* tree.h (TYPE_OVERFLOW_SANITIZED): Define.
[official-gcc.git] / gcc / gcse.c
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1 /* Partial redundancy elimination / Hoisting for RTL.
2 Copyright (C) 1997-2014 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
9 version.
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
14 for more details.
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/>. */
20 /* TODO
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
29 Aho, Sethi, Ullman
30 Addison-Wesley, 1988
32 Global Optimization by Suppression of Partial Redundancies
33 E. Morel, C. Renvoise
34 communications of the acm, Vol. 22, Num. 2, Feb. 1979
36 A Portable Machine-Independent Global Optimizer - Design and Measurements
37 Frederick Chow
38 Stanford Ph.D. thesis, Dec. 1983
40 A Fast Algorithm for Code Movement Optimization
41 D.M. Dhamdhere
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
51 D.M. Dhamdhere
52 ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991
54 Efficiently Computing Static Single Assignment Form and the Control
55 Dependence Graph
56 R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck
57 ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991
59 Lazy Code Motion
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
65 Thomas Ball
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
99 C. Click
100 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
102 Value Driven Redundancy Elimination
103 L.T. Simpson
104 Rice University Ph.D. thesis, Apr. 1996
106 Value Numbering
107 L.T. Simpson
108 Massively Scalar Compiler Project, Rice University, Sep. 1996
110 High Performance Compilers for Parallel Computing
111 Michael Wolfe
112 Addison-Wesley, 1996
114 Advanced Compiler Design and Implementation
115 Steven Muchnick
116 Morgan Kaufmann, 1997
118 Building an Optimizing Compiler
119 Robert Morgan
120 Digital Press, 1998
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.
135 #include "config.h"
136 #include "system.h"
137 #include "coretypes.h"
138 #include "tm.h"
139 #include "diagnostic-core.h"
140 #include "toplev.h"
142 #include "hard-reg-set.h"
143 #include "rtl.h"
144 #include "tree.h"
145 #include "tm_p.h"
146 #include "regs.h"
147 #include "ira.h"
148 #include "flags.h"
149 #include "insn-config.h"
150 #include "recog.h"
151 #include "predict.h"
152 #include "vec.h"
153 #include "hashtab.h"
154 #include "hash-set.h"
155 #include "machmode.h"
156 #include "input.h"
157 #include "function.h"
158 #include "dominance.h"
159 #include "cfg.h"
160 #include "cfgrtl.h"
161 #include "cfganal.h"
162 #include "lcm.h"
163 #include "cfgcleanup.h"
164 #include "basic-block.h"
165 #include "expr.h"
166 #include "except.h"
167 #include "ggc.h"
168 #include "params.h"
169 #include "cselib.h"
170 #include "intl.h"
171 #include "obstack.h"
172 #include "tree-pass.h"
173 #include "hash-table.h"
174 #include "df.h"
175 #include "dbgcnt.h"
176 #include "target.h"
177 #include "gcse.h"
179 /* We support GCSE via Partial Redundancy Elimination. PRE optimizations
180 are a superset of those done by classic GCSE.
182 Two passes of copy/constant propagation are done around PRE or hoisting
183 because the first one enables more GCSE and the second one helps to clean
184 up the copies that PRE and HOIST create. This is needed more for PRE than
185 for HOIST because code hoisting will try to use an existing register
186 containing the common subexpression rather than create a new one. This is
187 harder to do for PRE because of the code motion (which HOIST doesn't do).
189 Expressions we are interested in GCSE-ing are of the form
190 (set (pseudo-reg) (expression)).
191 Function want_to_gcse_p says what these are.
193 In addition, expressions in REG_EQUAL notes are candidates for GCSE-ing.
194 This allows PRE to hoist expressions that are expressed in multiple insns,
195 such as complex address calculations (e.g. for PIC code, or loads with a
196 high part and a low part).
198 PRE handles moving invariant expressions out of loops (by treating them as
199 partially redundant).
201 **********************
203 We used to support multiple passes but there are diminishing returns in
204 doing so. The first pass usually makes 90% of the changes that are doable.
205 A second pass can make a few more changes made possible by the first pass.
206 Experiments show any further passes don't make enough changes to justify
207 the expense.
209 A study of spec92 using an unlimited number of passes:
210 [1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83,
211 [6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2,
212 [12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1
214 It was found doing copy propagation between each pass enables further
215 substitutions.
217 This study was done before expressions in REG_EQUAL notes were added as
218 candidate expressions for optimization, and before the GIMPLE optimizers
219 were added. Probably, multiple passes is even less efficient now than
220 at the time when the study was conducted.
222 PRE is quite expensive in complicated functions because the DFA can take
223 a while to converge. Hence we only perform one pass.
225 **********************
227 The steps for PRE are:
229 1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
231 2) Perform the data flow analysis for PRE.
233 3) Delete the redundant instructions
235 4) Insert the required copies [if any] that make the partially
236 redundant instructions fully redundant.
238 5) For other reaching expressions, insert an instruction to copy the value
239 to a newly created pseudo that will reach the redundant instruction.
241 The deletion is done first so that when we do insertions we
242 know which pseudo reg to use.
244 Various papers have argued that PRE DFA is expensive (O(n^2)) and others
245 argue it is not. The number of iterations for the algorithm to converge
246 is typically 2-4 so I don't view it as that expensive (relatively speaking).
248 PRE GCSE depends heavily on the second CPROP pass to clean up the copies
249 we create. To make an expression reach the place where it's redundant,
250 the result of the expression is copied to a new register, and the redundant
251 expression is deleted by replacing it with this new register. Classic GCSE
252 doesn't have this problem as much as it computes the reaching defs of
253 each register in each block and thus can try to use an existing
254 register. */
256 /* GCSE global vars. */
258 struct target_gcse default_target_gcse;
259 #if SWITCHABLE_TARGET
260 struct target_gcse *this_target_gcse = &default_target_gcse;
261 #endif
263 /* Set to non-zero if CSE should run after all GCSE optimizations are done. */
264 int flag_rerun_cse_after_global_opts;
266 /* An obstack for our working variables. */
267 static struct obstack gcse_obstack;
269 /* Hash table of expressions. */
271 struct gcse_expr
273 /* The expression. */
274 rtx expr;
275 /* Index in the available expression bitmaps. */
276 int bitmap_index;
277 /* Next entry with the same hash. */
278 struct gcse_expr *next_same_hash;
279 /* List of anticipatable occurrences in basic blocks in the function.
280 An "anticipatable occurrence" is one that is the first occurrence in the
281 basic block, the operands are not modified in the basic block prior
282 to the occurrence and the output is not used between the start of
283 the block and the occurrence. */
284 struct gcse_occr *antic_occr;
285 /* List of available occurrence in basic blocks in the function.
286 An "available occurrence" is one that is the last occurrence in the
287 basic block and the operands are not modified by following statements in
288 the basic block [including this insn]. */
289 struct gcse_occr *avail_occr;
290 /* Non-null if the computation is PRE redundant.
291 The value is the newly created pseudo-reg to record a copy of the
292 expression in all the places that reach the redundant copy. */
293 rtx reaching_reg;
294 /* Maximum distance in instructions this expression can travel.
295 We avoid moving simple expressions for more than a few instructions
296 to keep register pressure under control.
297 A value of "0" removes restrictions on how far the expression can
298 travel. */
299 int max_distance;
302 /* Occurrence of an expression.
303 There is one per basic block. If a pattern appears more than once the
304 last appearance is used [or first for anticipatable expressions]. */
306 struct gcse_occr
308 /* Next occurrence of this expression. */
309 struct gcse_occr *next;
310 /* The insn that computes the expression. */
311 rtx_insn *insn;
312 /* Nonzero if this [anticipatable] occurrence has been deleted. */
313 char deleted_p;
314 /* Nonzero if this [available] occurrence has been copied to
315 reaching_reg. */
316 /* ??? This is mutually exclusive with deleted_p, so they could share
317 the same byte. */
318 char copied_p;
321 typedef struct gcse_occr *occr_t;
323 /* Expression hash tables.
324 Each hash table is an array of buckets.
325 ??? It is known that if it were an array of entries, structure elements
326 `next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is
327 not clear whether in the final analysis a sufficient amount of memory would
328 be saved as the size of the available expression bitmaps would be larger
329 [one could build a mapping table without holes afterwards though].
330 Someday I'll perform the computation and figure it out. */
332 struct gcse_hash_table_d
334 /* The table itself.
335 This is an array of `expr_hash_table_size' elements. */
336 struct gcse_expr **table;
338 /* Size of the hash table, in elements. */
339 unsigned int size;
341 /* Number of hash table elements. */
342 unsigned int n_elems;
345 /* Expression hash table. */
346 static struct gcse_hash_table_d expr_hash_table;
348 /* This is a list of expressions which are MEMs and will be used by load
349 or store motion.
350 Load motion tracks MEMs which aren't killed by anything except itself,
351 i.e. loads and stores to a single location.
352 We can then allow movement of these MEM refs with a little special
353 allowance. (all stores copy the same value to the reaching reg used
354 for the loads). This means all values used to store into memory must have
355 no side effects so we can re-issue the setter value. */
357 struct ls_expr
359 struct gcse_expr * expr; /* Gcse expression reference for LM. */
360 rtx pattern; /* Pattern of this mem. */
361 rtx pattern_regs; /* List of registers mentioned by the mem. */
362 rtx_insn_list *loads; /* INSN list of loads seen. */
363 rtx_insn_list *stores; /* INSN list of stores seen. */
364 struct ls_expr * next; /* Next in the list. */
365 int invalid; /* Invalid for some reason. */
366 int index; /* If it maps to a bitmap index. */
367 unsigned int hash_index; /* Index when in a hash table. */
368 rtx reaching_reg; /* Register to use when re-writing. */
371 /* Head of the list of load/store memory refs. */
372 static struct ls_expr * pre_ldst_mems = NULL;
374 struct pre_ldst_expr_hasher : typed_noop_remove <ls_expr>
376 typedef ls_expr value_type;
377 typedef value_type compare_type;
378 static inline hashval_t hash (const value_type *);
379 static inline bool equal (const value_type *, const compare_type *);
382 /* Hashtable helpers. */
383 inline hashval_t
384 pre_ldst_expr_hasher::hash (const value_type *x)
386 int do_not_record_p = 0;
387 return
388 hash_rtx (x->pattern, GET_MODE (x->pattern), &do_not_record_p, NULL, false);
391 static int expr_equiv_p (const_rtx, const_rtx);
393 inline bool
394 pre_ldst_expr_hasher::equal (const value_type *ptr1,
395 const compare_type *ptr2)
397 return expr_equiv_p (ptr1->pattern, ptr2->pattern);
400 /* Hashtable for the load/store memory refs. */
401 static hash_table<pre_ldst_expr_hasher> *pre_ldst_table;
403 /* Bitmap containing one bit for each register in the program.
404 Used when performing GCSE to track which registers have been set since
405 the start of the basic block. */
406 static regset reg_set_bitmap;
408 /* Array, indexed by basic block number for a list of insns which modify
409 memory within that block. */
410 static vec<rtx_insn *> *modify_mem_list;
411 static bitmap modify_mem_list_set;
413 typedef struct modify_pair_s
415 rtx dest; /* A MEM. */
416 rtx dest_addr; /* The canonical address of `dest'. */
417 } modify_pair;
420 /* This array parallels modify_mem_list, except that it stores MEMs
421 being set and their canonicalized memory addresses. */
422 static vec<modify_pair> *canon_modify_mem_list;
424 /* Bitmap indexed by block numbers to record which blocks contain
425 function calls. */
426 static bitmap blocks_with_calls;
428 /* Various variables for statistics gathering. */
430 /* Memory used in a pass.
