1 /* Partial redundancy elimination / Hoisting for RTL.
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
3 2006, 2007, 2008, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 3, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
22 - reordering of memory allocation and freeing to be more space efficient
23 - calc rough register pressure information and use the info to drive all
24 kinds of code motion (including code hoisting) in a unified way.
27 /* References searched while implementing this.
29 Compilers Principles, Techniques and Tools
33 Global Optimization by Suppression of Partial Redundancies
35 communications of the acm, Vol. 22, Num. 2, Feb. 1979
37 A Portable Machine-Independent Global Optimizer - Design and Measurements
39 Stanford Ph.D. thesis, Dec. 1983
41 A Fast Algorithm for Code Movement Optimization
43 SIGPLAN Notices, Vol. 23, Num. 10, Oct. 1988
45 A Solution to a Problem with Morel and Renvoise's
46 Global Optimization by Suppression of Partial Redundancies
47 K-H Drechsler, M.P. Stadel
48 ACM TOPLAS, Vol. 10, Num. 4, Oct. 1988
50 Practical Adaptation of the Global Optimization
51 Algorithm of Morel and Renvoise
53 ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991
55 Efficiently Computing Static Single Assignment Form and the Control
57 R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck
58 ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991
61 J. Knoop, O. Ruthing, B. Steffen
62 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
64 What's In a Region? Or Computing Control Dependence Regions in Near-Linear
65 Time for Reducible Flow Control
67 ACM Letters on Programming Languages and Systems,
68 Vol. 2, Num. 1-4, Mar-Dec 1993
70 An Efficient Representation for Sparse Sets
71 Preston Briggs, Linda Torczon
72 ACM Letters on Programming Languages and Systems,
73 Vol. 2, Num. 1-4, Mar-Dec 1993
75 A Variation of Knoop, Ruthing, and Steffen's Lazy Code Motion
76 K-H Drechsler, M.P. Stadel
77 ACM SIGPLAN Notices, Vol. 28, Num. 5, May 1993
79 Partial Dead Code Elimination
80 J. Knoop, O. Ruthing, B. Steffen
81 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
83 Effective Partial Redundancy Elimination
84 P. Briggs, K.D. Cooper
85 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
87 The Program Structure Tree: Computing Control Regions in Linear Time
88 R. Johnson, D. Pearson, K. Pingali
89 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
91 Optimal Code Motion: Theory and Practice
92 J. Knoop, O. Ruthing, B. Steffen
93 ACM TOPLAS, Vol. 16, Num. 4, Jul. 1994
95 The power of assignment motion
96 J. Knoop, O. Ruthing, B. Steffen
97 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
99 Global code motion / global value numbering
101 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
103 Value Driven Redundancy Elimination
105 Rice University Ph.D. thesis, Apr. 1996
109 Massively Scalar Compiler Project, Rice University, Sep. 1996
111 High Performance Compilers for Parallel Computing
115 Advanced Compiler Design and Implementation
117 Morgan Kaufmann, 1997
119 Building an Optimizing Compiler
123 People wishing to speed up the code here should read:
124 Elimination Algorithms for Data Flow Analysis
125 B.G. Ryder, M.C. Paull
126 ACM Computing Surveys, Vol. 18, Num. 3, Sep. 1986
128 How to Analyze Large Programs Efficiently and Informatively
129 D.M. Dhamdhere, B.K. Rosen, F.K. Zadeck
130 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
132 People wishing to do something different can find various possibilities
133 in the above papers and elsewhere.
138 #include "coretypes.h"
140 #include "diagnostic-core.h"
143 #include "hard-reg-set.h"
150 #include "insn-config.h"
152 #include "basic-block.h"
153 #include "function.h"
161 #include "tree-pass.h"
168 /* We support GCSE via Partial Redundancy Elimination. PRE optimizations
169 are a superset of those done by classic GCSE.
171 Two passes of copy/constant propagation are done around PRE or hoisting
172 because the first one enables more GCSE and the second one helps to clean
173 up the copies that PRE and HOIST create. This is needed more for PRE than
174 for HOIST because code hoisting will try to use an existing register
175 containing the common subexpression rather than create a new one. This is
176 harder to do for PRE because of the code motion (which HOIST doesn't do).
178 Expressions we are interested in GCSE-ing are of the form
179 (set (pseudo-reg) (expression)).
180 Function want_to_gcse_p says what these are.
182 In addition, expressions in REG_EQUAL notes are candidates for GCSE-ing.
183 This allows PRE to hoist expressions that are expressed in multiple insns,
184 such as complex address calculations (e.g. for PIC code, or loads with a
185 high part and a low part).
187 PRE handles moving invariant expressions out of loops (by treating them as
188 partially redundant).
190 **********************
192 We used to support multiple passes but there are diminishing returns in
193 doing so. The first pass usually makes 90% of the changes that are doable.
194 A second pass can make a few more changes made possible by the first pass.
195 Experiments show any further passes don't make enough changes to justify
198 A study of spec92 using an unlimited number of passes:
199 [1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83,
200 [6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2,
201 [12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1
203 It was found doing copy propagation between each pass enables further
206 This study was done before expressions in REG_EQUAL notes were added as
207 candidate expressions for optimization, and before the GIMPLE optimizers
208 were added. Probably, multiple passes is even less efficient now than
209 at the time when the study was conducted.
211 PRE is quite expensive in complicated functions because the DFA can take
212 a while to converge. Hence we only perform one pass.
214 **********************
216 The steps for PRE are:
218 1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
220 2) Perform the data flow analysis for PRE.
222 3) Delete the redundant instructions
224 4) Insert the required copies [if any] that make the partially
225 redundant instructions fully redundant.
227 5) For other reaching expressions, insert an instruction to copy the value
228 to a newly created pseudo that will reach the redundant instruction.
230 The deletion is done first so that when we do insertions we
231 know which pseudo reg to use.
233 Various papers have argued that PRE DFA is expensive (O(n^2)) and others
234 argue it is not. The number of iterations for the algorithm to converge
235 is typically 2-4 so I don't view it as that expensive (relatively speaking).
237 PRE GCSE depends heavily on the second CPROP pass to clean up the copies
238 we create. To make an expression reach the place where it's redundant,
239 the result of the expression is copied to a new register, and the redundant
240 expression is deleted by replacing it with this new register. Classic GCSE
241 doesn't have this problem as much as it computes the reaching defs of
242 each register in each block and thus can try to use an existing
245 /* GCSE global vars. */
247 struct target_gcse default_target_gcse
;
248 #if SWITCHABLE_TARGET
249 struct target_gcse
*this_target_gcse
= &default_target_gcse
;
252 /* Set to non-zero if CSE should run after all GCSE optimizations are done. */
253 int flag_rerun_cse_after_global_opts
;
255 /* An obstack for our working variables. */
256 static struct obstack gcse_obstack
;
258 struct reg_use
{rtx reg_rtx
; };
260 /* Hash table of expressions. */
264 /* The expression. */
266 /* Index in the available expression bitmaps. */
268 /* Next entry with the same hash. */
269 struct expr
*next_same_hash
;
270 /* List of anticipatable occurrences in basic blocks in the function.
271 An "anticipatable occurrence" is one that is the first occurrence in the
272 basic block, the operands are not modified in the basic block prior
273 to the occurrence and the output is not used between the start of
274 the block and the occurrence. */
275 struct occr
*antic_occr
;
276 /* List of available occurrence in basic blocks in the function.
277 An "available occurrence" is one that is the last occurrence in the
278 basic block and the operands are not modified by following statements in
279 the basic block [including this insn]. */
280 struct occr
*avail_occr
;
281 /* Non-null if the computation is PRE redundant.
282 The value is the newly created pseudo-reg to record a copy of the
283 expression in all the places that reach the redundant copy. */
285 /* Maximum distance in instructions this expression can travel.
286 We avoid moving simple expressions for more than a few instructions
287 to keep register pressure under control.
288 A value of "0" removes restrictions on how far the expression can
293 /* Occurrence of an expression.
294 There is one per basic block. If a pattern appears more than once the
295 last appearance is used [or first for anticipatable expressions]. */
299 /* Next occurrence of this expression. */
301 /* The insn that computes the expression. */
303 /* Nonzero if this [anticipatable] occurrence has been deleted. */
305 /* Nonzero if this [available] occurrence has been copied to
307 /* ??? This is mutually exclusive with deleted_p, so they could share
312 typedef struct occr
*occr_t
;
314 /* Expression hash tables.
315 Each hash table is an array of buckets.
316 ??? It is known that if it were an array of entries, structure elements
317 `next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is
318 not clear whether in the final analysis a sufficient amount of memory would
319 be saved as the size of the available expression bitmaps would be larger
320 [one could build a mapping table without holes afterwards though].
321 Someday I'll perform the computation and figure it out. */
326 This is an array of `expr_hash_table_size' elements. */
329 /* Size of the hash table, in elements. */
332 /* Number of hash table elements. */
333 unsigned int n_elems
;
336 /* Expression hash table. */
337 static struct hash_table_d expr_hash_table
;
339 /* This is a list of expressions which are MEMs and will be used by load
341 Load motion tracks MEMs which aren't killed by anything except itself,
342 i.e. loads and stores to a single location.
343 We can then allow movement of these MEM refs with a little special
344 allowance. (all stores copy the same value to the reaching reg used
345 for the loads). This means all values used to store into memory must have
346 no side effects so we can re-issue the setter value. */
350 struct expr
* expr
; /* Gcse expression reference for LM. */
351 rtx pattern
; /* Pattern of this mem. */
352 rtx pattern_regs
; /* List of registers mentioned by the mem. */
353 rtx loads
; /* INSN list of loads seen. */
354 rtx stores
; /* INSN list of stores seen. */
355 struct ls_expr
* next
; /* Next in the list. */
356 int invalid
; /* Invalid for some reason. */
357 int index
; /* If it maps to a bitmap index. */
358 unsigned int hash_index
; /* Index when in a hash table. */
359 rtx reaching_reg
; /* Register to use when re-writing. */
362 /* Head of the list of load/store memory refs. */
363 static struct ls_expr
* pre_ldst_mems
= NULL
;
365 /* Hashtable for the load/store memory refs. */
366 static htab_t pre_ldst_table
= NULL
;
368 /* Bitmap containing one bit for each register in the program.
369 Used when performing GCSE to track which registers have been set since
370 the start of the basic block. */
371 static regset reg_set_bitmap
;
373 /* Array, indexed by basic block number for a list of insns which modify
374 memory within that block. */
375 static vec
<rtx
> *modify_mem_list
;
376 static bitmap modify_mem_list_set
;
378 typedef struct modify_pair_s
380 rtx dest
; /* A MEM. */
381 rtx dest_addr
; /* The canonical address of `dest'. */
385 /* This array parallels modify_mem_list, except that it stores MEMs
386 being set and their canonicalized memory addresses. */
387 static vec
<modify_pair
> *canon_modify_mem_list
;
389 /* Bitmap indexed by block numbers to record which blocks contain
391 static bitmap blocks_with_calls
;
393 /* Various variables for statistics gathering. */
395 /* Memory used in a pass.
396 This isn't intended to be absolutely precise. Its intent is only
397 to keep an eye on memory usage. */
398 static int bytes_used
;
400 /* GCSE substitutions made. */
401 static int gcse_subst_count
;
402 /* Number of copy instructions created. */
403 static int gcse_create_count
;
405 /* Doing code hoisting. */
406 static bool doing_code_hoisting_p
= false;
408 /* For available exprs */
409 static sbitmap
*ae_kill
;
411 /* Data stored for each basic block. */
414 /* Maximal register pressure inside basic block for given register class
415 (defined only for the pressure classes). */
416 int max_reg_pressure
[N_REG_CLASSES
];
417 /* Recorded register pressure of basic block before trying to hoist
418 an expression. Will be used to restore the register pressure
419 if the expression should not be hoisted. */
421 /* Recorded register live_in info of basic block during code hoisting
422 process. BACKUP is used to record live_in info before trying to
423 hoist an expression, and will be used to restore LIVE_IN if the
424 expression should not be hoisted. */
425 bitmap live_in
, backup
;
428 #define BB_DATA(bb) ((struct bb_data *) (bb)->aux)
430 static basic_block curr_bb
;
432 /* Current register pressure for each pressure class. */
433 static int curr_reg_pressure
[N_REG_CLASSES
];
436 static void compute_can_copy (void);
437 static void *gmalloc (size_t) ATTRIBUTE_MALLOC
;
438 static void *gcalloc (size_t, size_t) ATTRIBUTE_MALLOC
;
439 static void *gcse_alloc (unsigned long);
440 static void alloc_gcse_mem (void);
441 static void free_gcse_mem (void);
442 static void hash_scan_insn (rtx
, struct hash_table_d
*);
443 static void hash_scan_set (rtx
, rtx
, struct hash_table_d
*);
444 static void hash_scan_clobber (rtx
, rtx
, struct hash_table_d
*);
445 static void hash_scan_call (rtx
, rtx
, struct hash_table_d
*);
446 static int want_to_gcse_p (rtx
, int *);
447 static int oprs_unchanged_p (const_rtx
, const_rtx
, int);
448 static int oprs_anticipatable_p (const_rtx
, const_rtx
);
449 static int oprs_available_p (const_rtx
, const_rtx
);
450 static void insert_expr_in_table (rtx
, enum machine_mode
, rtx
, int, int, int,
451 struct hash_table_d
*);
452 static unsigned int hash_expr (const_rtx
, enum machine_mode
, int *, int);
453 static int expr_equiv_p (const_rtx
, const_rtx
);
454 static void record_last_reg_set_info (rtx
, int);
455 static void record_last_mem_set_info (rtx
);
456 static void record_last_set_info (rtx
, const_rtx
, void *);
457 static void compute_hash_table (struct hash_table_d
*);
458 static void alloc_hash_table (struct hash_table_d
*);
459 static void free_hash_table (struct hash_table_d
*);
460 static void compute_hash_table_work (struct hash_table_d
*);
461 static void dump_hash_table (FILE *, const char *, struct hash_table_d
*);
462 static void compute_transp (const_rtx
, int, sbitmap
*);
463 static void compute_local_properties (sbitmap
*, sbitmap
*, sbitmap
*,
464 struct hash_table_d
*);
465 static void mems_conflict_for_gcse_p (rtx
, const_rtx
, void *);
466 static int load_killed_in_block_p (const_basic_block
, int, const_rtx
, int);
467 static void canon_list_insert (rtx
, const_rtx
, void *);
468 static void alloc_pre_mem (int, int);
469 static void free_pre_mem (void);
470 static struct edge_list
*compute_pre_data (void);
471 static int pre_expr_reaches_here_p (basic_block
, struct expr
*,
473 static void insert_insn_end_basic_block (struct expr
*, basic_block
);
474 static void pre_insert_copy_insn (struct expr
*, rtx
);
475 static void pre_insert_copies (void);
476 static int pre_delete (void);
477 static int pre_gcse (struct edge_list
*);
478 static int one_pre_gcse_pass (void);
479 static void add_label_notes (rtx
, rtx
);
480 static void alloc_code_hoist_mem (int, int);
481 static void free_code_hoist_mem (void);
482 static void compute_code_hoist_vbeinout (void);
483 static void compute_code_hoist_data (void);
484 static int should_hoist_expr_to_dom (basic_block
, struct expr
*, basic_block
,
485 sbitmap
, int, int *, enum reg_class
,
487 static int hoist_code (void);
488 static enum reg_class
get_regno_pressure_class (int regno
, int *nregs
);
489 static enum reg_class
get_pressure_class_and_nregs (rtx insn
, int *nregs
);
490 static int one_code_hoisting_pass (void);
491 static rtx
process_insert_insn (struct expr
*);
492 static int pre_edge_insert (struct edge_list
*, struct expr
**);
493 static int pre_expr_reaches_here_p_work (basic_block
, struct expr
*,
494 basic_block
, char *);
495 static struct ls_expr
* ldst_entry (rtx
);
496 static void free_ldst_entry (struct ls_expr
*);
497 static void free_ld_motion_mems (void);
498 static void print_ldst_list (FILE *);
499 static struct ls_expr
* find_rtx_in_ldst (rtx
);
500 static int simple_mem (const_rtx
);
501 static void invalidate_any_buried_refs (rtx
);
502 static void compute_ld_motion_mems (void);
503 static void trim_ld_motion_mems (void);
504 static void update_ld_motion_stores (struct expr
*);
505 static void clear_modify_mem_tables (void);
506 static void free_modify_mem_tables (void);
507 static rtx
gcse_emit_move_after (rtx
, rtx
, rtx
);
508 static bool is_too_expensive (const char *);
510 #define GNEW(T) ((T *) gmalloc (sizeof (T)))
511 #define GCNEW(T) ((T *) gcalloc (1, sizeof (T)))
513 #define GNEWVEC(T, N) ((T *) gmalloc (sizeof (T) * (N)))
514 #define GCNEWVEC(T, N) ((T *) gcalloc ((N), sizeof (T)))
516 #define GNEWVAR(T, S) ((T *) gmalloc ((S)))
517 #define GCNEWVAR(T, S) ((T *) gcalloc (1, (S)))
519 #define GOBNEW(T) ((T *) gcse_alloc (sizeof (T)))
520 #define GOBNEWVAR(T, S) ((T *) gcse_alloc ((S)))
522 /* Misc. utilities. */
525 (this_target_gcse->x_can_copy)
526 #define can_copy_init_p \
527 (this_target_gcse->x_can_copy_init_p)
529 /* Compute which modes support reg/reg copy operations. */
532 compute_can_copy (void)
535 #ifndef AVOID_CCMODE_COPIES
538 memset (can_copy
, 0, NUM_MACHINE_MODES
);
541 for (i
= 0; i
< NUM_MACHINE_MODES
; i
++)
542 if (GET_MODE_CLASS (i
) == MODE_CC
)
544 #ifdef AVOID_CCMODE_COPIES
547 reg
= gen_rtx_REG ((enum machine_mode
) i
, LAST_VIRTUAL_REGISTER
+ 1);
548 insn
= emit_insn (gen_rtx_SET (VOIDmode
, reg
, reg
));
549 if (recog (PATTERN (insn
), insn
, NULL
) >= 0)
559 /* Returns whether the mode supports reg/reg copy operations. */
562 can_copy_p (enum machine_mode mode
)
564 if (! can_copy_init_p
)
567 can_copy_init_p
= true;
570 return can_copy
[mode
] != 0;
573 /* Cover function to xmalloc to record bytes allocated. */
576 gmalloc (size_t size
)
579 return xmalloc (size
);
582 /* Cover function to xcalloc to record bytes allocated. */
585 gcalloc (size_t nelem
, size_t elsize
)
587 bytes_used
+= nelem
* elsize
;
588 return xcalloc (nelem
, elsize
);
591 /* Cover function to obstack_alloc. */
594 gcse_alloc (unsigned long size
)
597 return obstack_alloc (&gcse_obstack
, size
);
600 /* Allocate memory for the reg/memory set tracking tables.
