_count
);
3339 fprintf (gcse_file
, "%d insns created\n", gcse_create_count
);
3345 /* Compute copy/constant propagation working variables. */
3347 /* Local properties of assignments. */
3348 static sbitmap
*cprop_pavloc
;
3349 static sbitmap
*cprop_absaltered
;
3351 /* Global properties of assignments (computed from the local properties). */
3352 static sbitmap
*cprop_avin
;
3353 static sbitmap
*cprop_avout
;
3355 /* Allocate vars used for copy/const propagation. N_BLOCKS is the number of
3356 basic blocks. N_SETS is the number of sets. */
3359 alloc_cprop_mem (n_blocks
, n_sets
)
3360 int n_blocks
, n_sets
;
3362 cprop_pavloc
= sbitmap_vector_alloc (n_blocks
, n_sets
);
3363 cprop_absaltered
= sbitmap_vector_alloc (n_blocks
, n_sets
);
3365 cprop_avin
= sbitmap_vector_alloc (n_blocks
, n_sets
);
3366 cprop_avout
= sbitmap_vector_alloc (n_blocks
, n_sets
);
3369 /* Free vars used by copy/const propagation. */
3374 free (cprop_pavloc
);
3375 free (cprop_absaltered
);
3380 /* For each block, compute whether X is transparent. X is either an
3381 expression or an assignment [though we don't care which, for this context
3382 an assignment is treated as an expression]. For each block where an
3383 element of X is modified, set (SET_P == 1) or reset (SET_P == 0) the INDX
3387 compute_transp (x
, indx
, bmap
, set_p
)
3398 /* repeat is used to turn tail-recursion into iteration since GCC
3399 can't do it when there's no return value. */
3405 code
= GET_CODE (x
);
3411 if (REGNO (x
) < FIRST_PSEUDO_REGISTER
)
3413 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
3414 if (TEST_BIT (reg_set_in_block
[bb
], REGNO (x
)))
3415 SET_BIT (bmap
[bb
], indx
);
3419 for (r
= reg_set_table
[REGNO (x
)]; r
!= NULL
; r
= r
->next
)
3420 SET_BIT (bmap
[BLOCK_NUM (r
->insn
)], indx
);
3425 if (REGNO (x
) < FIRST_PSEUDO_REGISTER
)
3427 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
3428 if (TEST_BIT (reg_set_in_block
[bb
], REGNO (x
)))
3429 RESET_BIT (bmap
[bb
], indx
);
3433 for (r
= reg_set_table
[REGNO (x
)]; r
!= NULL
; r
= r
->next
)
3434 RESET_BIT (bmap
[BLOCK_NUM (r
->insn
)], indx
);
3443 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
3444 if (mem_set_in_block
[bb
])
3445 SET_BIT (bmap
[bb
], indx
);
3449 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
3450 if (mem_set_in_block
[bb
])
3451 RESET_BIT (bmap
[bb
], indx
);
3472 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
3476 /* If we are about to do the last recursive call
3477 needed at this level, change it into iteration.
3478 This function is called enough to be worth it. */
3485 compute_transp (XEXP (x
, i
), indx
, bmap
, set_p
);
3487 else if (fmt
[i
] == 'E')
3488 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
3489 compute_transp (XVECEXP (x
, i
, j
), indx
, bmap
, set_p
);
3493 /* Top level routine to do the dataflow analysis needed by copy/const
3497 compute_cprop_data ()
3499 compute_local_properties (cprop_absaltered
, cprop_pavloc
, NULL
, 1);
3500 compute_available (cprop_pavloc
, cprop_absaltered
,
3501 cprop_avout
, cprop_avin
);
3504 /* Copy/constant propagation. */
3506 /* Maximum number of register uses in an insn that we handle. */
3509 /* Table of uses found in an insn.
3510 Allocated statically to avoid alloc/free complexity and overhead. */
3511 static struct reg_use reg_use_table
[MAX_USES
];
3513 /* Index into `reg_use_table' while building it. */
3514 static int reg_use_count
;
3516 /* Set up a list of register numbers used in INSN. The found uses are stored
3517 in `reg_use_table'. `reg_use_count' is initialized to zero before entry,
3518 and contains the number of uses in the table upon exit.
3520 ??? If a register appears multiple times we will record it multiple times.
3521 This doesn't hurt anything but it will slow things down. */
3531 /* repeat is used to turn tail-recursion into iteration since GCC
3532 can't do it when there's no return value. */
3538 code
= GET_CODE (x
);
3542 if (reg_use_count
== MAX_USES
)
3545 reg_use_table
[reg_use_count
].reg_rtx
= x
;
3563 case ASM_INPUT
: /*FIXME*/
3567 if (GET_CODE (SET_DEST (x
)) == MEM
)
3568 find_used_regs (SET_DEST (x
));
3576 /* Recursively scan the operands of this expression. */
3578 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
3582 /* If we are about to do the last recursive call
3583 needed at this level, change it into iteration.
3584 This function is called enough to be worth it. */
3591 find_used_regs (XEXP (x
, i
));
3593 else if (fmt
[i
] == 'E')
3594 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
3595 find_used_regs (XVECEXP (x
, i
, j
));
3599 /* Try to replace all non-SET_DEST occurrences of FROM in INSN with TO.
3600 Returns non-zero is successful. */
3603 try_replace_reg (from
, to
, insn
)
3611 note
= find_reg_note (insn
, REG_EQUAL
, NULL_RTX
);
3614 note
= find_reg_note (insn
, REG_EQUIV
, NULL_RTX
);
3616 /* If this fails we could try to simplify the result of the
3617 replacement and attempt to recognize the simplified insn.
3619 But we need a general simplify_rtx that doesn't have pass
3620 specific state variables. I'm not aware of one at the moment. */
3622 success
= validate_replace_src (from
, to
, insn
);
3623 set
= single_set (insn
);
3625 /* We've failed to do replacement. Try to add REG_EQUAL note to not loose
3627 if (!success
&& !note
)
3632 note
= REG_NOTES (insn
) = gen_rtx_EXPR_LIST (REG_EQUAL
,
3633 copy_rtx (SET_SRC (set
)),
3637 /* Always do the replacement in REQ_EQUAL and REG_EQUIV notes. Also
3638 try to simplify them. */
3643 if (!validate_replace_rtx_subexp (from
, to
, insn
, &XEXP (note
, 0)))
3646 src
= XEXP (note
, 0);
3648 /* Try to simplify resulting note. */
3649 simplified
= simplify_rtx (src
);
3653 XEXP (note
, 0) = src
;
3656 /* REG_EQUAL may get simplified into register.
3657 We don't allow that. Remove that note. This code ought
3658 not to hapen, because previous code ought to syntetize
3659 reg-reg move, but be on the safe side. */
3660 else if (REG_P (src
))
3661 remove_note (insn
, note
);
3666 /* Find a set of REGNOs that are available on entry to INSN's block. Returns
3667 NULL no such set is found. */
3669 static struct expr
*
3670 find_avail_set (regno
, insn
)
3674 /* SET1 contains the last set found that can be returned to the caller for
3675 use in a substitution. */
3676 struct expr
*set1
= 0;
3678 /* Loops are not possible here. To get a loop we would need two sets
3679 available at the start of the block containing INSN. ie we would
3680 need two sets like this available at the start of the block:
3682 (set (reg X) (reg Y))
3683 (set (reg Y) (reg X))
3685 This can not happen since the set of (reg Y) would have killed the
3686 set of (reg X) making it unavailable at the start of this block. */
3690 struct expr
*set
= lookup_set (regno
, NULL_RTX
);
3692 /* Find a set that is available at the start of the block
3693 which contains INSN. */
3696 if (TEST_BIT (cprop_avin
[BLOCK_NUM (insn
)], set
->bitmap_index
))
3698 set
= next_set (regno
, set
);
3701 /* If no available set was found we've reached the end of the
3702 (possibly empty) copy chain. */
3706 if (GET_CODE (set
->expr
) != SET
)
3709 src
= SET_SRC (set
->expr
);
3711 /* We know the set is available.