431 This isn't intended to be absolutely precise. Its intent is only
432 to keep an eye on memory usage. */
433 static int bytes_used;
435 /* GCSE substitutions made. */
436 static int gcse_subst_count;
437 /* Number of copy instructions created. */
438 static int gcse_create_count;
440 /* Doing code hoisting. */
441 static bool doing_code_hoisting_p = false;
443 /* For available exprs */
444 static sbitmap *ae_kill;
446 /* Data stored for each basic block. */
447 struct bb_data
449 /* Maximal register pressure inside basic block for given register class
450 (defined only for the pressure classes). */
451 int max_reg_pressure[N_REG_CLASSES];
452 /* Recorded register pressure of basic block before trying to hoist
453 an expression. Will be used to restore the register pressure
454 if the expression should not be hoisted. */
455 int old_pressure;
456 /* Recorded register live_in info of basic block during code hoisting
457 process. BACKUP is used to record live_in info before trying to
458 hoist an expression, and will be used to restore LIVE_IN if the
459 expression should not be hoisted. */
460 bitmap live_in, backup;
463 #define BB_DATA(bb) ((struct bb_data *) (bb)->aux)
465 static basic_block curr_bb;
467 /* Current register pressure for each pressure class. */
468 static int curr_reg_pressure[N_REG_CLASSES];
471 static void compute_can_copy (void);
472 static void *gmalloc (size_t) ATTRIBUTE_MALLOC;
473 static void *gcalloc (size_t, size_t) ATTRIBUTE_MALLOC;
474 static void *gcse_alloc (unsigned long);
475 static void alloc_gcse_mem (void);
476 static void free_gcse_mem (void);
477 static void hash_scan_insn (rtx_insn *, struct gcse_hash_table_d *);
478 static void hash_scan_set (rtx, rtx_insn *, struct gcse_hash_table_d *);
479 static void hash_scan_clobber (rtx, rtx_insn *, struct gcse_hash_table_d *);
480 static void hash_scan_call (rtx, rtx_insn *, struct gcse_hash_table_d *);
481 static int want_to_gcse_p (rtx, int *);
482 static int oprs_unchanged_p (const_rtx, const rtx_insn *, int);
483 static int oprs_anticipatable_p (const_rtx, const rtx_insn *);
484 static int oprs_available_p (const_rtx, const rtx_insn *);
485 static void insert_expr_in_table (rtx, machine_mode, rtx_insn *, int, int,
486 int, struct gcse_hash_table_d *);
487 static unsigned int hash_expr (const_rtx, machine_mode, int *, int);
488 static void record_last_reg_set_info (rtx, int);
489 static void record_last_mem_set_info (rtx_insn *);
490 static void record_last_set_info (rtx, const_rtx, void *);
491 static void compute_hash_table (struct gcse_hash_table_d *);
492 static void alloc_hash_table (struct gcse_hash_table_d *);
493 static void free_hash_table (struct gcse_hash_table_d *);
494 static void compute_hash_table_work (struct gcse_hash_table_d *);
495 static void dump_hash_table (FILE *, const char *, struct gcse_hash_table_d *);
496 static void compute_transp (const_rtx, int, sbitmap *);
497 static void compute_local_properties (sbitmap *, sbitmap *, sbitmap *,
498 struct gcse_hash_table_d *);
499 static void mems_conflict_for_gcse_p (rtx, const_rtx, void *);
500 static int load_killed_in_block_p (const_basic_block, int, const_rtx, int);
501 static void canon_list_insert (rtx, const_rtx, void *);
502 static void alloc_pre_mem (int, int);
503 static void free_pre_mem (void);
504 static struct edge_list *compute_pre_data (void);
505 static int pre_expr_reaches_here_p (basic_block, struct gcse_expr *,
506 basic_block);
507 static void insert_insn_end_basic_block (struct gcse_expr *, basic_block);
508 static void pre_insert_copy_insn (struct gcse_expr *, rtx_insn *);
509 static void pre_insert_copies (void);
510 static int pre_delete (void);
511 static int pre_gcse (struct edge_list *);
512 static int one_pre_gcse_pass (void);
513 static void add_label_notes (rtx, rtx);
514 static void alloc_code_hoist_mem (int, int);
515 static void free_code_hoist_mem (void);
516 static void compute_code_hoist_vbeinout (void);
517 static void compute_code_hoist_data (void);
518 static int should_hoist_expr_to_dom (basic_block, struct gcse_expr *, basic_block,
519 sbitmap, int, int *, enum reg_class,
520 int *, bitmap, rtx_insn *);
521 static int hoist_code (void);
522 static enum reg_class get_regno_pressure_class (int regno, int *nregs);
523 static enum reg_class get_pressure_class_and_nregs (rtx_insn *insn, int *nregs);
524 static int one_code_hoisting_pass (void);
525 static rtx_insn *process_insert_insn (struct gcse_expr *);
526 static int pre_edge_insert (struct edge_list *, struct gcse_expr **);
527 static int pre_expr_reaches_here_p_work (basic_block, struct gcse_expr *,
528 basic_block, char *);
529 static struct ls_expr * ldst_entry (rtx);
530 static void free_ldst_entry (struct ls_expr *);
531 static void free_ld_motion_mems (void);
532 static void print_ldst_list (FILE *);
533 static struct ls_expr * find_rtx_in_ldst (rtx);
534 static int simple_mem (const_rtx);
535 static void invalidate_any_buried_refs (rtx);
536 static void compute_ld_motion_mems (void);
537 static void trim_ld_motion_mems (void);
538 static void update_ld_motion_stores (struct gcse_expr *);
539 static void clear_modify_mem_tables (void);
540 static void free_modify_mem_tables (void);
541 static rtx gcse_emit_move_after (rtx, rtx, rtx_insn *);
542 static bool is_too_expensive (const char *);
544 #define GNEW(T) ((T *) gmalloc (sizeof (T)))
545 #define GCNEW(T) ((T *) gcalloc (1, sizeof (T)))
547 #define GNEWVEC(T, N) ((T *) gmalloc (sizeof (T) * (N)))
548 #define GCNEWVEC(T, N) ((T *) gcalloc ((N), sizeof (T)))
550 #define GNEWVAR(T, S) ((T *) gmalloc ((S)))
551 #define GCNEWVAR(T, S) ((T *) gcalloc (1, (S)))
553 #define GOBNEW(T) ((T *) gcse_alloc (sizeof (T)))
554 #define GOBNEWVAR(T, S) ((T *) gcse_alloc ((S)))
556 /* Misc. utilities. */
558 #define can_copy \
559 (this_target_gcse->x_can_copy)
560 #define can_copy_init_p \
561 (this_target_gcse->x_can_copy_init_p)
563 /* Compute which modes support reg/reg copy operations. */
565 static void
566 compute_can_copy (void)
568 int i;
569 #ifndef AVOID_CCMODE_COPIES
570 rtx reg, insn;
571 #endif
572 memset (can_copy, 0, NUM_MACHINE_MODES);
574 start_sequence ();
575 for (i = 0; i < NUM_MACHINE_MODES; i++)
576 if (GET_MODE_CLASS (i) == MODE_CC)
578 #ifdef AVOID_CCMODE_COPIES
579 can_copy[i] = 0;
580 #else
581 reg = gen_rtx_REG ((machine_mode) i, LAST_VIRTUAL_REGISTER + 1);
582 insn = emit_insn (gen_rtx_SET (VOIDmode, reg, reg));
583 if (recog (PATTERN (insn), insn, NULL) >= 0)
584 can_copy[i] = 1;
585 #endif
587 else
588 can_copy[i] = 1;
590 end_sequence ();
593 /* Returns whether the mode supports reg/reg copy operations. */
595 bool
596 can_copy_p (machine_mode mode)
598 if (! can_copy_init_p)
600 compute_can_copy ();
601 can_copy_init_p = true;
604 return can_copy[mode] != 0;
607 /* Cover function to xmalloc to record bytes allocated. */
609 static void *
610 gmalloc (size_t size)
612 bytes_used += size;
613 return xmalloc (size);
616 /* Cover function to xcalloc to record bytes allocated. */
618 static void *
619 gcalloc (size_t nelem, size_t elsize)
621 bytes_used += nelem * elsize;
622 return xcalloc (nelem, elsize);
625 /* Cover function to obstack_alloc. */
627 static void *
628 gcse_alloc (unsigned long size)
630 bytes_used += size;
631 return obstack_alloc (&gcse_obstack, size);
634 /* Allocate memory for the reg/memory set tracking tables.
635 This is called at the start of each pass. */
637 static void
638 alloc_gcse_mem (void)
640 /* Allocate vars to track sets of regs. */
641 reg_set_bitmap = ALLOC_REG_SET (NULL);
643 /* Allocate array to keep a list of insns which modify memory in each
644 basic block. The two typedefs are needed to work around the
645 pre-processor limitation with template types in macro arguments. */
646 typedef vec<rtx_insn *> vec_rtx_heap;
647 typedef vec<modify_pair> vec_modify_pair_heap;
648 modify_mem_list = GCNEWVEC (vec_rtx_heap, last_basic_block_for_fn (cfun));
649 canon_modify_mem_list = GCNEWVEC (vec_modify_pair_heap,
650 last_basic_block_for_fn (cfun));
651 modify_mem_list_set = BITMAP_ALLOC (NULL);
652 blocks_with_calls = BITMAP_ALLOC (NULL);
655 /* Free memory allocated by alloc_gcse_mem. */
657 static void
658 free_gcse_mem (void)
660 FREE_REG_SET (reg_set_bitmap);
662 free_modify_mem_tables ();
663 BITMAP_FREE (modify_mem_list_set);
664 BITMAP_FREE (blocks_with_calls);
667 /* Compute the local properties of each recorded expression.
669 Local properties are those that are defined by the block, irrespective of
670 other blocks.
672 An expression is transparent in a block if its operands are not modified
673 in the block.
675 An expression is computed (locally available) in a block if it is computed
676 at least once and expression would contain the same value if the
677 computation was moved to the end of the block.
679 An expression is locally anticipatable in a block if it is computed at
680 least once and expression would contain the same value if the computation
681 was moved to the beginning of the block.
683 We call this routine for pre and code hoisting. They all compute
684 basically the same information and thus can easily share this code.
686 TRANSP, COMP, and ANTLOC are destination sbitmaps for recording local
687 properties. If NULL, then it is not necessary to compute or record that
688 particular property.
690 TABLE controls which hash table to look at. */
692 static void
693 compute_local_properties (sbitmap *transp, sbitmap *comp, sbitmap *antloc,
694 struct gcse_hash_table_d *table)
696 unsigned int i;
698 /* Initialize any bitmaps that were passed in. */
699 if (transp)
701 bitmap_vector_ones (transp, last_basic_block_for_fn (cfun));
704 if (comp)
705 bitmap_vector_clear (comp, last_basic_block_for_fn (cfun));
706 if (antloc)
707 bitmap_vector_clear (antloc, last_basic_block_for_fn (cfun));
709 for (i = 0; i < table->size; i++)
711 struct gcse_expr *expr;
713 for (expr = table->table[i]; expr != NULL; expr = expr->next_same_hash)
715 int indx = expr->bitmap_index;
716 struct gcse_occr *occr;
718 /* The expression is transparent in this block if it is not killed.
719 We start by assuming all are transparent [none are killed], and
720 then reset the bits for those that are. */
721 if (transp)
722 compute_transp (expr->expr, indx, transp);
724 /* The occurrences recorded in antic_occr are exactly those that
725 we want to set to nonzero in ANTLOC. */
726 if (antloc)
727 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
729 bitmap_set_bit (antloc[BLOCK_FOR_INSN (occr->insn)->index], indx);
731 /* While we're scanning the table, this is a good place to
732 initialize this. */
733 occr->deleted_p = 0;
736 /* The occurrences recorded in avail_occr are exactly those that
737 we want to set to nonzero in COMP. */
738 if (comp)
739 for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
741 bitmap_set_bit (comp[BLOCK_FOR_INSN (occr->insn)->index], indx);
743 /* While we're scanning the table, this is a good place to
744 initialize this. */
745 occr->copied_p = 0;
748 /* While we're scanning the table, this is a good place to
749 initialize this. */
750 expr->reaching_reg = 0;
755 /* Hash table support. */
757 struct reg_avail_info
759 basic_block last_bb;
760 int first_set;
761 int last_set;
764 static struct reg_avail_info *reg_avail_info;
765 static basic_block current_bb;
767 /* See whether X, the source of a set, is something we want to consider for
768 GCSE. */
770 static int
771 want_to_gcse_p (rtx x, int *max_distance_ptr)
773 #ifdef STACK_REGS
774 /* On register stack architectures, don't GCSE constants from the
775 constant pool, as the benefits are often swamped by the overhead
776 of shuffling the register stack between basic blocks. */
777 if (IS_STACK_MODE (GET_MODE (x)))
778 x = avoid_constant_pool_reference (x);
779 #endif
781 /* GCSE'ing constants:
783 We do not specifically distinguish between constant and non-constant
784 expressions in PRE and Hoist. We use set_src_cost below to limit
785 the maximum distance simple expressions can travel.
787 Nevertheless, constants are much easier to GCSE, and, hence,
788 it is easy to overdo the optimizations. Usually, excessive PRE and
789 Hoisting of constant leads to increased register pressure.
791 RA can deal with this by rematerialing some of the constants.
792 Therefore, it is important that the back-end generates sets of constants
793 in a way that allows reload rematerialize them under high register
794 pressure, i.e., a pseudo register with REG_EQUAL to constant
795 is set only once. Failing to do so will result in IRA/reload
796 spilling such constants under high register pressure instead of
797 rematerializing them. */
799 switch (GET_CODE (x))
801 case REG:
802 case SUBREG:
803 case CALL:
804 return 0;
806 CASE_CONST_ANY:
807 if (!doing_code_hoisting_p)
808 /* Do not PRE constants. */
809 return 0;
811 /* FALLTHRU */
813 default:
814 if (doing_code_hoisting_p)
815 /* PRE doesn't implement max_distance restriction. */
817 int cost;
818 int max_distance;
820 gcc_assert (!optimize_function_for_speed_p (cfun)
821 && optimize_function_for_size_p (cfun));
822 cost = set_src_cost (x, 0);
824 if (cost < COSTS_N_INSNS (GCSE_UNRESTRICTED_COST))
826 max_distance = (GCSE_COST_DISTANCE_RATIO * cost) / 10;
827 if (max_distance == 0)
828 return 0;
830 gcc_assert (max_distance > 0);
832 else
833 max_distance = 0;
835 if (max_distance_ptr)
836 *max_distance_ptr = max_distance;
839 return can_assign_to_reg_without_clobbers_p (x);
843 /* Used internally by can_assign_to_reg_without_clobbers_p. */
845 static GTY(()) rtx_insn *test_insn;
847 /* Return true if we can assign X to a pseudo register such that the
848 resulting insn does not result in clobbering a hard register as a
849 side-effect.
851 Additionally, if the target requires it, check that the resulting insn
852 can be copied. If it cannot, this means that X is special and probably
853 has hidden side-effects we don't want to mess with.