601 This is called at the start of each pass. */
604 alloc_gcse_mem (void)
606 /* Allocate vars to track sets of regs. */
607 reg_set_bitmap
= ALLOC_REG_SET (NULL
);
609 /* Allocate array to keep a list of insns which modify memory in each
610 basic block. The two typedefs are needed to work around the
611 pre-processor limitation with template types in macro arguments. */
612 typedef vec
<rtx
> vec_rtx_heap
;
613 typedef vec
<modify_pair
> vec_modify_pair_heap
;
614 modify_mem_list
= GCNEWVEC (vec_rtx_heap
, last_basic_block
);
615 canon_modify_mem_list
= GCNEWVEC (vec_modify_pair_heap
, last_basic_block
);
616 modify_mem_list_set
= BITMAP_ALLOC (NULL
);
617 blocks_with_calls
= BITMAP_ALLOC (NULL
);
620 /* Free memory allocated by alloc_gcse_mem. */
625 FREE_REG_SET (reg_set_bitmap
);
627 free_modify_mem_tables ();
628 BITMAP_FREE (modify_mem_list_set
);
629 BITMAP_FREE (blocks_with_calls
);
632 /* Compute the local properties of each recorded expression.
634 Local properties are those that are defined by the block, irrespective of
637 An expression is transparent in a block if its operands are not modified
640 An expression is computed (locally available) in a block if it is computed
641 at least once and expression would contain the same value if the
642 computation was moved to the end of the block.
644 An expression is locally anticipatable in a block if it is computed at
645 least once and expression would contain the same value if the computation
646 was moved to the beginning of the block.
648 We call this routine for pre and code hoisting. They all compute
649 basically the same information and thus can easily share this code.
651 TRANSP, COMP, and ANTLOC are destination sbitmaps for recording local
652 properties. If NULL, then it is not necessary to compute or record that
655 TABLE controls which hash table to look at. */
658 compute_local_properties (sbitmap
*transp
, sbitmap
*comp
, sbitmap
*antloc
,
659 struct hash_table_d
*table
)
663 /* Initialize any bitmaps that were passed in. */
666 bitmap_vector_ones (transp
, last_basic_block
);
670 bitmap_vector_clear (comp
, last_basic_block
);
672 bitmap_vector_clear (antloc
, last_basic_block
);
674 for (i
= 0; i
< table
->size
; i
++)
678 for (expr
= table
->table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
680 int indx
= expr
->bitmap_index
;
683 /* The expression is transparent in this block if it is not killed.
684 We start by assuming all are transparent [none are killed], and
685 then reset the bits for those that are. */
687 compute_transp (expr
->expr
, indx
, transp
);
689 /* The occurrences recorded in antic_occr are exactly those that
690 we want to set to nonzero in ANTLOC. */
692 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
694 bitmap_set_bit (antloc
[BLOCK_FOR_INSN (occr
->insn
)->index
], indx
);
696 /* While we're scanning the table, this is a good place to
701 /* The occurrences recorded in avail_occr are exactly those that
702 we want to set to nonzero in COMP. */
704 for (occr
= expr
->avail_occr
; occr
!= NULL
; occr
= occr
->next
)
706 bitmap_set_bit (comp
[BLOCK_FOR_INSN (occr
->insn
)->index
], indx
);
708 /* While we're scanning the table, this is a good place to
713 /* While we're scanning the table, this is a good place to
715 expr
->reaching_reg
= 0;
720 /* Hash table support. */
722 struct reg_avail_info
729 static struct reg_avail_info
*reg_avail_info
;
730 static basic_block current_bb
;
732 /* See whether X, the source of a set, is something we want to consider for
736 want_to_gcse_p (rtx x
, int *max_distance_ptr
)
739 /* On register stack architectures, don't GCSE constants from the
740 constant pool, as the benefits are often swamped by the overhead
741 of shuffling the register stack between basic blocks. */
742 if (IS_STACK_MODE (GET_MODE (x
)))
743 x
= avoid_constant_pool_reference (x
);
746 /* GCSE'ing constants:
748 We do not specifically distinguish between constant and non-constant
749 expressions in PRE and Hoist. We use set_src_cost below to limit
750 the maximum distance simple expressions can travel.
752 Nevertheless, constants are much easier to GCSE, and, hence,
753 it is easy to overdo the optimizations. Usually, excessive PRE and
754 Hoisting of constant leads to increased register pressure.
756 RA can deal with this by rematerialing some of the constants.
757 Therefore, it is important that the back-end generates sets of constants
758 in a way that allows reload rematerialize them under high register
759 pressure, i.e., a pseudo register with REG_EQUAL to constant
760 is set only once. Failing to do so will result in IRA/reload
761 spilling such constants under high register pressure instead of
762 rematerializing them. */
764 switch (GET_CODE (x
))
772 if (!doing_code_hoisting_p
)
773 /* Do not PRE constants. */
779 if (doing_code_hoisting_p
)
780 /* PRE doesn't implement max_distance restriction. */
785 gcc_assert (!optimize_function_for_speed_p (cfun
)
786 && optimize_function_for_size_p (cfun
));
787 cost
= set_src_cost (x
, 0);
789 if (cost
< COSTS_N_INSNS (GCSE_UNRESTRICTED_COST
))
791 max_distance
= (GCSE_COST_DISTANCE_RATIO
* cost
) / 10;
792 if (max_distance
== 0)
795 gcc_assert (max_distance
> 0);
800 if (max_distance_ptr
)
801 *max_distance_ptr
= max_distance
;
804 return can_assign_to_reg_without_clobbers_p (x
);
808 /* Used internally by can_assign_to_reg_without_clobbers_p. */
810 static GTY(()) rtx test_insn
;
812 /* Return true if we can assign X to a pseudo register such that the
813 resulting insn does not result in clobbering a hard register as a
816 Additionally, if the target requires it, check that the resulting insn
817 can be copied. If it cannot, this means that X is special and probably
818 has hidden side-effects we don't want to mess with.
820 This function is typically used by code motion passes, to verify
821 that it is safe to insert an insn without worrying about clobbering
822 maybe live hard regs. */
825 can_assign_to_reg_without_clobbers_p (rtx x
)
827 int num_clobbers
= 0;
830 /* If this is a valid operand, we are OK. If it's VOIDmode, we aren't. */
831 if (general_operand (x
, GET_MODE (x
)))
833 else if (GET_MODE (x
) == VOIDmode
)
836 /* Otherwise, check if we can make a valid insn from it. First initialize
837 our test insn if we haven't already. */
841 = make_insn_raw (gen_rtx_SET (VOIDmode
,
842 gen_rtx_REG (word_mode
,
843 FIRST_PSEUDO_REGISTER
* 2),
845 NEXT_INSN (test_insn
) = PREV_INSN (test_insn
) = 0;
848 /* Now make an insn like the one we would make when GCSE'ing and see if
850 PUT_MODE (SET_DEST (PATTERN (test_insn
)), GET_MODE (x
));
851 SET_SRC (PATTERN (test_insn
)) = x
;
853 icode
= recog (PATTERN (test_insn
), test_insn
, &num_clobbers
);
857 if (num_clobbers
> 0 && added_clobbers_hard_reg_p (icode
))
860 if (targetm
.cannot_copy_insn_p
&& targetm
.cannot_copy_insn_p (test_insn
))
866 /* Return nonzero if the operands of expression X are unchanged from the
867 start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
868 or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
871 oprs_unchanged_p (const_rtx x
, const_rtx insn
, int avail_p
)
885 struct reg_avail_info
*info
= ®_avail_info
[REGNO (x
)];
887 if (info
->last_bb
!= current_bb
)
890 return info
->last_set
< DF_INSN_LUID (insn
);
892 return info
->first_set
>= DF_INSN_LUID (insn
);
896 if (load_killed_in_block_p (current_bb
, DF_INSN_LUID (insn
),
900 return oprs_unchanged_p (XEXP (x
, 0), insn
, avail_p
);
924 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
928 /* If we are about to do the last recursive call needed at this
929 level, change it into iteration. This function is called enough
932 return oprs_unchanged_p (XEXP (x
, i
), insn
, avail_p
);
934 else if (! oprs_unchanged_p (XEXP (x
, i
), insn
, avail_p
))
937 else if (fmt
[i
] == 'E')
938 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
939 if (! oprs_unchanged_p (XVECEXP (x
, i
, j
), insn
, avail_p
))
946 /* Info passed from load_killed_in_block_p to mems_conflict_for_gcse_p. */
948 struct mem_conflict_info
950 /* A memory reference for a load instruction, mems_conflict_for_gcse_p will
951 see if a memory store conflicts with this memory load. */
954 /* True if mems_conflict_for_gcse_p finds a conflict between two memory
959 /* DEST is the output of an instruction. If it is a memory reference and
960 possibly conflicts with the load found in DATA, then communicate this
961 information back through DATA. */
964 mems_conflict_for_gcse_p (rtx dest
, const_rtx setter ATTRIBUTE_UNUSED
,
967 struct mem_conflict_info
*mci
= (struct mem_conflict_info
*) data
;
969 while (GET_CODE (dest
) == SUBREG
970 || GET_CODE (dest
) == ZERO_EXTRACT
971 || GET_CODE (dest
) == STRICT_LOW_PART
)
972 dest
= XEXP (dest
, 0);
974 /* If DEST is not a MEM, then it will not conflict with the load. Note
975 that function calls are assumed to clobber memory, but are handled
980 /* If we are setting a MEM in our list of specially recognized MEMs,
981 don't mark as killed this time. */
982 if (pre_ldst_mems
!= NULL
&& expr_equiv_p (dest
, mci
->mem
))
984 if (!find_rtx_in_ldst (dest
))
985 mci
->conflict
= true;
989 if (true_dependence (dest
, GET_MODE (dest
), mci
->mem
))
990 mci
->conflict
= true;
993 /* Return nonzero if the expression in X (a memory reference) is killed
994 in block BB before or after the insn with the LUID in UID_LIMIT.
995 AVAIL_P is nonzero for kills after UID_LIMIT, and zero for kills
998 To check the entire block, set UID_LIMIT to max_uid + 1 and
1002 load_killed_in_block_p (const_basic_block bb
, int uid_limit
, const_rtx x
,
1005 vec
<rtx
> list
= modify_mem_list
[bb
->index
];
1009 /* If this is a readonly then we aren't going to be changing it. */
1010 if (MEM_READONLY_P (x
))
1013 FOR_EACH_VEC_ELT_REVERSE (list
, ix
, setter
)
1015 struct mem_conflict_info mci
;
1017 /* Ignore entries in the list that do not apply. */
1019 && DF_INSN_LUID (setter
) < uid_limit
)
1021 && DF_INSN_LUID (setter
) > uid_limit
))
1024 /* If SETTER is a call everything is clobbered. Note that calls
1025 to pure functions are never put on the list, so we need not
1026 worry about them. */
1027 if (CALL_P (setter
))
1030 /* SETTER must be an INSN of some kind that sets memory. Call
1031 note_stores to examine each hunk of memory that is modified. */
1033 mci
.conflict
= false;
1034 note_stores (PATTERN (setter
), mems_conflict_for_gcse_p
, &mci
);
1041 /* Return nonzero if the operands of expression X are unchanged from
1042 the start of INSN's basic block up to but not including INSN. */
1045 oprs_anticipatable_p (const_rtx x
, const_rtx insn
)
1047 return oprs_unchanged_p (x
, insn
, 0);
1050 /* Return nonzero if the operands of expression X are unchanged from
1051 INSN to the end of INSN's basic block. */
1054 oprs_available_p (const_rtx x
, const_rtx insn
)
1056 return oprs_unchanged_p (x
, insn
, 1);
1059 /* Hash expression X.
1061 MODE is only used if X is a CONST_INT. DO_NOT_RECORD_P is a boolean
1062 indicating if a volatile operand is found or if the expression contains
1063 something we don't want to insert in the table. HASH_TABLE_SIZE is
1064 the current size of the hash table to be probed. */
1067 hash_expr (const_rtx x
, enum machine_mode mode
, int *do_not_record_p
,
1068 int hash_table_size
)
1072 *do_not_record_p
= 0;
1074 hash
= hash_rtx (x
, mode
, do_not_record_p
, NULL
, /*have_reg_qty=*/false);
1075 return hash
% hash_table_size
;
1078 /* Return nonzero if exp1 is equivalent to exp2. */
1081 expr_equiv_p (const_rtx x
, const_rtx y
)
1083 return exp_equiv_p (x
, y
, 0, true);
1086 /* Insert expression X in INSN in the hash TABLE.
