1 /* Partial redundancy elimination / Hoisting for RTL.
2 Copyright (C) 1997-2015 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
21 - reordering of memory allocation and freeing to be more space efficient
22 - calc rough register pressure information and use the info to drive all
23 kinds of code motion (including code hoisting) in a unified way.
26 /* References searched while implementing this.
28 Compilers Principles, Techniques and Tools
32 Global Optimization by Suppression of Partial Redundancies
34 communications of the acm, Vol. 22, Num. 2, Feb. 1979
36 A Portable Machine-Independent Global Optimizer - Design and Measurements
38 Stanford Ph.D. thesis, Dec. 1983
40 A Fast Algorithm for Code Movement Optimization
42 SIGPLAN Notices, Vol. 23, Num. 10, Oct. 1988
44 A Solution to a Problem with Morel and Renvoise's
45 Global Optimization by Suppression of Partial Redundancies
46 K-H Drechsler, M.P. Stadel
47 ACM TOPLAS, Vol. 10, Num. 4, Oct. 1988
49 Practical Adaptation of the Global Optimization
50 Algorithm of Morel and Renvoise
52 ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991
54 Efficiently Computing Static Single Assignment Form and the Control
56 R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck
57 ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991
60 J. Knoop, O. Ruthing, B. Steffen
61 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
63 What's In a Region? Or Computing Control Dependence Regions in Near-Linear
64 Time for Reducible Flow Control
66 ACM Letters on Programming Languages and Systems,
67 Vol. 2, Num. 1-4, Mar-Dec 1993
69 An Efficient Representation for Sparse Sets
70 Preston Briggs, Linda Torczon
71 ACM Letters on Programming Languages and Systems,
72 Vol. 2, Num. 1-4, Mar-Dec 1993
74 A Variation of Knoop, Ruthing, and Steffen's Lazy Code Motion
75 K-H Drechsler, M.P. Stadel
76 ACM SIGPLAN Notices, Vol. 28, Num. 5, May 1993
78 Partial Dead Code Elimination
79 J. Knoop, O. Ruthing, B. Steffen
80 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
82 Effective Partial Redundancy Elimination
83 P. Briggs, K.D. Cooper
84 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
86 The Program Structure Tree: Computing Control Regions in Linear Time
87 R. Johnson, D. Pearson, K. Pingali
88 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
90 Optimal Code Motion: Theory and Practice
91 J. Knoop, O. Ruthing, B. Steffen
92 ACM TOPLAS, Vol. 16, Num. 4, Jul. 1994
94 The power of assignment motion
95 J. Knoop, O. Ruthing, B. Steffen
96 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
98 Global code motion / global value numbering
100 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
102 Value Driven Redundancy Elimination
104 Rice University Ph.D. thesis, Apr. 1996
108 Massively Scalar Compiler Project, Rice University, Sep. 1996
110 High Performance Compilers for Parallel Computing
114 Advanced Compiler Design and Implementation
116 Morgan Kaufmann, 1997
118 Building an Optimizing Compiler
122 People wishing to speed up the code here should read:
123 Elimination Algorithms for Data Flow Analysis
124 B.G. Ryder, M.C. Paull
125 ACM Computing Surveys, Vol. 18, Num. 3, Sep. 1986
127 How to Analyze Large Programs Efficiently and Informatively
128 D.M. Dhamdhere, B.K. Rosen, F.K. Zadeck
129 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
131 People wishing to do something different can find various possibilities
132 in the above papers and elsewhere.
137 #include "coretypes.h"
139 #include "diagnostic-core.h"
141 #include "hard-reg-set.h"
143 #include "hash-set.h"
144 #include "machmode.h"
146 #include "double-int.h"
150 #include "wide-int.h"
157 #include "insn-config.h"
161 #include "function.h"
162 #include "dominance.h"
167 #include "cfgcleanup.h"
168 #include "basic-block.h"
176 #include "tree-pass.h"
177 #include "hash-table.h"
183 /* We support GCSE via Partial Redundancy Elimination. PRE optimizations
184 are a superset of those done by classic GCSE.
186 Two passes of copy/constant propagation are done around PRE or hoisting
187 because the first one enables more GCSE and the second one helps to clean
188 up the copies that PRE and HOIST create. This is needed more for PRE than
189 for HOIST because code hoisting will try to use an existing register
190 containing the common subexpression rather than create a new one. This is
191 harder to do for PRE because of the code motion (which HOIST doesn't do).
193 Expressions we are interested in GCSE-ing are of the form
194 (set (pseudo-reg) (expression)).
195 Function want_to_gcse_p says what these are.
197 In addition, expressions in REG_EQUAL notes are candidates for GCSE-ing.
198 This allows PRE to hoist expressions that are expressed in multiple insns,
199 such as complex address calculations (e.g. for PIC code, or loads with a
200 high part and a low part).
202 PRE handles moving invariant expressions out of loops (by treating them as
203 partially redundant).
205 **********************
207 We used to support multiple passes but there are diminishing returns in
208 doing so. The first pass usually makes 90% of the changes that are doable.
209 A second pass can make a few more changes made possible by the first pass.
210 Experiments show any further passes don't make enough changes to justify
213 A study of spec92 using an unlimited number of passes:
214 [1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83,
215 [6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2,
216 [12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1
218 It was found doing copy propagation between each pass enables further
221 This study was done before expressions in REG_EQUAL notes were added as
222 candidate expressions for optimization, and before the GIMPLE optimizers
223 were added. Probably, multiple passes is even less efficient now than
224 at the time when the study was conducted.
226 PRE is quite expensive in complicated functions because the DFA can take
227 a while to converge. Hence we only perform one pass.
229 **********************
231 The steps for PRE are:
233 1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
235 2) Perform the data flow analysis for PRE.
237 3) Delete the redundant instructions
239 4) Insert the required copies [if any] that make the partially
240 redundant instructions fully redundant.
242 5) For other reaching expressions, insert an instruction to copy the value
243 to a newly created pseudo that will reach the redundant instruction.
245 The deletion is done first so that when we do insertions we
246 know which pseudo reg to use.
248 Various papers have argued that PRE DFA is expensive (O(n^2)) and others
249 argue it is not. The number of iterations for the algorithm to converge
250 is typically 2-4 so I don't view it as that expensive (relatively speaking).
252 PRE GCSE depends heavily on the second CPROP pass to clean up the copies
253 we create. To make an expression reach the place where it's redundant,
254 the result of the expression is copied to a new register, and the redundant
255 expression is deleted by replacing it with this new register. Classic GCSE
256 doesn't have this problem as much as it computes the reaching defs of
257 each register in each block and thus can try to use an existing
260 /* GCSE global vars. */
262 struct target_gcse default_target_gcse
;
263 #if SWITCHABLE_TARGET
264 struct target_gcse
*this_target_gcse
= &default_target_gcse
;
267 /* Set to non-zero if CSE should run after all GCSE optimizations are done. */
268 int flag_rerun_cse_after_global_opts
;
270 /* An obstack for our working variables. */
271 static struct obstack gcse_obstack
;
273 /* Hash table of expressions. */
277 /* The expression. */
279 /* Index in the available expression bitmaps. */
281 /* Next entry with the same hash. */
282 struct gcse_expr
*next_same_hash
;
283 /* List of anticipatable occurrences in basic blocks in the function.
284 An "anticipatable occurrence" is one that is the first occurrence in the
285 basic block, the operands are not modified in the basic block prior
286 to the occurrence and the output is not used between the start of
287 the block and the occurrence. */
288 struct gcse_occr
*antic_occr
;
289 /* List of available occurrence in basic blocks in the function.
290 An "available occurrence" is one that is the last occurrence in the
291 basic block and the operands are not modified by following statements in
292 the basic block [including this insn]. */
293 struct gcse_occr
*avail_occr
;
294 /* Non-null if the computation is PRE redundant.
295 The value is the newly created pseudo-reg to record a copy of the
296 expression in all the places that reach the redundant copy. */
298 /* Maximum distance in instructions this expression can travel.
299 We avoid moving simple expressions for more than a few instructions
300 to keep register pressure under control.
301 A value of "0" removes restrictions on how far the expression can
306 /* Occurrence of an expression.
307 There is one per basic block. If a pattern appears more than once the
308 last appearance is used [or first for anticipatable expressions]. */
312 /* Next occurrence of this expression. */
313 struct gcse_occr
*next
;
314 /* The insn that computes the expression. */
316 /* Nonzero if this [anticipatable] occurrence has been deleted. */
318 /* Nonzero if this [available] occurrence has been copied to
320 /* ??? This is mutually exclusive with deleted_p, so they could share
325 typedef struct gcse_occr
*occr_t
;
327 /* Expression hash tables.
328 Each hash table is an array of buckets.
329 ??? It is known that if it were an array of entries, structure elements
330 `next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is
331 not clear whether in the final analysis a sufficient amount of memory would
332 be saved as the size of the available expression bitmaps would be larger
333 [one could build a mapping table without holes afterwards though].
334 Someday I'll perform the computation and figure it out. */
336 struct gcse_hash_table_d
339 This is an array of `expr_hash_table_size' elements. */
340 struct gcse_expr
**table
;
342 /* Size of the hash table, in elements. */
345 /* Number of hash table elements. */
346 unsigned int n_elems
;
349 /* Expression hash table. */
350 static struct gcse_hash_table_d expr_hash_table
;
352 /* This is a list of expressions which are MEMs and will be used by load
354 Load motion tracks MEMs which aren't killed by anything except itself,
355 i.e. loads and stores to a single location.
356 We can then allow movement of these MEM refs with a little special
357 allowance. (all stores copy the same value to the reaching reg used
358 for the loads). This means all values used to store into memory must have
359 no side effects so we can re-issue the setter value. */
363 struct gcse_expr
* expr
; /* Gcse expression reference for LM. */
364 rtx pattern
; /* Pattern of this mem. */
365 rtx pattern_regs
; /* List of registers mentioned by the mem. */
366 rtx_insn_list
*loads
; /* INSN list of loads seen. */
367 rtx_insn_list
*stores
; /* INSN list of stores seen. */
368 struct ls_expr
* next
; /* Next in the list. */
369 int invalid
; /* Invalid for some reason. */
370 int index
; /* If it maps to a bitmap index. */
371 unsigned int hash_index
; /* Index when in a hash table. */
372 rtx reaching_reg
; /* Register to use when re-writing. */
375 /* Head of the list of load/store memory refs. */
376 static struct ls_expr
* pre_ldst_mems
= NULL
;
378 struct pre_ldst_expr_hasher
: typed_noop_remove
<ls_expr
>
380 typedef ls_expr value_type
;
381 typedef value_type compare_type
;
382 static inline hashval_t
hash (const value_type
*);
383 static inline bool equal (const value_type
*, const compare_type
*);
386 /* Hashtable helpers. */
388 pre_ldst_expr_hasher::hash (const value_type
*x
)
390 int do_not_record_p
= 0;
392 hash_rtx (x
->pattern
, GET_MODE (x
->pattern
), &do_not_record_p
, NULL
, false);
395 static int expr_equiv_p (const_rtx
, const_rtx
);
398 pre_ldst_expr_hasher::equal (const value_type
*ptr1
,
399 const compare_type
*ptr2
)
401 return expr_equiv_p (ptr1
->pattern
, ptr2
->pattern
);
404 /* Hashtable for the load/store memory refs. */
405 static hash_table
<pre_ldst_expr_hasher
> *pre_ldst_table
;
407 /* Bitmap containing one bit for each register in the program.
408 Used when performing GCSE to track which registers have been set since
409 the start of the basic block. */
410 static regset reg_set_bitmap
;
412 /* Array, indexed by basic block number for a list of insns which modify
413 memory within that block. */
414 static vec
<rtx_insn
*> *modify_mem_list
;
415 static bitmap modify_mem_list_set
;
417 typedef struct modify_pair_s
419 rtx dest
; /* A MEM. */
420 rtx dest_addr
; /* The canonical address of `dest'. */
424 /* This array parallels modify_mem_list, except that it stores MEMs
425 being set and their canonicalized memory addresses. */
426 static vec
<modify_pair
> *canon_modify_mem_list
;
428 /* Bitmap indexed by block numbers to record which blocks contain
430 static bitmap blocks_with_calls
;
432 /* Various variables for statistics gathering. */
434 /* Memory used in a pass.
435 This isn't intended to be absolutely precise. Its intent is only
436 to keep an eye on memory usage. */
437 static int bytes_used
;
439 /* GCSE substitutions made. */
440 static int gcse_subst_count
;
441 /* Number of copy instructions created. */
442 static int gcse_create_count
;
444 /* Doing code hoisting. */
445 static bool doing_code_hoisting_p
= false;
447 /* For available exprs */
448 static sbitmap
*ae_kill
;
450 /* Data stored for each basic block. */
453 /* Maximal register pressure inside basic block for given register class
454 (defined only for the pressure classes). */
455 int max_reg_pressure
[N_REG_CLASSES
];
456 /* Recorded register pressure of basic block before trying to hoist
457 an expression. Will be used to restore the register pressure
458 if the expression should not be hoisted. */
460 /* Recorded register live_in info of basic block during code hoisting
461 process. BACKUP is used to record live_in info before trying to
462 hoist an expression, and will be used to restore LIVE_IN if the
463 expression should not be hoisted. */
464 bitmap live_in
, backup
;
467 #define BB_DATA(bb) ((struct bb_data *) (bb)->aux)
469 static basic_block curr_bb
;
471 /* Current register pressure for each pressure class. */
472 static int curr_reg_pressure
[N_REG_CLASSES
];
475 static void compute_can_copy (void);
476 static void *gmalloc (size_t) ATTRIBUTE_MALLOC
;
477 static void *gcalloc (size_t, size_t) ATTRIBUTE_MALLOC
;
478 static void *gcse_alloc (unsigned long);
479 static void alloc_gcse_mem (void);
480 static void free_gcse_mem (void);
481 static void hash_scan_insn (rtx_insn
*, struct gcse_hash_table_d
*);
482 static void hash_scan_set (rtx
, rtx_insn
*, struct gcse_hash_table_d
*);
483 static void hash_scan_clobber (rtx
, rtx_insn
*, struct gcse_hash_table_d
*);
484 static void hash_scan_call (rtx
, rtx_insn
*, struct gcse_hash_table_d
*);
485 static int want_to_gcse_p (rtx
, int *);
486 static int oprs_unchanged_p (const_rtx
, const rtx_insn
*, int);
487 static int oprs_anticipatable_p (const_rtx
, const rtx_insn
*);
488 static int oprs_available_p (const_rtx
, const rtx_insn
*);
489 static void insert_expr_in_table (rtx
, machine_mode
, rtx_insn
*, int, int,
490 int, struct gcse_hash_table_d
*);
491 static unsigned int hash_expr (const_rtx
, machine_mode
, int *, int);
492 static void record_last_reg_set_info (rtx
, int);
493 static void record_last_mem_set_info (rtx_insn
*);
494 static void record_last_set_info (rtx
, const_rtx
, void *);
495 static void compute_hash_table (struct gcse_hash_table_d
*);
496 static void alloc_hash_table (struct gcse_hash_table_d
*);
497 static void free_hash_table (struct gcse_hash_table_d
*);
498 static void compute_hash_table_work (struct gcse_hash_table_d
*);
499 static void dump_hash_table (FILE *, const char *, struct gcse_hash_table_d
*);
500 static void compute_transp (const_rtx
, int, sbitmap
*);
501 static void compute_local_properties (sbitmap
*, sbitmap
*, sbitmap
*,
502 struct gcse_hash_table_d
*);
503 static void mems_conflict_for_gcse_p (rtx
, const_rtx
, void *);
504 static int load_killed_in_block_p (const_basic_block
, int, const_rtx
, int);
505 static void canon_list_insert (rtx
, const_rtx
, void *);
506 static void alloc_pre_mem (int, int);
507 static void free_pre_mem (void);
508 static struct edge_list
*compute_pre_data (void);
509 static int pre_expr_reaches_here_p (basic_block
, struct gcse_expr
*,
511 static void insert_insn_end_basic_block (struct gcse_expr
*, basic_block
);
512 static void pre_insert_copy_insn (struct gcse_expr
*, rtx_insn
*);
513 static void pre_insert_copies (void);
514 static int pre_delete (void);
515 static int pre_gcse (struct edge_list
*);
516 static int one_pre_gcse_pass (void);
517 static void add_label_notes (rtx
, rtx
);
518 static void alloc_code_hoist_mem (int, int);
519 static void free_code_hoist_mem (void);
520 static void compute_code_hoist_vbeinout (void);
521 static void compute_code_hoist_data (void);
522 static int should_hoist_expr_to_dom (basic_block
, struct gcse_expr
*, basic_block
,
523 sbitmap
, int, int *, enum reg_class
,
524 int *, bitmap
, rtx_insn
*);
525 static int hoist_code (void);
526 static enum reg_class
get_regno_pressure_class (int regno
, int *nregs
);
527 static enum reg_class
get_pressure_class_and_nregs (rtx_insn
*insn
, int *nregs
);
528 static int one_code_hoisting_pass (void);
529 static rtx_insn
*process_insert_insn (struct gcse_expr
*);
530 static int pre_edge_insert (struct edge_list
*, struct gcse_expr
**);
531 static int pre_expr_reaches_here_p_work (basic_block
, struct gcse_expr
*,
532 basic_block
, char *);
533 static struct ls_expr
* ldst_entry (rtx
);
534 static void free_ldst_entry (struct ls_expr
*);
535 static void free_ld_motion_mems (void);
536 static void print_ldst_list (FILE *);
537 static struct ls_expr
* find_rtx_in_ldst (rtx
);
538 static int simple_mem (const_rtx
);
539 static void invalidate_any_buried_refs (rtx
);
540 static void compute_ld_motion_mems (void);
541 static void trim_ld_motion_mems (void);
542 static void update_ld_motion_stores (struct gcse_expr
*);
543 static void clear_modify_mem_tables (void);
544 static void free_modify_mem_tables (void);
545 static rtx
gcse_emit_move_after (rtx
, rtx
, rtx_insn
*);
546 static bool is_too_expensive (const char *);
548 #define GNEW(T) ((T *) gmalloc (sizeof (T)))
549 #define GCNEW(T) ((T *) gcalloc (1, sizeof (T)))
551 #define GNEWVEC(T, N) ((T *) gmalloc (sizeof (T) * (N)))
552 #define GCNEWVEC(T, N) ((T *) gcalloc ((N), sizeof (T)))
554 #define GNEWVAR(T, S) ((T *) gmalloc ((S)))
555 #define GCNEWVAR(T, S) ((T *) gcalloc (1, (S)))
557 #define GOBNEW(T) ((T *) gcse_alloc (sizeof (T)))
558 #define GOBNEWVAR(T, S) ((T *) gcse_alloc ((S)))
560 /* Misc. utilities. */
563 (this_target_gcse->x_can_copy)
564 #define can_copy_init_p \
565 (this_target_gcse->x_can_copy_init_p)
567 /* Compute which modes support reg/reg copy operations. */
570 compute_can_copy (void)
573 #ifndef AVOID_CCMODE_COPIES
576 memset (can_copy
, 0, NUM_MACHINE_MODES
);
579 for (i
= 0; i
< NUM_MACHINE_MODES
; i
++)
580 if (GET_MODE_CLASS (i
) == MODE_CC
)
582 #ifdef AVOID_CCMODE_COPIES
585 reg
= gen_rtx_REG ((machine_mode
) i
, LAST_VIRTUAL_REGISTER
+ 1);
586 insn
= emit_insn (gen_rtx_SET (VOIDmode
, reg
, reg
));
587 if (recog (PATTERN (insn
), insn
, NULL
) >= 0)
597 /* Returns whether the mode supports reg/reg copy operations. */
600 can_copy_p (machine_mode mode
)
602 if (! can_copy_init_p
)
605 can_copy_init_p
= true;
608 return can_copy
[mode
] != 0;
611 /* Cover function to xmalloc to record bytes allocated. */
614 gmalloc (size_t size
)
617 return xmalloc (size
);
620 /* Cover function to xcalloc to record bytes allocated. */
623 gcalloc (size_t nelem
, size_t elsize
)
625 bytes_used
+= nelem
* elsize
;
626 return xcalloc (nelem
, elsize
);
629 /* Cover function to obstack_alloc. */
632 gcse_alloc (unsigned long size
)
635 return obstack_alloc (&gcse_obstack
, size
);
638 /* Allocate memory for the reg/memory set tracking tables.