855 This function is typically used by code motion passes, to verify
856 that it is safe to insert an insn without worrying about clobbering
857 maybe live hard regs. */
859 bool
860 can_assign_to_reg_without_clobbers_p (rtx x)
862 int num_clobbers = 0;
863 int icode;
864 bool can_assign = false;
866 /* If this is a valid operand, we are OK. If it's VOIDmode, we aren't. */
867 if (general_operand (x, GET_MODE (x)))
868 return 1;
869 else if (GET_MODE (x) == VOIDmode)
870 return 0;
872 /* Otherwise, check if we can make a valid insn from it. First initialize
873 our test insn if we haven't already. */
874 if (test_insn == 0)
876 test_insn
877 = make_insn_raw (gen_rtx_SET (VOIDmode,
878 gen_rtx_REG (word_mode,
879 FIRST_PSEUDO_REGISTER * 2),
880 const0_rtx));
881 SET_NEXT_INSN (test_insn) = SET_PREV_INSN (test_insn) = 0;
882 INSN_LOCATION (test_insn) = UNKNOWN_LOCATION;
885 /* Now make an insn like the one we would make when GCSE'ing and see if
886 valid. */
887 PUT_MODE (SET_DEST (PATTERN (test_insn)), GET_MODE (x));
888 SET_SRC (PATTERN (test_insn)) = x;
890 icode = recog (PATTERN (test_insn), test_insn, &num_clobbers);
892 /* If the test insn is valid and doesn't need clobbers, and the target also
893 has no objections, we're good. */
894 if (icode >= 0
895 && (num_clobbers == 0 || !added_clobbers_hard_reg_p (icode))
896 && ! (targetm.cannot_copy_insn_p
897 && targetm.cannot_copy_insn_p (test_insn)))
898 can_assign = true;
900 /* Make sure test_insn doesn't have any pointers into GC space. */
901 SET_SRC (PATTERN (test_insn)) = NULL_RTX;
903 return can_assign;
906 /* Return nonzero if the operands of expression X are unchanged from the
907 start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
908 or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
910 static int
911 oprs_unchanged_p (const_rtx x, const rtx_insn *insn, int avail_p)
913 int i, j;
914 enum rtx_code code;
915 const char *fmt;
917 if (x == 0)
918 return 1;
920 code = GET_CODE (x);
921 switch (code)
923 case REG:
925 struct reg_avail_info *info = &reg_avail_info[REGNO (x)];
927 if (info->last_bb != current_bb)
928 return 1;
929 if (avail_p)
930 return info->last_set < DF_INSN_LUID (insn);
931 else
932 return info->first_set >= DF_INSN_LUID (insn);
935 case MEM:
936 if (! flag_gcse_lm
937 || load_killed_in_block_p (current_bb, DF_INSN_LUID (insn),
938 x, avail_p))
939 return 0;
940 else
941 return oprs_unchanged_p (XEXP (x, 0), insn, avail_p);
943 case PRE_DEC:
944 case PRE_INC:
945 case POST_DEC:
946 case POST_INC:
947 case PRE_MODIFY:
948 case POST_MODIFY:
949 return 0;
951 case PC:
952 case CC0: /*FIXME*/
953 case CONST:
954 CASE_CONST_ANY:
955 case SYMBOL_REF:
956 case LABEL_REF:
957 case ADDR_VEC:
958 case ADDR_DIFF_VEC:
959 return 1;
961 default:
962 break;
965 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
967 if (fmt[i] == 'e')
969 /* If we are about to do the last recursive call needed at this
970 level, change it into iteration. This function is called enough
971 to be worth it. */
972 if (i == 0)
973 return oprs_unchanged_p (XEXP (x, i), insn, avail_p);
975 else if (! oprs_unchanged_p (XEXP (x, i), insn, avail_p))
976 return 0;
978 else if (fmt[i] == 'E')
979 for (j = 0; j < XVECLEN (x, i); j++)
980 if (! oprs_unchanged_p (XVECEXP (x, i, j), insn, avail_p))
981 return 0;
984 return 1;
987 /* Info passed from load_killed_in_block_p to mems_conflict_for_gcse_p. */
989 struct mem_conflict_info
991 /* A memory reference for a load instruction, mems_conflict_for_gcse_p will
992 see if a memory store conflicts with this memory load. */
993 const_rtx mem;
995 /* True if mems_conflict_for_gcse_p finds a conflict between two memory
996 references. */
997 bool conflict;
1000 /* DEST is the output of an instruction. If it is a memory reference and
1001 possibly conflicts with the load found in DATA, then communicate this
1002 information back through DATA. */
1004 static void
1005 mems_conflict_for_gcse_p (rtx dest, const_rtx setter ATTRIBUTE_UNUSED,
1006 void *data)
1008 struct mem_conflict_info *mci = (struct mem_conflict_info *) data;
1010 while (GET_CODE (dest) == SUBREG
1011 || GET_CODE (dest) == ZERO_EXTRACT
1012 || GET_CODE (dest) == STRICT_LOW_PART)
1013 dest = XEXP (dest, 0);
1015 /* If DEST is not a MEM, then it will not conflict with the load. Note
1016 that function calls are assumed to clobber memory, but are handled
1017 elsewhere. */
1018 if (! MEM_P (dest))
1019 return;
1021 /* If we are setting a MEM in our list of specially recognized MEMs,
1022 don't mark as killed this time. */
1023 if (pre_ldst_mems != NULL && expr_equiv_p (dest, mci->mem))
1025 if (!find_rtx_in_ldst (dest))
1026 mci->conflict = true;
1027 return;
1030 if (true_dependence (dest, GET_MODE (dest), mci->mem))
1031 mci->conflict = true;
1034 /* Return nonzero if the expression in X (a memory reference) is killed
1035 in block BB before or after the insn with the LUID in UID_LIMIT.
1036 AVAIL_P is nonzero for kills after UID_LIMIT, and zero for kills
1037 before UID_LIMIT.
1039 To check the entire block, set UID_LIMIT to max_uid + 1 and
1040 AVAIL_P to 0. */
1042 static int
1043 load_killed_in_block_p (const_basic_block bb, int uid_limit, const_rtx x,
1044 int avail_p)
1046 vec<rtx_insn *> list = modify_mem_list[bb->index];
1047 rtx_insn *setter;
1048 unsigned ix;
1050 /* If this is a readonly then we aren't going to be changing it. */
1051 if (MEM_READONLY_P (x))
1052 return 0;
1054 FOR_EACH_VEC_ELT_REVERSE (list, ix, setter)
1056 struct mem_conflict_info mci;
1058 /* Ignore entries in the list that do not apply. */
1059 if ((avail_p
1060 && DF_INSN_LUID (setter) < uid_limit)
1061 || (! avail_p
1062 && DF_INSN_LUID (setter) > uid_limit))
1063 continue;
1065 /* If SETTER is a call everything is clobbered. Note that calls
1066 to pure functions are never put on the list, so we need not
1067 worry about them. */
1068 if (CALL_P (setter))
1069 return 1;
1071 /* SETTER must be an INSN of some kind that sets memory. Call
1072 note_stores to examine each hunk of memory that is modified. */
1073 mci.mem = x;
1074 mci.conflict = false;
1075 note_stores (PATTERN (setter), mems_conflict_for_gcse_p, &mci);
1076 if (mci.conflict)
1077 return 1;
1079 return 0;
1082 /* Return nonzero if the operands of expression X are unchanged from
1083 the start of INSN's basic block up to but not including INSN. */
1085 static int
1086 oprs_anticipatable_p (const_rtx x, const rtx_insn *insn)
1088 return oprs_unchanged_p (x, insn, 0);
1091 /* Return nonzero if the operands of expression X are unchanged from
1092 INSN to the end of INSN's basic block. */
1094 static int
1095 oprs_available_p (const_rtx x, const rtx_insn *insn)
1097 return oprs_unchanged_p (x, insn, 1);
1100 /* Hash expression X.
1102 MODE is only used if X is a CONST_INT. DO_NOT_RECORD_P is a boolean
1103 indicating if a volatile operand is found or if the expression contains
1104 something we don't want to insert in the table. HASH_TABLE_SIZE is
1105 the current size of the hash table to be probed. */
1107 static unsigned int
1108 hash_expr (const_rtx x, machine_mode mode, int *do_not_record_p,
1109 int hash_table_size)
1111 unsigned int hash;
1113 *do_not_record_p = 0;
1115 hash = hash_rtx (x, mode, do_not_record_p, NULL, /*have_reg_qty=*/false);
1116 return hash % hash_table_size;
1119 /* Return nonzero if exp1 is equivalent to exp2. */
1121 static int
1122 expr_equiv_p (const_rtx x, const_rtx y)
1124 return exp_equiv_p (x, y, 0, true);
1127 /* Insert expression X in INSN in the hash TABLE.
1128 If it is already present, record it as the last occurrence in INSN's
1129 basic block.
1131 MODE is the mode of the value X is being stored into.
1132 It is only used if X is a CONST_INT.
1134 ANTIC_P is nonzero if X is an anticipatable expression.
1135 AVAIL_P is nonzero if X is an available expression.
1137 MAX_DISTANCE is the maximum distance in instructions this expression can
1138 be moved. */
1140 static void
1141 insert_expr_in_table (rtx x, machine_mode mode, rtx_insn *insn,
1142 int antic_p,
1143 int avail_p, int max_distance, struct gcse_hash_table_d *table)
1145 int found, do_not_record_p;
1146 unsigned int hash;
1147 struct gcse_expr *cur_expr, *last_expr = NULL;
1148 struct gcse_occr *antic_occr, *avail_occr;
1150 hash = hash_expr (x, mode, &do_not_record_p, table->size);
1152 /* Do not insert expression in table if it contains volatile operands,
1153 or if hash_expr determines the expression is something we don't want
1154 to or can't handle. */
1155 if (do_not_record_p)
1156 return;
1158 cur_expr = table->table[hash];
1159 found = 0;
1161 while (cur_expr && 0 == (found = expr_equiv_p (cur_expr->expr, x)))
1163 /* If the expression isn't found, save a pointer to the end of
1164 the list. */
1165 last_expr = cur_expr;
1166 cur_expr = cur_expr->next_same_hash;
1169 if (! found)
1171 cur_expr = GOBNEW (struct gcse_expr);
1172 bytes_used += sizeof (struct gcse_expr);
1173 if (table->table[hash] == NULL)
1174 /* This is the first pattern that hashed to this index. */
1175 table->table[hash] = cur_expr;
1176 else
1177 /* Add EXPR to end of this hash chain. */
1178 last_expr->next_same_hash = cur_expr;
1180 /* Set the fields of the expr element. */
1181 cur_expr->expr = x;
1182 cur_expr->bitmap_index = table->n_elems++;
1183 cur_expr->next_same_hash = NULL;
1184 cur_expr->antic_occr = NULL;
1185 cur_expr->avail_occr = NULL;
1186 gcc_assert (max_distance >= 0);
1187 cur_expr->max_distance = max_distance;
1189 else
1190 gcc_assert (cur_expr->max_distance == max_distance);
1192 /* Now record the occurrence(s). */
1193 if (antic_p)
1195 antic_occr = cur_expr->antic_occr;
1197 if (antic_occr
1198 && BLOCK_FOR_INSN (antic_occr->insn) != BLOCK_FOR_INSN (insn))
1199 antic_occr = NULL;
1201 if (antic_occr)
1202 /* Found another instance of the expression in the same basic block.
1203 Prefer the currently recorded one. We want the first one in the
1204 block and the block is scanned from start to end. */
1205 ; /* nothing to do */
1206 else
1208 /* First occurrence of this expression in this basic block. */
1209 antic_occr = GOBNEW (struct gcse_occr);
1210 bytes_used += sizeof (struct gcse_occr);
1211 antic_occr->insn = insn;
1212 antic_occr->next = cur_expr->antic_occr;
1213 antic_occr->deleted_p = 0;
1214 cur_expr->antic_occr = antic_occr;
1218 if (avail_p)
1220 avail_occr = cur_expr->avail_occr;
1222 if (avail_occr
1223 && BLOCK_FOR_INSN (avail_occr->insn) == BLOCK_FOR_INSN (insn))
1225 /* Found another instance of the expression in the same basic block.
1226 Prefer this occurrence to the currently recorded one. We want
1227 the last one in the block and the block is scanned from start
1228 to end. */
1229 avail_occr->insn = insn;
1231 else
1233 /* First occurrence of this expression in this basic block. */
1234 avail_occr = GOBNEW (struct gcse_occr);
1235 bytes_used += sizeof (struct gcse_occr);
1236 avail_occr->insn = insn;
1237 avail_occr->next = cur_expr->avail_occr;
1238 avail_occr->deleted_p = 0;
1239 cur_expr->avail_occr = avail_occr;
1244 /* Scan SET present in INSN and add an entry to the hash TABLE. */
1246 static void
1247 hash_scan_set (rtx set, rtx_insn *insn, struct gcse_hash_table_d *table)
1249 rtx src = SET_SRC (set);
1250 rtx dest = SET_DEST (set);
1251 rtx note;
1253 if (GET_CODE (src) == CALL)
1254 hash_scan_call (src, insn, table);
1256 else if (REG_P (dest))
1258 unsigned int regno = REGNO (dest);
1259 int max_distance = 0;
1261 /* See if a REG_EQUAL note shows this equivalent to a simpler expression.
1263 This allows us to do a single GCSE pass and still eliminate
1264 redundant constants, addresses or other expressions that are
1265 constructed with multiple instructions.
1267 However, keep the original SRC if INSN is a simple reg-reg move.
1268 In this case, there will almost always be a REG_EQUAL note on the
1269 insn that sets SRC. By recording the REG_EQUAL value here as SRC
1270 for INSN, we miss copy propagation opportunities and we perform the
1271 same PRE GCSE operation repeatedly on the same REG_EQUAL value if we
1272 do more than one PRE GCSE pass.