3712 Now check that SRC is ANTLOC (i.e. none of the source operands
3713 have changed since the start of the block).
3715 If the source operand changed, we may still use it for the next
3716 iteration of this loop, but we may not use it for substitutions. */
3718 if (CONSTANT_P (src
) || oprs_not_set_p (src
, insn
))
3721 /* If the source of the set is anything except a register, then
3722 we have reached the end of the copy chain. */
3723 if (GET_CODE (src
) != REG
)
3726 /* Follow the copy chain, ie start another iteration of the loop
3727 and see if we have an available copy into SRC. */
3728 regno
= REGNO (src
);
3731 /* SET1 holds the last set that was available and anticipatable at
3736 /* Subroutine of cprop_insn that tries to propagate constants into
3737 JUMP_INSNS. INSN must be a conditional jump; COPY is a copy of it
3738 that we can use for substitutions.
3739 REG_USED is the use we will try to replace, SRC is the constant we
3740 will try to substitute for it.
3741 Returns nonzero if a change was made. */
3744 cprop_jump (insn
, copy
, reg_used
, src
)
3746 struct reg_use
*reg_used
;
3749 rtx set
= PATTERN (copy
);
3752 /* Replace the register with the appropriate constant. */
3753 replace_rtx (SET_SRC (set
), reg_used
->reg_rtx
, src
);
3755 temp
= simplify_ternary_operation (GET_CODE (SET_SRC (set
)),
3756 GET_MODE (SET_SRC (set
)),
3757 GET_MODE (XEXP (SET_SRC (set
), 0)),
3758 XEXP (SET_SRC (set
), 0),
3759 XEXP (SET_SRC (set
), 1),
3760 XEXP (SET_SRC (set
), 2));
3762 /* If no simplification can be made, then try the next
3767 SET_SRC (set
) = temp
;
3769 /* That may have changed the structure of TEMP, so
3770 force it to be rerecognized if it has not turned
3771 into a nop or unconditional jump. */
3773 INSN_CODE (copy
) = -1;
3774 if ((SET_DEST (set
) == pc_rtx
3775 && (SET_SRC (set
) == pc_rtx
3776 || GET_CODE (SET_SRC (set
)) == LABEL_REF
))
3777 || recog (PATTERN (copy
), copy
, NULL
) >= 0)
3779 /* This has either become an unconditional jump
3780 or a nop-jump. We'd like to delete nop jumps
3781 here, but doing so confuses gcse. So we just
3782 make the replacement and let later passes
3784 PATTERN (insn
) = set
;
3785 INSN_CODE (insn
) = -1;
3787 /* One less use of the label this insn used to jump to
3788 if we turned this into a NOP jump. */
3789 if (SET_SRC (set
) == pc_rtx
&& JUMP_LABEL (insn
) != 0)
3790 --LABEL_NUSES (JUMP_LABEL (insn
));
3792 /* If this has turned into an unconditional jump,
3793 then put a barrier after it so that the unreachable
3794 code will be deleted. */
3795 if (GET_CODE (SET_SRC (set
)) == LABEL_REF
)
3796 emit_barrier_after (insn
);
3798 run_jump_opt_after_gcse
= 1;
3801 if (gcse_file
!= NULL
)
3804 "CONST-PROP: Replacing reg %d in insn %d with constant ",
3805 REGNO (reg_used
->reg_rtx
), INSN_UID (insn
));
3806 print_rtl (gcse_file
, src
);
3807 fprintf (gcse_file
, "\n");
3817 /* Subroutine of cprop_insn that tries to propagate constants into JUMP_INSNS
3818 for machines that have CC0. INSN is a single set that stores into CC0;
3819 the insn following it is a conditional jump. REG_USED is the use we will
3820 try to replace, SRC is the constant we will try to substitute for it.
3821 Returns nonzero if a change was made. */
3824 cprop_cc0_jump (insn
, reg_used
, src
)
3826 struct reg_use
*reg_used
;
3829 rtx jump
= NEXT_INSN (insn
);
3830 rtx copy
= copy_rtx (jump
);
3831 rtx set
= PATTERN (copy
);
3833 /* We need to copy the source of the cc0 setter, as cprop_jump is going to
3834 substitute into it. */
3835 replace_rtx (SET_SRC (set
), cc0_rtx
, copy_rtx (SET_SRC (PATTERN (insn
))));
3836 if (! cprop_jump (jump
, copy
, reg_used
, src
))
3839 /* If we succeeded, delete the cc0 setter. */
3840 PUT_CODE (insn
, NOTE
);
3841 NOTE_LINE_NUMBER (insn
) = NOTE_INSN_DELETED
;
3842 NOTE_SOURCE_FILE (insn
) = 0;
3847 /* Perform constant and copy propagation on INSN.
3848 The result is non-zero if a change was made. */
3851 cprop_insn (insn
, alter_jumps
)
3855 struct reg_use
*reg_used
;
3859 /* Only propagate into SETs. Note that a conditional jump is a
3860 SET with pc_rtx as the destination. */
3861 if ((GET_CODE (insn
) != INSN
3862 && GET_CODE (insn
) != JUMP_INSN
)
3863 || GET_CODE (PATTERN (insn
)) != SET
)
3867 find_used_regs (PATTERN (insn
));
3869 note
= find_reg_note (insn
, REG_EQUIV
, NULL_RTX
);
3871 note
= find_reg_note (insn
, REG_EQUAL
, NULL_RTX
);
3873 /* We may win even when propagating constants into notes. */
3875 find_used_regs (XEXP (note
, 0));
3877 for (reg_used
= ®_use_table
[0]; reg_use_count
> 0;
3878 reg_used
++, reg_use_count
--)
3880 unsigned int regno
= REGNO (reg_used
->reg_rtx
);
3884 /* Ignore registers created by GCSE.
3885 We do this because ... */
3886 if (regno
>= max_gcse_regno
)
3889 /* If the register has already been set in this block, there's
3890 nothing we can do. */
3891 if (! oprs_not_set_p (reg_used
->reg_rtx
, insn
))
3894 /* Find an assignment that sets reg_used and is available
3895 at the start of the block. */
3896 set
= find_avail_set (regno
, insn
);
3901 /* ??? We might be able to handle PARALLELs. Later. */
3902 if (GET_CODE (pat
) != SET
)
3905 src
= SET_SRC (pat
);
3907 /* Constant propagation. */
3908 if (GET_CODE (src
) == CONST_INT
|| GET_CODE (src
) == CONST_DOUBLE
3909 || GET_CODE (src
) == SYMBOL_REF
)
3911 /* Handle normal insns first. */
3912 if (GET_CODE (insn
) == INSN
3913 && try_replace_reg (reg_used
->reg_rtx
, src
, insn
))
3917 if (gcse_file
!= NULL
)
3919 fprintf (gcse_file
, "CONST-PROP: Replacing reg %d in ",
3921 fprintf (gcse_file
, "insn %d with constant ",
3923 print_rtl (gcse_file
, src
);
3924 fprintf (gcse_file
, "\n");
3927 /* The original insn setting reg_used may or may not now be
3928 deletable. We leave the deletion to flow. */
3931 /* Try to propagate a CONST_INT into a conditional jump.
3932 We're pretty specific about what we will handle in this
3933 code, we can extend this as necessary over time.