639 This is called at the start of each pass. */
642 alloc_gcse_mem (void)
644 /* Allocate vars to track sets of regs. */
645 reg_set_bitmap
= ALLOC_REG_SET (NULL
);
647 /* Allocate array to keep a list of insns which modify memory in each
648 basic block. The two typedefs are needed to work around the
649 pre-processor limitation with template types in macro arguments. */
650 typedef vec
<rtx_insn
*> vec_rtx_heap
;
651 typedef vec
<modify_pair
> vec_modify_pair_heap
;
652 modify_mem_list
= GCNEWVEC (vec_rtx_heap
, last_basic_block_for_fn (cfun
));
653 canon_modify_mem_list
= GCNEWVEC (vec_modify_pair_heap
,
654 last_basic_block_for_fn (cfun
));
655 modify_mem_list_set
= BITMAP_ALLOC (NULL
);
656 blocks_with_calls
= BITMAP_ALLOC (NULL
);
659 /* Free memory allocated by alloc_gcse_mem. */
664 FREE_REG_SET (reg_set_bitmap
);
666 free_modify_mem_tables ();
667 BITMAP_FREE (modify_mem_list_set
);
668 BITMAP_FREE (blocks_with_calls
);
671 /* Compute the local properties of each recorded expression.
673 Local properties are those that are defined by the block, irrespective of
676 An expression is transparent in a block if its operands are not modified
679 An expression is computed (locally available) in a block if it is computed
680 at least once and expression would contain the same value if the
681 computation was moved to the end of the block.
683 An expression is locally anticipatable in a block if it is computed at
684 least once and expression would contain the same value if the computation
685 was moved to the beginning of the block.
687 We call this routine for pre and code hoisting. They all compute
688 basically the same information and thus can easily share this code.
690 TRANSP, COMP, and ANTLOC are destination sbitmaps for recording local
691 properties. If NULL, then it is not necessary to compute or record that
694 TABLE controls which hash table to look at. */
697 compute_local_properties (sbitmap
*transp
, sbitmap
*comp
, sbitmap
*antloc
,
698 struct gcse_hash_table_d
*table
)
702 /* Initialize any bitmaps that were passed in. */
705 bitmap_vector_ones (transp
, last_basic_block_for_fn (cfun
));
709 bitmap_vector_clear (comp
, last_basic_block_for_fn (cfun
));
711 bitmap_vector_clear (antloc
, last_basic_block_for_fn (cfun
));
713 for (i
= 0; i
< table
->size
; i
++)
715 struct gcse_expr
*expr
;
717 for (expr
= table
->table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
719 int indx
= expr
->bitmap_index
;
720 struct gcse_occr
*occr
;
722 /* The expression is transparent in this block if it is not killed.
723 We start by assuming all are transparent [none are killed], and
724 then reset the bits for those that are. */
726 compute_transp (expr
->expr
, indx
, transp
);
728 /* The occurrences recorded in antic_occr are exactly those that
729 we want to set to nonzero in ANTLOC. */
731 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
733 bitmap_set_bit (antloc
[BLOCK_FOR_INSN (occr
->insn
)->index
], indx
);
735 /* While we're scanning the table, this is a good place to
740 /* The occurrences recorded in avail_occr are exactly those that
741 we want to set to nonzero in COMP. */
743 for (occr
= expr
->avail_occr
; occr
!= NULL
; occr
= occr
->next
)
745 bitmap_set_bit (comp
[BLOCK_FOR_INSN (occr
->insn
)->index
], indx
);
747 /* While we're scanning the table, this is a good place to
752 /* While we're scanning the table, this is a good place to
754 expr
->reaching_reg
= 0;
759 /* Hash table support. */
761 struct reg_avail_info
768 static struct reg_avail_info
*reg_avail_info
;
769 static basic_block current_bb
;
771 /* See whether X, the source of a set, is something we want to consider for
775 want_to_gcse_p (rtx x
, int *max_distance_ptr
)
778 /* On register stack architectures, don't GCSE constants from the
779 constant pool, as the benefits are often swamped by the overhead
780 of shuffling the register stack between basic blocks. */
781 if (IS_STACK_MODE (GET_MODE (x
)))
782 x
= avoid_constant_pool_reference (x
);
785 /* GCSE'ing constants:
787 We do not specifically distinguish between constant and non-constant
788 expressions in PRE and Hoist. We use set_src_cost below to limit
789 the maximum distance simple expressions can travel.
791 Nevertheless, constants are much easier to GCSE, and, hence,
792 it is easy to overdo the optimizations. Usually, excessive PRE and
793 Hoisting of constant leads to increased register pressure.
795 RA can deal with this by rematerialing some of the constants.
796 Therefore, it is important that the back-end generates sets of constants
797 in a way that allows reload rematerialize them under high register
798 pressure, i.e., a pseudo register with REG_EQUAL to constant
799 is set only once. Failing to do so will result in IRA/reload
800 spilling such constants under high register pressure instead of
801 rematerializing them. */
803 switch (GET_CODE (x
))
811 if (!doing_code_hoisting_p
)
812 /* Do not PRE constants. */
818 if (doing_code_hoisting_p
)
819 /* PRE doesn't implement max_distance restriction. */
824 gcc_assert (!optimize_function_for_speed_p (cfun
)
825 && optimize_function_for_size_p (cfun
));
826 cost
= set_src_cost (x
, 0);
828 if (cost
< COSTS_N_INSNS (GCSE_UNRESTRICTED_COST
))
830 max_distance
= (GCSE_COST_DISTANCE_RATIO
* cost
) / 10;
831 if (max_distance
== 0)
834 gcc_assert (max_distance
> 0);
839 if (max_distance_ptr
)
840 *max_distance_ptr
= max_distance
;
843 return can_assign_to_reg_without_clobbers_p (x
);
847 /* Used internally by can_assign_to_reg_without_clobbers_p. */
849 static GTY(()) rtx_insn
*test_insn
;
851 /* Return true if we can assign X to a pseudo register such that the
852 resulting insn does not result in clobbering a hard register as a
855 Additionally, if the target requires it, check that the resulting insn
856 can be copied. If it cannot, this means that X is special and probably
857 has hidden side-effects we don't want to mess with.
859 This function is typically used by code motion passes, to verify
860 that it is safe to insert an insn without worrying about clobbering
861 maybe live hard regs. */
864 can_assign_to_reg_without_clobbers_p (rtx x
)
866 int num_clobbers
= 0;
868 bool can_assign
= false;
870 /* If this is a valid operand, we are OK. If it's VOIDmode, we aren't. */
871 if (general_operand (x
, GET_MODE (x
)))
873 else if (GET_MODE (x
) == VOIDmode
)
876 /* Otherwise, check if we can make a valid insn from it. First initialize
877 our test insn if we haven't already. */
881 = make_insn_raw (gen_rtx_SET (VOIDmode
,
882 gen_rtx_REG (word_mode
,
883 FIRST_PSEUDO_REGISTER
* 2),
885 SET_NEXT_INSN (test_insn
) = SET_PREV_INSN (test_insn
) = 0;
886 INSN_LOCATION (test_insn
) = UNKNOWN_LOCATION
;
889 /* Now make an insn like the one we would make when GCSE'ing and see if
891 PUT_MODE (SET_DEST (PATTERN (test_insn
)), GET_MODE (x
));
892 SET_SRC (PATTERN (test_insn
)) = x
;
894 icode
= recog (PATTERN (test_insn
), test_insn
, &num_clobbers
);
896 /* If the test insn is valid and doesn't need clobbers, and the target also
897 has no objections, we're good. */
899 && (num_clobbers
== 0 || !added_clobbers_hard_reg_p (icode
))
900 && ! (targetm
.cannot_copy_insn_p
901 && targetm
.cannot_copy_insn_p (test_insn
)))
904 /* Make sure test_insn doesn't have any pointers into GC space. */
905 SET_SRC (PATTERN (test_insn
)) = NULL_RTX
;
910 /* Return nonzero if the operands of expression X are unchanged from the
911 start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
912 or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
915 oprs_unchanged_p (const_rtx x
, const rtx_insn
*insn
, int avail_p
)
929 struct reg_avail_info
*info
= ®_avail_info
[REGNO (x
)];
931 if (info
->last_bb
!= current_bb
)
934 return info
->last_set
< DF_INSN_LUID (insn
);
936 return info
->first_set
>= DF_INSN_LUID (insn
);
941 || load_killed_in_block_p (current_bb
, DF_INSN_LUID (insn
),
945 return oprs_unchanged_p (XEXP (x
, 0), insn
, avail_p
);
969 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
973 /* If we are about to do the last recursive call needed at this
974 level, change it into iteration. This function is called enough
977 return oprs_unchanged_p (XEXP (x
, i
), insn
, avail_p
);
979 else if (! oprs_unchanged_p (XEXP (x
, i
), insn
, avail_p
))
982 else if (fmt
[i
] == 'E')
983 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
984 if (! oprs_unchanged_p (XVECEXP (x
, i
, j
), insn
, avail_p
))
991 /* Info passed from load_killed_in_block_p to mems_conflict_for_gcse_p. */
993 struct mem_conflict_info
995 /* A memory reference for a load instruction, mems_conflict_for_gcse_p will
996 see if a memory store conflicts with this memory load. */
999 /* True if mems_conflict_for_gcse_p finds a conflict between two memory
1004 /* DEST is the output of an instruction. If it is a memory reference and
1005 possibly conflicts with the load found in DATA, then communicate this
1006 information back through DATA. */
1009 mems_conflict_for_gcse_p (rtx dest
, const_rtx setter ATTRIBUTE_UNUSED
,
1012 struct mem_conflict_info
*mci
= (struct mem_conflict_info
*) data
;
1014 while (GET_CODE (dest
) == SUBREG
1015 || GET_CODE (dest
) == ZERO_EXTRACT
1016 || GET_CODE (dest
) == STRICT_LOW_PART
)
1017 dest
= XEXP (dest
, 0);
1019 /* If DEST is not a MEM, then it will not conflict with the load. Note
1020 that function calls are assumed to clobber memory, but are handled
1025 /* If we are setting a MEM in our list of specially recognized MEMs,
1026 don't mark as killed this time. */
1027 if (pre_ldst_mems
!= NULL
&& expr_equiv_p (dest
, mci
->mem
))
1029 if (!find_rtx_in_ldst (dest
))
1030 mci
->conflict
= true;
1034 if (true_dependence (dest
, GET_MODE (dest
), mci
->mem
))
1035 mci
->conflict
= true;
1038 /* Return nonzero if the expression in X (a memory reference) is killed
1039 in block BB before or after the insn with the LUID in UID_LIMIT.
1040 AVAIL_P is nonzero for kills after UID_LIMIT, and zero for kills
1043 To check the entire block, set UID_LIMIT to max_uid + 1 and
1047 load_killed_in_block_p (const_basic_block bb
, int uid_limit
, const_rtx x
,
1050 vec
<rtx_insn
*> list
= modify_mem_list
[bb
->index
];
1054 /* If this is a readonly then we aren't going to be changing it. */
1055 if (MEM_READONLY_P (x
))
1058 FOR_EACH_VEC_ELT_REVERSE (list
, ix
, setter
)
1060 struct mem_conflict_info mci
;
1062 /* Ignore entries in the list that do not apply. */
1064 && DF_INSN_LUID (setter
) < uid_limit
)
1066 && DF_INSN_LUID (setter
) > uid_limit
))
1069 /* If SETTER is a call everything is clobbered. Note that calls
1070 to pure functions are never put on the list, so we need not
1071 worry about them. */
1072 if (CALL_P (setter
))
1075 /* SETTER must be an INSN of some kind that sets memory. Call
1076 note_stores to examine each hunk of memory that is modified. */
1078 mci
.conflict
= false;
1079 note_stores (PATTERN (setter
), mems_conflict_for_gcse_p
, &mci
);
1086 /* Return nonzero if the operands of expression X are unchanged from
1087 the start of INSN's basic block up to but not including INSN. */
1090 oprs_anticipatable_p (const_rtx x
, const rtx_insn
*insn
)
1092 return oprs_unchanged_p (x
, insn
, 0);
1095 /* Return nonzero if the operands of expression X are unchanged from
1096 INSN to the end of INSN's basic block. */
1099 oprs_available_p (const_rtx x
, const rtx_insn
*insn
)
1101 return oprs_unchanged_p (x
, insn
, 1);
1104 /* Hash expression X.