1274 Note that this does not impede profitable constant propagations. We
1275 "look through" reg-reg sets in lookup_avail_set. */
1276 note = find_reg_equal_equiv_note (insn);
1277 if (note != 0
1278 && REG_NOTE_KIND (note) == REG_EQUAL
1279 && !REG_P (src)
1280 && want_to_gcse_p (XEXP (note, 0), NULL))
1281 src = XEXP (note, 0), set = gen_rtx_SET (VOIDmode, dest, src);
1283 /* Only record sets of pseudo-regs in the hash table. */
1284 if (regno >= FIRST_PSEUDO_REGISTER
1285 /* Don't GCSE something if we can't do a reg/reg copy. */
1286 && can_copy_p (GET_MODE (dest))
1287 /* GCSE commonly inserts instruction after the insn. We can't
1288 do that easily for EH edges so disable GCSE on these for now. */
1289 /* ??? We can now easily create new EH landing pads at the
1290 gimple level, for splitting edges; there's no reason we
1291 can't do the same thing at the rtl level. */
1292 && !can_throw_internal (insn)
1293 /* Is SET_SRC something we want to gcse? */
1294 && want_to_gcse_p (src, &max_distance)
1295 /* Don't CSE a nop. */
1296 && ! set_noop_p (set)
1297 /* Don't GCSE if it has attached REG_EQUIV note.
1298 At this point this only function parameters should have
1299 REG_EQUIV notes and if the argument slot is used somewhere
1300 explicitly, it means address of parameter has been taken,
1301 so we should not extend the lifetime of the pseudo. */
1302 && (note == NULL_RTX || ! MEM_P (XEXP (note, 0))))
1304 /* An expression is not anticipatable if its operands are
1305 modified before this insn or if this is not the only SET in
1306 this insn. The latter condition does not have to mean that
1307 SRC itself is not anticipatable, but we just will not be
1308 able to handle code motion of insns with multiple sets. */
1309 int antic_p = oprs_anticipatable_p (src, insn)
1310 && !multiple_sets (insn);
1311 /* An expression is not available if its operands are
1312 subsequently modified, including this insn. It's also not
1313 available if this is a branch, because we can't insert
1314 a set after the branch. */
1315 int avail_p = (oprs_available_p (src, insn)
1316 && ! JUMP_P (insn));
1318 insert_expr_in_table (src, GET_MODE (dest), insn, antic_p, avail_p,
1319 max_distance, table);
1322 /* In case of store we want to consider the memory value as available in
1323 the REG stored in that memory. This makes it possible to remove
1324 redundant loads from due to stores to the same location. */
1325 else if (flag_gcse_las && REG_P (src) && MEM_P (dest))
1327 unsigned int regno = REGNO (src);
1328 int max_distance = 0;
1330 /* Only record sets of pseudo-regs in the hash table. */
1331 if (regno >= FIRST_PSEUDO_REGISTER
1332 /* Don't GCSE something if we can't do a reg/reg copy. */
1333 && can_copy_p (GET_MODE (src))
1334 /* GCSE commonly inserts instruction after the insn. We can't
1335 do that easily for EH edges so disable GCSE on these for now. */
1336 && !can_throw_internal (insn)
1337 /* Is SET_DEST something we want to gcse? */
1338 && want_to_gcse_p (dest, &max_distance)
1339 /* Don't CSE a nop. */
1340 && ! set_noop_p (set)
1341 /* Don't GCSE if it has attached REG_EQUIV note.
1342 At this point this only function parameters should have
1343 REG_EQUIV notes and if the argument slot is used somewhere
1344 explicitly, it means address of parameter has been taken,
1345 so we should not extend the lifetime of the pseudo. */
1346 && ((note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) == 0
1347 || ! MEM_P (XEXP (note, 0))))
1349 /* Stores are never anticipatable. */
1350 int antic_p = 0;
1351 /* An expression is not available if its operands are
1352 subsequently modified, including this insn. It's also not
1353 available if this is a branch, because we can't insert
1354 a set after the branch. */
1355 int avail_p = oprs_available_p (dest, insn)
1356 && ! JUMP_P (insn);
1358 /* Record the memory expression (DEST) in the hash table. */
1359 insert_expr_in_table (dest, GET_MODE (dest), insn,
1360 antic_p, avail_p, max_distance, table);
1365 static void
1366 hash_scan_clobber (rtx x ATTRIBUTE_UNUSED, rtx_insn *insn ATTRIBUTE_UNUSED,
1367 struct gcse_hash_table_d *table ATTRIBUTE_UNUSED)
1369 /* Currently nothing to do. */
1372 static void
1373 hash_scan_call (rtx x ATTRIBUTE_UNUSED, rtx_insn *insn ATTRIBUTE_UNUSED,
1374 struct gcse_hash_table_d *table ATTRIBUTE_UNUSED)
1376 /* Currently nothing to do. */
1379 /* Process INSN and add hash table entries as appropriate. */
1381 static void
1382 hash_scan_insn (rtx_insn *insn, struct gcse_hash_table_d *table)
1384 rtx pat = PATTERN (insn);
1385 int i;
1387 /* Pick out the sets of INSN and for other forms of instructions record
1388 what's been modified. */
1390 if (GET_CODE (pat) == SET)
1391 hash_scan_set (pat, insn, table);
1393 else if (GET_CODE (pat) == CLOBBER)
1394 hash_scan_clobber (pat, insn, table);
1396 else if (GET_CODE (pat) == CALL)
1397 hash_scan_call (pat, insn, table);
1399 else if (GET_CODE (pat) == PARALLEL)
1400 for (i = 0; i < XVECLEN (pat, 0); i++)
1402 rtx x = XVECEXP (pat, 0, i);
1404 if (GET_CODE (x) == SET)
1405 hash_scan_set (x, insn, table);
1406 else if (GET_CODE (x) == CLOBBER)
1407 hash_scan_clobber (x, insn, table);
1408 else if (GET_CODE (x) == CALL)
1409 hash_scan_call (x, insn, table);
1413 /* Dump the hash table TABLE to file FILE under the name NAME. */
1415 static void
1416 dump_hash_table (FILE *file, const char *name, struct gcse_hash_table_d *table)
1418 int i;
1419 /* Flattened out table, so it's printed in proper order. */
1420 struct gcse_expr **flat_table;
1421 unsigned int *hash_val;
1422 struct gcse_expr *expr;
1424 flat_table = XCNEWVEC (struct gcse_expr *, table->n_elems);
1425 hash_val = XNEWVEC (unsigned int, table->n_elems);
1427 for (i = 0; i < (int) table->size; i++)
1428 for (expr = table->table[i]; expr != NULL; expr = expr->next_same_hash)
1430 flat_table[expr->bitmap_index] = expr;
1431 hash_val[expr->bitmap_index] = i;
1434 fprintf (file, "%s hash table (%d buckets, %d entries)\n",
1435 name, table->size, table->n_elems);
1437 for (i = 0; i < (int) table->n_elems; i++)
1438 if (flat_table[i] != 0)
1440 expr = flat_table[i];
1441 fprintf (file, "Index %d (hash value %d; max distance %d)\n ",
1442 expr->bitmap_index, hash_val[i], expr->max_distance);
1443 print_rtl (file, expr->expr);
1444 fprintf (file, "\n");
1447 fprintf (file, "\n");
1449 free (flat_table);
1450 free (hash_val);
1453 /* Record register first/last/block set information for REGNO in INSN.
1455 first_set records the first place in the block where the register
1456 is set and is used to compute "anticipatability".
1458 last_set records the last place in the block where the register
1459 is set and is used to compute "availability".
1461 last_bb records the block for which first_set and last_set are
1462 valid, as a quick test to invalidate them. */
1464 static void
1465 record_last_reg_set_info (rtx insn, int regno)
1467 struct reg_avail_info *info = &reg_avail_info[regno];
1468 int luid = DF_INSN_LUID (insn);
1470 info->last_set = luid;
1471 if (info->last_bb != current_bb)
1473 info->last_bb = current_bb;
1474 info->first_set = luid;
1478 /* Record all of the canonicalized MEMs of record_last_mem_set_info's insn.
1479 Note we store a pair of elements in the list, so they have to be
1480 taken off pairwise. */
1482 static void
1483 canon_list_insert (rtx dest ATTRIBUTE_UNUSED, const_rtx x ATTRIBUTE_UNUSED,
1484 void * v_insn)
1486 rtx dest_addr, insn;
1487 int bb;
1488 modify_pair pair;
1490 while (GET_CODE (dest) == SUBREG
1491 || GET_CODE (dest) == ZERO_EXTRACT
1492 || GET_CODE (dest) == STRICT_LOW_PART)
1493 dest = XEXP (dest, 0);
1495 /* If DEST is not a MEM, then it will not conflict with a load. Note
1496 that function calls are assumed to clobber memory, but are handled
1497 elsewhere. */
1499 if (! MEM_P (dest))
1500 return;
1502 dest_addr = get_addr (XEXP (dest, 0));
1503 dest_addr = canon_rtx (dest_addr);
1504 insn = (rtx) v_insn;
1505 bb = BLOCK_FOR_INSN (insn)->index;
1507 pair.dest = dest;
1508 pair.dest_addr = dest_addr;
1509 canon_modify_mem_list[bb].safe_push (pair);
1512 /* Record memory modification information for INSN. We do not actually care
1513 about the memory location(s) that are set, or even how they are set (consider
1514 a CALL_INSN). We merely need to record which insns modify memory. */
1516 static void
1517 record_last_mem_set_info (rtx_insn *insn)
1519 int bb;
1521 if (! flag_gcse_lm)
1522 return;
1524 /* load_killed_in_block_p will handle the case of calls clobbering
1525 everything. */
1526 bb = BLOCK_FOR_INSN (insn)->index;
1527 modify_mem_list[bb].safe_push (insn);
1528 bitmap_set_bit (modify_mem_list_set, bb);
1530 if (CALL_P (insn))
1531 bitmap_set_bit (blocks_with_calls, bb);
1532 else
1533 note_stores (PATTERN (insn), canon_list_insert, (void*) insn);
1536 /* Called from compute_hash_table via note_stores to handle one
1537 SET or CLOBBER in an insn. DATA is really the instruction in which
1538 the SET is taking place. */
1540 static void
1541 record_last_set_info (rtx dest, const_rtx setter ATTRIBUTE_UNUSED, void *data)
1543 rtx_insn *last_set_insn = (rtx_insn *) data;
1545 if (GET_CODE (dest) == SUBREG)
1546 dest = SUBREG_REG (dest);
1548 if (REG_P (dest))
1549 record_last_reg_set_info (last_set_insn, REGNO (dest));
1550 else if (MEM_P (dest)
1551 /* Ignore pushes, they clobber nothing. */
1552 && ! push_operand (dest, GET_MODE (dest)))
1553 record_last_mem_set_info (last_set_insn);
1556 /* Top level function to create an expression hash table.
1558 Expression entries are placed in the hash table if
1559 - they are of the form (set (pseudo-reg) src),
1560 - src is something we want to perform GCSE on,
1561 - none of the operands are subsequently modified in the block
1563 Currently src must be a pseudo-reg or a const_int.
1565 TABLE is the table computed. */
1567 static void
1568 compute_hash_table_work (struct gcse_hash_table_d *table)
1570 int i;
1572 /* re-Cache any INSN_LIST nodes we have allocated. */
1573 clear_modify_mem_tables ();
1574 /* Some working arrays used to track first and last set in each block. */
1575 reg_avail_info = GNEWVEC (struct reg_avail_info, max_reg_num ());
1577 for (i = 0; i < max_reg_num (); ++i)
1578 reg_avail_info[i].last_bb = NULL;
1580 FOR_EACH_BB_FN (current_bb, cfun)
1582 rtx_insn *insn;
1583 unsigned int regno;
1585 /* First pass over the instructions records information used to
1586 determine when registers and memory are first and last set. */
1587 FOR_BB_INSNS (current_bb, insn)
1589 if (!NONDEBUG_INSN_P (insn))
1590 continue;
1592 if (CALL_P (insn))
1594 hard_reg_set_iterator hrsi;
1595 EXECUTE_IF_SET_IN_HARD_REG_SET (regs_invalidated_by_call,
1596 0, regno, hrsi)
1597 record_last_reg_set_info (insn, regno);
1599 if (! RTL_CONST_OR_PURE_CALL_P (insn))
1600 record_last_mem_set_info (insn);
1603 note_stores (PATTERN (insn), record_last_set_info, insn);
1606 /* The next pass builds the hash table. */
1607 FOR_BB_INSNS (current_bb, insn)
1608 if (NONDEBUG_INSN_P (insn))
1609 hash_scan_insn (insn, table);
1612 free (reg_avail_info);
1613 reg_avail_info = NULL;
1616 /* Allocate space for the set/expr hash TABLE.
1617 It is used to determine the number of buckets to use. */
1619 static void
1620 alloc_hash_table (struct gcse_hash_table_d *table)
1622 int n;
1624 n = get_max_insn_count ();
1626 table->size = n / 4;
1627 if (table->size < 11)
1628 table->size = 11;
1630 /* Attempt to maintain efficient use of hash table.