1087 If it is already present, record it as the last occurrence in INSN's
1090 MODE is the mode of the value X is being stored into.
1091 It is only used if X is a CONST_INT.
1093 ANTIC_P is nonzero if X is an anticipatable expression.
1094 AVAIL_P is nonzero if X is an available expression.
1096 MAX_DISTANCE is the maximum distance in instructions this expression can
1100 insert_expr_in_table (rtx x
, enum machine_mode mode
, rtx insn
, int antic_p
,
1101 int avail_p
, int max_distance
, struct hash_table_d
*table
)
1103 int found
, do_not_record_p
;
1105 struct expr
*cur_expr
, *last_expr
= NULL
;
1106 struct occr
*antic_occr
, *avail_occr
;
1108 hash
= hash_expr (x
, mode
, &do_not_record_p
, table
->size
);
1110 /* Do not insert expression in table if it contains volatile operands,
1111 or if hash_expr determines the expression is something we don't want
1112 to or can't handle. */
1113 if (do_not_record_p
)
1116 cur_expr
= table
->table
[hash
];
1119 while (cur_expr
&& 0 == (found
= expr_equiv_p (cur_expr
->expr
, x
)))
1121 /* If the expression isn't found, save a pointer to the end of
1123 last_expr
= cur_expr
;
1124 cur_expr
= cur_expr
->next_same_hash
;
1129 cur_expr
= GOBNEW (struct expr
);
1130 bytes_used
+= sizeof (struct expr
);
1131 if (table
->table
[hash
] == NULL
)
1132 /* This is the first pattern that hashed to this index. */
1133 table
->table
[hash
] = cur_expr
;
1135 /* Add EXPR to end of this hash chain. */
1136 last_expr
->next_same_hash
= cur_expr
;
1138 /* Set the fields of the expr element. */
1140 cur_expr
->bitmap_index
= table
->n_elems
++;
1141 cur_expr
->next_same_hash
= NULL
;
1142 cur_expr
->antic_occr
= NULL
;
1143 cur_expr
->avail_occr
= NULL
;
1144 gcc_assert (max_distance
>= 0);
1145 cur_expr
->max_distance
= max_distance
;
1148 gcc_assert (cur_expr
->max_distance
== max_distance
);
1150 /* Now record the occurrence(s). */
1153 antic_occr
= cur_expr
->antic_occr
;
1156 && BLOCK_FOR_INSN (antic_occr
->insn
) != BLOCK_FOR_INSN (insn
))
1160 /* Found another instance of the expression in the same basic block.
1161 Prefer the currently recorded one. We want the first one in the
1162 block and the block is scanned from start to end. */
1163 ; /* nothing to do */
1166 /* First occurrence of this expression in this basic block. */
1167 antic_occr
= GOBNEW (struct occr
);
1168 bytes_used
+= sizeof (struct occr
);
1169 antic_occr
->insn
= insn
;
1170 antic_occr
->next
= cur_expr
->antic_occr
;
1171 antic_occr
->deleted_p
= 0;
1172 cur_expr
->antic_occr
= antic_occr
;
1178 avail_occr
= cur_expr
->avail_occr
;
1181 && BLOCK_FOR_INSN (avail_occr
->insn
) == BLOCK_FOR_INSN (insn
))
1183 /* Found another instance of the expression in the same basic block.
1184 Prefer this occurrence to the currently recorded one. We want
1185 the last one in the block and the block is scanned from start
1187 avail_occr
->insn
= insn
;
1191 /* First occurrence of this expression in this basic block. */
1192 avail_occr
= GOBNEW (struct occr
);
1193 bytes_used
+= sizeof (struct occr
);
1194 avail_occr
->insn
= insn
;
1195 avail_occr
->next
= cur_expr
->avail_occr
;
1196 avail_occr
->deleted_p
= 0;
1197 cur_expr
->avail_occr
= avail_occr
;
1202 /* Scan SET present in INSN and add an entry to the hash TABLE. */
1205 hash_scan_set (rtx set
, rtx insn
, struct hash_table_d
*table
)
1207 rtx src
= SET_SRC (set
);
1208 rtx dest
= SET_DEST (set
);
1211 if (GET_CODE (src
) == CALL
)
1212 hash_scan_call (src
, insn
, table
);
1214 else if (REG_P (dest
))
1216 unsigned int regno
= REGNO (dest
);
1217 int max_distance
= 0;
1219 /* See if a REG_EQUAL note shows this equivalent to a simpler expression.
1221 This allows us to do a single GCSE pass and still eliminate
1222 redundant constants, addresses or other expressions that are
1223 constructed with multiple instructions.
1225 However, keep the original SRC if INSN is a simple reg-reg move.
1226 In this case, there will almost always be a REG_EQUAL note on the
1227 insn that sets SRC. By recording the REG_EQUAL value here as SRC
1228 for INSN, we miss copy propagation opportunities and we perform the
1229 same PRE GCSE operation repeatedly on the same REG_EQUAL value if we
1230 do more than one PRE GCSE pass.
1232 Note that this does not impede profitable constant propagations. We
1233 "look through" reg-reg sets in lookup_avail_set. */
1234 note
= find_reg_equal_equiv_note (insn
);
1236 && REG_NOTE_KIND (note
) == REG_EQUAL
1238 && want_to_gcse_p (XEXP (note
, 0), NULL
))
1239 src
= XEXP (note
, 0), set
= gen_rtx_SET (VOIDmode
, dest
, src
);
1241 /* Only record sets of pseudo-regs in the hash table. */
1242 if (regno
>= FIRST_PSEUDO_REGISTER
1243 /* Don't GCSE something if we can't do a reg/reg copy. */
1244 && can_copy_p (GET_MODE (dest
))
1245 /* GCSE commonly inserts instruction after the insn. We can't
1246 do that easily for EH edges so disable GCSE on these for now. */
1247 /* ??? We can now easily create new EH landing pads at the
1248 gimple level, for splitting edges; there's no reason we
1249 can't do the same thing at the rtl level. */
1250 && !can_throw_internal (insn
)
1251 /* Is SET_SRC something we want to gcse? */
1252 && want_to_gcse_p (src
, &max_distance
)
1253 /* Don't CSE a nop. */
1254 && ! set_noop_p (set
)
1255 /* Don't GCSE if it has attached REG_EQUIV note.
1256 At this point this only function parameters should have
1257 REG_EQUIV notes and if the argument slot is used somewhere
1258 explicitly, it means address of parameter has been taken,
1259 so we should not extend the lifetime of the pseudo. */
1260 && (note
== NULL_RTX
|| ! MEM_P (XEXP (note
, 0))))
1262 /* An expression is not anticipatable if its operands are
1263 modified before this insn or if this is not the only SET in
1264 this insn. The latter condition does not have to mean that
1265 SRC itself is not anticipatable, but we just will not be
1266 able to handle code motion of insns with multiple sets. */
1267 int antic_p
= oprs_anticipatable_p (src
, insn
)
1268 && !multiple_sets (insn
);
1269 /* An expression is not available if its operands are
1270 subsequently modified, including this insn. It's also not
1271 available if this is a branch, because we can't insert
1272 a set after the branch. */
1273 int avail_p
= (oprs_available_p (src
, insn
)
1274 && ! JUMP_P (insn
));
1276 insert_expr_in_table (src
, GET_MODE (dest
), insn
, antic_p
, avail_p
,
1277 max_distance
, table
);
1280 /* In case of store we want to consider the memory value as available in
1281 the REG stored in that memory. This makes it possible to remove
1282 redundant loads from due to stores to the same location. */
1283 else if (flag_gcse_las
&& REG_P (src
) && MEM_P (dest
))
1285 unsigned int regno
= REGNO (src
);
1286 int max_distance
= 0;
1288 /* Only record sets of pseudo-regs in the hash table. */
1289 if (regno
>= FIRST_PSEUDO_REGISTER
1290 /* Don't GCSE something if we can't do a reg/reg copy. */
1291 && can_copy_p (GET_MODE (src
))
1292 /* GCSE commonly inserts instruction after the insn. We can't
1293 do that easily for EH edges so disable GCSE on these for now. */
1294 && !can_throw_internal (insn
)
1295 /* Is SET_DEST something we want to gcse? */
1296 && want_to_gcse_p (dest
, &max_distance
)
1297 /* Don't CSE a nop. */
1298 && ! set_noop_p (set
)
1299 /* Don't GCSE if it has attached REG_EQUIV note.
1300 At this point this only function parameters should have
1301 REG_EQUIV notes and if the argument slot is used somewhere
1302 explicitly, it means address of parameter has been taken,
1303 so we should not extend the lifetime of the pseudo. */
1304 && ((note
= find_reg_note (insn
, REG_EQUIV
, NULL_RTX
)) == 0
1305 || ! MEM_P (XEXP (note
, 0))))
1307 /* Stores are never anticipatable. */
1309 /* An expression is not available if its operands are
1310 subsequently modified, including this insn. It's also not
1311 available if this is a branch, because we can't insert
1312 a set after the branch. */
1313 int avail_p
= oprs_available_p (dest
, insn
)
1316 /* Record the memory expression (DEST) in the hash table. */
1317 insert_expr_in_table (dest
, GET_MODE (dest
), insn
,
1318 antic_p
, avail_p
, max_distance
, table
);
1324 hash_scan_clobber (rtx x ATTRIBUTE_UNUSED
, rtx insn ATTRIBUTE_UNUSED
,
1325 struct hash_table_d
*table ATTRIBUTE_UNUSED
)
1327 /* Currently nothing to do. */
1331 hash_scan_call (rtx x ATTRIBUTE_UNUSED
, rtx insn ATTRIBUTE_UNUSED
,
1332 struct hash_table_d
*table ATTRIBUTE_UNUSED
)
1334 /* Currently nothing to do. */
1337 /* Process INSN and add hash table entries as appropriate. */
1340 hash_scan_insn (rtx insn
, struct hash_table_d
*table
)
1342 rtx pat
= PATTERN (insn
);
1345 /* Pick out the sets of INSN and for other forms of instructions record
1346 what's been modified. */
1348 if (GET_CODE (pat
) == SET
)
1349 hash_scan_set (pat
, insn
, table
);
1351 else if (GET_CODE (pat
) == CLOBBER
)
1352 hash_scan_clobber (pat
, insn
, table
);
1354 else if (GET_CODE (pat
) == CALL
)
1355 hash_scan_call (pat
, insn
, table
);
1357 else if (GET_CODE (pat
) == PARALLEL
)
1358 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
1360 rtx x
= XVECEXP (pat
, 0, i
);
1362 if (GET_CODE (x
) == SET
)
1363 hash_scan_set (x
, insn
, table
);
1364 else if (GET_CODE (x
) == CLOBBER
)
1365 hash_scan_clobber (x
, insn
, table
);
1366 else if (GET_CODE (x
) == CALL
)
1367 hash_scan_call (x
, insn
, table
);
1371 /* Dump the hash table TABLE to file FILE under the name NAME. */
1374 dump_hash_table (FILE *file
, const char *name
, struct hash_table_d
*table
)
1377 /* Flattened out table, so it's printed in proper order. */
1378 struct expr
**flat_table
;
1379 unsigned int *hash_val
;
1382 flat_table
= XCNEWVEC (struct expr
*, table
->n_elems
);
1383 hash_val
= XNEWVEC (unsigned int, table
->n_elems
);
1385 for (i
= 0; i
< (int) table
->size
; i
++)
1386 for (expr
= table
->table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
1388 flat_table
[expr
->bitmap_index
] = expr
;
1389 hash_val
[expr
->bitmap_index
] = i
;
1392 fprintf (file
, "%s hash table (%d buckets, %d entries)\n",
1393 name
, table
->size
, table
->n_elems
);
1395 for (i
= 0; i
< (int) table
->n_elems
; i
++)
1396 if (flat_table
[i
] != 0)
1398 expr
= flat_table
[i
];
1399 fprintf (file
, "Index %d (hash value %d; max distance %d)\n ",
1400 expr
->bitmap_index
, hash_val
[i
], expr
->max_distance
);
1401 print_rtl (file
, expr
->expr
);
1402 fprintf (file
, "\n");
1405 fprintf (file
, "\n");
1411 /* Record register first/last/block set information for REGNO in INSN.
1413 first_set records the first place in the block where the register
1414 is set and is used to compute "anticipatability".
1416 last_set records the last place in the block where the register
1417 is set and is used to compute "availability".
1419 last_bb records the block for which first_set and last_set are
1420 valid, as a quick test to invalidate them. */
1423 record_last_reg_set_info (rtx insn
, int regno
)
1425 struct reg_avail_info
*info
= ®_avail_info
[regno
];
1426 int luid
= DF_INSN_LUID (insn
);
1428 info
->last_set
= luid
;
1429 if (info
->last_bb
!= current_bb
)
1431 info
->last_bb
= current_bb
;
1432 info
->first_set
= luid
;
1436 /* Record all of the canonicalized MEMs of record_last_mem_set_info's insn.
1437 Note we store a pair of elements in the list, so they have to be
1438 taken off pairwise. */
1441 canon_list_insert (rtx dest ATTRIBUTE_UNUSED
, const_rtx x ATTRIBUTE_UNUSED
,
1444 rtx dest_addr
, insn
;
1448 while (GET_CODE (dest
) == SUBREG
1449 || GET_CODE (dest
) == ZERO_EXTRACT
1450 || GET_CODE (dest
) == STRICT_LOW_PART
)
1451 dest
= XEXP (dest
, 0);
1453 /* If DEST is not a MEM, then it will not conflict with a load. Note
1454 that function calls are assumed to clobber memory, but are handled
1460 dest_addr
= get_addr (XEXP (dest
, 0));
1461 dest_addr
= canon_rtx (dest_addr
);
1462 insn
= (rtx
) v_insn
;
1463 bb
= BLOCK_FOR_INSN (insn
)->index
;
1466 pair
.dest_addr
= dest_addr
;
1467 canon_modify_mem_list
[bb
].safe_push (pair
);
1470 /* Record memory modification information for INSN. We do not actually care
1471 about the memory location(s) that are set, or even how they are set (consider
1472 a CALL_INSN). We merely need to record which insns modify memory. */
1475 record_last_mem_set_info (rtx insn
)
1477 int bb
= BLOCK_FOR_INSN (insn
)->index
;
1479 /* load_killed_in_block_p will handle the case of calls clobbering
1481 modify_mem_list
[bb
].safe_push (insn
);
1482 bitmap_set_bit (modify_mem_list_set
, bb
);
1485 bitmap_set_bit (blocks_with_calls
, bb
);
1487 note_stores (PATTERN (insn
), canon_list_insert
, (void*) insn
);
1490 /* Called from compute_hash_table via note_stores to handle one
1491 SET or CLOBBER in an insn. DATA is really the instruction in which
1492 the SET is taking place. */
1495 record_last_set_info (rtx dest
, const_rtx setter ATTRIBUTE_UNUSED
, void *data
)
1497 rtx last_set_insn
= (rtx
) data
;
1499 if (GET_CODE (dest
) == SUBREG
)
1500 dest
= SUBREG_REG (dest
);
1503 record_last_reg_set_info (last_set_insn
, REGNO (dest
));
1504 else if (MEM_P (dest
)
1505 /* Ignore pushes, they clobber nothing. */
1506 && ! push_operand (dest
, GET_MODE (dest
)))
1507 record_last_mem_set_info (last_set_insn
);
1510 /* Top level function to create an expression hash table.