3935 Right now the insn in question must look like
3936 (set (pc) (if_then_else ...)) */
3937 else if (alter_jumps
3938 && GET_CODE (insn
) == JUMP_INSN
3939 && condjump_p (insn
)
3940 && ! simplejump_p (insn
))
3941 changed
|= cprop_jump (insn
, copy_rtx (insn
), reg_used
, src
);
3943 /* Similar code for machines that use a pair of CC0 setter and
3944 conditional jump insn. */
3945 else if (alter_jumps
3946 && GET_CODE (PATTERN (insn
)) == SET
3947 && SET_DEST (PATTERN (insn
)) == cc0_rtx
3948 && GET_CODE (NEXT_INSN (insn
)) == JUMP_INSN
3949 && condjump_p (NEXT_INSN (insn
))
3950 && ! simplejump_p (NEXT_INSN (insn
)))
3951 changed
|= cprop_cc0_jump (insn
, reg_used
, src
);
3954 else if (GET_CODE (src
) == REG
3955 && REGNO (src
) >= FIRST_PSEUDO_REGISTER
3956 && REGNO (src
) != regno
)
3958 if (try_replace_reg (reg_used
->reg_rtx
, src
, insn
))
3962 if (gcse_file
!= NULL
)
3964 fprintf (gcse_file
, "COPY-PROP: Replacing reg %d in insn %d",
3965 regno
, INSN_UID (insn
));
3966 fprintf (gcse_file
, " with reg %d\n", REGNO (src
));
3969 /* The original insn setting reg_used may or may not now be
3970 deletable. We leave the deletion to flow. */
3971 /* FIXME: If it turns out that the insn isn't deletable,
3972 then we may have unnecessarily extended register lifetimes
3973 and made things worse. */
3981 /* Forward propagate copies. This includes copies and constants. Return
3982 non-zero if a change was made. */
3991 /* Note we start at block 1. */
3994 for (bb
= 1; bb
< n_basic_blocks
; bb
++)
3996 /* Reset tables used to keep track of what's still valid [since the
3997 start of the block]. */
3998 reset_opr_set_tables ();
4000 for (insn
= BLOCK_HEAD (bb
);
4001 insn
!= NULL
&& insn
!= NEXT_INSN (BLOCK_END (bb
));
4002 insn
= NEXT_INSN (insn
))
4006 changed
|= cprop_insn (insn
, alter_jumps
);
4008 /* Keep track of everything modified by this insn. */
4009 /* ??? Need to be careful w.r.t. mods done to INSN. Don't
4010 call mark_oprs_set if we turned the insn into a NOTE. */
4011 if (GET_CODE (insn
) != NOTE
)
4012 mark_oprs_set (insn
);
4017 if (gcse_file
!= NULL
)
4018 fprintf (gcse_file
, "\n");
4023 /* Perform one copy/constant propagation pass.
4024 F is the first insn in the function.
4025 PASS is the pass count. */
4028 one_cprop_pass (pass
, alter_jumps
)
4034 const_prop_count
= 0;
4035 copy_prop_count
= 0;
4037 alloc_set_hash_table (max_cuid
);
4038 compute_set_hash_table ();
4040 dump_hash_table (gcse_file
, "SET", set_hash_table
, set_hash_table_size
,
4044 alloc_cprop_mem (n_basic_blocks
, n_sets
);
4045 compute_cprop_data ();
4046 changed
= cprop (alter_jumps
);
4050 free_set_hash_table ();
4054 fprintf (gcse_file
, "CPROP of %s, pass %d: %d bytes needed, ",
4055 current_function_name
, pass
, bytes_used
);
4056 fprintf (gcse_file
, "%d const props, %d copy props\n\n",
4057 const_prop_count
, copy_prop_count
);
4063 /* Compute PRE+LCM working variables. */
4065 /* Local properties of expressions. */
4066 /* Nonzero for expressions that are transparent in the block. */
4067 static sbitmap
*transp
;
4069 /* Nonzero for expressions that are transparent at the end of the block.
4070 This is only zero for expressions killed by abnormal critical edge
4071 created by a calls. */
4072 static sbitmap
*transpout
;
4074 /* Nonzero for expressions that are computed (available) in the block. */
4075 static sbitmap
*comp
;
4077 /* Nonzero for expressions that are locally anticipatable in the block. */
4078 static sbitmap
*antloc
;
4080 /* Nonzero for expressions where this block is an optimal computation
4082 static sbitmap
*pre_optimal
;
4084 /* Nonzero for expressions which are redundant in a particular block. */
4085 static sbitmap
*pre_redundant
;
4087 /* Nonzero for expressions which should be inserted on a specific edge. */
4088 static sbitmap
*pre_insert_map
;
4090 /* Nonzero for expressions which should be deleted in a specific block. */
4091 static sbitmap
*pre_delete_map
;
4093 /* Contains the edge_list returned by pre_edge_lcm. */
4094 static struct edge_list
*edge_list
;
4096 /* Redundant insns. */
4097 static sbitmap pre_redundant_insns
;
4099 /* Allocate vars used for PRE analysis. */
4102 alloc_pre_mem (n_blocks
, n_exprs
)
4103 int n_blocks
, n_exprs
;
4105 transp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4106 comp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4107 antloc
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4110 pre_redundant
= NULL
;
4111 pre_insert_map
= NULL
;
4112 pre_delete_map
= NULL
;
4115 ae_kill
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4117 /* pre_insert and pre_delete are allocated later. */
4120 /* Free vars used for PRE analysis. */
4128 /* ANTLOC and AE_KILL are freed just after pre_lcm finishes. */
4133 free (pre_redundant
);
4135 free (pre_insert_map
);
4137 free (pre_delete_map
);
4144 transp
= comp
= NULL
;
4145 pre_optimal
= pre_redundant
= pre_insert_map
= pre_delete_map
= NULL
;
4146 ae_in
= ae_out
= NULL
;
4149 /* Top level routine to do the dataflow analysis needed by PRE. */
4156 compute_local_properties (transp
, comp
, antloc
, 0);
4157 sbitmap_vector_zero (ae_kill
, n_basic_blocks
);
4159 /* Compute ae_kill for each basic block using:
4163 This is significantly faster than compute_ae_kill. */
4165 for (i
= 0; i
< n_basic_blocks
; i
++)
4167 sbitmap_a_or_b (ae_kill
[i
], transp
[i
], comp
[i
]);
4168 sbitmap_not (ae_kill
[i
], ae_kill
[i
]);
4171 edge_list
= pre_edge_lcm (gcse_file
, n_exprs
, transp
, comp
, antloc
,
4172 ae_kill
, &pre_insert_map
, &pre_delete_map
);
4181 /* Return non-zero if an occurrence of expression EXPR in OCCR_BB would reach
4184 VISITED is a pointer to a working buffer for tracking which BB's have
4185 been visited. It is NULL for the top-level call.
4187 We treat reaching expressions that go through blocks containing the same
4188 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
4189 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
4190 2 as not reaching. The intent is to improve the probability of finding
4191 only one reaching expression and to reduce register lifetimes by picking
4192 the closest such expression. */
4195 pre_expr_reaches_here_p_work (occr_bb
, expr
, bb
, visited
)
4203 for (pred
= BASIC_BLOCK (bb
)->pred
; pred
!= NULL
; pred
= pred
->pred_next
)
4205 int pred_bb
= pred
->src
->index
;
4207 if (pred
->src
== ENTRY_BLOCK_PTR
4208 /* Has predecessor has already been visited? */
4209 || visited
[pred_bb
])
4210 ;/* Nothing to do. */
4212 /* Does this predecessor generate this expression? */
4213 else if (TEST_BIT (comp
[pred_bb
], expr
->bitmap_index
))
4215 /* Is this the occurrence we're looking for?
4216 Note that there's only one generating occurrence per block
4217 so we just need to check the block number. */
4218 if (occr_bb
== pred_bb
)
4221 visited
[pred_bb
] = 1;
4223 /* Ignore this predecessor if it kills the expression. */
4224 else if (! TEST_BIT (transp
[pred_bb
], expr
->bitmap_index
))
4225 visited
[pred_bb
] = 1;
4227 /* Neither gen nor kill. */
4230 visited
[pred_bb
] = 1;
4231 if (pre_expr_reaches_here_p_work (occr_bb
, expr
, pred_bb
, visited
))
4236 /* All paths have been checked. */
4240 /* The wrapper for pre_expr_reaches_here_work that ensures that any
4241 memory allocated for that function is returned. */
4244 pre_expr_reaches_here_p (occr_bb
, expr
, bb
)
4250 char *visited
= (char *) xcalloc (n_basic_blocks
, 1);
4252 rval
= pre_expr_reaches_here_p_work(occr_bb
, expr
, bb
, visited
);
4259 /* Given an expr, generate RTL which we can insert at the end of a BB,
4260 or on an edge. Set the block number of any insns generated to
4264 process_insert_insn (expr
)
4267 rtx reg
= expr
->reaching_reg
;
4268 rtx pat
, copied_expr
;
4272 copied_expr
= copy_rtx (expr
->expr
);
4273 emit_move_insn (reg
, copied_expr
);
4274 first_new_insn
= get_insns ();
4275 pat
= gen_sequence ();
4281 /* Add EXPR to the end of basic block BB.