1631 Making it an odd number is simplest for now.
1632 ??? Later take some measurements. */
1633 table->size |= 1;
1634 n = table->size * sizeof (struct gcse_expr *);
1635 table->table = GNEWVAR (struct gcse_expr *, n);
1638 /* Free things allocated by alloc_hash_table. */
1640 static void
1641 free_hash_table (struct gcse_hash_table_d *table)
1643 free (table->table);
1646 /* Compute the expression hash table TABLE. */
1648 static void
1649 compute_hash_table (struct gcse_hash_table_d *table)
1651 /* Initialize count of number of entries in hash table. */
1652 table->n_elems = 0;
1653 memset (table->table, 0, table->size * sizeof (struct gcse_expr *));
1655 compute_hash_table_work (table);
1658 /* Expression tracking support. */
1660 /* Clear canon_modify_mem_list and modify_mem_list tables. */
1661 static void
1662 clear_modify_mem_tables (void)
1664 unsigned i;
1665 bitmap_iterator bi;
1667 EXECUTE_IF_SET_IN_BITMAP (modify_mem_list_set, 0, i, bi)
1669 modify_mem_list[i].release ();
1670 canon_modify_mem_list[i].release ();
1672 bitmap_clear (modify_mem_list_set);
1673 bitmap_clear (blocks_with_calls);
1676 /* Release memory used by modify_mem_list_set. */
1678 static void
1679 free_modify_mem_tables (void)
1681 clear_modify_mem_tables ();
1682 free (modify_mem_list);
1683 free (canon_modify_mem_list);
1684 modify_mem_list = 0;
1685 canon_modify_mem_list = 0;
1688 /* For each block, compute whether X is transparent. X is either an
1689 expression or an assignment [though we don't care which, for this context
1690 an assignment is treated as an expression]. For each block where an
1691 element of X is modified, reset the INDX bit in BMAP. */
1693 static void
1694 compute_transp (const_rtx x, int indx, sbitmap *bmap)
1696 int i, j;
1697 enum rtx_code code;
1698 const char *fmt;
1700 /* repeat is used to turn tail-recursion into iteration since GCC
1701 can't do it when there's no return value. */
1702 repeat:
1704 if (x == 0)
1705 return;
1707 code = GET_CODE (x);
1708 switch (code)
1710 case REG:
1712 df_ref def;
1713 for (def = DF_REG_DEF_CHAIN (REGNO (x));
1714 def;
1715 def = DF_REF_NEXT_REG (def))
1716 bitmap_clear_bit (bmap[DF_REF_BB (def)->index], indx);
1719 return;
1721 case MEM:
1722 if (! MEM_READONLY_P (x))
1724 bitmap_iterator bi;
1725 unsigned bb_index;
1726 rtx x_addr;
1728 x_addr = get_addr (XEXP (x, 0));
1729 x_addr = canon_rtx (x_addr);
1731 /* First handle all the blocks with calls. We don't need to
1732 do any list walking for them. */
1733 EXECUTE_IF_SET_IN_BITMAP (blocks_with_calls, 0, bb_index, bi)
1735 bitmap_clear_bit (bmap[bb_index], indx);
1738 /* Now iterate over the blocks which have memory modifications
1739 but which do not have any calls. */
1740 EXECUTE_IF_AND_COMPL_IN_BITMAP (modify_mem_list_set,
1741 blocks_with_calls,
1742 0, bb_index, bi)
1744 vec<modify_pair> list
1745 = canon_modify_mem_list[bb_index];
1746 modify_pair *pair;
1747 unsigned ix;
1749 FOR_EACH_VEC_ELT_REVERSE (list, ix, pair)
1751 rtx dest = pair->dest;
1752 rtx dest_addr = pair->dest_addr;
1754 if (canon_true_dependence (dest, GET_MODE (dest),
1755 dest_addr, x, x_addr))
1757 bitmap_clear_bit (bmap[bb_index], indx);
1758 break;
1764 x = XEXP (x, 0);
1765 goto repeat;
1767 case PC:
1768 case CC0: /*FIXME*/
1769 case CONST:
1770 CASE_CONST_ANY:
1771 case SYMBOL_REF:
1772 case LABEL_REF:
1773 case ADDR_VEC:
1774 case ADDR_DIFF_VEC:
1775 return;
1777 default:
1778 break;
1781 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
1783 if (fmt[i] == 'e')
1785 /* If we are about to do the last recursive call
1786 needed at this level, change it into iteration.
1787 This function is called enough to be worth it. */
1788 if (i == 0)
1790 x = XEXP (x, i);
1791 goto repeat;
1794 compute_transp (XEXP (x, i), indx, bmap);
1796 else if (fmt[i] == 'E')
1797 for (j = 0; j < XVECLEN (x, i); j++)
1798 compute_transp (XVECEXP (x, i, j), indx, bmap);
1802 /* Compute PRE+LCM working variables. */
1804 /* Local properties of expressions. */
1806 /* Nonzero for expressions that are transparent in the block. */
1807 static sbitmap *transp;
1809 /* Nonzero for expressions that are computed (available) in the block. */
1810 static sbitmap *comp;
1812 /* Nonzero for expressions that are locally anticipatable in the block. */
1813 static sbitmap *antloc;
1815 /* Nonzero for expressions where this block is an optimal computation
1816 point. */
1817 static sbitmap *pre_optimal;
1819 /* Nonzero for expressions which are redundant in a particular block. */
1820 static sbitmap *pre_redundant;
1822 /* Nonzero for expressions which should be inserted on a specific edge. */
1823 static sbitmap *pre_insert_map;
1825 /* Nonzero for expressions which should be deleted in a specific block. */
1826 static sbitmap *pre_delete_map;
1828 /* Allocate vars used for PRE analysis. */
1830 static void
1831 alloc_pre_mem (int n_blocks, int n_exprs)
1833 transp = sbitmap_vector_alloc (n_blocks, n_exprs);
1834 comp = sbitmap_vector_alloc (n_blocks, n_exprs);
1835 antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
1837 pre_optimal = NULL;
1838 pre_redundant = NULL;
1839 pre_insert_map = NULL;
1840 pre_delete_map = NULL;
1841 ae_kill = sbitmap_vector_alloc (n_blocks, n_exprs);
1843 /* pre_insert and pre_delete are allocated later. */
1846 /* Free vars used for PRE analysis. */
1848 static void
1849 free_pre_mem (void)
1851 sbitmap_vector_free (transp);
1852 sbitmap_vector_free (comp);
1854 /* ANTLOC and AE_KILL are freed just after pre_lcm finishes. */
1856 if (pre_optimal)
1857 sbitmap_vector_free (pre_optimal);
1858 if (pre_redundant)
1859 sbitmap_vector_free (pre_redundant);
1860 if (pre_insert_map)
1861 sbitmap_vector_free (pre_insert_map);
1862 if (pre_delete_map)
1863 sbitmap_vector_free (pre_delete_map);
1865 transp = comp = NULL;
1866 pre_optimal = pre_redundant = pre_insert_map = pre_delete_map = NULL;
1869 /* Remove certain expressions from anticipatable and transparent
1870 sets of basic blocks that have incoming abnormal edge.
1871 For PRE remove potentially trapping expressions to avoid placing
1872 them on abnormal edges. For hoisting remove memory references that
1873 can be clobbered by calls. */
1875 static void
1876 prune_expressions (bool pre_p)
1878 sbitmap prune_exprs;
1879 struct gcse_expr *expr;
1880 unsigned int ui;
1881 basic_block bb;
1883 prune_exprs = sbitmap_alloc (expr_hash_table.n_elems);
1884 bitmap_clear (prune_exprs);
1885 for (ui = 0; ui < expr_hash_table.size; ui++)
1887 for (expr = expr_hash_table.table[ui]; expr; expr = expr->next_same_hash)
1889 /* Note potentially trapping expressions. */
1890 if (may_trap_p (expr->expr))
1892 bitmap_set_bit (prune_exprs, expr->bitmap_index);
1893 continue;
1896 if (!pre_p && MEM_P (expr->expr))
1897 /* Note memory references that can be clobbered by a call.
1898 We do not split abnormal edges in hoisting, so would
1899 a memory reference get hoisted along an abnormal edge,
1900 it would be placed /before/ the call. Therefore, only
1901 constant memory references can be hoisted along abnormal
1902 edges. */
1904 if (GET_CODE (XEXP (expr->expr, 0)) == SYMBOL_REF
1905 && CONSTANT_POOL_ADDRESS_P (XEXP (expr->expr, 0)))
1906 continue;
1908 if (MEM_READONLY_P (expr->expr)
1909 && !MEM_VOLATILE_P (expr->expr)
1910 && MEM_NOTRAP_P (expr->expr))
1911 /* Constant memory reference, e.g., a PIC address. */
1912 continue;
1914 /* ??? Optimally, we would use interprocedural alias
1915 analysis to determine if this mem is actually killed
1916 by this call. */
1918 bitmap_set_bit (prune_exprs, expr->bitmap_index);
1923 FOR_EACH_BB_FN (bb, cfun)
1925 edge e;
1926 edge_iterator ei;
1928 /* If the current block is the destination of an abnormal edge, we
1929 kill all trapping (for PRE) and memory (for hoist) expressions
1930 because we won't be able to properly place the instruction on
1931 the edge. So make them neither anticipatable nor transparent.
1932 This is fairly conservative.
1934 ??? For hoisting it may be necessary to check for set-and-jump
1935 instructions here, not just for abnormal edges. The general problem
1936 is that when an expression cannot not be placed right at the end of
1937 a basic block we should account for any side-effects of a subsequent
1938 jump instructions that could clobber the expression. It would
1939 be best to implement this check along the lines of
1940 should_hoist_expr_to_dom where the target block is already known
1941 and, hence, there's no need to conservatively prune expressions on
1942 "intermediate" set-and-jump instructions. */
1943 FOR_EACH_EDGE (e, ei, bb->preds)
1944 if ((e->flags & EDGE_ABNORMAL)
1945 && (pre_p || CALL_P (BB_END (e->src))))
1947 bitmap_and_compl (antloc[bb->index],
1948 antloc[bb->index], prune_exprs);
1949 bitmap_and_compl (transp[bb->index],
1950 transp[bb->index], prune_exprs);
1951 break;
1955 sbitmap_free (prune_exprs);
1958 /* It may be necessary to insert a large number of insns on edges to
1959 make the existing occurrences of expressions fully redundant. This
1960 routine examines the set of insertions and deletions and if the ratio
1961 of insertions to deletions is too high for a particular expression, then
1962 the expression is removed from the insertion/deletion sets.
1964 N_ELEMS is the number of elements in the hash table. */
1966 static void
1967 prune_insertions_deletions (int n_elems)
1969 sbitmap_iterator sbi;
1970 sbitmap prune_exprs;
1972 /* We always use I to iterate over blocks/edges and J to iterate over
1973 expressions. */
1974 unsigned int i, j;
1976 /* Counts for the number of times an expression needs to be inserted and
1977 number of times an expression can be removed as a result. */
1978 int *insertions = GCNEWVEC (int, n_elems);
1979 int *deletions = GCNEWVEC (int, n_elems);
1981 /* Set of expressions which require too many insertions relative to
1982 the number of deletions achieved. We will prune these out of the
1983 insertion/deletion sets. */
1984 prune_exprs = sbitmap_alloc (n_elems);
1985 bitmap_clear (prune_exprs);
1987 /* Iterate over the edges counting the number of times each expression
1988 needs to be inserted. */
1989 for (i = 0; i < (unsigned) n_edges_for_fn (cfun); i++)
1991 EXECUTE_IF_SET_IN_BITMAP (pre_insert_map[i], 0, j, sbi)
1992 insertions[j]++;
1995 /* Similarly for deletions, but those occur in blocks rather than on
1996 edges. */
1997 for (i = 0; i < (unsigned) last_basic_block_for_fn (cfun); i++)
1999 EXECUTE_IF_SET_IN_BITMAP (pre_delete_map[i], 0, j, sbi)
2000 deletions[j]++;
2003 /* Now that we have accurate counts, iterate over the elements in the
2004 hash table and see if any need too many insertions relative to the
2005 number of evaluations that can be removed. If so, mark them in
2006 PRUNE_EXPRS. */
2007 for (j = 0; j < (unsigned) n_elems; j++)
2008 if (deletions[j]
2009 && ((unsigned) insertions[j] / deletions[j]) > MAX_GCSE_INSERTION_RATIO)
2010 bitmap_set_bit (prune_exprs, j);
2012 /* Now prune PRE_INSERT_MAP and PRE_DELETE_MAP based on PRUNE_EXPRS. */
2013 EXECUTE_IF_SET_IN_BITMAP (prune_exprs, 0, j, sbi)
2015 for (i = 0; i < (unsigned) n_edges_for_fn (cfun); i++)
2016 bitmap_clear_bit (pre_insert_map[i], j);
2018 for (i = 0; i < (unsigned) last_basic_block_for_fn (cfun); i++)
2019 bitmap_clear_bit (pre_delete_map[i], j);
2022 sbitmap_free (prune_exprs);
2023 free (insertions);
2024 free (deletions);
2027 /* Top level routine to do the dataflow analysis needed by PRE. */
2029 static struct edge_list *
2030 compute_pre_data (void)
2032 struct edge_list *edge_list;
2033 basic_block bb;
2035 compute_local_properties (transp, comp, antloc, &expr_hash_table);
2036 prune_expressions (true);
2037 bitmap_vector_clear (ae_kill, last_basic_block_for_fn (cfun));
2039 /* Compute ae_kill for each basic block using:
2041 ~(TRANSP | COMP)
2044 FOR_EACH_BB_FN (bb, cfun)
2046 bitmap_ior (ae_kill[bb->index], transp[bb->index], comp[bb->index]);
2047 bitmap_not (ae_kill[bb->index], ae_kill[bb->index]);
2050 edge_list = pre_edge_lcm (expr_hash_table.n_elems, transp, comp, antloc,
2051 ae_kill, &pre_insert_map, &pre_delete_map);
2052 sbitmap_vector_free (antloc);
2053 antloc = NULL;
2054 sbitmap_vector_free (ae_kill);
2055 ae_kill = NULL;
2057 prune_insertions_deletions (expr_hash_table.n_elems);
2059 return edge_list;
2062 /* PRE utilities */
2064 /* Return nonzero if an occurrence of expression EXPR in OCCR_BB would reach
2065 block BB.