1106 MODE is only used if X is a CONST_INT. DO_NOT_RECORD_P is a boolean
1107 indicating if a volatile operand is found or if the expression contains
1108 something we don't want to insert in the table. HASH_TABLE_SIZE is
1109 the current size of the hash table to be probed. */
1112 hash_expr (const_rtx x
, machine_mode mode
, int *do_not_record_p
,
1113 int hash_table_size
)
1117 *do_not_record_p
= 0;
1119 hash
= hash_rtx (x
, mode
, do_not_record_p
, NULL
, /*have_reg_qty=*/false);
1120 return hash
% hash_table_size
;
1123 /* Return nonzero if exp1 is equivalent to exp2. */
1126 expr_equiv_p (const_rtx x
, const_rtx y
)
1128 return exp_equiv_p (x
, y
, 0, true);
1131 /* Insert expression X in INSN in the hash TABLE.
1132 If it is already present, record it as the last occurrence in INSN's
1135 MODE is the mode of the value X is being stored into.
1136 It is only used if X is a CONST_INT.
1138 ANTIC_P is nonzero if X is an anticipatable expression.
1139 AVAIL_P is nonzero if X is an available expression.
1141 MAX_DISTANCE is the maximum distance in instructions this expression can
1145 insert_expr_in_table (rtx x
, machine_mode mode
, rtx_insn
*insn
,
1147 int avail_p
, int max_distance
, struct gcse_hash_table_d
*table
)
1149 int found
, do_not_record_p
;
1151 struct gcse_expr
*cur_expr
, *last_expr
= NULL
;
1152 struct gcse_occr
*antic_occr
, *avail_occr
;
1154 hash
= hash_expr (x
, mode
, &do_not_record_p
, table
->size
);
1156 /* Do not insert expression in table if it contains volatile operands,
1157 or if hash_expr determines the expression is something we don't want
1158 to or can't handle. */
1159 if (do_not_record_p
)
1162 cur_expr
= table
->table
[hash
];
1165 while (cur_expr
&& 0 == (found
= expr_equiv_p (cur_expr
->expr
, x
)))
1167 /* If the expression isn't found, save a pointer to the end of
1169 last_expr
= cur_expr
;
1170 cur_expr
= cur_expr
->next_same_hash
;
1175 cur_expr
= GOBNEW (struct gcse_expr
);
1176 bytes_used
+= sizeof (struct gcse_expr
);
1177 if (table
->table
[hash
] == NULL
)
1178 /* This is the first pattern that hashed to this index. */
1179 table
->table
[hash
] = cur_expr
;
1181 /* Add EXPR to end of this hash chain. */
1182 last_expr
->next_same_hash
= cur_expr
;
1184 /* Set the fields of the expr element. */
1186 cur_expr
->bitmap_index
= table
->n_elems
++;
1187 cur_expr
->next_same_hash
= NULL
;
1188 cur_expr
->antic_occr
= NULL
;
1189 cur_expr
->avail_occr
= NULL
;
1190 gcc_assert (max_distance
>= 0);
1191 cur_expr
->max_distance
= max_distance
;
1194 gcc_assert (cur_expr
->max_distance
== max_distance
);
1196 /* Now record the occurrence(s). */
1199 antic_occr
= cur_expr
->antic_occr
;
1202 && BLOCK_FOR_INSN (antic_occr
->insn
) != BLOCK_FOR_INSN (insn
))
1206 /* Found another instance of the expression in the same basic block.
1207 Prefer the currently recorded one. We want the first one in the
1208 block and the block is scanned from start to end. */
1209 ; /* nothing to do */
1212 /* First occurrence of this expression in this basic block. */
1213 antic_occr
= GOBNEW (struct gcse_occr
);
1214 bytes_used
+= sizeof (struct gcse_occr
);
1215 antic_occr
->insn
= insn
;
1216 antic_occr
->next
= cur_expr
->antic_occr
;
1217 antic_occr
->deleted_p
= 0;
1218 cur_expr
->antic_occr
= antic_occr
;
1224 avail_occr
= cur_expr
->avail_occr
;
1227 && BLOCK_FOR_INSN (avail_occr
->insn
) == BLOCK_FOR_INSN (insn
))
1229 /* Found another instance of the expression in the same basic block.
1230 Prefer this occurrence to the currently recorded one. We want
1231 the last one in the block and the block is scanned from start
1233 avail_occr
->insn
= insn
;
1237 /* First occurrence of this expression in this basic block. */
1238 avail_occr
= GOBNEW (struct gcse_occr
);
1239 bytes_used
+= sizeof (struct gcse_occr
);
1240 avail_occr
->insn
= insn
;
1241 avail_occr
->next
= cur_expr
->avail_occr
;
1242 avail_occr
->deleted_p
= 0;
1243 cur_expr
->avail_occr
= avail_occr
;
1248 /* Scan SET present in INSN and add an entry to the hash TABLE. */
1251 hash_scan_set (rtx set
, rtx_insn
*insn
, struct gcse_hash_table_d
*table
)
1253 rtx src
= SET_SRC (set
);
1254 rtx dest
= SET_DEST (set
);
1257 if (GET_CODE (src
) == CALL
)
1258 hash_scan_call (src
, insn
, table
);
1260 else if (REG_P (dest
))
1262 unsigned int regno
= REGNO (dest
);
1263 int max_distance
= 0;
1265 /* See if a REG_EQUAL note shows this equivalent to a simpler expression.
1267 This allows us to do a single GCSE pass and still eliminate
1268 redundant constants, addresses or other expressions that are
1269 constructed with multiple instructions.
1271 However, keep the original SRC if INSN is a simple reg-reg move.
1272 In this case, there will almost always be a REG_EQUAL note on the
1273 insn that sets SRC. By recording the REG_EQUAL value here as SRC
1274 for INSN, we miss copy propagation opportunities and we perform the
1275 same PRE GCSE operation repeatedly on the same REG_EQUAL value if we
1276 do more than one PRE GCSE pass.
1278 Note that this does not impede profitable constant propagations. We
1279 "look through" reg-reg sets in lookup_avail_set. */
1280 note
= find_reg_equal_equiv_note (insn
);
1282 && REG_NOTE_KIND (note
) == REG_EQUAL
1284 && want_to_gcse_p (XEXP (note
, 0), NULL
))
1285 src
= XEXP (note
, 0), set
= gen_rtx_SET (VOIDmode
, dest
, src
);
1287 /* Only record sets of pseudo-regs in the hash table. */
1288 if (regno
>= FIRST_PSEUDO_REGISTER
1289 /* Don't GCSE something if we can't do a reg/reg copy. */
1290 && can_copy_p (GET_MODE (dest
))
1291 /* GCSE commonly inserts instruction after the insn. We can't
1292 do that easily for EH edges so disable GCSE on these for now. */
1293 /* ??? We can now easily create new EH landing pads at the
1294 gimple level, for splitting edges; there's no reason we
1295 can't do the same thing at the rtl level. */
1296 && !can_throw_internal (insn
)
1297 /* Is SET_SRC something we want to gcse? */
1298 && want_to_gcse_p (src
, &max_distance
)
1299 /* Don't CSE a nop. */
1300 && ! set_noop_p (set
)
1301 /* Don't GCSE if it has attached REG_EQUIV note.
1302 At this point this only function parameters should have
1303 REG_EQUIV notes and if the argument slot is used somewhere
1304 explicitly, it means address of parameter has been taken,
1305 so we should not extend the lifetime of the pseudo. */
1306 && (note
== NULL_RTX
|| ! MEM_P (XEXP (note
, 0))))
1308 /* An expression is not anticipatable if its operands are
1309 modified before this insn or if this is not the only SET in
1310 this insn. The latter condition does not have to mean that
1311 SRC itself is not anticipatable, but we just will not be
1312 able to handle code motion of insns with multiple sets. */
1313 int antic_p
= oprs_anticipatable_p (src
, insn
)
1314 && !multiple_sets (insn
);
1315 /* An expression is not available if its operands are
1316 subsequently modified, including this insn. It's also not
1317 available if this is a branch, because we can't insert
1318 a set after the branch. */
1319 int avail_p
= (oprs_available_p (src
, insn
)
1320 && ! JUMP_P (insn
));
1322 insert_expr_in_table (src
, GET_MODE (dest
), insn
, antic_p
, avail_p
,
1323 max_distance
, table
);
1326 /* In case of store we want to consider the memory value as available in
1327 the REG stored in that memory. This makes it possible to remove
1328 redundant loads from due to stores to the same location. */
1329 else if (flag_gcse_las
&& REG_P (src
) && MEM_P (dest
))
1331 unsigned int regno
= REGNO (src
);
1332 int max_distance
= 0;
1334 /* Only record sets of pseudo-regs in the hash table. */
1335 if (regno
>= FIRST_PSEUDO_REGISTER
1336 /* Don't GCSE something if we can't do a reg/reg copy. */
1337 && can_copy_p (GET_MODE (src
))
1338 /* GCSE commonly inserts instruction after the insn. We can't
1339 do that easily for EH edges so disable GCSE on these for now. */
1340 && !can_throw_internal (insn
)
1341 /* Is SET_DEST something we want to gcse? */
1342 && want_to_gcse_p (dest
, &max_distance
)
1343 /* Don't CSE a nop. */
1344 && ! set_noop_p (set
)
1345 /* Don't GCSE if it has attached REG_EQUIV note.
1346 At this point this only function parameters should have
1347 REG_EQUIV notes and if the argument slot is used somewhere
1348 explicitly, it means address of parameter has been taken,
1349 so we should not extend the lifetime of the pseudo. */
1350 && ((note
= find_reg_note (insn
, REG_EQUIV
, NULL_RTX
)) == 0
1351 || ! MEM_P (XEXP (note
, 0))))
1353 /* Stores are never anticipatable. */
1355 /* An expression is not available if its operands are
1356 subsequently modified, including this insn. It's also not
1357 available if this is a branch, because we can't insert
1358 a set after the branch. */
1359 int avail_p
= oprs_available_p (dest
, insn
)
1362 /* Record the memory expression (DEST) in the hash table. */
1363 insert_expr_in_table (dest
, GET_MODE (dest
), insn
,
1364 antic_p
, avail_p
, max_distance
, table
);
1370 hash_scan_clobber (rtx x ATTRIBUTE_UNUSED
, rtx_insn
*insn ATTRIBUTE_UNUSED
,
1371 struct gcse_hash_table_d
*table ATTRIBUTE_UNUSED
)
1373 /* Currently nothing to do. */
1377 hash_scan_call (rtx x ATTRIBUTE_UNUSED
, rtx_insn
*insn ATTRIBUTE_UNUSED
,
1378 struct gcse_hash_table_d
*table ATTRIBUTE_UNUSED
)
1380 /* Currently nothing to do. */
1383 /* Process INSN and add hash table entries as appropriate. */
1386 hash_scan_insn (rtx_insn
*insn
, struct gcse_hash_table_d
*table
)
1388 rtx pat
= PATTERN (insn
);
1391 /* Pick out the sets of INSN and for other forms of instructions record
1392 what's been modified. */
1394 if (GET_CODE (pat
) == SET
)
1395 hash_scan_set (pat
, insn
, table
);
1397 else if (GET_CODE (pat
) == CLOBBER
)
1398 hash_scan_clobber (pat
, insn
, table
);
1400 else if (GET_CODE (pat
) == CALL
)
1401 hash_scan_call (pat
, insn
, table
);
1403 else if (GET_CODE (pat
) == PARALLEL
)
1404 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
1406 rtx x
= XVECEXP (pat
, 0, i
);
1408 if (GET_CODE (x
) == SET
)
1409 hash_scan_set (x
, insn
, table
);
1410 else if (GET_CODE (x
) == CLOBBER
)
1411 hash_scan_clobber (x
, insn
, table
);
1412 else if (GET_CODE (x
) == CALL
)
1413 hash_scan_call (x
, insn
, table
);
1417 /* Dump the hash table TABLE to file FILE under the name NAME. */
1420 dump_hash_table (FILE *file
, const char *name
, struct gcse_hash_table_d
*table
)
1423 /* Flattened out table, so it's printed in proper order. */
1424 struct gcse_expr
**flat_table
;
1425 unsigned int *hash_val
;
1426 struct gcse_expr
*expr
;
1428 flat_table
= XCNEWVEC (struct gcse_expr
*, table
->n_elems
);
1429 hash_val
= XNEWVEC (unsigned int, table
->n_elems
);
1431 for (i
= 0; i
< (int) table
->size
; i
++)
1432 for (expr
= table
->table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
1434 flat_table
[expr
->bitmap_index
] = expr
;
1435 hash_val
[expr
->bitmap_index
] = i
;
1438 fprintf (file
, "%s hash table (%d buckets, %d entries)\n",
1439 name
, table
->size
, table
->n_elems
);
1441 for (i
= 0; i
< (int) table
->n_elems
; i
++)
1442 if (flat_table
[i
] != 0)
1444 expr
= flat_table
[i
];
1445 fprintf (file
, "Index %d (hash value %d; max distance %d)\n ",
1446 expr
->bitmap_index
, hash_val
[i
], expr
->max_distance
);
1447 print_rtl (file
, expr
->expr
);
1448 fprintf (file
, "\n");
1451 fprintf (file
, "\n");
1457 /* Record register first/last/block set information for REGNO in INSN.
1459 first_set records the first place in the block where the register
1460 is set and is used to compute "anticipatability".
1462 last_set records the last place in the block where the register
1463 is set and is used to compute "availability".
1465 last_bb records the block for which first_set and last_set are
1466 valid, as a quick test to invalidate them. */
1469 record_last_reg_set_info (rtx insn
, int regno
)
1471 struct reg_avail_info
*info
= ®_avail_info
[regno
];
1472 int luid
= DF_INSN_LUID (insn
);
1474 info
->last_set
= luid
;
1475 if (info
->last_bb
!= current_bb
)
1477 info
->last_bb
= current_bb
;
1478 info
->first_set
= luid
;
1482 /* Record all of the canonicalized MEMs of record_last_mem_set_info's insn.
1483 Note we store a pair of elements in the list, so they have to be
1484 taken off pairwise. */
1487 canon_list_insert (rtx dest ATTRIBUTE_UNUSED
, const_rtx x ATTRIBUTE_UNUSED
,
1490 rtx dest_addr
, insn
;
1494 while (GET_CODE (dest
) == SUBREG
1495 || GET_CODE (dest
) == ZERO_EXTRACT
1496 || GET_CODE (dest
) == STRICT_LOW_PART
)
1497 dest
= XEXP (dest
, 0);
1499 /* If DEST is not a MEM, then it will not conflict with a load. Note
1500 that function calls are assumed to clobber memory, but are handled
1506 dest_addr
= get_addr (XEXP (dest
, 0));
1507 dest_addr
= canon_rtx (dest_addr
);
1508 insn
= (rtx
) v_insn
;
1509 bb
= BLOCK_FOR_INSN (insn
)->index
;
1512 pair
.dest_addr
= dest_addr
;
1513 canon_modify_mem_list
[bb
].safe_push (pair
);
1516 /* Record memory modification information for INSN. We do not actually care
1517 about the memory location(s) that are set, or even how they are set (consider
1518 a CALL_INSN). We merely need to record which insns modify memory. */
1521 record_last_mem_set_info (rtx_insn
*insn
)
1528 /* load_killed_in_block_p will handle the case of calls clobbering
1530 bb
= BLOCK_FOR_INSN (insn
)->index
;
1531 modify_mem_list
[bb
].safe_push (insn
);
1532 bitmap_set_bit (modify_mem_list_set
, bb
);
1535 bitmap_set_bit (blocks_with_calls
, bb
);
1537 note_stores (PATTERN (insn
), canon_list_insert
, (void*) insn
);
1540 /* Called from compute_hash_table via note_stores to handle one
1541 SET or CLOBBER in an insn. DATA is really the instruction in which
1542 the SET is taking place. */
1545 record_last_set_info (rtx dest
, const_rtx setter ATTRIBUTE_UNUSED
, void *data
)
1547 rtx_insn
*last_set_insn
= (rtx_insn
*) data
;
1549 if (GET_CODE (dest
) == SUBREG
)
1550 dest
= SUBREG_REG (dest
);
1553 record_last_reg_set_info (last_set_insn
, REGNO (dest
));
1554 else if (MEM_P (dest
)
1555 /* Ignore pushes, they clobber nothing. */
1556 && ! push_operand (dest
, GET_MODE (dest
)))
1557 record_last_mem_set_info (last_set_insn
);
1560 /* Top level function to create an expression hash table.