4283 This is used by both the PRE and code hoisting.
4285 For PRE, we want to verify that the expr is either transparent
4286 or locally anticipatable in the target block. This check makes
4287 no sense for code hoisting. */
4290 insert_insn_end_bb (expr
, bb
, pre
)
4295 rtx insn
= BLOCK_END (bb
);
4297 rtx reg
= expr
->reaching_reg
;
4298 int regno
= REGNO (reg
);
4302 pat
= process_insert_insn (expr
);
4304 /* If the last insn is a jump, insert EXPR in front [taking care to
4305 handle cc0, etc. properly]. */
4307 if (GET_CODE (insn
) == JUMP_INSN
)
4313 /* If this is a jump table, then we can't insert stuff here. Since
4314 we know the previous real insn must be the tablejump, we insert
4315 the new instruction just before the tablejump. */
4316 if (GET_CODE (PATTERN (insn
)) == ADDR_VEC
4317 || GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
)
4318 insn
= prev_real_insn (insn
);
4321 /* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
4322 if cc0 isn't set. */
4323 note
= find_reg_note (insn
, REG_CC_SETTER
, NULL_RTX
);
4325 insn
= XEXP (note
, 0);
4328 rtx maybe_cc0_setter
= prev_nonnote_insn (insn
);
4329 if (maybe_cc0_setter
4330 && INSN_P (maybe_cc0_setter
)
4331 && sets_cc0_p (PATTERN (maybe_cc0_setter
)))
4332 insn
= maybe_cc0_setter
;
4335 /* FIXME: What if something in cc0/jump uses value set in new insn? */
4336 new_insn
= emit_block_insn_before (pat
, insn
, BASIC_BLOCK (bb
));
4339 /* Likewise if the last insn is a call, as will happen in the presence
4340 of exception handling. */
4341 else if (GET_CODE (insn
) == CALL_INSN
)
4343 HARD_REG_SET parm_regs
;
4347 /* Keeping in mind SMALL_REGISTER_CLASSES and parameters in registers,
4348 we search backward and place the instructions before the first
4349 parameter is loaded. Do this for everyone for consistency and a
4350 presumtion that we'll get better code elsewhere as well.
4352 It should always be the case that we can put these instructions
4353 anywhere in the basic block with performing PRE optimizations.
4357 && !TEST_BIT (antloc
[bb
], expr
->bitmap_index
)
4358 && !TEST_BIT (transp
[bb
], expr
->bitmap_index
))
4361 /* Since different machines initialize their parameter registers
4362 in different orders, assume nothing. Collect the set of all
4363 parameter registers. */
4364 CLEAR_HARD_REG_SET (parm_regs
);
4366 for (p
= CALL_INSN_FUNCTION_USAGE (insn
); p
; p
= XEXP (p
, 1))
4367 if (GET_CODE (XEXP (p
, 0)) == USE
4368 && GET_CODE (XEXP (XEXP (p
, 0), 0)) == REG
)
4370 if (REGNO (XEXP (XEXP (p
, 0), 0)) >= FIRST_PSEUDO_REGISTER
)
4373 SET_HARD_REG_BIT (parm_regs
, REGNO (XEXP (XEXP (p
, 0), 0)));
4377 /* Search backward for the first set of a register in this set. */
4378 while (nparm_regs
&& BLOCK_HEAD (bb
) != insn
)
4380 insn
= PREV_INSN (insn
);
4381 p
= single_set (insn
);
4382 if (p
&& GET_CODE (SET_DEST (p
)) == REG
4383 && REGNO (SET_DEST (p
)) < FIRST_PSEUDO_REGISTER
4384 && TEST_HARD_REG_BIT (parm_regs
, REGNO (SET_DEST (p
))))
4386 CLEAR_HARD_REG_BIT (parm_regs
, REGNO (SET_DEST (p
)));
4391 /* If we found all the parameter loads, then we want to insert
4392 before the first parameter load.
4394 If we did not find all the parameter loads, then we might have
4395 stopped on the head of the block, which could be a CODE_LABEL.
4396 If we inserted before the CODE_LABEL, then we would be putting
4397 the insn in the wrong basic block. In that case, put the insn
4398 after the CODE_LABEL. Also, respect NOTE_INSN_BASIC_BLOCK. */
4399 while (GET_CODE (insn
) == CODE_LABEL
4400 || NOTE_INSN_BASIC_BLOCK_P (insn
))
4401 insn
= NEXT_INSN (insn
);
4403 new_insn
= emit_block_insn_before (pat
, insn
, BASIC_BLOCK (bb
));
4407 new_insn
= emit_insn_after (pat
, insn
);
4408 BLOCK_END (bb
) = new_insn
;
4411 /* Keep block number table up to date.
4412 Note, PAT could be a multiple insn sequence, we have to make
4413 sure that each insn in the sequence is handled. */
4414 if (GET_CODE (pat
) == SEQUENCE
)
4416 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
4418 rtx insn
= XVECEXP (pat
, 0, i
);
4420 set_block_num (insn
, bb
);
4422 add_label_notes (PATTERN (insn
), new_insn
);
4424 note_stores (PATTERN (insn
), record_set_info
, insn
);
4429 add_label_notes (SET_SRC (pat
), new_insn
);
4430 set_block_num (new_insn
, bb
);
4432 /* Keep register set table up to date. */
4433 record_one_set (regno
, new_insn
);
4436 gcse_create_count
++;
4440 fprintf (gcse_file
, "PRE/HOIST: end of bb %d, insn %d, ",
4441 bb
, INSN_UID (new_insn
));
4442 fprintf (gcse_file
, "copying expression %d to reg %d\n",
4443 expr
->bitmap_index
, regno
);
4447 /* Insert partially redundant expressions on edges in the CFG to make
4448 the expressions fully redundant. */
4451 pre_edge_insert (edge_list
, index_map
)
4452 struct edge_list
*edge_list
;
4453 struct expr
**index_map
;
4455 int e
, i
, j
, num_edges
, set_size
, did_insert
= 0;
4458 /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge
4459 if it reaches any of the deleted expressions. */
4461 set_size
= pre_insert_map
[0]->size
;
4462 num_edges
= NUM_EDGES (edge_list
);
4463 inserted
= sbitmap_vector_alloc (num_edges
, n_exprs
);
4464 sbitmap_vector_zero (inserted
, num_edges
);
4466 for (e
= 0; e
< num_edges
; e
++)
4469 basic_block pred
= INDEX_EDGE_PRED_BB (edge_list
, e
);
4470 int bb
= pred
->index
;
4472 for (i
= indx
= 0; i
< set_size
; i
++, indx
+= SBITMAP_ELT_BITS
)
4474 SBITMAP_ELT_TYPE insert
= pre_insert_map
[e
]->elms
[i
];
4476 for (j
= indx
; insert
&& j
< n_exprs
; j
++, insert
>>= 1)
4477 if ((insert
& 1) != 0 && index_map
[j
]->reaching_reg
!= NULL_RTX
)
4479 struct expr
*expr
= index_map
[j
];
4482 /* Now look at each deleted occurence of this expression. */
4483 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
4485 if (! occr
->deleted_p
)
4488 /* Insert this expression on this edge if if it would
4489 reach the deleted occurence in BB. */
4490 if (!TEST_BIT (inserted
[e
], j
))
4493 edge eg
= INDEX_EDGE (edge_list
, e
);
4495 /* We can't insert anything on an abnormal and
4496 critical edge, so we insert the insn at the end of
4497 the previous block. There are several alternatives
4498 detailed in Morgans book P277 (sec 10.5) for
4499 handling this situation. This one is easiest for
4502 if ((eg
->flags
& EDGE_ABNORMAL
) == EDGE_ABNORMAL
)
4503 insert_insn_end_bb (index_map
[j
], bb
, 0);
4506 insn
= process_insert_insn (index_map
[j
]);
4507 insert_insn_on_edge (insn
, eg
);
4512 fprintf (gcse_file
, "PRE/HOIST: edge (%d,%d), ",
4514 INDEX_EDGE_SUCC_BB (edge_list
, e
)->index
);
4515 fprintf (gcse_file
, "copy expression %d\n",
4516 expr
->bitmap_index
);
4519 SET_BIT (inserted
[e
], j
);
4521 gcse_create_count
++;
4532 /* Copy the result of INSN to REG. INDX is the expression number. */
4535 pre_insert_copy_insn (expr
, insn
)
4539 rtx reg
= expr
->reaching_reg
;
4540 int regno
= REGNO (reg
);
4541 int indx
= expr
->bitmap_index
;
4542 rtx set
= single_set (insn
);
4544 int bb
= BLOCK_NUM (insn
);
4549 new_insn
= emit_insn_after (gen_rtx_SET (VOIDmode
, reg
, SET_DEST (set
)),
4552 /* Keep block number table up to date. */
4553 set_block_num (new_insn
, bb
);
4555 /* Keep register set table up to date. */
4556 record_one_set (regno
, new_insn
);
4557 if (insn
== BLOCK_END (bb
))
4558 BLOCK_END (bb
) = new_insn
;
4560 gcse_create_count
++;
4564 "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
4565 BLOCK_NUM (insn
), INSN_UID (new_insn
), indx
,
4566 INSN_UID (insn
), regno
);
4569 /* Copy available expressions that reach the redundant expression
4570 to `reaching_reg'. */
4573 pre_insert_copies ()
4580 /* For each available expression in the table, copy the result to
4581 `reaching_reg' if the expression reaches a deleted one.