2067 VISITED is a pointer to a working buffer for tracking which BB's have
2068 been visited. It is NULL for the top-level call.
2070 We treat reaching expressions that go through blocks containing the same
2071 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
2072 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
2073 2 as not reaching. The intent is to improve the probability of finding
2074 only one reaching expression and to reduce register lifetimes by picking
2075 the closest such expression. */
2077 static int
2078 pre_expr_reaches_here_p_work (basic_block occr_bb, struct gcse_expr *expr,
2079 basic_block bb, char *visited)
2081 edge pred;
2082 edge_iterator ei;
2084 FOR_EACH_EDGE (pred, ei, bb->preds)
2086 basic_block pred_bb = pred->src;
2088 if (pred->src == ENTRY_BLOCK_PTR_FOR_FN (cfun)
2089 /* Has predecessor has already been visited? */
2090 || visited[pred_bb->index])
2091 ;/* Nothing to do. */
2093 /* Does this predecessor generate this expression? */
2094 else if (bitmap_bit_p (comp[pred_bb->index], expr->bitmap_index))
2096 /* Is this the occurrence we're looking for?
2097 Note that there's only one generating occurrence per block
2098 so we just need to check the block number. */
2099 if (occr_bb == pred_bb)
2100 return 1;
2102 visited[pred_bb->index] = 1;
2104 /* Ignore this predecessor if it kills the expression. */
2105 else if (! bitmap_bit_p (transp[pred_bb->index], expr->bitmap_index))
2106 visited[pred_bb->index] = 1;
2108 /* Neither gen nor kill. */
2109 else
2111 visited[pred_bb->index] = 1;
2112 if (pre_expr_reaches_here_p_work (occr_bb, expr, pred_bb, visited))
2113 return 1;
2117 /* All paths have been checked. */
2118 return 0;
2121 /* The wrapper for pre_expr_reaches_here_work that ensures that any
2122 memory allocated for that function is returned. */
2124 static int
2125 pre_expr_reaches_here_p (basic_block occr_bb, struct gcse_expr *expr, basic_block bb)
2127 int rval;
2128 char *visited = XCNEWVEC (char, last_basic_block_for_fn (cfun));
2130 rval = pre_expr_reaches_here_p_work (occr_bb, expr, bb, visited);
2132 free (visited);
2133 return rval;
2136 /* Generate RTL to copy an EXPR to its `reaching_reg' and return it. */
2138 static rtx_insn *
2139 process_insert_insn (struct gcse_expr *expr)
2141 rtx reg = expr->reaching_reg;
2142 /* Copy the expression to make sure we don't have any sharing issues. */
2143 rtx exp = copy_rtx (expr->expr);
2144 rtx_insn *pat;
2146 start_sequence ();
2148 /* If the expression is something that's an operand, like a constant,
2149 just copy it to a register. */
2150 if (general_operand (exp, GET_MODE (reg)))
2151 emit_move_insn (reg, exp);
2153 /* Otherwise, make a new insn to compute this expression and make sure the
2154 insn will be recognized (this also adds any needed CLOBBERs). */
2155 else
2157 rtx_insn *insn = emit_insn (gen_rtx_SET (VOIDmode, reg, exp));
2159 if (insn_invalid_p (insn, false))
2160 gcc_unreachable ();
2163 pat = get_insns ();
2164 end_sequence ();
2166 return pat;
2169 /* Add EXPR to the end of basic block BB.
2171 This is used by both the PRE and code hoisting. */
2173 static void
2174 insert_insn_end_basic_block (struct gcse_expr *expr, basic_block bb)
2176 rtx_insn *insn = BB_END (bb);
2177 rtx_insn *new_insn;
2178 rtx reg = expr->reaching_reg;
2179 int regno = REGNO (reg);
2180 rtx_insn *pat, *pat_end;
2182 pat = process_insert_insn (expr);
2183 gcc_assert (pat && INSN_P (pat));
2185 pat_end = pat;
2186 while (NEXT_INSN (pat_end) != NULL_RTX)
2187 pat_end = NEXT_INSN (pat_end);
2189 /* If the last insn is a jump, insert EXPR in front [taking care to
2190 handle cc0, etc. properly]. Similarly we need to care trapping
2191 instructions in presence of non-call exceptions. */
2193 if (JUMP_P (insn)
2194 || (NONJUMP_INSN_P (insn)
2195 && (!single_succ_p (bb)
2196 || single_succ_edge (bb)->flags & EDGE_ABNORMAL)))
2198 #ifdef HAVE_cc0
2199 /* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
2200 if cc0 isn't set. */
2201 rtx note = find_reg_note (insn, REG_CC_SETTER, NULL_RTX);
2202 if (note)
2203 insn = safe_as_a <rtx_insn *> (XEXP (note, 0));
2204 else
2206 rtx_insn *maybe_cc0_setter = prev_nonnote_insn (insn);
2207 if (maybe_cc0_setter
2208 && INSN_P (maybe_cc0_setter)
2209 && sets_cc0_p (PATTERN (maybe_cc0_setter)))
2210 insn = maybe_cc0_setter;
2212 #endif
2213 /* FIXME: What if something in cc0/jump uses value set in new insn? */
2214 new_insn = emit_insn_before_noloc (pat, insn, bb);
2217 /* Likewise if the last insn is a call, as will happen in the presence
2218 of exception handling. */
2219 else if (CALL_P (insn)
2220 && (!single_succ_p (bb)
2221 || single_succ_edge (bb)->flags & EDGE_ABNORMAL))
2223 /* Keeping in mind targets with small register classes and parameters
2224 in registers, we search backward and place the instructions before
2225 the first parameter is loaded. Do this for everyone for consistency
2226 and a presumption that we'll get better code elsewhere as well. */
2228 /* Since different machines initialize their parameter registers
2229 in different orders, assume nothing. Collect the set of all
2230 parameter registers. */
2231 insn = find_first_parameter_load (insn, BB_HEAD (bb));
2233 /* If we found all the parameter loads, then we want to insert
2234 before the first parameter load.
2236 If we did not find all the parameter loads, then we might have
2237 stopped on the head of the block, which could be a CODE_LABEL.
2238 If we inserted before the CODE_LABEL, then we would be putting
2239 the insn in the wrong basic block. In that case, put the insn
2240 after the CODE_LABEL. Also, respect NOTE_INSN_BASIC_BLOCK. */
2241 while (LABEL_P (insn)
2242 || NOTE_INSN_BASIC_BLOCK_P (insn))
2243 insn = NEXT_INSN (insn);
2245 new_insn = emit_insn_before_noloc (pat, insn, bb);
2247 else
2248 new_insn = emit_insn_after_noloc (pat, insn, bb);
2250 while (1)
2252 if (INSN_P (pat))
2253 add_label_notes (PATTERN (pat), new_insn);
2254 if (pat == pat_end)
2255 break;
2256 pat = NEXT_INSN (pat);
2259 gcse_create_count++;
2261 if (dump_file)
2263 fprintf (dump_file, "PRE/HOIST: end of bb %d, insn %d, ",
2264 bb->index, INSN_UID (new_insn));
2265 fprintf (dump_file, "copying expression %d to reg %d\n",
2266 expr->bitmap_index, regno);
2270 /* Insert partially redundant expressions on edges in the CFG to make
2271 the expressions fully redundant. */
2273 static int
2274 pre_edge_insert (struct edge_list *edge_list, struct gcse_expr **index_map)
2276 int e, i, j, num_edges, set_size, did_insert = 0;
2277 sbitmap *inserted;
2279 /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge
2280 if it reaches any of the deleted expressions. */
2282 set_size = pre_insert_map[0]->size;
2283 num_edges = NUM_EDGES (edge_list);
2284 inserted = sbitmap_vector_alloc (num_edges, expr_hash_table.n_elems);
2285 bitmap_vector_clear (inserted, num_edges);
2287 for (e = 0; e < num_edges; e++)
2289 int indx;
2290 basic_block bb = INDEX_EDGE_PRED_BB (edge_list, e);
2292 for (i = indx = 0; i < set_size; i++, indx += SBITMAP_ELT_BITS)
2294 SBITMAP_ELT_TYPE insert = pre_insert_map[e]->elms[i];
2296 for (j = indx;
2297 insert && j < (int) expr_hash_table.n_elems;
2298 j++, insert >>= 1)
2299 if ((insert & 1) != 0 && index_map[j]->reaching_reg != NULL_RTX)
2301 struct gcse_expr *expr = index_map[j];
2302 struct gcse_occr *occr;
2304 /* Now look at each deleted occurrence of this expression. */
2305 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
2307 if (! occr->deleted_p)
2308 continue;
2310 /* Insert this expression on this edge if it would
2311 reach the deleted occurrence in BB. */
2312 if (!bitmap_bit_p (inserted[e], j))
2314 rtx_insn *insn;
2315 edge eg = INDEX_EDGE (edge_list, e);
2317 /* We can't insert anything on an abnormal and
2318 critical edge, so we insert the insn at the end of
2319 the previous block. There are several alternatives
2320 detailed in Morgans book P277 (sec 10.5) for
2321 handling this situation. This one is easiest for
2322 now. */
2324 if (eg->flags & EDGE_ABNORMAL)
2325 insert_insn_end_basic_block (index_map[j], bb);
2326 else
2328 insn = process_insert_insn (index_map[j]);
2329 insert_insn_on_edge (insn, eg);
2332 if (dump_file)
2334 fprintf (dump_file, "PRE: edge (%d,%d), ",
2335 bb->index,
2336 INDEX_EDGE_SUCC_BB (edge_list, e)->index);
2337 fprintf (dump_file, "copy expression %d\n",
2338 expr->bitmap_index);
2341 update_ld_motion_stores (expr);
2342 bitmap_set_bit (inserted[e], j);
2343 did_insert = 1;
2344 gcse_create_count++;
2351 sbitmap_vector_free (inserted);
2352 return did_insert;
2355 /* Copy the result of EXPR->EXPR generated by INSN to EXPR->REACHING_REG.
2356 Given "old_reg <- expr" (INSN), instead of adding after it
2357 reaching_reg <- old_reg
2358 it's better to do the following:
2359 reaching_reg <- expr
2360 old_reg <- reaching_reg
2361 because this way copy propagation can discover additional PRE
2362 opportunities. But if this fails, we try the old way.
2363 When "expr" is a store, i.e.
2364 given "MEM <- old_reg", instead of adding after it
2365 reaching_reg <- old_reg
2366 it's better to add it before as follows:
2367 reaching_reg <- old_reg
2368 MEM <- reaching_reg. */
2370 static void
2371 pre_insert_copy_insn (struct gcse_expr *expr, rtx_insn *insn)
2373 rtx reg = expr->reaching_reg;
2374 int regno = REGNO (reg);
2375 int indx = expr->bitmap_index;
2376 rtx pat = PATTERN (insn);
2377 rtx set, first_set, new_insn;
2378 rtx old_reg;
2379 int i;
2381 /* This block matches the logic in hash_scan_insn. */
2382 switch (GET_CODE (pat))
2384 case SET:
2385 set = pat;
2386 break;
2388 case PARALLEL:
2389 /* Search through the parallel looking for the set whose
2390 source was the expression that we're interested in. */
2391 first_set = NULL_RTX;
2392 set = NULL_RTX;
2393 for (i = 0; i < XVECLEN (pat, 0); i++)
2395 rtx x = XVECEXP (pat, 0, i);
2396 if (GET_CODE (x) == SET)
2398 /* If the source was a REG_EQUAL or REG_EQUIV note, we
2399 may not find an equivalent expression, but in this
2400 case the PARALLEL will have a single set. */
2401 if (first_set == NULL_RTX)
2402 first_set = x;
2403 if (expr_equiv_p (SET_SRC (x), expr->expr))
2405 set = x;
2406 break;
2411 gcc_assert (first_set);
2412 if (set == NULL_RTX)
2413 set = first_set;
2414 break;
2416 default:
2417 gcc_unreachable ();
2420 if (REG_P (SET_DEST (set)))
2422 old_reg = SET_DEST (set);
2423 /* Check if we can modify the set destination in the original insn. */
2424 if (validate_change (insn, &SET_DEST (set), reg, 0))
2426 new_insn = gen_move_insn (old_reg, reg);
2427 new_insn = emit_insn_after (new_insn, insn);
2429 else
2431 new_insn = gen_move_insn (reg, old_reg);
2432 new_insn = emit_insn_after (new_insn, insn);
2435 else /* This is possible only in case of a store to memory. */
2437 old_reg = SET_SRC (set);
2438 new_insn = gen_move_insn (reg, old_reg);
2440 /* Check if we can modify the set source in the original insn. */
2441 if (validate_change (insn, &SET_SRC (set), reg, 0))
2442 new_insn = emit_insn_before (new_insn, insn);
2443 else
2444 new_insn = emit_insn_after (new_insn, insn);
2447 gcse_create_count++;
2449 if (dump_file)
2450 fprintf (dump_file,
2451 "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
2452 BLOCK_FOR_INSN (insn)->index, INSN_UID (new_insn), indx,
2453 INSN_UID (insn), regno);
2456 /* Copy available expressions that reach the redundant expression
2457 to `reaching_reg'. */
2459 static void
2460 pre_insert_copies (void)
2462 unsigned int i, added_copy;
2463 struct gcse_expr *expr;
2464 struct gcse_occr *occr;
2465 struct gcse_occr *avail;
2467 /* For each available expression in the table, copy the result to
2468 `reaching_reg' if the expression reaches a deleted one.