1512 Expression entries are placed in the hash table if
1513 - they are of the form (set (pseudo-reg) src),
1514 - src is something we want to perform GCSE on,
1515 - none of the operands are subsequently modified in the block
1517 Currently src must be a pseudo-reg or a const_int.
1519 TABLE is the table computed. */
1522 compute_hash_table_work (struct hash_table_d
*table
)
1526 /* re-Cache any INSN_LIST nodes we have allocated. */
1527 clear_modify_mem_tables ();
1528 /* Some working arrays used to track first and last set in each block. */
1529 reg_avail_info
= GNEWVEC (struct reg_avail_info
, max_reg_num ());
1531 for (i
= 0; i
< max_reg_num (); ++i
)
1532 reg_avail_info
[i
].last_bb
= NULL
;
1534 FOR_EACH_BB (current_bb
)
1539 /* First pass over the instructions records information used to
1540 determine when registers and memory are first and last set. */
1541 FOR_BB_INSNS (current_bb
, insn
)
1543 if (!NONDEBUG_INSN_P (insn
))
1548 hard_reg_set_iterator hrsi
;
1549 EXECUTE_IF_SET_IN_HARD_REG_SET (regs_invalidated_by_call
,
1551 record_last_reg_set_info (insn
, regno
);
1553 if (! RTL_CONST_OR_PURE_CALL_P (insn
))
1554 record_last_mem_set_info (insn
);
1557 note_stores (PATTERN (insn
), record_last_set_info
, insn
);
1560 /* The next pass builds the hash table. */
1561 FOR_BB_INSNS (current_bb
, insn
)
1562 if (NONDEBUG_INSN_P (insn
))
1563 hash_scan_insn (insn
, table
);
1566 free (reg_avail_info
);
1567 reg_avail_info
= NULL
;
1570 /* Allocate space for the set/expr hash TABLE.
1571 It is used to determine the number of buckets to use. */
1574 alloc_hash_table (struct hash_table_d
*table
)
1578 n
= get_max_insn_count ();
1580 table
->size
= n
/ 4;
1581 if (table
->size
< 11)
1584 /* Attempt to maintain efficient use of hash table.
1585 Making it an odd number is simplest for now.
1586 ??? Later take some measurements. */
1588 n
= table
->size
* sizeof (struct expr
*);
1589 table
->table
= GNEWVAR (struct expr
*, n
);
1592 /* Free things allocated by alloc_hash_table. */
1595 free_hash_table (struct hash_table_d
*table
)
1597 free (table
->table
);
1600 /* Compute the expression hash table TABLE. */
1603 compute_hash_table (struct hash_table_d
*table
)
1605 /* Initialize count of number of entries in hash table. */
1607 memset (table
->table
, 0, table
->size
* sizeof (struct expr
*));
1609 compute_hash_table_work (table
);
1612 /* Expression tracking support. */
1614 /* Clear canon_modify_mem_list and modify_mem_list tables. */
1616 clear_modify_mem_tables (void)
1621 EXECUTE_IF_SET_IN_BITMAP (modify_mem_list_set
, 0, i
, bi
)
1623 modify_mem_list
[i
].release ();
1624 canon_modify_mem_list
[i
].release ();
1626 bitmap_clear (modify_mem_list_set
);
1627 bitmap_clear (blocks_with_calls
);
1630 /* Release memory used by modify_mem_list_set. */
1633 free_modify_mem_tables (void)
1635 clear_modify_mem_tables ();
1636 free (modify_mem_list
);
1637 free (canon_modify_mem_list
);
1638 modify_mem_list
= 0;
1639 canon_modify_mem_list
= 0;
1642 /* For each block, compute whether X is transparent. X is either an
1643 expression or an assignment [though we don't care which, for this context
1644 an assignment is treated as an expression]. For each block where an
1645 element of X is modified, reset the INDX bit in BMAP. */
1648 compute_transp (const_rtx x
, int indx
, sbitmap
*bmap
)
1654 /* repeat is used to turn tail-recursion into iteration since GCC
1655 can't do it when there's no return value. */
1661 code
= GET_CODE (x
);
1667 for (def
= DF_REG_DEF_CHAIN (REGNO (x
));
1669 def
= DF_REF_NEXT_REG (def
))
1670 bitmap_clear_bit (bmap
[DF_REF_BB (def
)->index
], indx
);
1676 if (! MEM_READONLY_P (x
))
1682 x_addr
= get_addr (XEXP (x
, 0));
1683 x_addr
= canon_rtx (x_addr
);
1685 /* First handle all the blocks with calls. We don't need to
1686 do any list walking for them. */
1687 EXECUTE_IF_SET_IN_BITMAP (blocks_with_calls
, 0, bb_index
, bi
)
1689 bitmap_clear_bit (bmap
[bb_index
], indx
);
1692 /* Now iterate over the blocks which have memory modifications
1693 but which do not have any calls. */
1694 EXECUTE_IF_AND_COMPL_IN_BITMAP (modify_mem_list_set
,
1698 vec
<modify_pair
> list
1699 = canon_modify_mem_list
[bb_index
];
1703 FOR_EACH_VEC_ELT_REVERSE (list
, ix
, pair
)
1705 rtx dest
= pair
->dest
;
1706 rtx dest_addr
= pair
->dest_addr
;
1708 if (canon_true_dependence (dest
, GET_MODE (dest
),
1709 dest_addr
, x
, x_addr
))
1710 bitmap_clear_bit (bmap
[bb_index
], indx
);
1732 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
1736 /* If we are about to do the last recursive call
1737 needed at this level, change it into iteration.
1738 This function is called enough to be worth it. */
1745 compute_transp (XEXP (x
, i
), indx
, bmap
);
1747 else if (fmt
[i
] == 'E')
1748 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1749 compute_transp (XVECEXP (x
, i
, j
), indx
, bmap
);
1753 /* Compute PRE+LCM working variables. */
1755 /* Local properties of expressions. */
1757 /* Nonzero for expressions that are transparent in the block. */
1758 static sbitmap
*transp
;
1760 /* Nonzero for expressions that are computed (available) in the block. */
1761 static sbitmap
*comp
;
1763 /* Nonzero for expressions that are locally anticipatable in the block. */
1764 static sbitmap
*antloc
;
1766 /* Nonzero for expressions where this block is an optimal computation
1768 static sbitmap
*pre_optimal
;
1770 /* Nonzero for expressions which are redundant in a particular block. */
1771 static sbitmap
*pre_redundant
;
1773 /* Nonzero for expressions which should be inserted on a specific edge. */
1774 static sbitmap
*pre_insert_map
;
1776 /* Nonzero for expressions which should be deleted in a specific block. */
1777 static sbitmap
*pre_delete_map
;
1779 /* Allocate vars used for PRE analysis. */
1782 alloc_pre_mem (int n_blocks
, int n_exprs
)
1784 transp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
1785 comp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
1786 antloc
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
1789 pre_redundant
= NULL
;
1790 pre_insert_map
= NULL
;
1791 pre_delete_map
= NULL
;
1792 ae_kill
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
1794 /* pre_insert and pre_delete are allocated later. */
1797 /* Free vars used for PRE analysis. */
1802 sbitmap_vector_free (transp
);
1803 sbitmap_vector_free (comp
);
1805 /* ANTLOC and AE_KILL are freed just after pre_lcm finishes. */
1808 sbitmap_vector_free (pre_optimal
);
1810 sbitmap_vector_free (pre_redundant
);
1812 sbitmap_vector_free (pre_insert_map
);
1814 sbitmap_vector_free (pre_delete_map
);
1816 transp
= comp
= NULL
;
1817 pre_optimal
= pre_redundant
= pre_insert_map
= pre_delete_map
= NULL
;
1820 /* Remove certain expressions from anticipatable and transparent
1821 sets of basic blocks that have incoming abnormal edge.
1822 For PRE remove potentially trapping expressions to avoid placing
1823 them on abnormal edges. For hoisting remove memory references that
1824 can be clobbered by calls. */
1827 prune_expressions (bool pre_p
)
1829 sbitmap prune_exprs
;
1834 prune_exprs
= sbitmap_alloc (expr_hash_table
.n_elems
);
1835 bitmap_clear (prune_exprs
);
1836 for (ui
= 0; ui
< expr_hash_table
.size
; ui
++)
1838 for (expr
= expr_hash_table
.table
[ui
]; expr
; expr
= expr
->next_same_hash
)
1840 /* Note potentially trapping expressions. */
1841 if (may_trap_p (expr
->expr
))
1843 bitmap_set_bit (prune_exprs
, expr
->bitmap_index
);
1847 if (!pre_p
&& MEM_P (expr
->expr
))
1848 /* Note memory references that can be clobbered by a call.
1849 We do not split abnormal edges in hoisting, so would
1850 a memory reference get hoisted along an abnormal edge,
1851 it would be placed /before/ the call. Therefore, only
1852 constant memory references can be hoisted along abnormal
1855 if (GET_CODE (XEXP (expr
->expr
, 0)) == SYMBOL_REF
1856 && CONSTANT_POOL_ADDRESS_P (XEXP (expr
->expr
, 0)))
1859 if (MEM_READONLY_P (expr
->expr
)
1860 && !MEM_VOLATILE_P (expr
->expr
)
1861 && MEM_NOTRAP_P (expr
->expr
))
1862 /* Constant memory reference, e.g., a PIC address. */
1865 /* ??? Optimally, we would use interprocedural alias
1866 analysis to determine if this mem is actually killed
1869 bitmap_set_bit (prune_exprs
, expr
->bitmap_index
);
1879 /* If the current block is the destination of an abnormal edge, we
1880 kill all trapping (for PRE) and memory (for hoist) expressions
1881 because we won't be able to properly place the instruction on
1882 the edge. So make them neither anticipatable nor transparent.
1883 This is fairly conservative.
1885 ??? For hoisting it may be necessary to check for set-and-jump
1886 instructions here, not just for abnormal edges. The general problem
1887 is that when an expression cannot not be placed right at the end of
1888 a basic block we should account for any side-effects of a subsequent
1889 jump instructions that could clobber the expression. It would
1890 be best to implement this check along the lines of
1891 should_hoist_expr_to_dom where the target block is already known
1892 and, hence, there's no need to conservatively prune expressions on
1893 "intermediate" set-and-jump instructions. */
1894 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1895 if ((e
->flags
& EDGE_ABNORMAL
)
1896 && (pre_p
|| CALL_P (BB_END (e
->src
))))
1898 bitmap_and_compl (antloc
[bb
->index
],
1899 antloc
[bb
->index
], prune_exprs
);
1900 bitmap_and_compl (transp
[bb
->index
],
1901 transp
[bb
->index
], prune_exprs
);
1906 sbitmap_free (prune_exprs
);
1909 /* It may be necessary to insert a large number of insns on edges to
1910 make the existing occurrences of expressions fully redundant. This
1911 routine examines the set of insertions and deletions and if the ratio
1912 of insertions to deletions is too high for a particular expression, then
1913 the expression is removed from the insertion/deletion sets.
1915 N_ELEMS is the number of elements in the hash table. */
1918 prune_insertions_deletions (int n_elems
)
1920 sbitmap_iterator sbi
;
1921 sbitmap prune_exprs
;
1923 /* We always use I to iterate over blocks/edges and J to iterate over
1927 /* Counts for the number of times an expression needs to be inserted and
1928 number of times an expression can be removed as a result. */
1929 int *insertions
= GCNEWVEC (int, n_elems
);
1930 int *deletions
= GCNEWVEC (int, n_elems
);
1932 /* Set of expressions which require too many insertions relative to
1933 the number of deletions achieved. We will prune these out of the
1934 insertion/deletion sets. */
1935 prune_exprs
= sbitmap_alloc (n_elems
);
1936 bitmap_clear (prune_exprs
);
1938 /* Iterate over the edges counting the number of times each expression
1939 needs to be inserted. */
1940 for (i
= 0; i
< (unsigned) n_edges
; i
++)
1942 EXECUTE_IF_SET_IN_BITMAP (pre_insert_map
[i
], 0, j
, sbi
)
1946 /* Similarly for deletions, but those occur in blocks rather than on
1948 for (i
= 0; i
< (unsigned) last_basic_block
; i
++)
1950 EXECUTE_IF_SET_IN_BITMAP (pre_delete_map
[i
], 0, j
, sbi
)
1954 /* Now that we have accurate counts, iterate over the elements in the
1955 hash table and see if any need too many insertions relative to the
1956 number of evaluations that can be removed. If so, mark them in
1958 for (j
= 0; j
< (unsigned) n_elems
; j
++)
1960 && ((unsigned) insertions
[j
] / deletions
[j
]) > MAX_GCSE_INSERTION_RATIO
)
1961 bitmap_set_bit (prune_exprs
, j
);
1963 /* Now prune PRE_INSERT_MAP and PRE_DELETE_MAP based on PRUNE_EXPRS. */
1964 EXECUTE_IF_SET_IN_BITMAP (prune_exprs
, 0, j
, sbi
)
1966 for (i
= 0; i
< (unsigned) n_edges
; i
++)
1967 bitmap_clear_bit (pre_insert_map
[i
], j
);
1969 for (i
= 0; i
< (unsigned) last_basic_block
; i
++)
1970 bitmap_clear_bit (pre_delete_map
[i
], j
);
1973 sbitmap_free (prune_exprs
);
1978 /* Top level routine to do the dataflow analysis needed by PRE. */
1980 static struct edge_list
*
1981 compute_pre_data (void)
1983 struct edge_list
*edge_list
;
1986 compute_local_properties (transp
, comp
, antloc
, &expr_hash_table
);
1987 prune_expressions (true);
1988 bitmap_vector_clear (ae_kill
, last_basic_block
);
1990 /* Compute ae_kill for each basic block using:
1997 bitmap_ior (ae_kill
[bb
->index
], transp
[bb
->index
], comp
[bb
->index
]);
1998 bitmap_not (ae_kill
[bb
->index
], ae_kill
[bb
->index
]);
2001 edge_list
= pre_edge_lcm (expr_hash_table
.n_elems
, transp
, comp
, antloc
,
2002 ae_kill
, &pre_insert_map
, &pre_delete_map
);
2003 sbitmap_vector_free (antloc
);
2005 sbitmap_vector_free (ae_kill
);
2008 prune_insertions_deletions (expr_hash_table
.n_elems
);
2015 /* Return nonzero if an occurrence of expression EXPR in OCCR_BB would reach
2018 VISITED is a pointer to a working buffer for tracking which BB's have
2019 been visited. It is NULL for the top-level call.
2021 We treat reaching expressions that go through blocks containing the same
2022 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
2023 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
2024 2 as not reaching. The intent is to improve the probability of finding
2025 only one reaching expression and to reduce register lifetimes by picking
2026 the closest such expression. */
2029 pre_expr_reaches_here_p_work (basic_block occr_bb
, struct expr
*expr
,
2030 basic_block bb
, char *visited
)
2035 FOR_EACH_EDGE (pred
, ei
, bb
->preds
)
2037 basic_block pred_bb
= pred
->src
;
2039 if (pred
->src
== ENTRY_BLOCK_PTR
2040 /* Has predecessor has already been visited? */
2041 || visited
[pred_bb
->index
])
2042 ;/* Nothing to do. */
2044 /* Does this predecessor generate this expression? */
2045 else if (bitmap_bit_p (comp
[pred_bb
->index
], expr
->bitmap_index
))
2047 /* Is this the occurrence we're looking for?