1562 Expression entries are placed in the hash table if
1563 - they are of the form (set (pseudo-reg) src),
1564 - src is something we want to perform GCSE on,
1565 - none of the operands are subsequently modified in the block
1567 Currently src must be a pseudo-reg or a const_int.
1569 TABLE is the table computed. */
1572 compute_hash_table_work (struct gcse_hash_table_d
*table
)
1576 /* re-Cache any INSN_LIST nodes we have allocated. */
1577 clear_modify_mem_tables ();
1578 /* Some working arrays used to track first and last set in each block. */
1579 reg_avail_info
= GNEWVEC (struct reg_avail_info
, max_reg_num ());
1581 for (i
= 0; i
< max_reg_num (); ++i
)
1582 reg_avail_info
[i
].last_bb
= NULL
;
1584 FOR_EACH_BB_FN (current_bb
, cfun
)
1589 /* First pass over the instructions records information used to
1590 determine when registers and memory are first and last set. */
1591 FOR_BB_INSNS (current_bb
, insn
)
1593 if (!NONDEBUG_INSN_P (insn
))
1598 hard_reg_set_iterator hrsi
;
1599 EXECUTE_IF_SET_IN_HARD_REG_SET (regs_invalidated_by_call
,
1601 record_last_reg_set_info (insn
, regno
);
1603 if (! RTL_CONST_OR_PURE_CALL_P (insn
))
1604 record_last_mem_set_info (insn
);
1607 note_stores (PATTERN (insn
), record_last_set_info
, insn
);
1610 /* The next pass builds the hash table. */
1611 FOR_BB_INSNS (current_bb
, insn
)
1612 if (NONDEBUG_INSN_P (insn
))
1613 hash_scan_insn (insn
, table
);
1616 free (reg_avail_info
);
1617 reg_avail_info
= NULL
;
1620 /* Allocate space for the set/expr hash TABLE.
1621 It is used to determine the number of buckets to use. */
1624 alloc_hash_table (struct gcse_hash_table_d
*table
)
1628 n
= get_max_insn_count ();
1630 table
->size
= n
/ 4;
1631 if (table
->size
< 11)
1634 /* Attempt to maintain efficient use of hash table.
1635 Making it an odd number is simplest for now.
1636 ??? Later take some measurements. */
1638 n
= table
->size
* sizeof (struct gcse_expr
*);
1639 table
->table
= GNEWVAR (struct gcse_expr
*, n
);
1642 /* Free things allocated by alloc_hash_table. */
1645 free_hash_table (struct gcse_hash_table_d
*table
)
1647 free (table
->table
);
1650 /* Compute the expression hash table TABLE. */
1653 compute_hash_table (struct gcse_hash_table_d
*table
)
1655 /* Initialize count of number of entries in hash table. */
1657 memset (table
->table
, 0, table
->size
* sizeof (struct gcse_expr
*));
1659 compute_hash_table_work (table
);
1662 /* Expression tracking support. */
1664 /* Clear canon_modify_mem_list and modify_mem_list tables. */
1666 clear_modify_mem_tables (void)
1671 EXECUTE_IF_SET_IN_BITMAP (modify_mem_list_set
, 0, i
, bi
)
1673 modify_mem_list
[i
].release ();
1674 canon_modify_mem_list
[i
].release ();
1676 bitmap_clear (modify_mem_list_set
);
1677 bitmap_clear (blocks_with_calls
);
1680 /* Release memory used by modify_mem_list_set. */
1683 free_modify_mem_tables (void)
1685 clear_modify_mem_tables ();
1686 free (modify_mem_list
);
1687 free (canon_modify_mem_list
);
1688 modify_mem_list
= 0;
1689 canon_modify_mem_list
= 0;
1692 /* For each block, compute whether X is transparent. X is either an
1693 expression or an assignment [though we don't care which, for this context
1694 an assignment is treated as an expression]. For each block where an
1695 element of X is modified, reset the INDX bit in BMAP. */
1698 compute_transp (const_rtx x
, int indx
, sbitmap
*bmap
)
1704 /* repeat is used to turn tail-recursion into iteration since GCC
1705 can't do it when there's no return value. */
1711 code
= GET_CODE (x
);
1717 for (def
= DF_REG_DEF_CHAIN (REGNO (x
));
1719 def
= DF_REF_NEXT_REG (def
))
1720 bitmap_clear_bit (bmap
[DF_REF_BB (def
)->index
], indx
);
1726 if (! MEM_READONLY_P (x
))
1732 x_addr
= get_addr (XEXP (x
, 0));
1733 x_addr
= canon_rtx (x_addr
);
1735 /* First handle all the blocks with calls. We don't need to
1736 do any list walking for them. */
1737 EXECUTE_IF_SET_IN_BITMAP (blocks_with_calls
, 0, bb_index
, bi
)
1739 bitmap_clear_bit (bmap
[bb_index
], indx
);
1742 /* Now iterate over the blocks which have memory modifications
1743 but which do not have any calls. */
1744 EXECUTE_IF_AND_COMPL_IN_BITMAP (modify_mem_list_set
,
1748 vec
<modify_pair
> list
1749 = canon_modify_mem_list
[bb_index
];
1753 FOR_EACH_VEC_ELT_REVERSE (list
, ix
, pair
)
1755 rtx dest
= pair
->dest
;
1756 rtx dest_addr
= pair
->dest_addr
;
1758 if (canon_true_dependence (dest
, GET_MODE (dest
),
1759 dest_addr
, x
, x_addr
))
1761 bitmap_clear_bit (bmap
[bb_index
], indx
);
1785 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
1789 /* If we are about to do the last recursive call
1790 needed at this level, change it into iteration.
1791 This function is called enough to be worth it. */
1798 compute_transp (XEXP (x
, i
), indx
, bmap
);
1800 else if (fmt
[i
] == 'E')
1801 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1802 compute_transp (XVECEXP (x
, i
, j
), indx
, bmap
);
1806 /* Compute PRE+LCM working variables. */
1808 /* Local properties of expressions. */
1810 /* Nonzero for expressions that are transparent in the block. */
1811 static sbitmap
*transp
;
1813 /* Nonzero for expressions that are computed (available) in the block. */
1814 static sbitmap
*comp
;
1816 /* Nonzero for expressions that are locally anticipatable in the block. */
1817 static sbitmap
*antloc
;
1819 /* Nonzero for expressions where this block is an optimal computation
1821 static sbitmap
*pre_optimal
;
1823 /* Nonzero for expressions which are redundant in a particular block. */
1824 static sbitmap
*pre_redundant
;
1826 /* Nonzero for expressions which should be inserted on a specific edge. */
1827 static sbitmap
*pre_insert_map
;
1829 /* Nonzero for expressions which should be deleted in a specific block. */
1830 static sbitmap
*pre_delete_map
;
1832 /* Allocate vars used for PRE analysis. */
1835 alloc_pre_mem (int n_blocks
, int n_exprs
)
1837 transp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
1838 comp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
1839 antloc
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
1842 pre_redundant
= NULL
;
1843 pre_insert_map
= NULL
;
1844 pre_delete_map
= NULL
;
1845 ae_kill
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
1847 /* pre_insert and pre_delete are allocated later. */
1850 /* Free vars used for PRE analysis. */
1855 sbitmap_vector_free (transp
);
1856 sbitmap_vector_free (comp
);
1858 /* ANTLOC and AE_KILL are freed just after pre_lcm finishes. */
1861 sbitmap_vector_free (pre_optimal
);
1863 sbitmap_vector_free (pre_redundant
);
1865 sbitmap_vector_free (pre_insert_map
);
1867 sbitmap_vector_free (pre_delete_map
);
1869 transp
= comp
= NULL
;
1870 pre_optimal
= pre_redundant
= pre_insert_map
= pre_delete_map
= NULL
;
1873 /* Remove certain expressions from anticipatable and transparent
1874 sets of basic blocks that have incoming abnormal edge.
1875 For PRE remove potentially trapping expressions to avoid placing
1876 them on abnormal edges. For hoisting remove memory references that
1877 can be clobbered by calls. */
1880 prune_expressions (bool pre_p
)
1882 sbitmap prune_exprs
;
1883 struct gcse_expr
*expr
;
1887 prune_exprs
= sbitmap_alloc (expr_hash_table
.n_elems
);
1888 bitmap_clear (prune_exprs
);
1889 for (ui
= 0; ui
< expr_hash_table
.size
; ui
++)
1891 for (expr
= expr_hash_table
.table
[ui
]; expr
; expr
= expr
->next_same_hash
)
1893 /* Note potentially trapping expressions. */
1894 if (may_trap_p (expr
->expr
))
1896 bitmap_set_bit (prune_exprs
, expr
->bitmap_index
);
1900 if (!pre_p
&& MEM_P (expr
->expr
))
1901 /* Note memory references that can be clobbered by a call.
1902 We do not split abnormal edges in hoisting, so would
1903 a memory reference get hoisted along an abnormal edge,
1904 it would be placed /before/ the call. Therefore, only
1905 constant memory references can be hoisted along abnormal
1908 if (GET_CODE (XEXP (expr
->expr
, 0)) == SYMBOL_REF
1909 && CONSTANT_POOL_ADDRESS_P (XEXP (expr
->expr
, 0)))
1912 if (MEM_READONLY_P (expr
->expr
)
1913 && !MEM_VOLATILE_P (expr
->expr
)
1914 && MEM_NOTRAP_P (expr
->expr
))
1915 /* Constant memory reference, e.g., a PIC address. */
1918 /* ??? Optimally, we would use interprocedural alias
1919 analysis to determine if this mem is actually killed
1922 bitmap_set_bit (prune_exprs
, expr
->bitmap_index
);
1927 FOR_EACH_BB_FN (bb
, cfun
)
1932 /* If the current block is the destination of an abnormal edge, we
1933 kill all trapping (for PRE) and memory (for hoist) expressions
1934 because we won't be able to properly place the instruction on
1935 the edge. So make them neither anticipatable nor transparent.
1936 This is fairly conservative.
1938 ??? For hoisting it may be necessary to check for set-and-jump
1939 instructions here, not just for abnormal edges. The general problem
1940 is that when an expression cannot not be placed right at the end of
1941 a basic block we should account for any side-effects of a subsequent
1942 jump instructions that could clobber the expression. It would
1943 be best to implement this check along the lines of
1944 should_hoist_expr_to_dom where the target block is already known
1945 and, hence, there's no need to conservatively prune expressions on
1946 "intermediate" set-and-jump instructions. */
1947 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1948 if ((e
->flags
& EDGE_ABNORMAL
)
1949 && (pre_p
|| CALL_P (BB_END (e
->src
))))
1951 bitmap_and_compl (antloc
[bb
->index
],
1952 antloc
[bb
->index
], prune_exprs
);
1953 bitmap_and_compl (transp
[bb
->index
],
1954 transp
[bb
->index
], prune_exprs
);
1959 sbitmap_free (prune_exprs
);
1962 /* It may be necessary to insert a large number of insns on edges to
1963 make the existing occurrences of expressions fully redundant. This
1964 routine examines the set of insertions and deletions and if the ratio
1965 of insertions to deletions is too high for a particular expression, then
1966 the expression is removed from the insertion/deletion sets.
1968 N_ELEMS is the number of elements in the hash table. */
1971 prune_insertions_deletions (int n_elems
)
1973 sbitmap_iterator sbi
;
1974 sbitmap prune_exprs
;
1976 /* We always use I to iterate over blocks/edges and J to iterate over
1980 /* Counts for the number of times an expression needs to be inserted and
1981 number of times an expression can be removed as a result. */
1982 int *insertions
= GCNEWVEC (int, n_elems
);
1983 int *deletions
= GCNEWVEC (int, n_elems
);
1985 /* Set of expressions which require too many insertions relative to
1986 the number of deletions achieved. We will prune these out of the
1987 insertion/deletion sets. */
1988 prune_exprs
= sbitmap_alloc (n_elems
);
1989 bitmap_clear (prune_exprs
);
1991 /* Iterate over the edges counting the number of times each expression
1992 needs to be inserted. */
1993 for (i
= 0; i
< (unsigned) n_edges_for_fn (cfun
); i
++)
1995 EXECUTE_IF_SET_IN_BITMAP (pre_insert_map
[i
], 0, j
, sbi
)
1999 /* Similarly for deletions, but those occur in blocks rather than on
2001 for (i
= 0; i
< (unsigned) last_basic_block_for_fn (cfun
); i
++)
2003 EXECUTE_IF_SET_IN_BITMAP (pre_delete_map
[i
], 0, j
, sbi
)
2007 /* Now that we have accurate counts, iterate over the elements in the
2008 hash table and see if any need too many insertions relative to the
2009 number of evaluations that can be removed. If so, mark them in
2011 for (j
= 0; j
< (unsigned) n_elems
; j
++)
2013 && ((unsigned) insertions
[j
] / deletions
[j
]) > MAX_GCSE_INSERTION_RATIO
)
2014 bitmap_set_bit (prune_exprs
, j
);
2016 /* Now prune PRE_INSERT_MAP and PRE_DELETE_MAP based on PRUNE_EXPRS. */
2017 EXECUTE_IF_SET_IN_BITMAP (prune_exprs
, 0, j
, sbi
)
2019 for (i
= 0; i
< (unsigned) n_edges_for_fn (cfun
); i
++)
2020 bitmap_clear_bit (pre_insert_map
[i
], j
);
2022 for (i
= 0; i
< (unsigned) last_basic_block_for_fn (cfun
); i
++)
2023 bitmap_clear_bit (pre_delete_map
[i
], j
);
2026 sbitmap_free (prune_exprs
);
2031 /* Top level routine to do the dataflow analysis needed by PRE. */
2033 static struct edge_list
*
2034 compute_pre_data (void)
2036 struct edge_list
*edge_list
;
2039 compute_local_properties (transp
, comp
, antloc
, &expr_hash_table
);
2040 prune_expressions (true);
2041 bitmap_vector_clear (ae_kill
, last_basic_block_for_fn (cfun
));
2043 /* Compute ae_kill for each basic block using:
2048 FOR_EACH_BB_FN (bb
, cfun
)
2050 bitmap_ior (ae_kill
[bb
->index
], transp
[bb
->index
], comp
[bb
->index
]);
2051 bitmap_not (ae_kill
[bb
->index
], ae_kill
[bb
->index
]);
2054 edge_list
= pre_edge_lcm (expr_hash_table
.n_elems
, transp
, comp
, antloc
,
2055 ae_kill
, &pre_insert_map
, &pre_delete_map
);
2056 sbitmap_vector_free (antloc
);
2058 sbitmap_vector_free (ae_kill
);
2061 prune_insertions_deletions (expr_hash_table
.n_elems
);
2068 /* Return nonzero if an occurrence of expression EXPR in OCCR_BB would reach
2071 VISITED is a pointer to a working buffer for tracking which BB's have
2072 been visited. It is NULL for the top-level call.
2074 We treat reaching expressions that go through blocks containing the same
2075 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
2076 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
2077 2 as not reaching. The intent is to improve the probability of finding
2078 only one reaching expression and to reduce register lifetimes by picking
2079 the closest such expression. */
2082 pre_expr_reaches_here_p_work (basic_block occr_bb
, struct gcse_expr
*expr
,
2083 basic_block bb
, char *visited
)
2088 FOR_EACH_EDGE (pred
, ei
, bb
->preds
)
2090 basic_block pred_bb
= pred
->src
;
2092 if (pred
->src
== ENTRY_BLOCK_PTR_FOR_FN (cfun
)
2093 /* Has predecessor has already been visited? */
2094 || visited
[pred_bb
->index
])
2095 ;/* Nothing to do. */
2097 /* Does this predecessor generate this expression? */
2098 else if (bitmap_bit_p (comp
[pred_bb
->index
], expr
->bitmap_index
))
2100 /* Is this the occurrence we're looking for?