2470 ??? The current algorithm is rather brute force.
2471 Need to do some profiling. */
2473 for (i = 0; i < expr_hash_table.size; i++)
2474 for (expr = expr_hash_table.table[i]; expr; expr = expr->next_same_hash)
2476 /* If the basic block isn't reachable, PPOUT will be TRUE. However,
2477 we don't want to insert a copy here because the expression may not
2478 really be redundant. So only insert an insn if the expression was
2479 deleted. This test also avoids further processing if the
2480 expression wasn't deleted anywhere. */
2481 if (expr->reaching_reg == NULL)
2482 continue;
2484 /* Set when we add a copy for that expression. */
2485 added_copy = 0;
2487 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
2489 if (! occr->deleted_p)
2490 continue;
2492 for (avail = expr->avail_occr; avail != NULL; avail = avail->next)
2494 rtx_insn *insn = avail->insn;
2496 /* No need to handle this one if handled already. */
2497 if (avail->copied_p)
2498 continue;
2500 /* Don't handle this one if it's a redundant one. */
2501 if (insn->deleted ())
2502 continue;
2504 /* Or if the expression doesn't reach the deleted one. */
2505 if (! pre_expr_reaches_here_p (BLOCK_FOR_INSN (avail->insn),
2506 expr,
2507 BLOCK_FOR_INSN (occr->insn)))
2508 continue;
2510 added_copy = 1;
2512 /* Copy the result of avail to reaching_reg. */
2513 pre_insert_copy_insn (expr, insn);
2514 avail->copied_p = 1;
2518 if (added_copy)
2519 update_ld_motion_stores (expr);
2523 struct set_data
2525 rtx_insn *insn;
2526 const_rtx set;
2527 int nsets;
2530 /* Increment number of sets and record set in DATA. */
2532 static void
2533 record_set_data (rtx dest, const_rtx set, void *data)
2535 struct set_data *s = (struct set_data *)data;
2537 if (GET_CODE (set) == SET)
2539 /* We allow insns having multiple sets, where all but one are
2540 dead as single set insns. In the common case only a single
2541 set is present, so we want to avoid checking for REG_UNUSED
2542 notes unless necessary. */
2543 if (s->nsets == 1
2544 && find_reg_note (s->insn, REG_UNUSED, SET_DEST (s->set))
2545 && !side_effects_p (s->set))
2546 s->nsets = 0;
2548 if (!s->nsets)
2550 /* Record this set. */
2551 s->nsets += 1;
2552 s->set = set;
2554 else if (!find_reg_note (s->insn, REG_UNUSED, dest)
2555 || side_effects_p (set))
2556 s->nsets += 1;
2560 static const_rtx
2561 single_set_gcse (rtx_insn *insn)
2563 struct set_data s;
2564 rtx pattern;
2566 gcc_assert (INSN_P (insn));
2568 /* Optimize common case. */
2569 pattern = PATTERN (insn);
2570 if (GET_CODE (pattern) == SET)
2571 return pattern;
2573 s.insn = insn;
2574 s.nsets = 0;
2575 note_stores (pattern, record_set_data, &s);
2577 /* Considered invariant insns have exactly one set. */
2578 gcc_assert (s.nsets == 1);
2579 return s.set;
2582 /* Emit move from SRC to DEST noting the equivalence with expression computed
2583 in INSN. */
2585 static rtx
2586 gcse_emit_move_after (rtx dest, rtx src, rtx_insn *insn)
2588 rtx_insn *new_rtx;
2589 const_rtx set = single_set_gcse (insn);
2590 rtx set2;
2591 rtx note;
2592 rtx eqv = NULL_RTX;
2594 /* This should never fail since we're creating a reg->reg copy
2595 we've verified to be valid. */
2597 new_rtx = emit_insn_after (gen_move_insn (dest, src), insn);
2599 /* Note the equivalence for local CSE pass. Take the note from the old
2600 set if there was one. Otherwise record the SET_SRC from the old set
2601 unless DEST is also an operand of the SET_SRC. */
2602 set2 = single_set (new_rtx);
2603 if (!set2 || !rtx_equal_p (SET_DEST (set2), dest))
2604 return new_rtx;
2605 if ((note = find_reg_equal_equiv_note (insn)))
2606 eqv = XEXP (note, 0);
2607 else if (! REG_P (dest)
2608 || ! reg_mentioned_p (dest, SET_SRC (set)))
2609 eqv = SET_SRC (set);
2611 if (eqv != NULL_RTX)
2612 set_unique_reg_note (new_rtx, REG_EQUAL, copy_insn_1 (eqv));
2614 return new_rtx;
2617 /* Delete redundant computations.
2618 Deletion is done by changing the insn to copy the `reaching_reg' of
2619 the expression into the result of the SET. It is left to later passes
2620 to propagate the copy or eliminate it.
2622 Return nonzero if a change is made. */
2624 static int
2625 pre_delete (void)
2627 unsigned int i;
2628 int changed;
2629 struct gcse_expr *expr;
2630 struct gcse_occr *occr;
2632 changed = 0;
2633 for (i = 0; i < expr_hash_table.size; i++)
2634 for (expr = expr_hash_table.table[i]; expr; expr = expr->next_same_hash)
2636 int indx = expr->bitmap_index;
2638 /* We only need to search antic_occr since we require ANTLOC != 0. */
2639 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
2641 rtx_insn *insn = occr->insn;
2642 rtx set;
2643 basic_block bb = BLOCK_FOR_INSN (insn);
2645 /* We only delete insns that have a single_set. */
2646 if (bitmap_bit_p (pre_delete_map[bb->index], indx)
2647 && (set = single_set (insn)) != 0
2648 && dbg_cnt (pre_insn))
2650 /* Create a pseudo-reg to store the result of reaching
2651 expressions into. Get the mode for the new pseudo from
2652 the mode of the original destination pseudo. */
2653 if (expr->reaching_reg == NULL)
2654 expr->reaching_reg = gen_reg_rtx_and_attrs (SET_DEST (set));
2656 gcse_emit_move_after (SET_DEST (set), expr->reaching_reg, insn);
2657 delete_insn (insn);
2658 occr->deleted_p = 1;
2659 changed = 1;
2660 gcse_subst_count++;
2662 if (dump_file)
2664 fprintf (dump_file,
2665 "PRE: redundant insn %d (expression %d) in ",
2666 INSN_UID (insn), indx);
2667 fprintf (dump_file, "bb %d, reaching reg is %d\n",
2668 bb->index, REGNO (expr->reaching_reg));
2674 return changed;
2677 /* Perform GCSE optimizations using PRE.
2678 This is called by one_pre_gcse_pass after all the dataflow analysis
2679 has been done.
2681 This is based on the original Morel-Renvoise paper Fred Chow's thesis, and
2682 lazy code motion from Knoop, Ruthing and Steffen as described in Advanced
2683 Compiler Design and Implementation.
2685 ??? A new pseudo reg is created to hold the reaching expression. The nice
2686 thing about the classical approach is that it would try to use an existing
2687 reg. If the register can't be adequately optimized [i.e. we introduce
2688 reload problems], one could add a pass here to propagate the new register
2689 through the block.
2691 ??? We don't handle single sets in PARALLELs because we're [currently] not
2692 able to copy the rest of the parallel when we insert copies to create full
2693 redundancies from partial redundancies. However, there's no reason why we
2694 can't handle PARALLELs in the cases where there are no partial
2695 redundancies. */
2697 static int
2698 pre_gcse (struct edge_list *edge_list)
2700 unsigned int i;
2701 int did_insert, changed;
2702 struct gcse_expr **index_map;
2703 struct gcse_expr *expr;
2705 /* Compute a mapping from expression number (`bitmap_index') to
2706 hash table entry. */
2708 index_map = XCNEWVEC (struct gcse_expr *, expr_hash_table.n_elems);
2709 for (i = 0; i < expr_hash_table.size; i++)
2710 for (expr = expr_hash_table.table[i]; expr; expr = expr->next_same_hash)
2711 index_map[expr->bitmap_index] = expr;
2713 /* Delete the redundant insns first so that
2714 - we know what register to use for the new insns and for the other
2715 ones with reaching expressions
2716 - we know which insns are redundant when we go to create copies */
2718 changed = pre_delete ();
2719 did_insert = pre_edge_insert (edge_list, index_map);
2721 /* In other places with reaching expressions, copy the expression to the
2722 specially allocated pseudo-reg that reaches the redundant expr. */
2723 pre_insert_copies ();
2724 if (did_insert)
2726 commit_edge_insertions ();
2727 changed = 1;
2730 free (index_map);
2731 return changed;
2734 /* Top level routine to perform one PRE GCSE pass.
2736 Return nonzero if a change was made. */
2738 static int
2739 one_pre_gcse_pass (void)
2741 int changed = 0;
2743 gcse_subst_count = 0;
2744 gcse_create_count = 0;
2746 /* Return if there's nothing to do, or it is too expensive. */
2747 if (n_basic_blocks_for_fn (cfun) <= NUM_FIXED_BLOCKS + 1
2748 || is_too_expensive (_("PRE disabled")))
2749 return 0;
2751 /* We need alias. */
2752 init_alias_analysis ();
2754 bytes_used = 0;
2755 gcc_obstack_init (&gcse_obstack);
2756 alloc_gcse_mem ();
2758 alloc_hash_table (&expr_hash_table);
2759 add_noreturn_fake_exit_edges ();
2760 if (flag_gcse_lm)
2761 compute_ld_motion_mems ();
2763 compute_hash_table (&expr_hash_table);
2764 if (flag_gcse_lm)
2765 trim_ld_motion_mems ();
2766 if (dump_file)
2767 dump_hash_table (dump_file, "Expression", &expr_hash_table);
2769 if (expr_hash_table.n_elems > 0)
2771 struct edge_list *edge_list;
2772 alloc_pre_mem (last_basic_block_for_fn (cfun), expr_hash_table.n_elems);
2773 edge_list = compute_pre_data ();
2774 changed |= pre_gcse (edge_list);
2775 free_edge_list (edge_list);
2776 free_pre_mem ();
2779 if (flag_gcse_lm)
2780 free_ld_motion_mems ();
2781 remove_fake_exit_edges ();
2782 free_hash_table (&expr_hash_table);
2784 free_gcse_mem ();
2785 obstack_free (&gcse_obstack, NULL);
2787 /* We are finished with alias. */
2788 end_alias_analysis ();
2790 if (dump_file)
2792 fprintf (dump_file, "PRE GCSE of %s, %d basic blocks, %d bytes needed, ",
2793 current_function_name (), n_basic_blocks_for_fn (cfun),
2794 bytes_used);
2795 fprintf (dump_file, "%d substs, %d insns created\n",
2796 gcse_subst_count, gcse_create_count);
2799 return changed;
2802 /* If X contains any LABEL_REF's, add REG_LABEL_OPERAND notes for them
2803 to INSN. If such notes are added to an insn which references a
2804 CODE_LABEL, the LABEL_NUSES count is incremented. We have to add
2805 that note, because the following loop optimization pass requires
2806 them. */
2808 /* ??? If there was a jump optimization pass after gcse and before loop,
2809 then we would not need to do this here, because jump would add the
2810 necessary REG_LABEL_OPERAND and REG_LABEL_TARGET notes. */
2812 static void
2813 add_label_notes (rtx x, rtx insn)
2815 enum rtx_code code = GET_CODE (x);
2816 int i, j;
2817 const char *fmt;
2819 if (code == LABEL_REF && !LABEL_REF_NONLOCAL_P (x))
2821 /* This code used to ignore labels that referred to dispatch tables to
2822 avoid flow generating (slightly) worse code.
2824 We no longer ignore such label references (see LABEL_REF handling in
2825 mark_jump_label for additional information). */
2827 /* There's no reason for current users to emit jump-insns with
2828 such a LABEL_REF, so we don't have to handle REG_LABEL_TARGET
2829 notes. */
2830 gcc_assert (!JUMP_P (insn));
2831 add_reg_note (insn, REG_LABEL_OPERAND, LABEL_REF_LABEL (x));
2833 if (LABEL_P (LABEL_REF_LABEL (x)))
2834 LABEL_NUSES (LABEL_REF_LABEL (x))++;
2836 return;
2839 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
2841 if (fmt[i] == 'e')
2842 add_label_notes (XEXP (x, i), insn);
2843 else if (fmt[i] == 'E')
2844 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
2845 add_label_notes (XVECEXP (x, i, j), insn);
2849 /* Code Hoisting variables and subroutines. */
2851 /* Very busy expressions. */
2852 static sbitmap *hoist_vbein;
2853 static sbitmap *hoist_vbeout;
2855 /* ??? We could compute post dominators and run this algorithm in
2856 reverse to perform tail merging, doing so would probably be
2857 more effective than the tail merging code in jump.c.