4583 ??? The current algorithm is rather brute force.
4584 Need to do some profiling. */
4586 for (i
= 0; i
< expr_hash_table_size
; i
++)
4587 for (expr
= expr_hash_table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
4589 /* If the basic block isn't reachable, PPOUT will be TRUE. However,
4590 we don't want to insert a copy here because the expression may not
4591 really be redundant. So only insert an insn if the expression was
4592 deleted. This test also avoids further processing if the
4593 expression wasn't deleted anywhere. */
4594 if (expr
->reaching_reg
== NULL
)
4597 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
4599 if (! occr
->deleted_p
)
4602 for (avail
= expr
->avail_occr
; avail
!= NULL
; avail
= avail
->next
)
4604 rtx insn
= avail
->insn
;
4606 /* No need to handle this one if handled already. */
4607 if (avail
->copied_p
)
4610 /* Don't handle this one if it's a redundant one. */
4611 if (TEST_BIT (pre_redundant_insns
, INSN_CUID (insn
)))
4614 /* Or if the expression doesn't reach the deleted one. */
4615 if (! pre_expr_reaches_here_p (BLOCK_NUM (avail
->insn
), expr
,
4616 BLOCK_NUM (occr
->insn
)))
4619 /* Copy the result of avail to reaching_reg. */
4620 pre_insert_copy_insn (expr
, insn
);
4621 avail
->copied_p
= 1;
4627 /* Delete redundant computations.
4628 Deletion is done by changing the insn to copy the `reaching_reg' of
4629 the expression into the result of the SET. It is left to later passes
4630 (cprop, cse2, flow, combine, regmove) to propagate the copy or eliminate it.
4632 Returns non-zero if a change is made. */
4643 for (i
= 0; i
< expr_hash_table_size
; i
++)
4644 for (expr
= expr_hash_table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
4646 int indx
= expr
->bitmap_index
;
4648 /* We only need to search antic_occr since we require
4651 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
4653 rtx insn
= occr
->insn
;
4655 int bb
= BLOCK_NUM (insn
);
4657 if (TEST_BIT (pre_delete_map
[bb
], indx
))
4659 set
= single_set (insn
);
4663 /* Create a pseudo-reg to store the result of reaching
4664 expressions into. Get the mode for the new pseudo from
4665 the mode of the original destination pseudo. */
4666 if (expr
->reaching_reg
== NULL
)
4668 = gen_reg_rtx (GET_MODE (SET_DEST (set
)));
4670 /* In theory this should never fail since we're creating
4673 However, on the x86 some of the movXX patterns actually
4674 contain clobbers of scratch regs. This may cause the
4675 insn created by validate_change to not match any pattern
4676 and thus cause validate_change to fail. */
4677 if (validate_change (insn
, &SET_SRC (set
),
4678 expr
->reaching_reg
, 0))
4680 occr
->deleted_p
= 1;
4681 SET_BIT (pre_redundant_insns
, INSN_CUID (insn
));
4689 "PRE: redundant insn %d (expression %d) in ",
4690 INSN_UID (insn
), indx
);
4691 fprintf (gcse_file
, "bb %d, reaching reg is %d\n",
4692 bb
, REGNO (expr
->reaching_reg
));
4701 /* Perform GCSE optimizations using PRE.
4702 This is called by one_pre_gcse_pass after all the dataflow analysis
4705 This is based on the original Morel-Renvoise paper Fred Chow's thesis, and
4706 lazy code motion from Knoop, Ruthing and Steffen as described in Advanced
4707 Compiler Design and Implementation.
4709 ??? A new pseudo reg is created to hold the reaching expression. The nice
4710 thing about the classical approach is that it would try to use an existing
4711 reg. If the register can't be adequately optimized [i.e. we introduce
4712 reload problems], one could add a pass here to propagate the new register
4715 ??? We don't handle single sets in PARALLELs because we're [currently] not
4716 able to copy the rest of the parallel when we insert copies to create full
4717 redundancies from partial redundancies. However, there's no reason why we
4718 can't handle PARALLELs in the cases where there are no partial
4725 int did_insert
, changed
;
4726 struct expr
**index_map
;
4729 /* Compute a mapping from expression number (`bitmap_index') to
4730 hash table entry. */
4732 index_map
= (struct expr
**) xcalloc (n_exprs
, sizeof (struct expr
*));
4733 for (i
= 0; i
< expr_hash_table_size
; i
++)
4734 for (expr
= expr_hash_table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
4735 index_map
[expr
->bitmap_index
] = expr
;
4737 /* Reset bitmap used to track which insns are redundant. */
4738 pre_redundant_insns
= sbitmap_alloc (max_cuid
);
4739 sbitmap_zero (pre_redundant_insns
);
4741 /* Delete the redundant insns first so that
4742 - we know what register to use for the new insns and for the other
4743 ones with reaching expressions
4744 - we know which insns are redundant when we go to create copies */
4746 changed
= pre_delete ();
4748 did_insert
= pre_edge_insert (edge_list
, index_map
);
4750 /* In other places with reaching expressions, copy the expression to the
4751 specially allocated pseudo-reg that reaches the redundant expr. */
4752 pre_insert_copies ();
4755 commit_edge_insertions ();
4760 free (pre_redundant_insns
);
4764 /* Top level routine to perform one PRE GCSE pass.
4766 Return non-zero if a change was made. */
4769 one_pre_gcse_pass (pass
)
4774 gcse_subst_count
= 0;
4775 gcse_create_count
= 0;
4777 alloc_expr_hash_table (max_cuid
);
4778 add_noreturn_fake_exit_edges ();
4779 compute_expr_hash_table ();
4781 dump_hash_table (gcse_file
, "Expression", expr_hash_table
,
4782 expr_hash_table_size
, n_exprs
);
4786 alloc_pre_mem (n_basic_blocks
, n_exprs
);
4787 compute_pre_data ();
4788 changed
|= pre_gcse ();
4789 free_edge_list (edge_list
);
4793 remove_fake_edges ();
4794 free_expr_hash_table ();
4798 fprintf (gcse_file
, "\nPRE GCSE of %s, pass %d: %d bytes needed, ",
4799 current_function_name
, pass
, bytes_used
);
4800 fprintf (gcse_file
, "%d substs, %d insns created\n",
4801 gcse_subst_count
, gcse_create_count
);
4807 /* If X contains any LABEL_REF's, add REG_LABEL notes for them to INSN.