2101 Note that there's only one generating occurrence per block
2102 so we just need to check the block number. */
2103 if (occr_bb
== pred_bb
)
2106 visited
[pred_bb
->index
] = 1;
2108 /* Ignore this predecessor if it kills the expression. */
2109 else if (! bitmap_bit_p (transp
[pred_bb
->index
], expr
->bitmap_index
))
2110 visited
[pred_bb
->index
] = 1;
2112 /* Neither gen nor kill. */
2115 visited
[pred_bb
->index
] = 1;
2116 if (pre_expr_reaches_here_p_work (occr_bb
, expr
, pred_bb
, visited
))
2121 /* All paths have been checked. */
2125 /* The wrapper for pre_expr_reaches_here_work that ensures that any
2126 memory allocated for that function is returned. */
2129 pre_expr_reaches_here_p (basic_block occr_bb
, struct gcse_expr
*expr
, basic_block bb
)
2132 char *visited
= XCNEWVEC (char, last_basic_block_for_fn (cfun
));
2134 rval
= pre_expr_reaches_here_p_work (occr_bb
, expr
, bb
, visited
);
2140 /* Generate RTL to copy an EXPR to its `reaching_reg' and return it. */
2143 process_insert_insn (struct gcse_expr
*expr
)
2145 rtx reg
= expr
->reaching_reg
;
2146 /* Copy the expression to make sure we don't have any sharing issues. */
2147 rtx exp
= copy_rtx (expr
->expr
);
2152 /* If the expression is something that's an operand, like a constant,
2153 just copy it to a register. */
2154 if (general_operand (exp
, GET_MODE (reg
)))
2155 emit_move_insn (reg
, exp
);
2157 /* Otherwise, make a new insn to compute this expression and make sure the
2158 insn will be recognized (this also adds any needed CLOBBERs). */
2161 rtx_insn
*insn
= emit_insn (gen_rtx_SET (VOIDmode
, reg
, exp
));
2163 if (insn_invalid_p (insn
, false))
2173 /* Add EXPR to the end of basic block BB.
2175 This is used by both the PRE and code hoisting. */
2178 insert_insn_end_basic_block (struct gcse_expr
*expr
, basic_block bb
)
2180 rtx_insn
*insn
= BB_END (bb
);
2182 rtx reg
= expr
->reaching_reg
;
2183 int regno
= REGNO (reg
);
2184 rtx_insn
*pat
, *pat_end
;
2186 pat
= process_insert_insn (expr
);
2187 gcc_assert (pat
&& INSN_P (pat
));
2190 while (NEXT_INSN (pat_end
) != NULL_RTX
)
2191 pat_end
= NEXT_INSN (pat_end
);
2193 /* If the last insn is a jump, insert EXPR in front [taking care to
2194 handle cc0, etc. properly]. Similarly we need to care trapping
2195 instructions in presence of non-call exceptions. */
2198 || (NONJUMP_INSN_P (insn
)
2199 && (!single_succ_p (bb
)
2200 || single_succ_edge (bb
)->flags
& EDGE_ABNORMAL
)))
2203 /* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
2204 if cc0 isn't set. */
2205 rtx note
= find_reg_note (insn
, REG_CC_SETTER
, NULL_RTX
);
2207 insn
= safe_as_a
<rtx_insn
*> (XEXP (note
, 0));
2210 rtx_insn
*maybe_cc0_setter
= prev_nonnote_insn (insn
);
2211 if (maybe_cc0_setter
2212 && INSN_P (maybe_cc0_setter
)
2213 && sets_cc0_p (PATTERN (maybe_cc0_setter
)))
2214 insn
= maybe_cc0_setter
;
2217 /* FIXME: What if something in cc0/jump uses value set in new insn? */
2218 new_insn
= emit_insn_before_noloc (pat
, insn
, bb
);
2221 /* Likewise if the last insn is a call, as will happen in the presence
2222 of exception handling. */
2223 else if (CALL_P (insn
)
2224 && (!single_succ_p (bb
)
2225 || single_succ_edge (bb
)->flags
& EDGE_ABNORMAL
))
2227 /* Keeping in mind targets with small register classes and parameters
2228 in registers, we search backward and place the instructions before
2229 the first parameter is loaded. Do this for everyone for consistency
2230 and a presumption that we'll get better code elsewhere as well. */
2232 /* Since different machines initialize their parameter registers
2233 in different orders, assume nothing. Collect the set of all
2234 parameter registers. */
2235 insn
= find_first_parameter_load (insn
, BB_HEAD (bb
));
2237 /* If we found all the parameter loads, then we want to insert
2238 before the first parameter load.
2240 If we did not find all the parameter loads, then we might have
2241 stopped on the head of the block, which could be a CODE_LABEL.
2242 If we inserted before the CODE_LABEL, then we would be putting
2243 the insn in the wrong basic block. In that case, put the insn
2244 after the CODE_LABEL. Also, respect NOTE_INSN_BASIC_BLOCK. */
2245 while (LABEL_P (insn
)
2246 || NOTE_INSN_BASIC_BLOCK_P (insn
))
2247 insn
= NEXT_INSN (insn
);
2249 new_insn
= emit_insn_before_noloc (pat
, insn
, bb
);
2252 new_insn
= emit_insn_after_noloc (pat
, insn
, bb
);
2257 add_label_notes (PATTERN (pat
), new_insn
);
2260 pat
= NEXT_INSN (pat
);
2263 gcse_create_count
++;
2267 fprintf (dump_file
, "PRE/HOIST: end of bb %d, insn %d, ",
2268 bb
->index
, INSN_UID (new_insn
));
2269 fprintf (dump_file
, "copying expression %d to reg %d\n",
2270 expr
->bitmap_index
, regno
);
2274 /* Insert partially redundant expressions on edges in the CFG to make
2275 the expressions fully redundant. */
2278 pre_edge_insert (struct edge_list
*edge_list
, struct gcse_expr
**index_map
)
2280 int e
, i
, j
, num_edges
, set_size
, did_insert
= 0;
2283 /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge
2284 if it reaches any of the deleted expressions. */
2286 set_size
= pre_insert_map
[0]->size
;
2287 num_edges
= NUM_EDGES (edge_list
);
2288 inserted
= sbitmap_vector_alloc (num_edges
, expr_hash_table
.n_elems
);
2289 bitmap_vector_clear (inserted
, num_edges
);
2291 for (e
= 0; e
< num_edges
; e
++)
2294 basic_block bb
= INDEX_EDGE_PRED_BB (edge_list
, e
);
2296 for (i
= indx
= 0; i
< set_size
; i
++, indx
+= SBITMAP_ELT_BITS
)
2298 SBITMAP_ELT_TYPE insert
= pre_insert_map
[e
]->elms
[i
];
2301 insert
&& j
< (int) expr_hash_table
.n_elems
;
2303 if ((insert
& 1) != 0 && index_map
[j
]->reaching_reg
!= NULL_RTX
)
2305 struct gcse_expr
*expr
= index_map
[j
];
2306 struct gcse_occr
*occr
;
2308 /* Now look at each deleted occurrence of this expression. */
2309 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
2311 if (! occr
->deleted_p
)
2314 /* Insert this expression on this edge if it would
2315 reach the deleted occurrence in BB. */
2316 if (!bitmap_bit_p (inserted
[e
], j
))
2319 edge eg
= INDEX_EDGE (edge_list
, e
);
2321 /* We can't insert anything on an abnormal and
2322 critical edge, so we insert the insn at the end of
2323 the previous block. There are several alternatives
2324 detailed in Morgans book P277 (sec 10.5) for
2325 handling this situation. This one is easiest for
2328 if (eg
->flags
& EDGE_ABNORMAL
)
2329 insert_insn_end_basic_block (index_map
[j
], bb
);
2332 insn
= process_insert_insn (index_map
[j
]);
2333 insert_insn_on_edge (insn
, eg
);
2338 fprintf (dump_file
, "PRE: edge (%d,%d), ",
2340 INDEX_EDGE_SUCC_BB (edge_list
, e
)->index
);
2341 fprintf (dump_file
, "copy expression %d\n",
2342 expr
->bitmap_index
);
2345 update_ld_motion_stores (expr
);
2346 bitmap_set_bit (inserted
[e
], j
);
2348 gcse_create_count
++;
2355 sbitmap_vector_free (inserted
);
2359 /* Copy the result of EXPR->EXPR generated by INSN to EXPR->REACHING_REG.
2360 Given "old_reg <- expr" (INSN), instead of adding after it
2361 reaching_reg <- old_reg
2362 it's better to do the following:
2363 reaching_reg <- expr
2364 old_reg <- reaching_reg
2365 because this way copy propagation can discover additional PRE
2366 opportunities. But if this fails, we try the old way.
2367 When "expr" is a store, i.e.
2368 given "MEM <- old_reg", instead of adding after it
2369 reaching_reg <- old_reg
2370 it's better to add it before as follows:
2371 reaching_reg <- old_reg
2372 MEM <- reaching_reg. */
2375 pre_insert_copy_insn (struct gcse_expr
*expr
, rtx_insn
*insn
)
2377 rtx reg
= expr
->reaching_reg
;
2378 int regno
= REGNO (reg
);
2379 int indx
= expr
->bitmap_index
;
2380 rtx pat
= PATTERN (insn
);
2381 rtx set
, first_set
, new_insn
;
2385 /* This block matches the logic in hash_scan_insn. */
2386 switch (GET_CODE (pat
))
2393 /* Search through the parallel looking for the set whose
2394 source was the expression that we're interested in. */
2395 first_set
= NULL_RTX
;
2397 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
2399 rtx x
= XVECEXP (pat
, 0, i
);
2400 if (GET_CODE (x
) == SET
)
2402 /* If the source was a REG_EQUAL or REG_EQUIV note, we
2403 may not find an equivalent expression, but in this
2404 case the PARALLEL will have a single set. */
2405 if (first_set
== NULL_RTX
)
2407 if (expr_equiv_p (SET_SRC (x
), expr
->expr
))
2415 gcc_assert (first_set
);
2416 if (set
== NULL_RTX
)
2424 if (REG_P (SET_DEST (set
)))
2426 old_reg
= SET_DEST (set
);
2427 /* Check if we can modify the set destination in the original insn. */
2428 if (validate_change (insn
, &SET_DEST (set
), reg
, 0))
2430 new_insn
= gen_move_insn (old_reg
, reg
);
2431 new_insn
= emit_insn_after (new_insn
, insn
);
2435 new_insn
= gen_move_insn (reg
, old_reg
);
2436 new_insn
= emit_insn_after (new_insn
, insn
);
2439 else /* This is possible only in case of a store to memory. */
2441 old_reg
= SET_SRC (set
);
2442 new_insn
= gen_move_insn (reg
, old_reg
);
2444 /* Check if we can modify the set source in the original insn. */
2445 if (validate_change (insn
, &SET_SRC (set
), reg
, 0))
2446 new_insn
= emit_insn_before (new_insn
, insn
);
2448 new_insn
= emit_insn_after (new_insn
, insn
);
2451 gcse_create_count
++;
2455 "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
2456 BLOCK_FOR_INSN (insn
)->index
, INSN_UID (new_insn
), indx
,
2457 INSN_UID (insn
), regno
);
2460 /* Copy available expressions that reach the redundant expression
2461 to `reaching_reg'. */
2464 pre_insert_copies (void)
2466 unsigned int i
, added_copy
;
2467 struct gcse_expr
*expr
;
2468 struct gcse_occr
*occr
;
2469 struct gcse_occr
*avail
;
2471 /* For each available expression in the table, copy the result to
2472 `reaching_reg' if the expression reaches a deleted one.
2474 ??? The current algorithm is rather brute force.
2475 Need to do some profiling. */
2477 for (i
= 0; i
< expr_hash_table
.size
; i
++)
2478 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
2480 /* If the basic block isn't reachable, PPOUT will be TRUE. However,
2481 we don't want to insert a copy here because the expression may not
2482 really be redundant. So only insert an insn if the expression was
2483 deleted. This test also avoids further processing if the
2484 expression wasn't deleted anywhere. */
2485 if (expr
->reaching_reg
== NULL
)
2488 /* Set when we add a copy for that expression. */
2491 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
2493 if (! occr
->deleted_p
)
2496 for (avail
= expr
->avail_occr
; avail
!= NULL
; avail
= avail
->next
)
2498 rtx_insn
*insn
= avail
->insn
;
2500 /* No need to handle this one if handled already. */
2501 if (avail
->copied_p
)
2504 /* Don't handle this one if it's a redundant one. */
2505 if (insn
->deleted ())
2508 /* Or if the expression doesn't reach the deleted one. */
2509 if (! pre_expr_reaches_here_p (BLOCK_FOR_INSN (avail
->insn
),
2511 BLOCK_FOR_INSN (occr
->insn
)))
2516 /* Copy the result of avail to reaching_reg. */
2517 pre_insert_copy_insn (expr
, insn
);
2518 avail
->copied_p
= 1;
2523 update_ld_motion_stores (expr
);
2534 /* Increment number of sets and record set in DATA. */
2537 record_set_data (rtx dest
, const_rtx set
, void *data
)
2539 struct set_data
*s
= (struct set_data
*)data
;
2541 if (GET_CODE (set
) == SET
)
2543 /* We allow insns having multiple sets, where all but one are
2544 dead as single set insns. In the common case only a single
2545 set is present, so we want to avoid checking for REG_UNUSED
2546 notes unless necessary. */
2548 && find_reg_note (s
->insn
, REG_UNUSED
, SET_DEST (s
->set
))
2549 && !side_effects_p (s
->set
))
2554 /* Record this set. */
2558 else if (!find_reg_note (s
->insn
, REG_UNUSED
, dest
)
2559 || side_effects_p (set
))
2565 single_set_gcse (rtx_insn
*insn
)
2570 gcc_assert (INSN_P (insn
));
2572 /* Optimize common case. */
2573 pattern
= PATTERN (insn
);
2574 if (GET_CODE (pattern
) == SET
)
2579 note_stores (pattern
, record_set_data
, &s
);
2581 /* Considered invariant insns have exactly one set. */
2582 gcc_assert (s
.nsets
== 1);
2586 /* Emit move from SRC to DEST noting the equivalence with expression computed
2590 gcse_emit_move_after (rtx dest
, rtx src
, rtx_insn
*insn
)
2593 const_rtx set
= single_set_gcse (insn
);
2598 /* This should never fail since we're creating a reg->reg copy
2599 we've verified to be valid. */
2601 new_rtx
= emit_insn_after (gen_move_insn (dest
, src
), insn
);
2603 /* Note the equivalence for local CSE pass. Take the note from the old
2604 set if there was one. Otherwise record the SET_SRC from the old set
2605 unless DEST is also an operand of the SET_SRC. */
2606 set2
= single_set (new_rtx
);
2607 if (!set2
|| !rtx_equal_p (SET_DEST (set2
), dest
))
2609 if ((note
= find_reg_equal_equiv_note (insn
)))
2610 eqv
= XEXP (note
, 0);
2611 else if (! REG_P (dest
)
2612 || ! reg_mentioned_p (dest
, SET_SRC (set
)))
2613 eqv
= SET_SRC (set
);
2615 if (eqv
!= NULL_RTX
)
2616 set_unique_reg_note (new_rtx
, REG_EQUAL
, copy_insn_1 (eqv
));
2621 /* Delete redundant computations.
2622 Deletion is done by changing the insn to copy the `reaching_reg' of
2623 the expression into the result of the SET. It is left to later passes
2624 to propagate the copy or eliminate it.
2626 Return nonzero if a change is made. */
2633 struct gcse_expr
*expr
;
2634 struct gcse_occr
*occr
;
2637 for (i
= 0; i
< expr_hash_table
.size
; i
++)
2638 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
2640 int indx
= expr
->bitmap_index
;
2642 /* We only need to search antic_occr since we require ANTLOC != 0. */
2643 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
2645 rtx_insn
*insn
= occr
->insn
;
2647 basic_block bb
= BLOCK_FOR_INSN (insn
);
2649 /* We only delete insns that have a single_set. */
2650 if (bitmap_bit_p (pre_delete_map
[bb
->index
], indx
)
2651 && (set
= single_set (insn
)) != 0
2652 && dbg_cnt (pre_insn
))
2654 /* Create a pseudo-reg to store the result of reaching
2655 expressions into. Get the mode for the new pseudo from
2656 the mode of the original destination pseudo. */
2657 if (expr
->reaching_reg
== NULL
)
2658 expr
->reaching_reg
= gen_reg_rtx_and_attrs (SET_DEST (set
));
2660 gcse_emit_move_after (SET_DEST (set
), expr
->reaching_reg
, insn
);
2662 occr
->deleted_p
= 1;
2669 "PRE: redundant insn %d (expression %d) in ",
2670 INSN_UID (insn
), indx
);
2671 fprintf (dump_file
, "bb %d, reaching reg is %d\n",
2672 bb
->index
, REGNO (expr
->reaching_reg
));
2681 /* Perform GCSE optimizations using PRE.