2048 Note that there's only one generating occurrence per block
2049 so we just need to check the block number. */
2050 if (occr_bb
== pred_bb
)
2053 visited
[pred_bb
->index
] = 1;
2055 /* Ignore this predecessor if it kills the expression. */
2056 else if (! bitmap_bit_p (transp
[pred_bb
->index
], expr
->bitmap_index
))
2057 visited
[pred_bb
->index
] = 1;
2059 /* Neither gen nor kill. */
2062 visited
[pred_bb
->index
] = 1;
2063 if (pre_expr_reaches_here_p_work (occr_bb
, expr
, pred_bb
, visited
))
2068 /* All paths have been checked. */
2072 /* The wrapper for pre_expr_reaches_here_work that ensures that any
2073 memory allocated for that function is returned. */
2076 pre_expr_reaches_here_p (basic_block occr_bb
, struct expr
*expr
, basic_block bb
)
2079 char *visited
= XCNEWVEC (char, last_basic_block
);
2081 rval
= pre_expr_reaches_here_p_work (occr_bb
, expr
, bb
, visited
);
2087 /* Generate RTL to copy an EXPR to its `reaching_reg' and return it. */
2090 process_insert_insn (struct expr
*expr
)
2092 rtx reg
= expr
->reaching_reg
;
2093 /* Copy the expression to make sure we don't have any sharing issues. */
2094 rtx exp
= copy_rtx (expr
->expr
);
2099 /* If the expression is something that's an operand, like a constant,
2100 just copy it to a register. */
2101 if (general_operand (exp
, GET_MODE (reg
)))
2102 emit_move_insn (reg
, exp
);
2104 /* Otherwise, make a new insn to compute this expression and make sure the
2105 insn will be recognized (this also adds any needed CLOBBERs). */
2108 rtx insn
= emit_insn (gen_rtx_SET (VOIDmode
, reg
, exp
));
2110 if (insn_invalid_p (insn
, false))
2120 /* Add EXPR to the end of basic block BB.
2122 This is used by both the PRE and code hoisting. */
2125 insert_insn_end_basic_block (struct expr
*expr
, basic_block bb
)
2127 rtx insn
= BB_END (bb
);
2129 rtx reg
= expr
->reaching_reg
;
2130 int regno
= REGNO (reg
);
2133 pat
= process_insert_insn (expr
);
2134 gcc_assert (pat
&& INSN_P (pat
));
2137 while (NEXT_INSN (pat_end
) != NULL_RTX
)
2138 pat_end
= NEXT_INSN (pat_end
);
2140 /* If the last insn is a jump, insert EXPR in front [taking care to
2141 handle cc0, etc. properly]. Similarly we need to care trapping
2142 instructions in presence of non-call exceptions. */
2145 || (NONJUMP_INSN_P (insn
)
2146 && (!single_succ_p (bb
)
2147 || single_succ_edge (bb
)->flags
& EDGE_ABNORMAL
)))
2153 /* If this is a jump table, then we can't insert stuff here. Since
2154 we know the previous real insn must be the tablejump, we insert
2155 the new instruction just before the tablejump. */
2156 if (GET_CODE (PATTERN (insn
)) == ADDR_VEC
2157 || GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
)
2158 insn
= prev_active_insn (insn
);
2161 /* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
2162 if cc0 isn't set. */
2163 note
= find_reg_note (insn
, REG_CC_SETTER
, NULL_RTX
);
2165 insn
= XEXP (note
, 0);
2168 rtx maybe_cc0_setter
= prev_nonnote_insn (insn
);
2169 if (maybe_cc0_setter
2170 && INSN_P (maybe_cc0_setter
)
2171 && sets_cc0_p (PATTERN (maybe_cc0_setter
)))
2172 insn
= maybe_cc0_setter
;
2175 /* FIXME: What if something in cc0/jump uses value set in new insn? */
2176 new_insn
= emit_insn_before_noloc (pat
, insn
, bb
);
2179 /* Likewise if the last insn is a call, as will happen in the presence
2180 of exception handling. */
2181 else if (CALL_P (insn
)
2182 && (!single_succ_p (bb
)
2183 || single_succ_edge (bb
)->flags
& EDGE_ABNORMAL
))
2185 /* Keeping in mind targets with small register classes and parameters
2186 in registers, we search backward and place the instructions before
2187 the first parameter is loaded. Do this for everyone for consistency
2188 and a presumption that we'll get better code elsewhere as well. */
2190 /* Since different machines initialize their parameter registers
2191 in different orders, assume nothing. Collect the set of all
2192 parameter registers. */
2193 insn
= find_first_parameter_load (insn
, BB_HEAD (bb
));
2195 /* If we found all the parameter loads, then we want to insert
2196 before the first parameter load.
2198 If we did not find all the parameter loads, then we might have
2199 stopped on the head of the block, which could be a CODE_LABEL.
2200 If we inserted before the CODE_LABEL, then we would be putting
2201 the insn in the wrong basic block. In that case, put the insn
2202 after the CODE_LABEL. Also, respect NOTE_INSN_BASIC_BLOCK. */
2203 while (LABEL_P (insn
)
2204 || NOTE_INSN_BASIC_BLOCK_P (insn
))
2205 insn
= NEXT_INSN (insn
);
2207 new_insn
= emit_insn_before_noloc (pat
, insn
, bb
);
2210 new_insn
= emit_insn_after_noloc (pat
, insn
, bb
);
2215 add_label_notes (PATTERN (pat
), new_insn
);
2218 pat
= NEXT_INSN (pat
);
2221 gcse_create_count
++;
2225 fprintf (dump_file
, "PRE/HOIST: end of bb %d, insn %d, ",
2226 bb
->index
, INSN_UID (new_insn
));
2227 fprintf (dump_file
, "copying expression %d to reg %d\n",
2228 expr
->bitmap_index
, regno
);
2232 /* Insert partially redundant expressions on edges in the CFG to make
2233 the expressions fully redundant. */
2236 pre_edge_insert (struct edge_list
*edge_list
, struct expr
**index_map
)
2238 int e
, i
, j
, num_edges
, set_size
, did_insert
= 0;
2241 /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge
2242 if it reaches any of the deleted expressions. */
2244 set_size
= pre_insert_map
[0]->size
;
2245 num_edges
= NUM_EDGES (edge_list
);
2246 inserted
= sbitmap_vector_alloc (num_edges
, expr_hash_table
.n_elems
);
2247 bitmap_vector_clear (inserted
, num_edges
);
2249 for (e
= 0; e
< num_edges
; e
++)
2252 basic_block bb
= INDEX_EDGE_PRED_BB (edge_list
, e
);
2254 for (i
= indx
= 0; i
< set_size
; i
++, indx
+= SBITMAP_ELT_BITS
)
2256 SBITMAP_ELT_TYPE insert
= pre_insert_map
[e
]->elms
[i
];
2259 insert
&& j
< (int) expr_hash_table
.n_elems
;
2261 if ((insert
& 1) != 0 && index_map
[j
]->reaching_reg
!= NULL_RTX
)
2263 struct expr
*expr
= index_map
[j
];
2266 /* Now look at each deleted occurrence of this expression. */
2267 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
2269 if (! occr
->deleted_p
)
2272 /* Insert this expression on this edge if it would
2273 reach the deleted occurrence in BB. */
2274 if (!bitmap_bit_p (inserted
[e
], j
))
2277 edge eg
= INDEX_EDGE (edge_list
, e
);
2279 /* We can't insert anything on an abnormal and
2280 critical edge, so we insert the insn at the end of
2281 the previous block. There are several alternatives
2282 detailed in Morgans book P277 (sec 10.5) for
2283 handling this situation. This one is easiest for
2286 if (eg
->flags
& EDGE_ABNORMAL
)
2287 insert_insn_end_basic_block (index_map
[j
], bb
);
2290 insn
= process_insert_insn (index_map
[j
]);
2291 insert_insn_on_edge (insn
, eg
);
2296 fprintf (dump_file
, "PRE: edge (%d,%d), ",
2298 INDEX_EDGE_SUCC_BB (edge_list
, e
)->index
);
2299 fprintf (dump_file
, "copy expression %d\n",
2300 expr
->bitmap_index
);
2303 update_ld_motion_stores (expr
);
2304 bitmap_set_bit (inserted
[e
], j
);
2306 gcse_create_count
++;
2313 sbitmap_vector_free (inserted
);
2317 /* Copy the result of EXPR->EXPR generated by INSN to EXPR->REACHING_REG.
2318 Given "old_reg <- expr" (INSN), instead of adding after it
2319 reaching_reg <- old_reg
2320 it's better to do the following:
2321 reaching_reg <- expr
2322 old_reg <- reaching_reg
2323 because this way copy propagation can discover additional PRE
2324 opportunities. But if this fails, we try the old way.
2325 When "expr" is a store, i.e.
2326 given "MEM <- old_reg", instead of adding after it
2327 reaching_reg <- old_reg
2328 it's better to add it before as follows:
2329 reaching_reg <- old_reg
2330 MEM <- reaching_reg. */
2333 pre_insert_copy_insn (struct expr
*expr
, rtx insn
)
2335 rtx reg
= expr
->reaching_reg
;
2336 int regno
= REGNO (reg
);
2337 int indx
= expr
->bitmap_index
;
2338 rtx pat
= PATTERN (insn
);
2339 rtx set
, first_set
, new_insn
;
2343 /* This block matches the logic in hash_scan_insn. */
2344 switch (GET_CODE (pat
))
2351 /* Search through the parallel looking for the set whose
2352 source was the expression that we're interested in. */
2353 first_set
= NULL_RTX
;
2355 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
2357 rtx x
= XVECEXP (pat
, 0, i
);
2358 if (GET_CODE (x
) == SET
)
2360 /* If the source was a REG_EQUAL or REG_EQUIV note, we
2361 may not find an equivalent expression, but in this
2362 case the PARALLEL will have a single set. */
2363 if (first_set
== NULL_RTX
)
2365 if (expr_equiv_p (SET_SRC (x
), expr
->expr
))
2373 gcc_assert (first_set
);
2374 if (set
== NULL_RTX
)
2382 if (REG_P (SET_DEST (set
)))
2384 old_reg
= SET_DEST (set
);
2385 /* Check if we can modify the set destination in the original insn. */
2386 if (validate_change (insn
, &SET_DEST (set
), reg
, 0))
2388 new_insn
= gen_move_insn (old_reg
, reg
);
2389 new_insn
= emit_insn_after (new_insn
, insn
);
2393 new_insn
= gen_move_insn (reg
, old_reg
);
2394 new_insn
= emit_insn_after (new_insn
, insn
);
2397 else /* This is possible only in case of a store to memory. */
2399 old_reg
= SET_SRC (set
);
2400 new_insn
= gen_move_insn (reg
, old_reg
);
2402 /* Check if we can modify the set source in the original insn. */
2403 if (validate_change (insn
, &SET_SRC (set
), reg
, 0))
2404 new_insn
= emit_insn_before (new_insn
, insn
);
2406 new_insn
= emit_insn_after (new_insn
, insn
);
2409 gcse_create_count
++;
2413 "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
2414 BLOCK_FOR_INSN (insn
)->index
, INSN_UID (new_insn
), indx
,
2415 INSN_UID (insn
), regno
);
2418 /* Copy available expressions that reach the redundant expression
2419 to `reaching_reg'. */
2422 pre_insert_copies (void)
2424 unsigned int i
, added_copy
;
2429 /* For each available expression in the table, copy the result to
2430 `reaching_reg' if the expression reaches a deleted one.
2432 ??? The current algorithm is rather brute force.
2433 Need to do some profiling. */
2435 for (i
= 0; i
< expr_hash_table
.size
; i
++)
2436 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
2438 /* If the basic block isn't reachable, PPOUT will be TRUE. However,
2439 we don't want to insert a copy here because the expression may not
2440 really be redundant. So only insert an insn if the expression was
2441 deleted. This test also avoids further processing if the
2442 expression wasn't deleted anywhere. */
2443 if (expr
->reaching_reg
== NULL
)
2446 /* Set when we add a copy for that expression. */
2449 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
2451 if (! occr
->deleted_p
)
2454 for (avail
= expr
->avail_occr
; avail
!= NULL
; avail
= avail
->next
)
2456 rtx insn
= avail
->insn
;
2458 /* No need to handle this one if handled already. */
2459 if (avail
->copied_p
)
2462 /* Don't handle this one if it's a redundant one. */
2463 if (INSN_DELETED_P (insn
))
2466 /* Or if the expression doesn't reach the deleted one. */
2467 if (! pre_expr_reaches_here_p (BLOCK_FOR_INSN (avail
->insn
),
2469 BLOCK_FOR_INSN (occr
->insn
)))
2474 /* Copy the result of avail to reaching_reg. */
2475 pre_insert_copy_insn (expr
, insn
);
2476 avail
->copied_p
= 1;
2481 update_ld_motion_stores (expr
);
2485 /* Emit move from SRC to DEST noting the equivalence with expression computed
2489 gcse_emit_move_after (rtx dest
, rtx src
, rtx insn
)
2492 rtx set
= single_set (insn
), set2
;
2496 /* This should never fail since we're creating a reg->reg copy
2497 we've verified to be valid. */
2499 new_rtx
= emit_insn_after (gen_move_insn (dest
, src
), insn
);
2501 /* Note the equivalence for local CSE pass. */
2502 set2
= single_set (new_rtx
);
2503 if (!set2
|| !rtx_equal_p (SET_DEST (set2
), dest
))
2505 if ((note
= find_reg_equal_equiv_note (insn
)))
2506 eqv
= XEXP (note
, 0);
2508 eqv
= SET_SRC (set
);
2510 set_unique_reg_note (new_rtx
, REG_EQUAL
, copy_insn_1 (eqv
));
2515 /* Delete redundant computations.
2516 Deletion is done by changing the insn to copy the `reaching_reg' of
2517 the expression into the result of the SET. It is left to later passes
2518 (cprop, cse2, flow, combine, regmove) to propagate the copy or eliminate it.
2520 Return nonzero if a change is made. */
2531 for (i
= 0; i
< expr_hash_table
.size
; i
++)
2532 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
2534 int indx
= expr
->bitmap_index
;
2536 /* We only need to search antic_occr since we require ANTLOC != 0. */
2537 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
2539 rtx insn
= occr
->insn
;
2541 basic_block bb
= BLOCK_FOR_INSN (insn
);
2543 /* We only delete insns that have a single_set. */
2544 if (bitmap_bit_p (pre_delete_map
[bb
->index
], indx
)
2545 && (set
= single_set (insn
)) != 0
2546 && dbg_cnt (pre_insn
))
2548 /* Create a pseudo-reg to store the result of reaching
2549 expressions into. Get the mode for the new pseudo from
2550 the mode of the original destination pseudo. */
2551 if (expr
->reaching_reg
== NULL
)
2552 expr
->reaching_reg
= gen_reg_rtx_and_attrs (SET_DEST (set
));
2554 gcse_emit_move_after (SET_DEST (set
), expr
->reaching_reg
, insn
);
2556 occr
->deleted_p
= 1;
2563 "PRE: redundant insn %d (expression %d) in ",
2564 INSN_UID (insn
), indx
);
2565 fprintf (dump_file
, "bb %d, reaching reg is %d\n",
2566 bb
->index
, REGNO (expr
->reaching_reg
));
2575 /* Perform GCSE optimizations using PRE.
2576 This is called by one_pre_gcse_pass after all the dataflow analysis
2579 This is based on the original Morel-Renvoise paper Fred Chow's thesis, and
2580 lazy code motion from Knoop, Ruthing and Steffen as described in Advanced
2581 Compiler Design and Implementation.
2583 ??? A new pseudo reg is created to hold the reaching expression. The nice
2584 thing about the classical approach is that it would try to use an existing
2585 reg. If the register can't be adequately optimized [i.e. we introduce
2586 reload problems], one could add a pass here to propagate the new register
2589 ??? We don't handle single sets in PARALLELs because we're [currently] not
2590 able to copy the rest of the parallel when we insert copies to create full
2591 redundancies from partial redundancies. However, there's no reason why we
2592 can't handle PARALLELs in the cases where there are no partial
2596 pre_gcse (struct edge_list
*edge_list
)
2599 int did_insert
, changed
;
2600 struct expr
**index_map
;
2603 /* Compute a mapping from expression number (`bitmap_index') to
2604 hash table entry. */
2606 index_map
= XCNEWVEC (struct expr
*, expr_hash_table
.n_elems
);
2607 for (i
= 0; i
< expr_hash_table
.size
; i
++)
2608 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
2609 index_map
[expr
->bitmap_index
] = expr
;
2611 /* Delete the redundant insns first so that
2612 - we know what register to use for the new insns and for the other
2613 ones with reaching expressions
2614 - we know which insns are redundant when we go to create copies */
2616 changed
= pre_delete ();
2617 did_insert
= pre_edge_insert (edge_list
, index_map
);
2619 /* In other places with reaching expressions, copy the expression to the
2620 specially allocated pseudo-reg that reaches the redundant expr. */
2621 pre_insert_copies ();
2624 commit_edge_insertions ();
2632 /* Top level routine to perform one PRE GCSE pass.