4808 We have to add REG_LABEL notes, because the following loop optimization
4809 pass requires them. */
4811 /* ??? This is very similar to the loop.c add_label_notes function. We
4812 could probably share code here. */
4814 /* ??? If there was a jump optimization pass after gcse and before loop,
4815 then we would not need to do this here, because jump would add the
4816 necessary REG_LABEL notes. */
4819 add_label_notes (x
, insn
)
4823 enum rtx_code code
= GET_CODE (x
);
4827 if (code
== LABEL_REF
&& !LABEL_REF_NONLOCAL_P (x
))
4829 /* This code used to ignore labels that referred to dispatch tables to
4830 avoid flow generating (slighly) worse code.
4832 We no longer ignore such label references (see LABEL_REF handling in
4833 mark_jump_label for additional information). */
4835 REG_NOTES (insn
) = gen_rtx_EXPR_LIST (REG_LABEL
, XEXP (x
, 0),
4840 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
4843 add_label_notes (XEXP (x
, i
), insn
);
4844 else if (fmt
[i
] == 'E')
4845 for (j
= XVECLEN (x
, i
) - 1; j
>= 0; j
--)
4846 add_label_notes (XVECEXP (x
, i
, j
), insn
);
4850 /* Compute transparent outgoing information for each block.
4852 An expression is transparent to an edge unless it is killed by
4853 the edge itself. This can only happen with abnormal control flow,
4854 when the edge is traversed through a call. This happens with
4855 non-local labels and exceptions.
4857 This would not be necessary if we split the edge. While this is
4858 normally impossible for abnormal critical edges, with some effort
4859 it should be possible with exception handling, since we still have
4860 control over which handler should be invoked. But due to increased
4861 EH table sizes, this may not be worthwhile. */
4864 compute_transpout ()
4870 sbitmap_vector_ones (transpout
, n_basic_blocks
);
4872 for (bb
= 0; bb
< n_basic_blocks
; ++bb
)
4874 /* Note that flow inserted a nop a the end of basic blocks that
4875 end in call instructions for reasons other than abnormal
4877 if (GET_CODE (BLOCK_END (bb
)) != CALL_INSN
)
4880 for (i
= 0; i
< expr_hash_table_size
; i
++)
4881 for (expr
= expr_hash_table
[i
]; expr
; expr
= expr
->next_same_hash
)
4882 if (GET_CODE (expr
->expr
) == MEM
)
4884 if (GET_CODE (XEXP (expr
->expr
, 0)) == SYMBOL_REF
4885 && CONSTANT_POOL_ADDRESS_P (XEXP (expr
->expr
, 0)))
4888 /* ??? Optimally, we would use interprocedural alias
4889 analysis to determine if this mem is actually killed
4891 RESET_BIT (transpout
[bb
], expr
->bitmap_index
);
4896 /* Removal of useless null pointer checks */
4898 /* Called via note_stores. X is set by SETTER. If X is a register we must
4899 invalidate nonnull_local and set nonnull_killed. DATA is really a
4900 `null_pointer_info *'.
4902 We ignore hard registers. */
4905 invalidate_nonnull_info (x
, setter
, data
)
4907 rtx setter ATTRIBUTE_UNUSED
;
4911 struct null_pointer_info
*npi
= (struct null_pointer_info
*) data
;
4913 while (GET_CODE (x
) == SUBREG
)
4916 /* Ignore anything that is not a register or is a hard register. */
4917 if (GET_CODE (x
) != REG
4918 || REGNO (x
) < npi
->min_reg
4919 || REGNO (x
) >= npi
->max_reg
)
4922 regno
= REGNO (x
) - npi
->min_reg
;
4924 RESET_BIT (npi
->nonnull_local
[npi
->current_block
], regno
);
4925 SET_BIT (npi
->nonnull_killed
[npi
->current_block
], regno
);
4928 /* Do null-pointer check elimination for the registers indicated in
4929 NPI. NONNULL_AVIN and NONNULL_AVOUT are pre-allocated sbitmaps;
4930 they are not our responsibility to free. */
4933 delete_null_pointer_checks_1 (block_reg
, nonnull_avin
, nonnull_avout
, npi
)
4934 unsigned int *block_reg
;
4935 sbitmap
*nonnull_avin
;
4936 sbitmap
*nonnull_avout
;
4937 struct null_pointer_info
*npi
;
4941 sbitmap
*nonnull_local
= npi
->nonnull_local
;
4942 sbitmap
*nonnull_killed
= npi
->nonnull_killed
;
4944 /* Compute local properties, nonnull and killed. A register will have
4945 the nonnull property if at the end of the current block its value is
4946 known to be nonnull. The killed property indicates that somewhere in
4947 the block any information we had about the register is killed.
4949 Note that a register can have both properties in a single block. That
4950 indicates that it's killed, then later in the block a new value is
4952 sbitmap_vector_zero (nonnull_local
, n_basic_blocks
);
4953 sbitmap_vector_zero (nonnull_killed
, n_basic_blocks
);
4955 for (current_block
= 0; current_block
< n_basic_blocks
; current_block
++)
4957 rtx insn
, stop_insn
;
4959 /* Set the current block for invalidate_nonnull_info. */
4960 npi
->current_block
= current_block
;
4962 /* Scan each insn in the basic block looking for memory references and
4964 stop_insn
= NEXT_INSN (BLOCK_END (current_block
));
4965 for (insn
= BLOCK_HEAD (current_block
);
4967 insn
= NEXT_INSN (insn
))
4972 /* Ignore anything that is not a normal insn. */
4973 if (! INSN_P (insn
))
4976 /* Basically ignore anything that is not a simple SET. We do have
4977 to make sure to invalidate nonnull_local and set nonnull_killed
4978 for such insns though. */
4979 set
= single_set (insn
);
4982 note_stores (PATTERN (insn
), invalidate_nonnull_info
, npi
);
4986 /* See if we've got a useable memory load. We handle it first
4987 in case it uses its address register as a dest (which kills
4988 the nonnull property). */
4989 if (GET_CODE (SET_SRC (set
)) == MEM
4990 && GET_CODE ((reg
= XEXP (SET_SRC (set
), 0))) == REG
4991 && REGNO (reg
) >= npi
->min_reg
4992 && REGNO (reg
) < npi
->max_reg
)
4993 SET_BIT (nonnull_local
[current_block
],
4994 REGNO (reg
) - npi
->min_reg
);
4996 /* Now invalidate stuff clobbered by this insn. */
4997 note_stores (PATTERN (insn
), invalidate_nonnull_info
, npi
);
4999 /* And handle stores, we do these last since any sets in INSN can
5000 not kill the nonnull property if it is derived from a MEM
5001 appearing in a SET_DEST. */
5002 if (GET_CODE (SET_DEST (set
)) == MEM
5003 && GET_CODE ((reg
= XEXP (SET_DEST (set
), 0))) == REG
5004 && REGNO (reg
) >= npi
->min_reg
5005 && REGNO (reg
) < npi
->max_reg
)
5006 SET_BIT (nonnull_local
[current_block
],
5007 REGNO (reg
) - npi
->min_reg
);
5011 /* Now compute global properties based on the local properties. This
5012 is a classic global availablity algorithm. */
5013 compute_available (nonnull_local
, nonnull_killed
,
5014 nonnull_avout
, nonnull_avin
);
5016 /* Now look at each bb and see if it ends with a compare of a value
5018 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
5020 rtx last_insn
= BLOCK_END (bb
);
5021 rtx condition
, earliest
;
5022 int compare_and_branch
;
5024 /* Since MIN_REG is always at least FIRST_PSEUDO_REGISTER, and
5025 since BLOCK_REG[BB] is zero if this block did not end with a
5026 comparison against zero, this condition works. */
5027 if (block_reg
[bb
] < npi
->min_reg
5028 || block_reg
[bb
] >= npi
->max_reg
)
5031 /* LAST_INSN is a conditional jump. Get its condition. */
5032 condition
= get_condition (last_insn
, &earliest
);
5034 /* If we can't determine the condition then skip. */
5038 /* Is the register known to have a nonzero value? */
5039 if (!TEST_BIT (nonnull_avout
[bb
], block_reg
[bb
] - npi
->min_reg
))
5042 /* Try to compute whether the compare/branch at the loop end is one or
5043 two instructions. */
5044 if (earliest
== last_insn
)
5045 compare_and_branch
= 1;
5046 else if (earliest
== prev_nonnote_insn (last_insn
))
5047 compare_and_branch
= 2;
5051 /* We know the register in this comparison is nonnull at exit from
5052 this block. We can optimize this comparison. */
5053 if (GET_CODE (condition
) == NE
)
5057 new_jump
= emit_jump_insn_before (gen_jump (JUMP_LABEL (last_insn
)),
5059 JUMP_LABEL (new_jump
) = JUMP_LABEL (last_insn
);
5060 LABEL_NUSES (JUMP_LABEL (new_jump
))++;
5061 emit_barrier_after (new_jump
);
5063 delete_insn (last_insn
);
5064 if (compare_and_branch
== 2)
5065 delete_insn (earliest
);
5067 /* Don't check this block again. (Note that BLOCK_END is
5068 invalid here; we deleted the last instruction in the
5074 /* Find EQ/NE comparisons against zero which can be (indirectly) evaluated
5077 This is conceptually similar to global constant/copy propagation and
5078 classic global CSE (it even uses the same dataflow equations as cprop).