2682 This is called by one_pre_gcse_pass after all the dataflow analysis
2685 This is based on the original Morel-Renvoise paper Fred Chow's thesis, and
2686 lazy code motion from Knoop, Ruthing and Steffen as described in Advanced
2687 Compiler Design and Implementation.
2689 ??? A new pseudo reg is created to hold the reaching expression. The nice
2690 thing about the classical approach is that it would try to use an existing
2691 reg. If the register can't be adequately optimized [i.e. we introduce
2692 reload problems], one could add a pass here to propagate the new register
2695 ??? We don't handle single sets in PARALLELs because we're [currently] not
2696 able to copy the rest of the parallel when we insert copies to create full
2697 redundancies from partial redundancies. However, there's no reason why we
2698 can't handle PARALLELs in the cases where there are no partial
2702 pre_gcse (struct edge_list
*edge_list
)
2705 int did_insert
, changed
;
2706 struct gcse_expr
**index_map
;
2707 struct gcse_expr
*expr
;
2709 /* Compute a mapping from expression number (`bitmap_index') to
2710 hash table entry. */
2712 index_map
= XCNEWVEC (struct gcse_expr
*, expr_hash_table
.n_elems
);
2713 for (i
= 0; i
< expr_hash_table
.size
; i
++)
2714 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
2715 index_map
[expr
->bitmap_index
] = expr
;
2717 /* Delete the redundant insns first so that
2718 - we know what register to use for the new insns and for the other
2719 ones with reaching expressions
2720 - we know which insns are redundant when we go to create copies */
2722 changed
= pre_delete ();
2723 did_insert
= pre_edge_insert (edge_list
, index_map
);
2725 /* In other places with reaching expressions, copy the expression to the
2726 specially allocated pseudo-reg that reaches the redundant expr. */
2727 pre_insert_copies ();
2730 commit_edge_insertions ();
2738 /* Top level routine to perform one PRE GCSE pass.
2740 Return nonzero if a change was made. */
2743 one_pre_gcse_pass (void)
2747 gcse_subst_count
= 0;
2748 gcse_create_count
= 0;
2750 /* Return if there's nothing to do, or it is too expensive. */
2751 if (n_basic_blocks_for_fn (cfun
) <= NUM_FIXED_BLOCKS
+ 1
2752 || is_too_expensive (_("PRE disabled")))
2755 /* We need alias. */
2756 init_alias_analysis ();
2759 gcc_obstack_init (&gcse_obstack
);
2762 alloc_hash_table (&expr_hash_table
);
2763 add_noreturn_fake_exit_edges ();
2765 compute_ld_motion_mems ();
2767 compute_hash_table (&expr_hash_table
);
2769 trim_ld_motion_mems ();
2771 dump_hash_table (dump_file
, "Expression", &expr_hash_table
);
2773 if (expr_hash_table
.n_elems
> 0)
2775 struct edge_list
*edge_list
;
2776 alloc_pre_mem (last_basic_block_for_fn (cfun
), expr_hash_table
.n_elems
);
2777 edge_list
= compute_pre_data ();
2778 changed
|= pre_gcse (edge_list
);
2779 free_edge_list (edge_list
);
2784 free_ld_motion_mems ();
2785 remove_fake_exit_edges ();
2786 free_hash_table (&expr_hash_table
);
2789 obstack_free (&gcse_obstack
, NULL
);
2791 /* We are finished with alias. */
2792 end_alias_analysis ();
2796 fprintf (dump_file
, "PRE GCSE of %s, %d basic blocks, %d bytes needed, ",
2797 current_function_name (), n_basic_blocks_for_fn (cfun
),
2799 fprintf (dump_file
, "%d substs, %d insns created\n",
2800 gcse_subst_count
, gcse_create_count
);
2806 /* If X contains any LABEL_REF's, add REG_LABEL_OPERAND notes for them
2807 to INSN. If such notes are added to an insn which references a
2808 CODE_LABEL, the LABEL_NUSES count is incremented. We have to add
2809 that note, because the following loop optimization pass requires
2812 /* ??? If there was a jump optimization pass after gcse and before loop,
2813 then we would not need to do this here, because jump would add the
2814 necessary REG_LABEL_OPERAND and REG_LABEL_TARGET notes. */
2817 add_label_notes (rtx x
, rtx insn
)
2819 enum rtx_code code
= GET_CODE (x
);
2823 if (code
== LABEL_REF
&& !LABEL_REF_NONLOCAL_P (x
))
2825 /* This code used to ignore labels that referred to dispatch tables to
2826 avoid flow generating (slightly) worse code.
2828 We no longer ignore such label references (see LABEL_REF handling in
2829 mark_jump_label for additional information). */
2831 /* There's no reason for current users to emit jump-insns with
2832 such a LABEL_REF, so we don't have to handle REG_LABEL_TARGET
2834 gcc_assert (!JUMP_P (insn
));
2835 add_reg_note (insn
, REG_LABEL_OPERAND
, LABEL_REF_LABEL (x
));
2837 if (LABEL_P (LABEL_REF_LABEL (x
)))
2838 LABEL_NUSES (LABEL_REF_LABEL (x
))++;
2843 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
2846 add_label_notes (XEXP (x
, i
), insn
);
2847 else if (fmt
[i
] == 'E')
2848 for (j
= XVECLEN (x
, i
) - 1; j
>= 0; j
--)
2849 add_label_notes (XVECEXP (x
, i
, j
), insn
);
2853 /* Code Hoisting variables and subroutines. */
2855 /* Very busy expressions. */
2856 static sbitmap
*hoist_vbein
;
2857 static sbitmap
*hoist_vbeout
;
2859 /* ??? We could compute post dominators and run this algorithm in
2860 reverse to perform tail merging, doing so would probably be
2861 more effective than the tail merging code in jump.c.
2863 It's unclear if tail merging could be run in parallel with
2864 code hoisting. It would be nice. */
2866 /* Allocate vars used for code hoisting analysis. */
2869 alloc_code_hoist_mem (int n_blocks
, int n_exprs
)
2871 antloc
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2872 transp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2873 comp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2875 hoist_vbein
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2876 hoist_vbeout
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2879 /* Free vars used for code hoisting analysis. */
2882 free_code_hoist_mem (void)
2884 sbitmap_vector_free (antloc
);
2885 sbitmap_vector_free (transp
);
2886 sbitmap_vector_free (comp
);
2888 sbitmap_vector_free (hoist_vbein
);
2889 sbitmap_vector_free (hoist_vbeout
);
2891 free_dominance_info (CDI_DOMINATORS
);
2894 /* Compute the very busy expressions at entry/exit from each block.
2896 An expression is very busy if all paths from a given point
2897 compute the expression. */
2900 compute_code_hoist_vbeinout (void)
2902 int changed
, passes
;
2905 bitmap_vector_clear (hoist_vbeout
, last_basic_block_for_fn (cfun
));
2906 bitmap_vector_clear (hoist_vbein
, last_basic_block_for_fn (cfun
));
2915 /* We scan the blocks in the reverse order to speed up
2917 FOR_EACH_BB_REVERSE_FN (bb
, cfun
)
2919 if (bb
->next_bb
!= EXIT_BLOCK_PTR_FOR_FN (cfun
))
2921 bitmap_intersection_of_succs (hoist_vbeout
[bb
->index
],
2924 /* Include expressions in VBEout that are calculated
2925 in BB and available at its end. */
2926 bitmap_ior (hoist_vbeout
[bb
->index
],
2927 hoist_vbeout
[bb
->index
], comp
[bb
->index
]);
2930 changed
|= bitmap_or_and (hoist_vbein
[bb
->index
],
2932 hoist_vbeout
[bb
->index
],
2941 fprintf (dump_file
, "hoisting vbeinout computation: %d passes\n", passes
);
2943 FOR_EACH_BB_FN (bb
, cfun
)
2945 fprintf (dump_file
, "vbein (%d): ", bb
->index
);
2946 dump_bitmap_file (dump_file
, hoist_vbein
[bb
->index
]);
2947 fprintf (dump_file
, "vbeout(%d): ", bb
->index
);
2948 dump_bitmap_file (dump_file
, hoist_vbeout
[bb
->index
]);
2953 /* Top level routine to do the dataflow analysis needed by code hoisting. */
2956 compute_code_hoist_data (void)
2958 compute_local_properties (transp
, comp
, antloc
, &expr_hash_table
);
2959 prune_expressions (false);
2960 compute_code_hoist_vbeinout ();
2961 calculate_dominance_info (CDI_DOMINATORS
);
2963 fprintf (dump_file
, "\n");
2966 /* Update register pressure for BB when hoisting an expression from
2967 instruction FROM, if live ranges of inputs are shrunk. Also
2968 maintain live_in information if live range of register referred
2971 Return 0 if register pressure doesn't change, otherwise return
2972 the number by which register pressure is decreased.
2974 NOTE: Register pressure won't be increased in this function. */
2977 update_bb_reg_pressure (basic_block bb
, rtx_insn
*from
)
2981 basic_block succ_bb
;
2985 int decreased_pressure
= 0;
2987 enum reg_class pressure_class
;
2989 FOR_EACH_INSN_USE (use
, from
)
2991 dreg
= DF_REF_REAL_REG (use
);
2992 /* The live range of register is shrunk only if it isn't:
2993 1. referred on any path from the end of this block to EXIT, or
2994 2. referred by insns other than FROM in this block. */
2995 FOR_EACH_EDGE (succ
, ei
, bb
->succs
)
2997 succ_bb
= succ
->dest
;
2998 if (succ_bb
== EXIT_BLOCK_PTR_FOR_FN (cfun
))
3001 if (bitmap_bit_p (BB_DATA (succ_bb
)->live_in
, REGNO (dreg
)))
3007 op_ref
= DF_REG_USE_CHAIN (REGNO (dreg
));
3008 for (; op_ref
; op_ref
= DF_REF_NEXT_REG (op_ref
))
3010 if (!DF_REF_INSN_INFO (op_ref
))
3013 insn
= DF_REF_INSN (op_ref
);
3014 if (BLOCK_FOR_INSN (insn
) == bb
3015 && NONDEBUG_INSN_P (insn
) && insn
!= from
)
3019 pressure_class
= get_regno_pressure_class (REGNO (dreg
), &nregs
);
3020 /* Decrease register pressure and update live_in information for
3022 if (!op_ref
&& pressure_class
!= NO_REGS
)
3024 decreased_pressure
+= nregs
;
3025 BB_DATA (bb
)->max_reg_pressure
[pressure_class
] -= nregs
;
3026 bitmap_clear_bit (BB_DATA (bb
)->live_in
, REGNO (dreg
));
3029 return decreased_pressure
;
3032 /* Determine if the expression EXPR should be hoisted to EXPR_BB up in
3033 flow graph, if it can reach BB unimpared. Stop the search if the
3034 expression would need to be moved more than DISTANCE instructions.
3036 DISTANCE is the number of instructions through which EXPR can be
3037 hoisted up in flow graph.
3039 BB_SIZE points to an array which contains the number of instructions
3040 for each basic block.
3042 PRESSURE_CLASS and NREGS are register class and number of hard registers
3045 HOISTED_BBS points to a bitmap indicating basic blocks through which
3048 FROM is the instruction from which EXPR is hoisted.
3050 It's unclear exactly what Muchnick meant by "unimpared". It seems
3051 to me that the expression must either be computed or transparent in
3052 *every* block in the path(s) from EXPR_BB to BB. Any other definition
3053 would allow the expression to be hoisted out of loops, even if
3054 the expression wasn't a loop invariant.
3056 Contrast this to reachability for PRE where an expression is
3057 considered reachable if *any* path reaches instead of *all*
3061 should_hoist_expr_to_dom (basic_block expr_bb
, struct gcse_expr
*expr
,
3062 basic_block bb
, sbitmap visited
, int distance
,
3063 int *bb_size
, enum reg_class pressure_class
,
3064 int *nregs
, bitmap hoisted_bbs
, rtx_insn
*from
)
3069 sbitmap_iterator sbi
;
3070 int visited_allocated_locally
= 0;
3071 int decreased_pressure
= 0;
3073 if (flag_ira_hoist_pressure
)
3075 /* Record old information of basic block BB when it is visited
3076 at the first time. */
3077 if (!bitmap_bit_p (hoisted_bbs
, bb
->index
))
3079 struct bb_data
*data
= BB_DATA (bb
);
3080 bitmap_copy (data
->backup
, data
->live_in
);
3081 data
->old_pressure
= data
->max_reg_pressure
[pressure_class
];
3083 decreased_pressure
= update_bb_reg_pressure (bb
, from
);
3085 /* Terminate the search if distance, for which EXPR is allowed to move,
3089 if (flag_ira_hoist_pressure
)
3091 /* Prefer to hoist EXPR if register pressure is decreased. */
3092 if (decreased_pressure
> *nregs
)
3093 distance
+= bb_size
[bb
->index
];
3094 /* Let EXPR be hoisted through basic block at no cost if one
3095 of following conditions is satisfied:
3097 1. The basic block has low register pressure.
3098 2. Register pressure won't be increases after hoisting EXPR.
3100 Constant expressions is handled conservatively, because
3101 hoisting constant expression aggressively results in worse
3102 code. This decision is made by the observation of CSiBE
3103 on ARM target, while it has no obvious effect on other
3104 targets like x86, x86_64, mips and powerpc. */
3105 else if (CONST_INT_P (expr
->expr
)
3106 || (BB_DATA (bb
)->max_reg_pressure
[pressure_class
]
3107 >= ira_class_hard_regs_num
[pressure_class
]
3108 && decreased_pressure
< *nregs
))
3109 distance
-= bb_size
[bb
->index
];
3112 distance
-= bb_size
[bb
->index
];
3118 gcc_assert (distance
== 0);
3120 if (visited
== NULL
)
3122 visited_allocated_locally
= 1;
3123 visited
= sbitmap_alloc (last_basic_block_for_fn (cfun
));
3124 bitmap_clear (visited
);
3127 FOR_EACH_EDGE (pred
, ei
, bb
->preds
)
3129 basic_block pred_bb
= pred
->src
;
3131 if (pred
->src
== ENTRY_BLOCK_PTR_FOR_FN (cfun
))
3133 else if (pred_bb
== expr_bb
)
3135 else if (bitmap_bit_p (visited
, pred_bb
->index
))
3137 else if (! bitmap_bit_p (transp
[pred_bb
->index
], expr
->bitmap_index
))
3142 bitmap_set_bit (visited
, pred_bb
->index
);
3143 if (! should_hoist_expr_to_dom (expr_bb
, expr
, pred_bb
,
3144 visited
, distance
, bb_size
,
3145 pressure_class
, nregs
,
3150 if (visited_allocated_locally
)
3152 /* If EXPR can be hoisted to expr_bb, record basic blocks through
3153 which EXPR is hoisted in hoisted_bbs. */
3154 if (flag_ira_hoist_pressure
&& !pred
)
3156 /* Record the basic block from which EXPR is hoisted. */
3157 bitmap_set_bit (visited
, bb
->index
);
3158 EXECUTE_IF_SET_IN_BITMAP (visited
, 0, i
, sbi
)
3159 bitmap_set_bit (hoisted_bbs
, i
);
3161 sbitmap_free (visited
);
3164 return (pred
== NULL
);
3167 /* Find occurrence in BB. */
3169 static struct gcse_occr
*
3170 find_occr_in_bb (struct gcse_occr
*occr
, basic_block bb
)
3172 /* Find the right occurrence of this expression. */
3173 while (occr
&& BLOCK_FOR_INSN (occr
->insn
) != bb
)
3179 /* Actually perform code hoisting.
3181 The code hoisting pass can hoist multiple computations of the same
3182 expression along dominated path to a dominating basic block, like
3183 from b2/b3 to b1 as depicted below:
3193 Unfortunately code hoisting generally extends the live range of an
3194 output pseudo register, which increases register pressure and hurts
3195 register allocation. To address this issue, an attribute MAX_DISTANCE
3196 is computed and attached to each expression. The attribute is computed
3197 from rtx cost of the corresponding expression and it's used to control
3198 how long the expression can be hoisted up in flow graph. As the
3199 expression is hoisted up in flow graph, GCC decreases its DISTANCE
3200 and stops the hoist if DISTANCE reaches 0. Code hoisting can decrease
3201 register pressure if live ranges of inputs are shrunk.
3203 Option "-fira-hoist-pressure" implements register pressure directed
3204 hoist based on upper method. The rationale is:
3205 1. Calculate register pressure for each basic block by reusing IRA
3207 2. When expression is hoisted through one basic block, GCC checks
3208 the change of live ranges for inputs/output. The basic block's
3209 register pressure will be increased because of extended live
3210 range of output. However, register pressure will be decreased
3211 if the live ranges of inputs are shrunk.