2634 Return nonzero if a change was made. */
2637 one_pre_gcse_pass (void)
2641 gcse_subst_count
= 0;
2642 gcse_create_count
= 0;
2644 /* Return if there's nothing to do, or it is too expensive. */
2645 if (n_basic_blocks
<= NUM_FIXED_BLOCKS
+ 1
2646 || is_too_expensive (_("PRE disabled")))
2649 /* We need alias. */
2650 init_alias_analysis ();
2653 gcc_obstack_init (&gcse_obstack
);
2656 alloc_hash_table (&expr_hash_table
);
2657 add_noreturn_fake_exit_edges ();
2659 compute_ld_motion_mems ();
2661 compute_hash_table (&expr_hash_table
);
2663 trim_ld_motion_mems ();
2665 dump_hash_table (dump_file
, "Expression", &expr_hash_table
);
2667 if (expr_hash_table
.n_elems
> 0)
2669 struct edge_list
*edge_list
;
2670 alloc_pre_mem (last_basic_block
, expr_hash_table
.n_elems
);
2671 edge_list
= compute_pre_data ();
2672 changed
|= pre_gcse (edge_list
);
2673 free_edge_list (edge_list
);
2678 free_ld_motion_mems ();
2679 remove_fake_exit_edges ();
2680 free_hash_table (&expr_hash_table
);
2683 obstack_free (&gcse_obstack
, NULL
);
2685 /* We are finished with alias. */
2686 end_alias_analysis ();
2690 fprintf (dump_file
, "PRE GCSE of %s, %d basic blocks, %d bytes needed, ",
2691 current_function_name (), n_basic_blocks
, bytes_used
);
2692 fprintf (dump_file
, "%d substs, %d insns created\n",
2693 gcse_subst_count
, gcse_create_count
);
2699 /* If X contains any LABEL_REF's, add REG_LABEL_OPERAND notes for them
2700 to INSN. If such notes are added to an insn which references a
2701 CODE_LABEL, the LABEL_NUSES count is incremented. We have to add
2702 that note, because the following loop optimization pass requires
2705 /* ??? If there was a jump optimization pass after gcse and before loop,
2706 then we would not need to do this here, because jump would add the
2707 necessary REG_LABEL_OPERAND and REG_LABEL_TARGET notes. */
2710 add_label_notes (rtx x
, rtx insn
)
2712 enum rtx_code code
= GET_CODE (x
);
2716 if (code
== LABEL_REF
&& !LABEL_REF_NONLOCAL_P (x
))
2718 /* This code used to ignore labels that referred to dispatch tables to
2719 avoid flow generating (slightly) worse code.
2721 We no longer ignore such label references (see LABEL_REF handling in
2722 mark_jump_label for additional information). */
2724 /* There's no reason for current users to emit jump-insns with
2725 such a LABEL_REF, so we don't have to handle REG_LABEL_TARGET
2727 gcc_assert (!JUMP_P (insn
));
2728 add_reg_note (insn
, REG_LABEL_OPERAND
, XEXP (x
, 0));
2730 if (LABEL_P (XEXP (x
, 0)))
2731 LABEL_NUSES (XEXP (x
, 0))++;
2736 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
2739 add_label_notes (XEXP (x
, i
), insn
);
2740 else if (fmt
[i
] == 'E')
2741 for (j
= XVECLEN (x
, i
) - 1; j
>= 0; j
--)
2742 add_label_notes (XVECEXP (x
, i
, j
), insn
);
2746 /* Code Hoisting variables and subroutines. */
2748 /* Very busy expressions. */
2749 static sbitmap
*hoist_vbein
;
2750 static sbitmap
*hoist_vbeout
;
2752 /* ??? We could compute post dominators and run this algorithm in
2753 reverse to perform tail merging, doing so would probably be
2754 more effective than the tail merging code in jump.c.
2756 It's unclear if tail merging could be run in parallel with
2757 code hoisting. It would be nice. */
2759 /* Allocate vars used for code hoisting analysis. */
2762 alloc_code_hoist_mem (int n_blocks
, int n_exprs
)
2764 antloc
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2765 transp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2766 comp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2768 hoist_vbein
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2769 hoist_vbeout
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2772 /* Free vars used for code hoisting analysis. */
2775 free_code_hoist_mem (void)
2777 sbitmap_vector_free (antloc
);
2778 sbitmap_vector_free (transp
);
2779 sbitmap_vector_free (comp
);
2781 sbitmap_vector_free (hoist_vbein
);
2782 sbitmap_vector_free (hoist_vbeout
);
2784 free_dominance_info (CDI_DOMINATORS
);
2787 /* Compute the very busy expressions at entry/exit from each block.
2789 An expression is very busy if all paths from a given point
2790 compute the expression. */
2793 compute_code_hoist_vbeinout (void)
2795 int changed
, passes
;
2798 bitmap_vector_clear (hoist_vbeout
, last_basic_block
);
2799 bitmap_vector_clear (hoist_vbein
, last_basic_block
);
2808 /* We scan the blocks in the reverse order to speed up
2810 FOR_EACH_BB_REVERSE (bb
)
2812 if (bb
->next_bb
!= EXIT_BLOCK_PTR
)
2814 bitmap_intersection_of_succs (hoist_vbeout
[bb
->index
],
2817 /* Include expressions in VBEout that are calculated
2818 in BB and available at its end. */
2819 bitmap_ior (hoist_vbeout
[bb
->index
],
2820 hoist_vbeout
[bb
->index
], comp
[bb
->index
]);
2823 changed
|= bitmap_or_and (hoist_vbein
[bb
->index
],
2825 hoist_vbeout
[bb
->index
],
2834 fprintf (dump_file
, "hoisting vbeinout computation: %d passes\n", passes
);
2838 fprintf (dump_file
, "vbein (%d): ", bb
->index
);
2839 dump_bitmap_file (dump_file
, hoist_vbein
[bb
->index
]);
2840 fprintf (dump_file
, "vbeout(%d): ", bb
->index
);
2841 dump_bitmap_file (dump_file
, hoist_vbeout
[bb
->index
]);
2846 /* Top level routine to do the dataflow analysis needed by code hoisting. */
2849 compute_code_hoist_data (void)
2851 compute_local_properties (transp
, comp
, antloc
, &expr_hash_table
);
2852 prune_expressions (false);
2853 compute_code_hoist_vbeinout ();
2854 calculate_dominance_info (CDI_DOMINATORS
);
2856 fprintf (dump_file
, "\n");
2859 /* Update register pressure for BB when hoisting an expression from
2860 instruction FROM, if live ranges of inputs are shrunk. Also
2861 maintain live_in information if live range of register referred
2864 Return 0 if register pressure doesn't change, otherwise return
2865 the number by which register pressure is decreased.
2867 NOTE: Register pressure won't be increased in this function. */
2870 update_bb_reg_pressure (basic_block bb
, rtx from
)
2873 basic_block succ_bb
;
2877 int decreased_pressure
= 0;
2879 enum reg_class pressure_class
;
2881 for (op
= DF_INSN_USES (from
); *op
; op
++)
2883 dreg
= DF_REF_REAL_REG (*op
);
2884 /* The live range of register is shrunk only if it isn't:
2885 1. referred on any path from the end of this block to EXIT, or
2886 2. referred by insns other than FROM in this block. */
2887 FOR_EACH_EDGE (succ
, ei
, bb
->succs
)
2889 succ_bb
= succ
->dest
;
2890 if (succ_bb
== EXIT_BLOCK_PTR
)
2893 if (bitmap_bit_p (BB_DATA (succ_bb
)->live_in
, REGNO (dreg
)))
2899 op_ref
= DF_REG_USE_CHAIN (REGNO (dreg
));
2900 for (; op_ref
; op_ref
= DF_REF_NEXT_REG (op_ref
))
2902 if (!DF_REF_INSN_INFO (op_ref
))
2905 insn
= DF_REF_INSN (op_ref
);
2906 if (BLOCK_FOR_INSN (insn
) == bb
2907 && NONDEBUG_INSN_P (insn
) && insn
!= from
)
2911 pressure_class
= get_regno_pressure_class (REGNO (dreg
), &nregs
);
2912 /* Decrease register pressure and update live_in information for
2914 if (!op_ref
&& pressure_class
!= NO_REGS
)
2916 decreased_pressure
+= nregs
;
2917 BB_DATA (bb
)->max_reg_pressure
[pressure_class
] -= nregs
;
2918 bitmap_clear_bit (BB_DATA (bb
)->live_in
, REGNO (dreg
));
2921 return decreased_pressure
;
2924 /* Determine if the expression EXPR should be hoisted to EXPR_BB up in
2925 flow graph, if it can reach BB unimpared. Stop the search if the
2926 expression would need to be moved more than DISTANCE instructions.
2928 DISTANCE is the number of instructions through which EXPR can be
2929 hoisted up in flow graph.
2931 BB_SIZE points to an array which contains the number of instructions
2932 for each basic block.
2934 PRESSURE_CLASS and NREGS are register class and number of hard registers
2937 HOISTED_BBS points to a bitmap indicating basic blocks through which
2940 FROM is the instruction from which EXPR is hoisted.
2942 It's unclear exactly what Muchnick meant by "unimpared". It seems
2943 to me that the expression must either be computed or transparent in
2944 *every* block in the path(s) from EXPR_BB to BB. Any other definition
2945 would allow the expression to be hoisted out of loops, even if
2946 the expression wasn't a loop invariant.
2948 Contrast this to reachability for PRE where an expression is
2949 considered reachable if *any* path reaches instead of *all*
2953 should_hoist_expr_to_dom (basic_block expr_bb
, struct expr
*expr
,
2954 basic_block bb
, sbitmap visited
, int distance
,
2955 int *bb_size
, enum reg_class pressure_class
,
2956 int *nregs
, bitmap hoisted_bbs
, rtx from
)
2961 sbitmap_iterator sbi
;
2962 int visited_allocated_locally
= 0;
2963 int decreased_pressure
= 0;
2965 if (flag_ira_hoist_pressure
)
2967 /* Record old information of basic block BB when it is visited
2968 at the first time. */
2969 if (!bitmap_bit_p (hoisted_bbs
, bb
->index
))
2971 struct bb_data
*data
= BB_DATA (bb
);
2972 bitmap_copy (data
->backup
, data
->live_in
);
2973 data
->old_pressure
= data
->max_reg_pressure
[pressure_class
];
2975 decreased_pressure
= update_bb_reg_pressure (bb
, from
);
2977 /* Terminate the search if distance, for which EXPR is allowed to move,
2981 if (flag_ira_hoist_pressure
)
2983 /* Prefer to hoist EXPR if register pressure is decreased. */
2984 if (decreased_pressure
> *nregs
)
2985 distance
+= bb_size
[bb
->index
];
2986 /* Let EXPR be hoisted through basic block at no cost if one
2987 of following conditions is satisfied:
2989 1. The basic block has low register pressure.
2990 2. Register pressure won't be increases after hoisting EXPR.
2992 Constant expressions is handled conservatively, because
2993 hoisting constant expression aggressively results in worse
2994 code. This decision is made by the observation of CSiBE
2995 on ARM target, while it has no obvious effect on other
2996 targets like x86, x86_64, mips and powerpc. */
2997 else if (CONST_INT_P (expr
->expr
)
2998 || (BB_DATA (bb
)->max_reg_pressure
[pressure_class
]
2999 >= ira_class_hard_regs_num
[pressure_class
]
3000 && decreased_pressure
< *nregs
))
3001 distance
-= bb_size
[bb
->index
];
3004 distance
-= bb_size
[bb
->index
];
3010 gcc_assert (distance
== 0);
3012 if (visited
== NULL
)
3014 visited_allocated_locally
= 1;
3015 visited
= sbitmap_alloc (last_basic_block
);
3016 bitmap_clear (visited
);
3019 FOR_EACH_EDGE (pred
, ei
, bb
->preds
)
3021 basic_block pred_bb
= pred
->src
;
3023 if (pred
->src
== ENTRY_BLOCK_PTR
)
3025 else if (pred_bb
== expr_bb
)
3027 else if (bitmap_bit_p (visited
, pred_bb
->index
))
3029 else if (! bitmap_bit_p (transp
[pred_bb
->index
], expr
->bitmap_index
))
3034 bitmap_set_bit (visited
, pred_bb
->index
);
3035 if (! should_hoist_expr_to_dom (expr_bb
, expr
, pred_bb
,
3036 visited
, distance
, bb_size
,
3037 pressure_class
, nregs
,
3042 if (visited_allocated_locally
)
3044 /* If EXPR can be hoisted to expr_bb, record basic blocks through
3045 which EXPR is hoisted in hoisted_bbs. */
3046 if (flag_ira_hoist_pressure
&& !pred
)
3048 /* Record the basic block from which EXPR is hoisted. */
3049 bitmap_set_bit (visited
, bb
->index
);
3050 EXECUTE_IF_SET_IN_BITMAP (visited
, 0, i
, sbi
)
3051 bitmap_set_bit (hoisted_bbs
, i
);
3053 sbitmap_free (visited
);
3056 return (pred
== NULL
);
3059 /* Find occurrence in BB. */
3061 static struct occr
*
3062 find_occr_in_bb (struct occr
*occr
, basic_block bb
)
3064 /* Find the right occurrence of this expression. */
3065 while (occr
&& BLOCK_FOR_INSN (occr
->insn
) != bb
)
3071 /* Actually perform code hoisting.
3073 The code hoisting pass can hoist multiple computations of the same
3074 expression along dominated path to a dominating basic block, like
3075 from b2/b3 to b1 as depicted below:
3085 Unfortunately code hoisting generally extends the live range of an
3086 output pseudo register, which increases register pressure and hurts
3087 register allocation. To address this issue, an attribute MAX_DISTANCE
3088 is computed and attached to each expression. The attribute is computed
3089 from rtx cost of the corresponding expression and it's used to control
3090 how long the expression can be hoisted up in flow graph. As the
3091 expression is hoisted up in flow graph, GCC decreases its DISTANCE
3092 and stops the hoist if DISTANCE reaches 0. Code hoisting can decrease
3093 register pressure if live ranges of inputs are shrunk.
3095 Option "-fira-hoist-pressure" implements register pressure directed
3096 hoist based on upper method. The rationale is:
3097 1. Calculate register pressure for each basic block by reusing IRA
3099 2. When expression is hoisted through one basic block, GCC checks
3100 the change of live ranges for inputs/output. The basic block's
3101 register pressure will be increased because of extended live
3102 range of output. However, register pressure will be decreased
3103 if the live ranges of inputs are shrunk.
3104 3. After knowing how hoisting affects register pressure, GCC prefers
3105 to hoist the expression if it can decrease register pressure, by
3106 increasing DISTANCE of the corresponding expression.