5080 If a register is used as memory address with the form (mem (reg)), then we
5081 know that REG can not be zero at that point in the program. Any instruction
5082 which sets REG "kills" this property.
5084 So, if every path leading to a conditional branch has an available memory
5085 reference of that form, then we know the register can not have the value
5086 zero at the conditional branch.
5088 So we merely need to compute the local properies and propagate that data
5089 around the cfg, then optimize where possible.
5091 We run this pass two times. Once before CSE, then again after CSE. This
5092 has proven to be the most profitable approach. It is rare for new
5093 optimization opportunities of this nature to appear after the first CSE
5096 This could probably be integrated with global cprop with a little work. */
5099 delete_null_pointer_checks (f
)
5100 rtx f ATTRIBUTE_UNUSED
;
5102 sbitmap
*nonnull_avin
, *nonnull_avout
;
5103 unsigned int *block_reg
;
5108 struct null_pointer_info npi
;
5110 /* If we have only a single block, then there's nothing to do. */
5111 if (n_basic_blocks
<= 1)
5114 /* Trying to perform global optimizations on flow graphs which have
5115 a high connectivity will take a long time and is unlikely to be
5116 particularly useful.
5118 In normal circumstances a cfg should have about twice has many edges
5119 as blocks. But we do not want to punish small functions which have
5120 a couple switch statements. So we require a relatively large number
5121 of basic blocks and the ratio of edges to blocks to be high. */
5122 if (n_basic_blocks
> 1000 && n_edges
/ n_basic_blocks
>= 20)
5125 /* We need four bitmaps, each with a bit for each register in each
5127 max_reg
= max_reg_num ();
5128 regs_per_pass
= get_bitmap_width (4, n_basic_blocks
, max_reg
);
5130 /* Allocate bitmaps to hold local and global properties. */
5131 npi
.nonnull_local
= sbitmap_vector_alloc (n_basic_blocks
, regs_per_pass
);
5132 npi
.nonnull_killed
= sbitmap_vector_alloc (n_basic_blocks
, regs_per_pass
);
5133 nonnull_avin
= sbitmap_vector_alloc (n_basic_blocks
, regs_per_pass
);
5134 nonnull_avout
= sbitmap_vector_alloc (n_basic_blocks
, regs_per_pass
);
5136 /* Go through the basic blocks, seeing whether or not each block
5137 ends with a conditional branch whose condition is a comparison
5138 against zero. Record the register compared in BLOCK_REG. */
5139 block_reg
= (unsigned int *) xcalloc (n_basic_blocks
, sizeof (int));
5140 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
5142 rtx last_insn
= BLOCK_END (bb
);
5143 rtx condition
, earliest
, reg
;
5145 /* We only want conditional branches. */
5146 if (GET_CODE (last_insn
) != JUMP_INSN
5147 || !any_condjump_p (last_insn
)
5148 || !onlyjump_p (last_insn
))
5151 /* LAST_INSN is a conditional jump. Get its condition. */
5152 condition
= get_condition (last_insn
, &earliest
);
5154 /* If we were unable to get the condition, or it is not a equality
5155 comparison against zero then there's nothing we can do. */
5157 || (GET_CODE (condition
) != NE
&& GET_CODE (condition
) != EQ
)
5158 || GET_CODE (XEXP (condition
, 1)) != CONST_INT
5159 || (XEXP (condition
, 1)
5160 != CONST0_RTX (GET_MODE (XEXP (condition
, 0)))))
5163 /* We must be checking a register against zero. */
5164 reg
= XEXP (condition
, 0);
5165 if (GET_CODE (reg
) != REG
)
5168 block_reg
[bb
] = REGNO (reg
);
5171 /* Go through the algorithm for each block of registers. */
5172 for (reg
= FIRST_PSEUDO_REGISTER
; reg
< max_reg
; reg
+= regs_per_pass
)
5175 npi
.max_reg
= MIN (reg
+ regs_per_pass
, max_reg
);
5176 delete_null_pointer_checks_1 (block_reg
, nonnull_avin
,
5177 nonnull_avout
, &npi
);
5180 /* Free the table of registers compared at the end of every block. */
5184 free (npi
.nonnull_local
);
5185 free (npi
.nonnull_killed
);
5186 free (nonnull_avin
);
5187 free (nonnull_avout
);
5190 /* Code Hoisting variables and subroutines. */
5192 /* Very busy expressions. */
5193 static sbitmap
*hoist_vbein
;
5194 static sbitmap
*hoist_vbeout
;
5196 /* Hoistable expressions. */
5197 static sbitmap
*hoist_exprs
;
5199 /* Dominator bitmaps. */
5200 static sbitmap
*dominators
;
5202 /* ??? We could compute post dominators and run this algorithm in
5203 reverse to to perform tail merging, doing so would probably be
5204 more effective than the tail merging code in jump.c.
5206 It's unclear if tail merging could be run in parallel with
5207 code hoisting. It would be nice. */
5209 /* Allocate vars used for code hoisting analysis. */
5212 alloc_code_hoist_mem (n_blocks
, n_exprs
)
5213 int n_blocks
, n_exprs
;
5215 antloc
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5216 transp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5217 comp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5219 hoist_vbein
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5220 hoist_vbeout
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5221 hoist_exprs
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5222 transpout
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5224 dominators
= sbitmap_vector_alloc (n_blocks
, n_blocks
);
5227 /* Free vars used for code hoisting analysis. */
5230 free_code_hoist_mem ()
5237 free (hoist_vbeout
);
5244 /* Compute the very busy expressions at entry/exit from each block.