3212 3. After knowing how hoisting affects register pressure, GCC prefers
3213 to hoist the expression if it can decrease register pressure, by
3214 increasing DISTANCE of the corresponding expression.
3215 4. If hoisting the expression increases register pressure, GCC checks
3216 register pressure of the basic block and decrease DISTANCE only if
3217 the register pressure is high. In other words, expression will be
3218 hoisted through at no cost if the basic block has low register
3220 5. Update register pressure information for basic blocks through
3221 which expression is hoisted. */
3226 basic_block bb
, dominated
;
3227 vec
<basic_block
> dom_tree_walk
;
3228 unsigned int dom_tree_walk_index
;
3229 vec
<basic_block
> domby
;
3230 unsigned int i
, j
, k
;
3231 struct gcse_expr
**index_map
;
3232 struct gcse_expr
*expr
;
3236 struct bb_data
*data
;
3237 /* Basic blocks that have occurrences reachable from BB. */
3239 /* Basic blocks through which expr is hoisted. */
3240 bitmap hoisted_bbs
= NULL
;
3243 /* Compute a mapping from expression number (`bitmap_index') to
3244 hash table entry. */
3246 index_map
= XCNEWVEC (struct gcse_expr
*, expr_hash_table
.n_elems
);
3247 for (i
= 0; i
< expr_hash_table
.size
; i
++)
3248 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
3249 index_map
[expr
->bitmap_index
] = expr
;
3251 /* Calculate sizes of basic blocks and note how far
3252 each instruction is from the start of its block. We then use this
3253 data to restrict distance an expression can travel. */
3255 to_bb_head
= XCNEWVEC (int, get_max_uid ());
3256 bb_size
= XCNEWVEC (int, last_basic_block_for_fn (cfun
));
3258 FOR_EACH_BB_FN (bb
, cfun
)
3264 FOR_BB_INSNS (bb
, insn
)
3266 /* Don't count debug instructions to avoid them affecting
3267 decision choices. */
3268 if (NONDEBUG_INSN_P (insn
))
3269 to_bb_head
[INSN_UID (insn
)] = to_head
++;
3272 bb_size
[bb
->index
] = to_head
;
3275 gcc_assert (EDGE_COUNT (ENTRY_BLOCK_PTR_FOR_FN (cfun
)->succs
) == 1
3276 && (EDGE_SUCC (ENTRY_BLOCK_PTR_FOR_FN (cfun
), 0)->dest
3277 == ENTRY_BLOCK_PTR_FOR_FN (cfun
)->next_bb
));
3279 from_bbs
= BITMAP_ALLOC (NULL
);
3280 if (flag_ira_hoist_pressure
)
3281 hoisted_bbs
= BITMAP_ALLOC (NULL
);
3283 dom_tree_walk
= get_all_dominated_blocks (CDI_DOMINATORS
,
3284 ENTRY_BLOCK_PTR_FOR_FN (cfun
)->next_bb
);
3286 /* Walk over each basic block looking for potentially hoistable
3287 expressions, nothing gets hoisted from the entry block. */
3288 FOR_EACH_VEC_ELT (dom_tree_walk
, dom_tree_walk_index
, bb
)
3290 domby
= get_dominated_to_depth (CDI_DOMINATORS
, bb
, MAX_HOIST_DEPTH
);
3292 if (domby
.length () == 0)
3295 /* Examine each expression that is very busy at the exit of this
3296 block. These are the potentially hoistable expressions. */
3297 for (i
= 0; i
< SBITMAP_SIZE (hoist_vbeout
[bb
->index
]); i
++)
3299 if (bitmap_bit_p (hoist_vbeout
[bb
->index
], i
))
3302 enum reg_class pressure_class
= NO_REGS
;
3303 /* Current expression. */
3304 struct gcse_expr
*expr
= index_map
[i
];
3305 /* Number of occurrences of EXPR that can be hoisted to BB. */
3307 /* Occurrences reachable from BB. */
3308 vec
<occr_t
> occrs_to_hoist
= vNULL
;
3309 /* We want to insert the expression into BB only once, so
3310 note when we've inserted it. */
3311 int insn_inserted_p
;
3314 /* If an expression is computed in BB and is available at end of
3315 BB, hoist all occurrences dominated by BB to BB. */
3316 if (bitmap_bit_p (comp
[bb
->index
], i
))
3318 occr
= find_occr_in_bb (expr
->antic_occr
, bb
);
3322 /* An occurrence might've been already deleted
3323 while processing a dominator of BB. */
3324 if (!occr
->deleted_p
)
3326 gcc_assert (NONDEBUG_INSN_P (occr
->insn
));
3334 /* We've found a potentially hoistable expression, now
3335 we look at every block BB dominates to see if it
3336 computes the expression. */
3337 FOR_EACH_VEC_ELT (domby
, j
, dominated
)
3341 /* Ignore self dominance. */
3342 if (bb
== dominated
)
3344 /* We've found a dominated block, now see if it computes
3345 the busy expression and whether or not moving that
3346 expression to the "beginning" of that block is safe. */
3347 if (!bitmap_bit_p (antloc
[dominated
->index
], i
))
3350 occr
= find_occr_in_bb (expr
->antic_occr
, dominated
);
3353 /* An occurrence might've been already deleted
3354 while processing a dominator of BB. */
3355 if (occr
->deleted_p
)
3357 gcc_assert (NONDEBUG_INSN_P (occr
->insn
));
3359 max_distance
= expr
->max_distance
;
3360 if (max_distance
> 0)
3361 /* Adjust MAX_DISTANCE to account for the fact that
3362 OCCR won't have to travel all of DOMINATED, but
3364 max_distance
+= (bb_size
[dominated
->index
]
3365 - to_bb_head
[INSN_UID (occr
->insn
)]);
3367 pressure_class
= get_pressure_class_and_nregs (occr
->insn
,
3370 /* Note if the expression should be hoisted from the dominated
3371 block to BB if it can reach DOMINATED unimpared.
3373 Keep track of how many times this expression is hoistable
3374 from a dominated block into BB. */
3375 if (should_hoist_expr_to_dom (bb
, expr
, dominated
, NULL
,
3376 max_distance
, bb_size
,
3377 pressure_class
, &nregs
,
3378 hoisted_bbs
, occr
->insn
))
3381 occrs_to_hoist
.safe_push (occr
);
3382 bitmap_set_bit (from_bbs
, dominated
->index
);
3386 /* If we found more than one hoistable occurrence of this
3387 expression, then note it in the vector of expressions to
3388 hoist. It makes no sense to hoist things which are computed
3389 in only one BB, and doing so tends to pessimize register
3390 allocation. One could increase this value to try harder
3391 to avoid any possible code expansion due to register
3392 allocation issues; however experiments have shown that
3393 the vast majority of hoistable expressions are only movable
3394 from two successors, so raising this threshold is likely
3395 to nullify any benefit we get from code hoisting. */
3396 if (hoistable
> 1 && dbg_cnt (hoist_insn
))
3398 /* If (hoistable != vec::length), then there is
3399 an occurrence of EXPR in BB itself. Don't waste
3400 time looking for LCA in this case. */
3401 if ((unsigned) hoistable
== occrs_to_hoist
.length ())
3405 lca
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3408 /* Punt, it's better to hoist these occurrences to
3410 occrs_to_hoist
.release ();
3414 /* Punt, no point hoisting a single occurrence. */
3415 occrs_to_hoist
.release ();
3417 if (flag_ira_hoist_pressure
3418 && !occrs_to_hoist
.is_empty ())
3420 /* Increase register pressure of basic blocks to which
3421 expr is hoisted because of extended live range of
3423 data
= BB_DATA (bb
);
3424 data
->max_reg_pressure
[pressure_class
] += nregs
;
3425 EXECUTE_IF_SET_IN_BITMAP (hoisted_bbs
, 0, k
, bi
)
3427 data
= BB_DATA (BASIC_BLOCK_FOR_FN (cfun
, k
));
3428 data
->max_reg_pressure
[pressure_class
] += nregs
;
3431 else if (flag_ira_hoist_pressure
)
3433 /* Restore register pressure and live_in info for basic
3434 blocks recorded in hoisted_bbs when expr will not be
3436 EXECUTE_IF_SET_IN_BITMAP (hoisted_bbs
, 0, k
, bi
)
3438 data
= BB_DATA (BASIC_BLOCK_FOR_FN (cfun
, k
));
3439 bitmap_copy (data
->live_in
, data
->backup
);
3440 data
->max_reg_pressure
[pressure_class
]
3441 = data
->old_pressure
;
3445 if (flag_ira_hoist_pressure
)
3446 bitmap_clear (hoisted_bbs
);
3448 insn_inserted_p
= 0;
3450 /* Walk through occurrences of I'th expressions we want
3451 to hoist to BB and make the transformations. */
3452 FOR_EACH_VEC_ELT (occrs_to_hoist
, j
, occr
)
3457 gcc_assert (!occr
->deleted_p
);
3460 set
= single_set_gcse (insn
);
3462 /* Create a pseudo-reg to store the result of reaching
3463 expressions into. Get the mode for the new pseudo
3464 from the mode of the original destination pseudo.
3466 It is important to use new pseudos whenever we
3467 emit a set. This will allow reload to use
3468 rematerialization for such registers. */
3469 if (!insn_inserted_p
)
3471 = gen_reg_rtx_and_attrs (SET_DEST (set
));
3473 gcse_emit_move_after (SET_DEST (set
), expr
->reaching_reg
,
3476 occr
->deleted_p
= 1;
3480 if (!insn_inserted_p
)
3482 insert_insn_end_basic_block (expr
, bb
);
3483 insn_inserted_p
= 1;
3487 occrs_to_hoist
.release ();
3488 bitmap_clear (from_bbs
);
3494 dom_tree_walk
.release ();
3495 BITMAP_FREE (from_bbs
);
3496 if (flag_ira_hoist_pressure
)
3497 BITMAP_FREE (hoisted_bbs
);
3506 /* Return pressure class and number of needed hard registers (through
3507 *NREGS) of register REGNO. */
3508 static enum reg_class
3509 get_regno_pressure_class (int regno
, int *nregs
)
3511 if (regno
>= FIRST_PSEUDO_REGISTER
)
3513 enum reg_class pressure_class
;
3515 pressure_class
= reg_allocno_class (regno
);
3516 pressure_class
= ira_pressure_class_translate
[pressure_class
];
3518 = ira_reg_class_max_nregs
[pressure_class
][PSEUDO_REGNO_MODE (regno
)];
3519 return pressure_class
;
3521 else if (! TEST_HARD_REG_BIT (ira_no_alloc_regs
, regno
)
3522 && ! TEST_HARD_REG_BIT (eliminable_regset
, regno
))
3525 return ira_pressure_class_translate
[REGNO_REG_CLASS (regno
)];
3534 /* Return pressure class and number of hard registers (through *NREGS)
3535 for destination of INSN. */
3536 static enum reg_class
3537 get_pressure_class_and_nregs (rtx_insn
*insn
, int *nregs
)
3540 enum reg_class pressure_class
;
3541 const_rtx set
= single_set_gcse (insn
);
3543 reg
= SET_DEST (set
);
3544 if (GET_CODE (reg
) == SUBREG
)
3545 reg
= SUBREG_REG (reg
);
3549 pressure_class
= NO_REGS
;
3553 gcc_assert (REG_P (reg
));
3554 pressure_class
= reg_allocno_class (REGNO (reg
));
3555 pressure_class
= ira_pressure_class_translate
[pressure_class
];
3557 = ira_reg_class_max_nregs
[pressure_class
][GET_MODE (SET_SRC (set
))];
3559 return pressure_class
;
3562 /* Increase (if INCR_P) or decrease current register pressure for
3565 change_pressure (int regno
, bool incr_p
)
3568 enum reg_class pressure_class
;
3570 pressure_class
= get_regno_pressure_class (regno
, &nregs
);
3572 curr_reg_pressure
[pressure_class
] -= nregs
;
3575 curr_reg_pressure
[pressure_class
] += nregs
;
3576 if (BB_DATA (curr_bb
)->max_reg_pressure
[pressure_class
]
3577 < curr_reg_pressure
[pressure_class
])
3578 BB_DATA (curr_bb
)->max_reg_pressure
[pressure_class
]
3579 = curr_reg_pressure
[pressure_class
];
3583 /* Calculate register pressure for each basic block by walking insns
3584 from last to first. */
3586 calculate_bb_reg_pressure (void)
3592 bitmap curr_regs_live
;
3596 ira_setup_eliminable_regset ();
3597 curr_regs_live
= BITMAP_ALLOC (®_obstack
);
3598 FOR_EACH_BB_FN (bb
, cfun
)
3601 BB_DATA (bb
)->live_in
= BITMAP_ALLOC (NULL
);
3602 BB_DATA (bb
)->backup
= BITMAP_ALLOC (NULL
);
3603 bitmap_copy (BB_DATA (bb
)->live_in
, df_get_live_in (bb
));
3604 bitmap_copy (curr_regs_live
, df_get_live_out (bb
));
3605 for (i
= 0; i
< ira_pressure_classes_num
; i
++)
3606 curr_reg_pressure
[ira_pressure_classes
[i
]] = 0;
3607 EXECUTE_IF_SET_IN_BITMAP (curr_regs_live
, 0, j
, bi
)
3608 change_pressure (j
, true);
3610 FOR_BB_INSNS_REVERSE (bb
, insn
)
3616 if (! NONDEBUG_INSN_P (insn
))
3619 FOR_EACH_INSN_DEF (def
, insn
)
3621 dreg
= DF_REF_REAL_REG (def
);
3622 gcc_assert (REG_P (dreg
));
3623 regno
= REGNO (dreg
);
3624 if (!(DF_REF_FLAGS (def
)
3625 & (DF_REF_PARTIAL
| DF_REF_CONDITIONAL
)))
3627 if (bitmap_clear_bit (curr_regs_live
, regno
))
3628 change_pressure (regno
, false);
3632 FOR_EACH_INSN_USE (use
, insn
)
3634 dreg
= DF_REF_REAL_REG (use
);
3635 gcc_assert (REG_P (dreg
));
3636 regno
= REGNO (dreg
);
3637 if (bitmap_set_bit (curr_regs_live
, regno
))
3638 change_pressure (regno
, true);
3642 BITMAP_FREE (curr_regs_live
);
3644 if (dump_file
== NULL
)
3647 fprintf (dump_file
, "\nRegister Pressure: \n");
3648 FOR_EACH_BB_FN (bb
, cfun
)
3650 fprintf (dump_file
, " Basic block %d: \n", bb
->index
);
3651 for (i
= 0; (int) i
< ira_pressure_classes_num
; i
++)
3653 enum reg_class pressure_class
;
3655 pressure_class
= ira_pressure_classes
[i
];
3656 if (BB_DATA (bb
)->max_reg_pressure
[pressure_class
] == 0)
3659 fprintf (dump_file
, " %s=%d\n", reg_class_names
[pressure_class
],
3660 BB_DATA (bb
)->max_reg_pressure
[pressure_class
]);
3663 fprintf (dump_file
, "\n");
3666 /* Top level routine to perform one code hoisting (aka unification) pass
3668 Return nonzero if a change was made. */
3671 one_code_hoisting_pass (void)
3675 gcse_subst_count
= 0;
3676 gcse_create_count
= 0;
3678 /* Return if there's nothing to do, or it is too expensive. */
3679 if (n_basic_blocks_for_fn (cfun
) <= NUM_FIXED_BLOCKS
+ 1
3680 || is_too_expensive (_("GCSE disabled")))
3683 doing_code_hoisting_p
= true;
3685 /* Calculate register pressure for each basic block. */
3686 if (flag_ira_hoist_pressure
)
3688 regstat_init_n_sets_and_refs ();
3689 ira_set_pseudo_classes (false, dump_file
);
3690 alloc_aux_for_blocks (sizeof (struct bb_data
));
3691 calculate_bb_reg_pressure ();
3692 regstat_free_n_sets_and_refs ();
3695 /* We need alias. */
3696 init_alias_analysis ();
3699 gcc_obstack_init (&gcse_obstack
);
3702 alloc_hash_table (&expr_hash_table
);
3703 compute_hash_table (&expr_hash_table
);
3705 dump_hash_table (dump_file
, "Code Hosting Expressions", &expr_hash_table
);
3707 if (expr_hash_table
.n_elems
> 0)
3709 alloc_code_hoist_mem (last_basic_block_for_fn (cfun
),
3710 expr_hash_table
.n_elems
);
3711 compute_code_hoist_data ();
3712 changed
= hoist_code ();
3713 free_code_hoist_mem ();
3716 if (flag_ira_hoist_pressure
)
3718 free_aux_for_blocks ();
3721 free_hash_table (&expr_hash_table
);
3723 obstack_free (&gcse_obstack
, NULL
);
3725 /* We are finished with alias. */
3726 end_alias_analysis ();
3730 fprintf (dump_file
, "HOIST of %s, %d basic blocks, %d bytes needed, ",
3731 current_function_name (), n_basic_blocks_for_fn (cfun
),
3733 fprintf (dump_file
, "%d substs, %d insns created\n",
3734 gcse_subst_count
, gcse_create_count
);
3737 doing_code_hoisting_p
= false;
3742 /* Here we provide the things required to do store motion towards the exit.