3107 4. If hoisting the expression increases register pressure, GCC checks
3108 register pressure of the basic block and decrease DISTANCE only if
3109 the register pressure is high. In other words, expression will be
3110 hoisted through at no cost if the basic block has low register
3112 5. Update register pressure information for basic blocks through
3113 which expression is hoisted. */
3118 basic_block bb
, dominated
;
3119 vec
<basic_block
> dom_tree_walk
;
3120 unsigned int dom_tree_walk_index
;
3121 vec
<basic_block
> domby
;
3122 unsigned int i
, j
, k
;
3123 struct expr
**index_map
;
3128 struct bb_data
*data
;
3129 /* Basic blocks that have occurrences reachable from BB. */
3131 /* Basic blocks through which expr is hoisted. */
3132 bitmap hoisted_bbs
= NULL
;
3135 /* Compute a mapping from expression number (`bitmap_index') to
3136 hash table entry. */
3138 index_map
= XCNEWVEC (struct expr
*, expr_hash_table
.n_elems
);
3139 for (i
= 0; i
< expr_hash_table
.size
; i
++)
3140 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
3141 index_map
[expr
->bitmap_index
] = expr
;
3143 /* Calculate sizes of basic blocks and note how far
3144 each instruction is from the start of its block. We then use this
3145 data to restrict distance an expression can travel. */
3147 to_bb_head
= XCNEWVEC (int, get_max_uid ());
3148 bb_size
= XCNEWVEC (int, last_basic_block
);
3156 FOR_BB_INSNS (bb
, insn
)
3158 /* Don't count debug instructions to avoid them affecting
3159 decision choices. */
3160 if (NONDEBUG_INSN_P (insn
))
3161 to_bb_head
[INSN_UID (insn
)] = to_head
++;
3164 bb_size
[bb
->index
] = to_head
;
3167 gcc_assert (EDGE_COUNT (ENTRY_BLOCK_PTR
->succs
) == 1
3168 && (EDGE_SUCC (ENTRY_BLOCK_PTR
, 0)->dest
3169 == ENTRY_BLOCK_PTR
->next_bb
));
3171 from_bbs
= BITMAP_ALLOC (NULL
);
3172 if (flag_ira_hoist_pressure
)
3173 hoisted_bbs
= BITMAP_ALLOC (NULL
);
3175 dom_tree_walk
= get_all_dominated_blocks (CDI_DOMINATORS
,
3176 ENTRY_BLOCK_PTR
->next_bb
);
3178 /* Walk over each basic block looking for potentially hoistable
3179 expressions, nothing gets hoisted from the entry block. */
3180 FOR_EACH_VEC_ELT (dom_tree_walk
, dom_tree_walk_index
, bb
)
3182 domby
= get_dominated_to_depth (CDI_DOMINATORS
, bb
, MAX_HOIST_DEPTH
);
3184 if (domby
.length () == 0)
3187 /* Examine each expression that is very busy at the exit of this
3188 block. These are the potentially hoistable expressions. */
3189 for (i
= 0; i
< SBITMAP_SIZE (hoist_vbeout
[bb
->index
]); i
++)
3191 if (bitmap_bit_p (hoist_vbeout
[bb
->index
], i
))
3194 enum reg_class pressure_class
= NO_REGS
;
3195 /* Current expression. */
3196 struct expr
*expr
= index_map
[i
];
3197 /* Number of occurrences of EXPR that can be hoisted to BB. */
3199 /* Occurrences reachable from BB. */
3200 vec
<occr_t
> occrs_to_hoist
= vNULL
;
3201 /* We want to insert the expression into BB only once, so
3202 note when we've inserted it. */
3203 int insn_inserted_p
;
3206 /* If an expression is computed in BB and is available at end of
3207 BB, hoist all occurrences dominated by BB to BB. */
3208 if (bitmap_bit_p (comp
[bb
->index
], i
))
3210 occr
= find_occr_in_bb (expr
->antic_occr
, bb
);
3214 /* An occurrence might've been already deleted
3215 while processing a dominator of BB. */
3216 if (!occr
->deleted_p
)
3218 gcc_assert (NONDEBUG_INSN_P (occr
->insn
));
3226 /* We've found a potentially hoistable expression, now
3227 we look at every block BB dominates to see if it
3228 computes the expression. */
3229 FOR_EACH_VEC_ELT (domby
, j
, dominated
)
3233 /* Ignore self dominance. */
3234 if (bb
== dominated
)
3236 /* We've found a dominated block, now see if it computes
3237 the busy expression and whether or not moving that
3238 expression to the "beginning" of that block is safe. */
3239 if (!bitmap_bit_p (antloc
[dominated
->index
], i
))
3242 occr
= find_occr_in_bb (expr
->antic_occr
, dominated
);
3245 /* An occurrence might've been already deleted
3246 while processing a dominator of BB. */
3247 if (occr
->deleted_p
)
3249 gcc_assert (NONDEBUG_INSN_P (occr
->insn
));
3251 max_distance
= expr
->max_distance
;
3252 if (max_distance
> 0)
3253 /* Adjust MAX_DISTANCE to account for the fact that
3254 OCCR won't have to travel all of DOMINATED, but
3256 max_distance
+= (bb_size
[dominated
->index
]
3257 - to_bb_head
[INSN_UID (occr
->insn
)]);
3259 pressure_class
= get_pressure_class_and_nregs (occr
->insn
,
3262 /* Note if the expression should be hoisted from the dominated
3263 block to BB if it can reach DOMINATED unimpared.
3265 Keep track of how many times this expression is hoistable
3266 from a dominated block into BB. */
3267 if (should_hoist_expr_to_dom (bb
, expr
, dominated
, NULL
,
3268 max_distance
, bb_size
,
3269 pressure_class
, &nregs
,
3270 hoisted_bbs
, occr
->insn
))
3273 occrs_to_hoist
.safe_push (occr
);
3274 bitmap_set_bit (from_bbs
, dominated
->index
);
3278 /* If we found more than one hoistable occurrence of this
3279 expression, then note it in the vector of expressions to
3280 hoist. It makes no sense to hoist things which are computed
3281 in only one BB, and doing so tends to pessimize register
3282 allocation. One could increase this value to try harder
3283 to avoid any possible code expansion due to register
3284 allocation issues; however experiments have shown that
3285 the vast majority of hoistable expressions are only movable
3286 from two successors, so raising this threshold is likely
3287 to nullify any benefit we get from code hoisting. */
3288 if (hoistable
> 1 && dbg_cnt (hoist_insn
))
3290 /* If (hoistable != vec::length), then there is
3291 an occurrence of EXPR in BB itself. Don't waste
3292 time looking for LCA in this case. */
3293 if ((unsigned) hoistable
== occrs_to_hoist
.length ())
3297 lca
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3300 /* Punt, it's better to hoist these occurrences to
3302 occrs_to_hoist
.release ();
3306 /* Punt, no point hoisting a single occurence. */
3307 occrs_to_hoist
.release ();
3309 if (flag_ira_hoist_pressure
3310 && !occrs_to_hoist
.is_empty ())
3312 /* Increase register pressure of basic blocks to which
3313 expr is hoisted because of extended live range of
3315 data
= BB_DATA (bb
);
3316 data
->max_reg_pressure
[pressure_class
] += nregs
;
3317 EXECUTE_IF_SET_IN_BITMAP (hoisted_bbs
, 0, k
, bi
)
3319 data
= BB_DATA (BASIC_BLOCK (k
));
3320 data
->max_reg_pressure
[pressure_class
] += nregs
;
3323 else if (flag_ira_hoist_pressure
)
3325 /* Restore register pressure and live_in info for basic
3326 blocks recorded in hoisted_bbs when expr will not be
3328 EXECUTE_IF_SET_IN_BITMAP (hoisted_bbs
, 0, k
, bi
)
3330 data
= BB_DATA (BASIC_BLOCK (k
));
3331 bitmap_copy (data
->live_in
, data
->backup
);
3332 data
->max_reg_pressure
[pressure_class
]
3333 = data
->old_pressure
;
3337 if (flag_ira_hoist_pressure
)
3338 bitmap_clear (hoisted_bbs
);
3340 insn_inserted_p
= 0;
3342 /* Walk through occurrences of I'th expressions we want
3343 to hoist to BB and make the transformations. */
3344 FOR_EACH_VEC_ELT (occrs_to_hoist
, j
, occr
)
3349 gcc_assert (!occr
->deleted_p
);
3352 set
= single_set (insn
);
3355 /* Create a pseudo-reg to store the result of reaching
3356 expressions into. Get the mode for the new pseudo
3357 from the mode of the original destination pseudo.
3359 It is important to use new pseudos whenever we
3360 emit a set. This will allow reload to use
3361 rematerialization for such registers. */
3362 if (!insn_inserted_p
)
3364 = gen_reg_rtx_and_attrs (SET_DEST (set
));
3366 gcse_emit_move_after (SET_DEST (set
), expr
->reaching_reg
,
3369 occr
->deleted_p
= 1;
3373 if (!insn_inserted_p
)
3375 insert_insn_end_basic_block (expr
, bb
);
3376 insn_inserted_p
= 1;
3380 occrs_to_hoist
.release ();
3381 bitmap_clear (from_bbs
);
3387 dom_tree_walk
.release ();
3388 BITMAP_FREE (from_bbs
);
3389 if (flag_ira_hoist_pressure
)
3390 BITMAP_FREE (hoisted_bbs
);
3399 /* Return pressure class and number of needed hard registers (through
3400 *NREGS) of register REGNO. */
3401 static enum reg_class
3402 get_regno_pressure_class (int regno
, int *nregs
)
3404 if (regno
>= FIRST_PSEUDO_REGISTER
)
3406 enum reg_class pressure_class
;
3408 pressure_class
= reg_allocno_class (regno
);
3409 pressure_class
= ira_pressure_class_translate
[pressure_class
];
3411 = ira_reg_class_max_nregs
[pressure_class
][PSEUDO_REGNO_MODE (regno
)];
3412 return pressure_class
;
3414 else if (! TEST_HARD_REG_BIT (ira_no_alloc_regs
, regno
)
3415 && ! TEST_HARD_REG_BIT (eliminable_regset
, regno
))
3418 return ira_pressure_class_translate
[REGNO_REG_CLASS (regno
)];
3427 /* Return pressure class and number of hard registers (through *NREGS)
3428 for destination of INSN. */
3429 static enum reg_class
3430 get_pressure_class_and_nregs (rtx insn
, int *nregs
)
3433 enum reg_class pressure_class
;
3434 rtx set
= single_set (insn
);
3436 /* Considered invariant insns have only one set. */
3437 gcc_assert (set
!= NULL_RTX
);
3438 reg
= SET_DEST (set
);
3439 if (GET_CODE (reg
) == SUBREG
)
3440 reg
= SUBREG_REG (reg
);
3444 pressure_class
= NO_REGS
;
3448 gcc_assert (REG_P (reg
));
3449 pressure_class
= reg_allocno_class (REGNO (reg
));
3450 pressure_class
= ira_pressure_class_translate
[pressure_class
];
3452 = ira_reg_class_max_nregs
[pressure_class
][GET_MODE (SET_SRC (set
))];
3454 return pressure_class
;
3457 /* Increase (if INCR_P) or decrease current register pressure for
3460 change_pressure (int regno
, bool incr_p
)
3463 enum reg_class pressure_class
;
3465 pressure_class
= get_regno_pressure_class (regno
, &nregs
);
3467 curr_reg_pressure
[pressure_class
] -= nregs
;
3470 curr_reg_pressure
[pressure_class
] += nregs
;
3471 if (BB_DATA (curr_bb
)->max_reg_pressure
[pressure_class
]
3472 < curr_reg_pressure
[pressure_class
])
3473 BB_DATA (curr_bb
)->max_reg_pressure
[pressure_class
]
3474 = curr_reg_pressure
[pressure_class
];
3478 /* Calculate register pressure for each basic block by walking insns
3479 from last to first. */
3481 calculate_bb_reg_pressure (void)
3487 bitmap curr_regs_live
;
3491 ira_setup_eliminable_regset (false);
3492 curr_regs_live
= BITMAP_ALLOC (®_obstack
);
3496 BB_DATA (bb
)->live_in
= BITMAP_ALLOC (NULL
);
3497 BB_DATA (bb
)->backup
= BITMAP_ALLOC (NULL
);
3498 bitmap_copy (BB_DATA (bb
)->live_in
, df_get_live_in (bb
));
3499 bitmap_copy (curr_regs_live
, df_get_live_out (bb
));
3500 for (i
= 0; i
< ira_pressure_classes_num
; i
++)
3501 curr_reg_pressure
[ira_pressure_classes
[i
]] = 0;
3502 EXECUTE_IF_SET_IN_BITMAP (curr_regs_live
, 0, j
, bi
)
3503 change_pressure (j
, true);
3505 FOR_BB_INSNS_REVERSE (bb
, insn
)
3509 df_ref
*def_rec
, *use_rec
;
3511 if (! NONDEBUG_INSN_P (insn
))
3514 for (def_rec
= DF_INSN_DEFS (insn
); *def_rec
; def_rec
++)
3516 dreg
= DF_REF_REAL_REG (*def_rec
);
3517 gcc_assert (REG_P (dreg
));
3518 regno
= REGNO (dreg
);
3519 if (!(DF_REF_FLAGS (*def_rec
)
3520 & (DF_REF_PARTIAL
| DF_REF_CONDITIONAL
)))
3522 if (bitmap_clear_bit (curr_regs_live
, regno
))
3523 change_pressure (regno
, false);
3527 for (use_rec
= DF_INSN_USES (insn
); *use_rec
; use_rec
++)
3529 dreg
= DF_REF_REAL_REG (*use_rec
);
3530 gcc_assert (REG_P (dreg
));
3531 regno
= REGNO (dreg
);
3532 if (bitmap_set_bit (curr_regs_live
, regno
))
3533 change_pressure (regno
, true);
3537 BITMAP_FREE (curr_regs_live
);
3539 if (dump_file
== NULL
)
3542 fprintf (dump_file
, "\nRegister Pressure: \n");
3545 fprintf (dump_file
, " Basic block %d: \n", bb
->index
);
3546 for (i
= 0; (int) i
< ira_pressure_classes_num
; i
++)
3548 enum reg_class pressure_class
;
3550 pressure_class
= ira_pressure_classes
[i
];
3551 if (BB_DATA (bb
)->max_reg_pressure
[pressure_class
] == 0)
3554 fprintf (dump_file
, " %s=%d\n", reg_class_names
[pressure_class
],
3555 BB_DATA (bb
)->max_reg_pressure
[pressure_class
]);
3558 fprintf (dump_file
, "\n");
3561 /* Top level routine to perform one code hoisting (aka unification) pass
3563 Return nonzero if a change was made. */
3566 one_code_hoisting_pass (void)
3570 gcse_subst_count
= 0;
3571 gcse_create_count
= 0;
3573 /* Return if there's nothing to do, or it is too expensive. */
3574 if (n_basic_blocks
<= NUM_FIXED_BLOCKS
+ 1
3575 || is_too_expensive (_("GCSE disabled")))
3578 doing_code_hoisting_p
= true;
3580 /* Calculate register pressure for each basic block. */
3581 if (flag_ira_hoist_pressure
)
3583 regstat_init_n_sets_and_refs ();
3584 ira_set_pseudo_classes (false, dump_file
);
3585 alloc_aux_for_blocks (sizeof (struct bb_data
));
3586 calculate_bb_reg_pressure ();
3587 regstat_free_n_sets_and_refs ();
3590 /* We need alias. */
3591 init_alias_analysis ();
3594 gcc_obstack_init (&gcse_obstack
);
3597 alloc_hash_table (&expr_hash_table
);
3598 compute_hash_table (&expr_hash_table
);
3600 dump_hash_table (dump_file
, "Code Hosting Expressions", &expr_hash_table
);
3602 if (expr_hash_table
.n_elems
> 0)
3604 alloc_code_hoist_mem (last_basic_block
, expr_hash_table
.n_elems
);
3605 compute_code_hoist_data ();
3606 changed
= hoist_code ();
3607 free_code_hoist_mem ();
3610 if (flag_ira_hoist_pressure
)
3612 free_aux_for_blocks ();
3615 free_hash_table (&expr_hash_table
);
3617 obstack_free (&gcse_obstack
, NULL
);
3619 /* We are finished with alias. */
3620 end_alias_analysis ();
3624 fprintf (dump_file
, "HOIST of %s, %d basic blocks, %d bytes needed, ",
3625 current_function_name (), n_basic_blocks
, bytes_used
);
3626 fprintf (dump_file
, "%d substs, %d insns created\n",
3627 gcse_subst_count
, gcse_create_count
);
3630 doing_code_hoisting_p
= false;
3635 /* Here we provide the things required to do store motion towards the exit.