5246 An expression is very busy if all paths from a given point
5247 compute the expression. */
5250 compute_code_hoist_vbeinout ()
5252 int bb
, changed
, passes
;
5254 sbitmap_vector_zero (hoist_vbeout
, n_basic_blocks
);
5255 sbitmap_vector_zero (hoist_vbein
, n_basic_blocks
);
5264 /* We scan the blocks in the reverse order to speed up
5266 for (bb
= n_basic_blocks
- 1; bb
>= 0; bb
--)
5268 changed
|= sbitmap_a_or_b_and_c (hoist_vbein
[bb
], antloc
[bb
],
5269 hoist_vbeout
[bb
], transp
[bb
]);
5270 if (bb
!= n_basic_blocks
- 1)
5271 sbitmap_intersection_of_succs (hoist_vbeout
[bb
], hoist_vbein
, bb
);
5278 fprintf (gcse_file
, "hoisting vbeinout computation: %d passes\n", passes
);
5281 /* Top level routine to do the dataflow analysis needed by code hoisting. */
5284 compute_code_hoist_data ()
5286 compute_local_properties (transp
, comp
, antloc
, 0);
5287 compute_transpout ();
5288 compute_code_hoist_vbeinout ();
5289 compute_flow_dominators (dominators
, NULL
);
5291 fprintf (gcse_file
, "\n");
5294 /* Determine if the expression identified by EXPR_INDEX would
5295 reach BB unimpared if it was placed at the end of EXPR_BB.
5297 It's unclear exactly what Muchnick meant by "unimpared". It seems
5298 to me that the expression must either be computed or transparent in
5299 *every* block in the path(s) from EXPR_BB to BB. Any other definition
5300 would allow the expression to be hoisted out of loops, even if
5301 the expression wasn't a loop invariant.
5303 Contrast this to reachability for PRE where an expression is
5304 considered reachable if *any* path reaches instead of *all*
5308 hoist_expr_reaches_here_p (expr_bb
, expr_index
, bb
, visited
)
5315 int visited_allocated_locally
= 0;
5318 if (visited
== NULL
)
5320 visited_allocated_locally
= 1;
5321 visited
= xcalloc (n_basic_blocks
, 1);
5324 visited
[expr_bb
] = 1;
5325 for (pred
= BASIC_BLOCK (bb
)->pred
; pred
!= NULL
; pred
= pred
->pred_next
)
5327 int pred_bb
= pred
->src
->index
;
5329 if (pred
->src
== ENTRY_BLOCK_PTR
)
5331 else if (visited
[pred_bb
])
5334 /* Does this predecessor generate this expression? */
5335 else if (TEST_BIT (comp
[pred_bb
], expr_index
))
5337 else if (! TEST_BIT (transp
[pred_bb
], expr_index
))
5343 visited
[pred_bb
] = 1;
5344 if (! hoist_expr_reaches_here_p (expr_bb
, expr_index
,
5349 if (visited_allocated_locally
)
5352 return (pred
== NULL
);
5355 /* Actually perform code hoisting. */
5362 struct expr
**index_map
;
5365 sbitmap_vector_zero (hoist_exprs
, n_basic_blocks
);
5367 /* Compute a mapping from expression number (`bitmap_index') to
5368 hash table entry. */
5370 index_map
= (struct expr
**) xcalloc (n_exprs
, sizeof (struct expr
*));
5371 for (i
= 0; i
< expr_hash_table_size
; i
++)
5372 for (expr
= expr_hash_table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
5373 index_map
[expr
->bitmap_index
] = expr
;
5375 /* Walk over each basic block looking for potentially hoistable
5376 expressions, nothing gets hoisted from the entry block. */
5377 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
5380 int insn_inserted_p
;
5382 /* Examine each expression that is very busy at the exit of this
5383 block. These are the potentially hoistable expressions. */
5384 for (i
= 0; i
< hoist_vbeout
[bb
]->n_bits
; i
++)
5388 if (TEST_BIT (hoist_vbeout
[bb
], i
) && TEST_BIT (transpout
[bb
], i
))
5390 /* We've found a potentially hoistable expression, now
5391 we look at every block BB dominates to see if it
5392 computes the expression. */
5393 for (dominated
= 0; dominated
< n_basic_blocks
; dominated
++)
5395 /* Ignore self dominance. */
5397 || ! TEST_BIT (dominators
[dominated
], bb
))
5400 /* We've found a dominated block, now see if it computes
5401 the busy expression and whether or not moving that
5402 expression to the "beginning" of that block is safe. */
5403 if (!TEST_BIT (antloc
[dominated
], i
))
5406 /* Note if the expression would reach the dominated block
5407 unimpared if it was placed at the end of BB.
5409 Keep track of how many times this expression is hoistable
5410 from a dominated block into BB. */
5411 if (hoist_expr_reaches_here_p (bb
, i
, dominated
, NULL
))
5415 /* If we found more than one hoistable occurence of this
5416 expression, then note it in the bitmap of expressions to
5417 hoist. It makes no sense to hoist things which are computed
5418 in only one BB, and doing so tends to pessimize register
5419 allocation. One could increase this value to try harder
5420 to avoid any possible code expansion due to register
5421 allocation issues; however experiments have shown that
5422 the vast majority of hoistable expressions are only movable
5423 from two successors, so raising this threshhold is likely
5424 to nullify any benefit we get from code hoisting. */
5427 SET_BIT (hoist_exprs
[bb
], i
);
5433 /* If we found nothing to hoist, then quit now. */
5437 /* Loop over all the hoistable expressions. */
5438 for (i
= 0; i
< hoist_exprs
[bb
]->n_bits
; i
++)
5440 /* We want to insert the expression into BB only once, so
5441 note when we've inserted it. */
5442 insn_inserted_p
= 0;
5444 /* These tests should be the same as the tests above. */
5445 if (TEST_BIT (hoist_vbeout
[bb
], i
))
5447 /* We've found a potentially hoistable expression, now
5448 we look at every block BB dominates to see if it
5449 computes the expression. */
5450 for (dominated
= 0; dominated
< n_basic_blocks
; dominated
++)
5452 /* Ignore self dominance. */
5454 || ! TEST_BIT (dominators
[dominated
], bb
))
5457 /* We've found a dominated block, now see if it computes
5458 the busy expression and whether or not moving that
5459 expression to the "beginning" of that block is safe. */
5460 if (!TEST_BIT (antloc
[dominated
], i
))
5463 /* The expression is computed in the dominated block and
5464 it would be safe to compute it at the start of the
5465 dominated block. Now we have to determine if the
5466 expresion would reach the dominated block if it was
5467 placed at the end of BB. */
5468 if (hoist_expr_reaches_here_p (bb
, i
, dominated
, NULL
))
5470 struct expr
*expr
= index_map
[i
];
5471 struct occr
*occr
= expr
->antic_occr
;
5475 /* Find the right occurence of this expression. */
5476 while (BLOCK_NUM (occr
->insn
) != dominated
&& occr
)
5479 /* Should never happen. */
5485 set
= single_set (insn
);
5489 /* Create a pseudo-reg to store the result of reaching
5490 expressions into. Get the mode for the new pseudo
5491 from the mode of the original destination pseudo. */
5492 if (expr
->reaching_reg
== NULL
)
5494 = gen_reg_rtx (GET_MODE (SET_DEST (set
)));
5496 /* In theory this should never fail since we're creating
5499 However, on the x86 some of the movXX patterns
5500 actually contain clobbers of scratch regs. This may
5501 cause the insn created by validate_change to not
5502 match any pattern and thus cause validate_change to
5504 if (validate_change (insn
, &SET_SRC (set
),
5505 expr
->reaching_reg
, 0))
5507 occr
->deleted_p
= 1;
5508 if (!insn_inserted_p
)
5510 insert_insn_end_bb (index_map
[i
], bb
, 0);
5511 insn_inserted_p
= 1;
5523 /* Top level routine to perform one code hoisting (aka unification) pass
5525 Return non-zero if a change was made. */
5528 one_code_hoisting_pass ()
5532 alloc_expr_hash_table (max_cuid
);
5533 compute_expr_hash_table ();
5535 dump_hash_table (gcse_file
, "Code Hosting Expressions", expr_hash_table
,
5536 expr_hash_table_size
, n_exprs
);
5540 alloc_code_hoist_mem (n_basic_blocks
, n_exprs
);
5541 compute_code_hoist_data ();
5543 free_code_hoist_mem ();
5546 free_expr_hash_table ();