3743 In order for this to be effective, gcse also needed to be taught how to
3744 move a load when it is killed only by a store to itself.
3749 void foo(float scale)
3751 for (i=0; i<10; i++)
3755 'i' is both loaded and stored to in the loop. Normally, gcse cannot move
3756 the load out since its live around the loop, and stored at the bottom
3759 The 'Load Motion' referred to and implemented in this file is
3760 an enhancement to gcse which when using edge based LCM, recognizes
3761 this situation and allows gcse to move the load out of the loop.
3763 Once gcse has hoisted the load, store motion can then push this
3764 load towards the exit, and we end up with no loads or stores of 'i'
3767 /* This will search the ldst list for a matching expression. If it
3768 doesn't find one, we create one and initialize it. */
3770 static struct ls_expr
*
3773 int do_not_record_p
= 0;
3774 struct ls_expr
* ptr
;
3779 hash
= hash_rtx (x
, GET_MODE (x
), &do_not_record_p
,
3780 NULL
, /*have_reg_qty=*/false);
3783 slot
= pre_ldst_table
->find_slot_with_hash (&e
, hash
, INSERT
);
3787 ptr
= XNEW (struct ls_expr
);
3789 ptr
->next
= pre_ldst_mems
;
3792 ptr
->pattern_regs
= NULL_RTX
;
3795 ptr
->reaching_reg
= NULL_RTX
;
3798 ptr
->hash_index
= hash
;
3799 pre_ldst_mems
= ptr
;
3805 /* Free up an individual ldst entry. */
3808 free_ldst_entry (struct ls_expr
* ptr
)
3810 free_INSN_LIST_list (& ptr
->loads
);
3811 free_INSN_LIST_list (& ptr
->stores
);
3816 /* Free up all memory associated with the ldst list. */
3819 free_ld_motion_mems (void)
3821 delete pre_ldst_table
;
3822 pre_ldst_table
= NULL
;
3824 while (pre_ldst_mems
)
3826 struct ls_expr
* tmp
= pre_ldst_mems
;
3828 pre_ldst_mems
= pre_ldst_mems
->next
;
3830 free_ldst_entry (tmp
);
3833 pre_ldst_mems
= NULL
;
3836 /* Dump debugging info about the ldst list. */
3839 print_ldst_list (FILE * file
)
3841 struct ls_expr
* ptr
;
3843 fprintf (file
, "LDST list: \n");
3845 for (ptr
= pre_ldst_mems
; ptr
!= NULL
; ptr
= ptr
->next
)
3847 fprintf (file
, " Pattern (%3d): ", ptr
->index
);
3849 print_rtl (file
, ptr
->pattern
);
3851 fprintf (file
, "\n Loads : ");
3854 print_rtl (file
, ptr
->loads
);
3856 fprintf (file
, "(nil)");
3858 fprintf (file
, "\n Stores : ");
3861 print_rtl (file
, ptr
->stores
);
3863 fprintf (file
, "(nil)");
3865 fprintf (file
, "\n\n");
3868 fprintf (file
, "\n");
3871 /* Returns 1 if X is in the list of ldst only expressions. */
3873 static struct ls_expr
*
3874 find_rtx_in_ldst (rtx x
)
3878 if (!pre_ldst_table
)
3881 slot
= pre_ldst_table
->find_slot (&e
, NO_INSERT
);
3882 if (!slot
|| (*slot
)->invalid
)
3887 /* Load Motion for loads which only kill themselves. */
3889 /* Return true if x, a MEM, is a simple access with no side effects.
3890 These are the types of loads we consider for the ld_motion list,
3891 otherwise we let the usual aliasing take care of it. */
3894 simple_mem (const_rtx x
)
3896 if (MEM_VOLATILE_P (x
))
3899 if (GET_MODE (x
) == BLKmode
)
3902 /* If we are handling exceptions, we must be careful with memory references
3903 that may trap. If we are not, the behavior is undefined, so we may just
3905 if (cfun
->can_throw_non_call_exceptions
&& may_trap_p (x
))
3908 if (side_effects_p (x
))
3911 /* Do not consider function arguments passed on stack. */
3912 if (reg_mentioned_p (stack_pointer_rtx
, x
))
3915 if (flag_float_store
&& FLOAT_MODE_P (GET_MODE (x
)))
3921 /* Make sure there isn't a buried reference in this pattern anywhere.
3922 If there is, invalidate the entry for it since we're not capable
3923 of fixing it up just yet.. We have to be sure we know about ALL
3924 loads since the aliasing code will allow all entries in the
3925 ld_motion list to not-alias itself. If we miss a load, we will get
3926 the wrong value since gcse might common it and we won't know to
3930 invalidate_any_buried_refs (rtx x
)
3934 struct ls_expr
* ptr
;
3936 /* Invalidate it in the list. */
3937 if (MEM_P (x
) && simple_mem (x
))
3939 ptr
= ldst_entry (x
);
3943 /* Recursively process the insn. */
3944 fmt
= GET_RTX_FORMAT (GET_CODE (x
));
3946 for (i
= GET_RTX_LENGTH (GET_CODE (x
)) - 1; i
>= 0; i
--)
3949 invalidate_any_buried_refs (XEXP (x
, i
));
3950 else if (fmt
[i
] == 'E')
3951 for (j
= XVECLEN (x
, i
) - 1; j
>= 0; j
--)
3952 invalidate_any_buried_refs (XVECEXP (x
, i
, j
));
3956 /* Find all the 'simple' MEMs which are used in LOADs and STORES. Simple
3957 being defined as MEM loads and stores to symbols, with no side effects
3958 and no registers in the expression. For a MEM destination, we also
3959 check that the insn is still valid if we replace the destination with a
3960 REG, as is done in update_ld_motion_stores. If there are any uses/defs
3961 which don't match this criteria, they are invalidated and trimmed out
3965 compute_ld_motion_mems (void)
3967 struct ls_expr
* ptr
;
3971 pre_ldst_mems
= NULL
;
3972 pre_ldst_table
= new hash_table
<pre_ldst_expr_hasher
> (13);
3974 FOR_EACH_BB_FN (bb
, cfun
)
3976 FOR_BB_INSNS (bb
, insn
)
3978 if (NONDEBUG_INSN_P (insn
))
3980 if (GET_CODE (PATTERN (insn
)) == SET
)
3982 rtx src
= SET_SRC (PATTERN (insn
));
3983 rtx dest
= SET_DEST (PATTERN (insn
));
3984 rtx note
= find_reg_equal_equiv_note (insn
);
3987 /* Check for a simple LOAD... */
3988 if (MEM_P (src
) && simple_mem (src
))
3990 ptr
= ldst_entry (src
);
3992 ptr
->loads
= alloc_INSN_LIST (insn
, ptr
->loads
);
3998 /* Make sure there isn't a buried load somewhere. */
3999 invalidate_any_buried_refs (src
);
4002 if (note
!= 0 && REG_NOTE_KIND (note
) == REG_EQUAL
)
4003 src_eq
= XEXP (note
, 0);
4007 if (src_eq
!= NULL_RTX
4008 && !(MEM_P (src_eq
) && simple_mem (src_eq
)))
4009 invalidate_any_buried_refs (src_eq
);
4011 /* Check for stores. Don't worry about aliased ones, they
4012 will block any movement we might do later. We only care
4013 about this exact pattern since those are the only
4014 circumstance that we will ignore the aliasing info. */
4015 if (MEM_P (dest
) && simple_mem (dest
))
4017 ptr
= ldst_entry (dest
);
4020 && GET_CODE (src
) != ASM_OPERANDS
4021 /* Check for REG manually since want_to_gcse_p
4022 returns 0 for all REGs. */
4023 && can_assign_to_reg_without_clobbers_p (src
))
4024 ptr
->stores
= alloc_INSN_LIST (insn
, ptr
->stores
);
4030 invalidate_any_buried_refs (PATTERN (insn
));
4036 /* Remove any references that have been either invalidated or are not in the
4037 expression list for pre gcse. */
4040 trim_ld_motion_mems (void)
4042 struct ls_expr
* * last
= & pre_ldst_mems
;
4043 struct ls_expr
* ptr
= pre_ldst_mems
;
4047 struct gcse_expr
* expr
;
4049 /* Delete if entry has been made invalid. */
4052 /* Delete if we cannot find this mem in the expression list. */
4053 unsigned int hash
= ptr
->hash_index
% expr_hash_table
.size
;
4055 for (expr
= expr_hash_table
.table
[hash
];
4057 expr
= expr
->next_same_hash
)
4058 if (expr_equiv_p (expr
->expr
, ptr
->pattern
))
4062 expr
= (struct gcse_expr
*) 0;
4066 /* Set the expression field if we are keeping it. */
4074 pre_ldst_table
->remove_elt_with_hash (ptr
, ptr
->hash_index
);
4075 free_ldst_entry (ptr
);
4080 /* Show the world what we've found. */
4081 if (dump_file
&& pre_ldst_mems
!= NULL
)
4082 print_ldst_list (dump_file
);
4085 /* This routine will take an expression which we are replacing with
4086 a reaching register, and update any stores that are needed if
4087 that expression is in the ld_motion list. Stores are updated by
4088 copying their SRC to the reaching register, and then storing
4089 the reaching register into the store location. These keeps the
4090 correct value in the reaching register for the loads. */
4093 update_ld_motion_stores (struct gcse_expr
* expr
)
4095 struct ls_expr
* mem_ptr
;
4097 if ((mem_ptr
= find_rtx_in_ldst (expr
->expr
)))
4099 /* We can try to find just the REACHED stores, but is shouldn't
4100 matter to set the reaching reg everywhere... some might be
4101 dead and should be eliminated later. */
4103 /* We replace (set mem expr) with (set reg expr) (set mem reg)
4104 where reg is the reaching reg used in the load. We checked in
4105 compute_ld_motion_mems that we can replace (set mem expr) with
4106 (set reg expr) in that insn. */
4107 rtx list
= mem_ptr
->stores
;
4109 for ( ; list
!= NULL_RTX
; list
= XEXP (list
, 1))
4111 rtx_insn
*insn
= as_a
<rtx_insn
*> (XEXP (list
, 0));
4112 rtx pat
= PATTERN (insn
);
4113 rtx src
= SET_SRC (pat
);
4114 rtx reg
= expr
->reaching_reg
;
4117 /* If we've already copied it, continue. */
4118 if (expr
->reaching_reg
== src
)
4123 fprintf (dump_file
, "PRE: store updated with reaching reg ");
4124 print_rtl (dump_file
, reg
);
4125 fprintf (dump_file
, ":\n ");
4126 print_inline_rtx (dump_file
, insn
, 8);
4127 fprintf (dump_file
, "\n");
4130 copy
= gen_move_insn (reg
, copy_rtx (SET_SRC (pat
)));
4131 emit_insn_before (copy
, insn
);
4132 SET_SRC (pat
) = reg
;
4133 df_insn_rescan (insn
);
4135 /* un-recognize this pattern since it's probably different now. */
4136 INSN_CODE (insn
) = -1;
4137 gcse_create_count
++;
4142 /* Return true if the graph is too expensive to optimize. PASS is the
4143 optimization about to be performed. */
4146 is_too_expensive (const char *pass
)
4148 /* Trying to perform global optimizations on flow graphs which have
4149 a high connectivity will take a long time and is unlikely to be
4150 particularly useful.
4152 In normal circumstances a cfg should have about twice as many
4153 edges as blocks. But we do not want to punish small functions
4154 which have a couple switch statements. Rather than simply
4155 threshold the number of blocks, uses something with a more
4156 graceful degradation. */
4157 if (n_edges_for_fn (cfun
) > 20000 + n_basic_blocks_for_fn (cfun
) * 4)
4159 warning (OPT_Wdisabled_optimization
,
4160 "%s: %d basic blocks and %d edges/basic block",
4161 pass
, n_basic_blocks_for_fn (cfun
),
4162 n_edges_for_fn (cfun
) / n_basic_blocks_for_fn (cfun
));
4167 /* If allocating memory for the dataflow bitmaps would take up too much
4168 storage it's better just to disable the optimization. */
4169 if ((n_basic_blocks_for_fn (cfun
)
4170 * SBITMAP_SET_SIZE (max_reg_num ())
4171 * sizeof (SBITMAP_ELT_TYPE
)) > MAX_GCSE_MEMORY
)
4173 warning (OPT_Wdisabled_optimization
,
4174 "%s: %d basic blocks and %d registers",
4175 pass
, n_basic_blocks_for_fn (cfun
), max_reg_num ());
4184 execute_rtl_pre (void)
4187 delete_unreachable_blocks ();
4189 changed
= one_pre_gcse_pass ();
4190 flag_rerun_cse_after_global_opts
|= changed
;
4197 execute_rtl_hoist (void)
4200 delete_unreachable_blocks ();
4202 changed
= one_code_hoisting_pass ();
4203 flag_rerun_cse_after_global_opts
|= changed
;
4211 const pass_data pass_data_rtl_pre
=
4213 RTL_PASS
, /* type */
4214 "rtl pre", /* name */
4215 OPTGROUP_NONE
, /* optinfo_flags */
4217 PROP_cfglayout
, /* properties_required */
4218 0, /* properties_provided */
4219 0, /* properties_destroyed */
4220 0, /* todo_flags_start */
4221 TODO_df_finish
, /* todo_flags_finish */
4224 class pass_rtl_pre
: public rtl_opt_pass
4227 pass_rtl_pre (gcc::context
*ctxt
)
4228 : rtl_opt_pass (pass_data_rtl_pre
, ctxt
)
4231 /* opt_pass methods: */
4232 virtual bool gate (function
*);
4233 virtual unsigned int execute (function
*) { return execute_rtl_pre (); }
4235 }; // class pass_rtl_pre
4237 /* We do not construct an accurate cfg in functions which call
4238 setjmp, so none of these passes runs if the function calls
4240 FIXME: Should just handle setjmp via REG_SETJMP notes. */
4243 pass_rtl_pre::gate (function
*fun
)
4245 return optimize
> 0 && flag_gcse
4246 && !fun
->calls_setjmp
4247 && optimize_function_for_speed_p (fun
)
4254 make_pass_rtl_pre (gcc::context
*ctxt
)
4256 return new pass_rtl_pre (ctxt
);
4261 const pass_data pass_data_rtl_hoist
=
4263 RTL_PASS
, /* type */
4265 OPTGROUP_NONE
, /* optinfo_flags */
4266 TV_HOIST
, /* tv_id */
4267 PROP_cfglayout
, /* properties_required */
4268 0, /* properties_provided */
4269 0, /* properties_destroyed */
4270 0, /* todo_flags_start */
4271 TODO_df_finish
, /* todo_flags_finish */
4274 class pass_rtl_hoist
: public rtl_opt_pass
4277 pass_rtl_hoist (gcc::context
*ctxt
)
4278 : rtl_opt_pass (pass_data_rtl_hoist
, ctxt
)
4281 /* opt_pass methods: */
4282 virtual bool gate (function
*);
4283 virtual unsigned int execute (function
*) { return execute_rtl_hoist (); }
4285 }; // class pass_rtl_hoist
4288 pass_rtl_hoist::gate (function
*)
4290 return optimize
> 0 && flag_gcse
4291 && !cfun
->calls_setjmp
4292 /* It does not make sense to run code hoisting unless we are optimizing
4293 for code size -- it rarely makes programs faster, and can make then
4294 bigger if we did PRE (when optimizing for space, we don't run PRE). */
4295 && optimize_function_for_size_p (cfun
)
4302 make_pass_rtl_hoist (gcc::context
*ctxt
)
4304 return new pass_rtl_hoist (ctxt
);
4307 /* Reset all state within gcse.c so that we can rerun the compiler
4308 within the same process. For use by toplev::finalize. */
4311 gcse_c_finalize (void)
4316 #include "gt-gcse.h"