3636 In order for this to be effective, gcse also needed to be taught how to
3637 move a load when it is killed only by a store to itself.
3642 void foo(float scale)
3644 for (i=0; i<10; i++)
3648 'i' is both loaded and stored to in the loop. Normally, gcse cannot move
3649 the load out since its live around the loop, and stored at the bottom
3652 The 'Load Motion' referred to and implemented in this file is
3653 an enhancement to gcse which when using edge based LCM, recognizes
3654 this situation and allows gcse to move the load out of the loop.
3656 Once gcse has hoisted the load, store motion can then push this
3657 load towards the exit, and we end up with no loads or stores of 'i'
3661 pre_ldst_expr_hash (const void *p
)
3663 int do_not_record_p
= 0;
3664 const struct ls_expr
*const x
= (const struct ls_expr
*) p
;
3666 hash_rtx (x
->pattern
, GET_MODE (x
->pattern
), &do_not_record_p
, NULL
, false);
3670 pre_ldst_expr_eq (const void *p1
, const void *p2
)
3672 const struct ls_expr
*const ptr1
= (const struct ls_expr
*) p1
,
3673 *const ptr2
= (const struct ls_expr
*) p2
;
3674 return expr_equiv_p (ptr1
->pattern
, ptr2
->pattern
);
3677 /* This will search the ldst list for a matching expression. If it
3678 doesn't find one, we create one and initialize it. */
3680 static struct ls_expr
*
3683 int do_not_record_p
= 0;
3684 struct ls_expr
* ptr
;
3689 hash
= hash_rtx (x
, GET_MODE (x
), &do_not_record_p
,
3690 NULL
, /*have_reg_qty=*/false);
3693 slot
= htab_find_slot_with_hash (pre_ldst_table
, &e
, hash
, INSERT
);
3695 return (struct ls_expr
*)*slot
;
3697 ptr
= XNEW (struct ls_expr
);
3699 ptr
->next
= pre_ldst_mems
;
3702 ptr
->pattern_regs
= NULL_RTX
;
3703 ptr
->loads
= NULL_RTX
;
3704 ptr
->stores
= NULL_RTX
;
3705 ptr
->reaching_reg
= NULL_RTX
;
3708 ptr
->hash_index
= hash
;
3709 pre_ldst_mems
= ptr
;
3715 /* Free up an individual ldst entry. */
3718 free_ldst_entry (struct ls_expr
* ptr
)
3720 free_INSN_LIST_list (& ptr
->loads
);
3721 free_INSN_LIST_list (& ptr
->stores
);
3726 /* Free up all memory associated with the ldst list. */
3729 free_ld_motion_mems (void)
3732 htab_delete (pre_ldst_table
);
3733 pre_ldst_table
= NULL
;
3735 while (pre_ldst_mems
)
3737 struct ls_expr
* tmp
= pre_ldst_mems
;
3739 pre_ldst_mems
= pre_ldst_mems
->next
;
3741 free_ldst_entry (tmp
);
3744 pre_ldst_mems
= NULL
;
3747 /* Dump debugging info about the ldst list. */
3750 print_ldst_list (FILE * file
)
3752 struct ls_expr
* ptr
;
3754 fprintf (file
, "LDST list: \n");
3756 for (ptr
= pre_ldst_mems
; ptr
!= NULL
; ptr
= ptr
->next
)
3758 fprintf (file
, " Pattern (%3d): ", ptr
->index
);
3760 print_rtl (file
, ptr
->pattern
);
3762 fprintf (file
, "\n Loads : ");
3765 print_rtl (file
, ptr
->loads
);
3767 fprintf (file
, "(nil)");
3769 fprintf (file
, "\n Stores : ");
3772 print_rtl (file
, ptr
->stores
);
3774 fprintf (file
, "(nil)");
3776 fprintf (file
, "\n\n");
3779 fprintf (file
, "\n");
3782 /* Returns 1 if X is in the list of ldst only expressions. */
3784 static struct ls_expr
*
3785 find_rtx_in_ldst (rtx x
)
3789 if (!pre_ldst_table
)
3792 slot
= htab_find_slot (pre_ldst_table
, &e
, NO_INSERT
);
3793 if (!slot
|| ((struct ls_expr
*)*slot
)->invalid
)
3795 return (struct ls_expr
*) *slot
;
3798 /* Load Motion for loads which only kill themselves. */
3800 /* Return true if x, a MEM, is a simple access with no side effects.
3801 These are the types of loads we consider for the ld_motion list,
3802 otherwise we let the usual aliasing take care of it. */
3805 simple_mem (const_rtx x
)
3807 if (MEM_VOLATILE_P (x
))
3810 if (GET_MODE (x
) == BLKmode
)
3813 /* If we are handling exceptions, we must be careful with memory references
3814 that may trap. If we are not, the behavior is undefined, so we may just
3816 if (cfun
->can_throw_non_call_exceptions
&& may_trap_p (x
))
3819 if (side_effects_p (x
))
3822 /* Do not consider function arguments passed on stack. */
3823 if (reg_mentioned_p (stack_pointer_rtx
, x
))
3826 if (flag_float_store
&& FLOAT_MODE_P (GET_MODE (x
)))
3832 /* Make sure there isn't a buried reference in this pattern anywhere.
3833 If there is, invalidate the entry for it since we're not capable
3834 of fixing it up just yet.. We have to be sure we know about ALL
3835 loads since the aliasing code will allow all entries in the
3836 ld_motion list to not-alias itself. If we miss a load, we will get
3837 the wrong value since gcse might common it and we won't know to
3841 invalidate_any_buried_refs (rtx x
)
3845 struct ls_expr
* ptr
;
3847 /* Invalidate it in the list. */
3848 if (MEM_P (x
) && simple_mem (x
))
3850 ptr
= ldst_entry (x
);
3854 /* Recursively process the insn. */
3855 fmt
= GET_RTX_FORMAT (GET_CODE (x
));
3857 for (i
= GET_RTX_LENGTH (GET_CODE (x
)) - 1; i
>= 0; i
--)
3860 invalidate_any_buried_refs (XEXP (x
, i
));
3861 else if (fmt
[i
] == 'E')
3862 for (j
= XVECLEN (x
, i
) - 1; j
>= 0; j
--)
3863 invalidate_any_buried_refs (XVECEXP (x
, i
, j
));
3867 /* Find all the 'simple' MEMs which are used in LOADs and STORES. Simple
3868 being defined as MEM loads and stores to symbols, with no side effects
3869 and no registers in the expression. For a MEM destination, we also
3870 check that the insn is still valid if we replace the destination with a
3871 REG, as is done in update_ld_motion_stores. If there are any uses/defs
3872 which don't match this criteria, they are invalidated and trimmed out
3876 compute_ld_motion_mems (void)
3878 struct ls_expr
* ptr
;
3882 pre_ldst_mems
= NULL
;
3884 = htab_create (13, pre_ldst_expr_hash
, pre_ldst_expr_eq
, NULL
);
3888 FOR_BB_INSNS (bb
, insn
)
3890 if (NONDEBUG_INSN_P (insn
))
3892 if (GET_CODE (PATTERN (insn
)) == SET
)
3894 rtx src
= SET_SRC (PATTERN (insn
));
3895 rtx dest
= SET_DEST (PATTERN (insn
));
3897 /* Check for a simple LOAD... */
3898 if (MEM_P (src
) && simple_mem (src
))
3900 ptr
= ldst_entry (src
);
3902 ptr
->loads
= alloc_INSN_LIST (insn
, ptr
->loads
);
3908 /* Make sure there isn't a buried load somewhere. */
3909 invalidate_any_buried_refs (src
);
3912 /* Check for stores. Don't worry about aliased ones, they
3913 will block any movement we might do later. We only care
3914 about this exact pattern since those are the only
3915 circumstance that we will ignore the aliasing info. */
3916 if (MEM_P (dest
) && simple_mem (dest
))
3918 ptr
= ldst_entry (dest
);
3921 && GET_CODE (src
) != ASM_OPERANDS
3922 /* Check for REG manually since want_to_gcse_p
3923 returns 0 for all REGs. */
3924 && can_assign_to_reg_without_clobbers_p (src
))
3925 ptr
->stores
= alloc_INSN_LIST (insn
, ptr
->stores
);
3931 invalidate_any_buried_refs (PATTERN (insn
));
3937 /* Remove any references that have been either invalidated or are not in the
3938 expression list for pre gcse. */
3941 trim_ld_motion_mems (void)
3943 struct ls_expr
* * last
= & pre_ldst_mems
;
3944 struct ls_expr
* ptr
= pre_ldst_mems
;
3950 /* Delete if entry has been made invalid. */
3953 /* Delete if we cannot find this mem in the expression list. */
3954 unsigned int hash
= ptr
->hash_index
% expr_hash_table
.size
;
3956 for (expr
= expr_hash_table
.table
[hash
];
3958 expr
= expr
->next_same_hash
)
3959 if (expr_equiv_p (expr
->expr
, ptr
->pattern
))
3963 expr
= (struct expr
*) 0;
3967 /* Set the expression field if we are keeping it. */
3975 htab_remove_elt_with_hash (pre_ldst_table
, ptr
, ptr
->hash_index
);
3976 free_ldst_entry (ptr
);
3981 /* Show the world what we've found. */
3982 if (dump_file
&& pre_ldst_mems
!= NULL
)
3983 print_ldst_list (dump_file
);
3986 /* This routine will take an expression which we are replacing with
3987 a reaching register, and update any stores that are needed if
3988 that expression is in the ld_motion list. Stores are updated by
3989 copying their SRC to the reaching register, and then storing
3990 the reaching register into the store location. These keeps the
3991 correct value in the reaching register for the loads. */
3994 update_ld_motion_stores (struct expr
* expr
)
3996 struct ls_expr
* mem_ptr
;
3998 if ((mem_ptr
= find_rtx_in_ldst (expr
->expr
)))
4000 /* We can try to find just the REACHED stores, but is shouldn't
4001 matter to set the reaching reg everywhere... some might be
4002 dead and should be eliminated later. */
4004 /* We replace (set mem expr) with (set reg expr) (set mem reg)
4005 where reg is the reaching reg used in the load. We checked in
4006 compute_ld_motion_mems that we can replace (set mem expr) with
4007 (set reg expr) in that insn. */
4008 rtx list
= mem_ptr
->stores
;
4010 for ( ; list
!= NULL_RTX
; list
= XEXP (list
, 1))
4012 rtx insn
= XEXP (list
, 0);
4013 rtx pat
= PATTERN (insn
);
4014 rtx src
= SET_SRC (pat
);
4015 rtx reg
= expr
->reaching_reg
;
4018 /* If we've already copied it, continue. */
4019 if (expr
->reaching_reg
== src
)
4024 fprintf (dump_file
, "PRE: store updated with reaching reg ");
4025 print_rtl (dump_file
, reg
);
4026 fprintf (dump_file
, ":\n ");
4027 print_inline_rtx (dump_file
, insn
, 8);
4028 fprintf (dump_file
, "\n");
4031 copy
= gen_move_insn (reg
, copy_rtx (SET_SRC (pat
)));
4032 emit_insn_before (copy
, insn
);
4033 SET_SRC (pat
) = reg
;
4034 df_insn_rescan (insn
);
4036 /* un-recognize this pattern since it's probably different now. */
4037 INSN_CODE (insn
) = -1;
4038 gcse_create_count
++;
4043 /* Return true if the graph is too expensive to optimize. PASS is the
4044 optimization about to be performed. */
4047 is_too_expensive (const char *pass
)
4049 /* Trying to perform global optimizations on flow graphs which have
4050 a high connectivity will take a long time and is unlikely to be
4051 particularly useful.
4053 In normal circumstances a cfg should have about twice as many
4054 edges as blocks. But we do not want to punish small functions
4055 which have a couple switch statements. Rather than simply
4056 threshold the number of blocks, uses something with a more
4057 graceful degradation. */
4058 if (n_edges
> 20000 + n_basic_blocks
* 4)
4060 warning (OPT_Wdisabled_optimization
,
4061 "%s: %d basic blocks and %d edges/basic block",
4062 pass
, n_basic_blocks
, n_edges
/ n_basic_blocks
);
4067 /* If allocating memory for the dataflow bitmaps would take up too much
4068 storage it's better just to disable the optimization. */
4070 * SBITMAP_SET_SIZE (max_reg_num ())
4071 * sizeof (SBITMAP_ELT_TYPE
)) > MAX_GCSE_MEMORY
)
4073 warning (OPT_Wdisabled_optimization
,
4074 "%s: %d basic blocks and %d registers",
4075 pass
, n_basic_blocks
, max_reg_num ());
4083 /* All the passes implemented in this file. Each pass has its
4084 own gate and execute function, and at the end of the file a
4085 pass definition for passes.c.
4087 We do not construct an accurate cfg in functions which call
4088 setjmp, so none of these passes runs if the function calls
4090 FIXME: Should just handle setjmp via REG_SETJMP notes. */
4095 return optimize
> 0 && flag_gcse
4096 && !cfun
->calls_setjmp
4097 && optimize_function_for_speed_p (cfun
)
4102 execute_rtl_pre (void)
4105 delete_unreachable_blocks ();
4107 changed
= one_pre_gcse_pass ();
4108 flag_rerun_cse_after_global_opts
|= changed
;
4115 gate_rtl_hoist (void)
4117 return optimize
> 0 && flag_gcse
4118 && !cfun
->calls_setjmp
4119 /* It does not make sense to run code hoisting unless we are optimizing
4120 for code size -- it rarely makes programs faster, and can make then
4121 bigger if we did PRE (when optimizing for space, we don't run PRE). */
4122 && optimize_function_for_size_p (cfun
)
4127 execute_rtl_hoist (void)
4130 delete_unreachable_blocks ();
4132 changed
= one_code_hoisting_pass ();
4133 flag_rerun_cse_after_global_opts
|= changed
;
4139 struct rtl_opt_pass pass_rtl_pre
=
4143 "rtl pre", /* name */
4144 OPTGROUP_NONE
, /* optinfo_flags */
4145 gate_rtl_pre
, /* gate */
4146 execute_rtl_pre
, /* execute */
4149 0, /* static_pass_number */
4151 PROP_cfglayout
, /* properties_required */
4152 0, /* properties_provided */
4153 0, /* properties_destroyed */
4154 0, /* todo_flags_start */
4155 TODO_df_finish
| TODO_verify_rtl_sharing
|
4156 TODO_verify_flow
| TODO_ggc_collect
/* todo_flags_finish */
4160 struct rtl_opt_pass pass_rtl_hoist
=
4165 OPTGROUP_NONE
, /* optinfo_flags */
4166 gate_rtl_hoist
, /* gate */
4167 execute_rtl_hoist
, /* execute */
4170 0, /* static_pass_number */
4171 TV_HOIST
, /* tv_id */
4172 PROP_cfglayout
, /* properties_required */
4173 0, /* properties_provided */
4174 0, /* properties_destroyed */
4175 0, /* todo_flags_start */
4176 TODO_df_finish
| TODO_verify_rtl_sharing
|
4177 TODO_verify_flow
| TODO_ggc_collect
/* todo_flags_finish */
4181 #include "gt-gcse.h"