2859 It's unclear if tail merging could be run in parallel with
2860 code hoisting. It would be nice. */
2862 /* Allocate vars used for code hoisting analysis. */
2864 static void
2865 alloc_code_hoist_mem (int n_blocks, int n_exprs)
2867 antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
2868 transp = sbitmap_vector_alloc (n_blocks, n_exprs);
2869 comp = sbitmap_vector_alloc (n_blocks, n_exprs);
2871 hoist_vbein = sbitmap_vector_alloc (n_blocks, n_exprs);
2872 hoist_vbeout = sbitmap_vector_alloc (n_blocks, n_exprs);
2875 /* Free vars used for code hoisting analysis. */
2877 static void
2878 free_code_hoist_mem (void)
2880 sbitmap_vector_free (antloc);
2881 sbitmap_vector_free (transp);
2882 sbitmap_vector_free (comp);
2884 sbitmap_vector_free (hoist_vbein);
2885 sbitmap_vector_free (hoist_vbeout);
2887 free_dominance_info (CDI_DOMINATORS);
2890 /* Compute the very busy expressions at entry/exit from each block.
2892 An expression is very busy if all paths from a given point
2893 compute the expression. */
2895 static void
2896 compute_code_hoist_vbeinout (void)
2898 int changed, passes;
2899 basic_block bb;
2901 bitmap_vector_clear (hoist_vbeout, last_basic_block_for_fn (cfun));
2902 bitmap_vector_clear (hoist_vbein, last_basic_block_for_fn (cfun));
2904 passes = 0;
2905 changed = 1;
2907 while (changed)
2909 changed = 0;
2911 /* We scan the blocks in the reverse order to speed up
2912 the convergence. */
2913 FOR_EACH_BB_REVERSE_FN (bb, cfun)
2915 if (bb->next_bb != EXIT_BLOCK_PTR_FOR_FN (cfun))
2917 bitmap_intersection_of_succs (hoist_vbeout[bb->index],
2918 hoist_vbein, bb);
2920 /* Include expressions in VBEout that are calculated
2921 in BB and available at its end. */
2922 bitmap_ior (hoist_vbeout[bb->index],
2923 hoist_vbeout[bb->index], comp[bb->index]);
2926 changed |= bitmap_or_and (hoist_vbein[bb->index],
2927 antloc[bb->index],
2928 hoist_vbeout[bb->index],
2929 transp[bb->index]);
2932 passes++;
2935 if (dump_file)
2937 fprintf (dump_file, "hoisting vbeinout computation: %d passes\n", passes);
2939 FOR_EACH_BB_FN (bb, cfun)
2941 fprintf (dump_file, "vbein (%d): ", bb->index);
2942 dump_bitmap_file (dump_file, hoist_vbein[bb->index]);
2943 fprintf (dump_file, "vbeout(%d): ", bb->index);
2944 dump_bitmap_file (dump_file, hoist_vbeout[bb->index]);
2949 /* Top level routine to do the dataflow analysis needed by code hoisting. */
2951 static void
2952 compute_code_hoist_data (void)
2954 compute_local_properties (transp, comp, antloc, &expr_hash_table);
2955 prune_expressions (false);
2956 compute_code_hoist_vbeinout ();
2957 calculate_dominance_info (CDI_DOMINATORS);
2958 if (dump_file)
2959 fprintf (dump_file, "\n");
2962 /* Update register pressure for BB when hoisting an expression from
2963 instruction FROM, if live ranges of inputs are shrunk. Also
2964 maintain live_in information if live range of register referred
2965 in FROM is shrunk.
2967 Return 0 if register pressure doesn't change, otherwise return
2968 the number by which register pressure is decreased.
2970 NOTE: Register pressure won't be increased in this function. */
2972 static int
2973 update_bb_reg_pressure (basic_block bb, rtx_insn *from)
2975 rtx dreg;
2976 rtx_insn *insn;
2977 basic_block succ_bb;
2978 df_ref use, op_ref;
2979 edge succ;
2980 edge_iterator ei;
2981 int decreased_pressure = 0;
2982 int nregs;
2983 enum reg_class pressure_class;
2985 FOR_EACH_INSN_USE (use, from)
2987 dreg = DF_REF_REAL_REG (use);
2988 /* The live range of register is shrunk only if it isn't:
2989 1. referred on any path from the end of this block to EXIT, or
2990 2. referred by insns other than FROM in this block. */
2991 FOR_EACH_EDGE (succ, ei, bb->succs)
2993 succ_bb = succ->dest;
2994 if (succ_bb == EXIT_BLOCK_PTR_FOR_FN (cfun))
2995 continue;
2997 if (bitmap_bit_p (BB_DATA (succ_bb)->live_in, REGNO (dreg)))
2998 break;
3000 if (succ != NULL)
3001 continue;
3003 op_ref = DF_REG_USE_CHAIN (REGNO (dreg));
3004 for (; op_ref; op_ref = DF_REF_NEXT_REG (op_ref))
3006 if (!DF_REF_INSN_INFO (op_ref))
3007 continue;
3009 insn = DF_REF_INSN (op_ref);
3010 if (BLOCK_FOR_INSN (insn) == bb
3011 && NONDEBUG_INSN_P (insn) && insn != from)
3012 break;
3015 pressure_class = get_regno_pressure_class (REGNO (dreg), &nregs);
3016 /* Decrease register pressure and update live_in information for
3017 this block. */
3018 if (!op_ref && pressure_class != NO_REGS)
3020 decreased_pressure += nregs;
3021 BB_DATA (bb)->max_reg_pressure[pressure_class] -= nregs;
3022 bitmap_clear_bit (BB_DATA (bb)->live_in, REGNO (dreg));
3025 return decreased_pressure;
3028 /* Determine if the expression EXPR should be hoisted to EXPR_BB up in
3029 flow graph, if it can reach BB unimpared. Stop the search if the
3030 expression would need to be moved more than DISTANCE instructions.
3032 DISTANCE is the number of instructions through which EXPR can be
3033 hoisted up in flow graph.
3035 BB_SIZE points to an array which contains the number of instructions
3036 for each basic block.
3038 PRESSURE_CLASS and NREGS are register class and number of hard registers
3039 for storing EXPR.
3041 HOISTED_BBS points to a bitmap indicating basic blocks through which
3042 EXPR is hoisted.
3044 FROM is the instruction from which EXPR is hoisted.
3046 It's unclear exactly what Muchnick meant by "unimpared". It seems
3047 to me that the expression must either be computed or transparent in
3048 *every* block in the path(s) from EXPR_BB to BB. Any other definition
3049 would allow the expression to be hoisted out of loops, even if
3050 the expression wasn't a loop invariant.
3052 Contrast this to reachability for PRE where an expression is
3053 considered reachable if *any* path reaches instead of *all*
3054 paths. */
3056 static int
3057 should_hoist_expr_to_dom (basic_block expr_bb, struct gcse_expr *expr,
3058 basic_block bb, sbitmap visited, int distance,
3059 int *bb_size, enum reg_class pressure_class,
3060 int *nregs, bitmap hoisted_bbs, rtx_insn *from)
3062 unsigned int i;
3063 edge pred;
3064 edge_iterator ei;
3065 sbitmap_iterator sbi;
3066 int visited_allocated_locally = 0;
3067 int decreased_pressure = 0;
3069 if (flag_ira_hoist_pressure)
3071 /* Record old information of basic block BB when it is visited
3072 at the first time. */
3073 if (!bitmap_bit_p (hoisted_bbs, bb->index))
3075 struct bb_data *data = BB_DATA (bb);
3076 bitmap_copy (data->backup, data->live_in);
3077 data->old_pressure = data->max_reg_pressure[pressure_class];
3079 decreased_pressure = update_bb_reg_pressure (bb, from);
3081 /* Terminate the search if distance, for which EXPR is allowed to move,
3082 is exhausted. */
3083 if (distance > 0)
3085 if (flag_ira_hoist_pressure)
3087 /* Prefer to hoist EXPR if register pressure is decreased. */
3088 if (decreased_pressure > *nregs)
3089 distance += bb_size[bb->index];
3090 /* Let EXPR be hoisted through basic block at no cost if one
3091 of following conditions is satisfied:
3093 1. The basic block has low register pressure.
3094 2. Register pressure won't be increases after hoisting EXPR.
3096 Constant expressions is handled conservatively, because
3097 hoisting constant expression aggressively results in worse
3098 code. This decision is made by the observation of CSiBE
3099 on ARM target, while it has no obvious effect on other
3100 targets like x86, x86_64, mips and powerpc. */
3101 else if (CONST_INT_P (expr->expr)
3102 || (BB_DATA (bb)->max_reg_pressure[pressure_class]
3103 >= ira_class_hard_regs_num[pressure_class]
3104 && decreased_pressure < *nregs))
3105 distance -= bb_size[bb->index];
3107 else
3108 distance -= bb_size[bb->index];
3110 if (distance <= 0)
3111 return 0;
3113 else
3114 gcc_assert (distance == 0);
3116 if (visited == NULL)
3118 visited_allocated_locally = 1;
3119 visited = sbitmap_alloc (last_basic_block_for_fn (cfun));
3120 bitmap_clear (visited);
3123 FOR_EACH_EDGE (pred, ei, bb->preds)
3125 basic_block pred_bb = pred->src;
3127 if (pred->src == ENTRY_BLOCK_PTR_FOR_FN (cfun))
3128 break;
3129 else if (pred_bb == expr_bb)
3130 continue;
3131 else if (bitmap_bit_p (visited, pred_bb->index))
3132 continue;
3133 else if (! bitmap_bit_p (transp[pred_bb->index], expr->bitmap_index))
3134 break;
3135 /* Not killed. */
3136 else
3138 bitmap_set_bit (visited, pred_bb->index);
3139 if (! should_hoist_expr_to_dom (expr_bb, expr, pred_bb,
3140 visited, distance, bb_size,
3141 pressure_class, nregs,
3142 hoisted_bbs, from))
3143 break;
3146 if (visited_allocated_locally)
3148 /* If EXPR can be hoisted to expr_bb, record basic blocks through
3149 which EXPR is hoisted in hoisted_bbs. */
3150 if (flag_ira_hoist_pressure && !pred)
3152 /* Record the basic block from which EXPR is hoisted. */
3153 bitmap_set_bit (visited, bb->index);
3154 EXECUTE_IF_SET_IN_BITMAP (visited, 0, i, sbi)
3155 bitmap_set_bit (hoisted_bbs, i);
3157 sbitmap_free (visited);
3160 return (pred == NULL);
3163 /* Find occurrence in BB. */
3165 static struct gcse_occr *
3166 find_occr_in_bb (struct gcse_occr *occr, basic_block bb)
3168 /* Find the right occurrence of this expression. */
3169 while (occr && BLOCK_FOR_INSN (occr->insn) != bb)
3170 occr = occr->next;
3172 return occr;
3175 /* Actually perform code hoisting.
3177 The code hoisting pass can hoist multiple computations of the same
3178 expression along dominated path to a dominating basic block, like
3179 from b2/b3 to b1 as depicted below:
3181 b1 ------
3182 /\ |
3183 / \ |
3184 bx by distance
3185 / \ |
3186 / \ |
3187 b2 b3 ------
3189 Unfortunately code hoisting generally extends the live range of an
3190 output pseudo register, which increases register pressure and hurts
3191 register allocation. To address this issue, an attribute MAX_DISTANCE
3192 is computed and attached to each expression. The attribute is computed
3193 from rtx cost of the corresponding expression and it's used to control
3194 how long the expression can be hoisted up in flow graph. As the
3195 expression is hoisted up in flow graph, GCC decreases its DISTANCE
3196 and stops the hoist if DISTANCE reaches 0. Code hoisting can decrease
3197 register pressure if live ranges of inputs are shrunk.
3199 Option "-fira-hoist-pressure" implements register pressure directed
3200 hoist based on upper method. The rationale is:
3201 1. Calculate register pressure for each basic block by reusing IRA
3202 facility.
3203 2. When expression is hoisted through one basic block, GCC checks
3204 the change of live ranges for inputs/output. The basic block's
3205 register pressure will be increased because of extended live
3206 range of output. However, register pressure will be decreased
3207 if the live ranges of inputs are shrunk.
3208 3. After knowing how hoisting affects register pressure, GCC prefers
3209 to hoist the expression if it can decrease register pressure, by
3210 increasing DISTANCE of the corresponding expression.
3211 4. If hoisting the expression increases register pressure, GCC checks
3212 register pressure of the basic block and decrease DISTANCE only if
3213 the register pressure is high. In other words, expression will be
3214 hoisted through at no cost if the basic block has low register
3215 pressure.
3216 5. Update register pressure information for basic blocks through
3217 which expression is hoisted. */
3219 static int
3220 hoist_code (void)
3222 basic_block bb, dominated;
3223 vec<basic_block> dom_tree_walk;
3224 unsigned int dom_tree_walk_index;
3225 vec<basic_block> domby;
3226 unsigned int i, j, k;
3227 struct gcse_expr **index_map;
3228 struct gcse_expr *expr;
3229 int *to_bb_head;
3230 int *bb_size;
3231 int changed = 0;
3232 struct bb_data *data;
3233 /* Basic blocks that have occurrences reachable from BB. */
3234 bitmap from_bbs;
3235 /* Basic blocks through which expr is hoisted. */
3236 bitmap hoisted_bbs = NULL;
3237 bitmap_iterator bi;
3239 /* Compute a mapping from expression number (`bitmap_index') to
3240 hash table entry. */
3242 index_map = XCNEWVEC (struct gcse_expr *, expr_hash_table.n_elems);
3243 for (i = 0; i < expr_hash_table.size; i++)
3244 for (expr = expr_hash_table.table[i]; expr; expr = expr->next_same_hash)
3245 index_map[expr->bitmap_index] = expr;
3247 /* Calculate sizes of basic blocks and note how far
3248 each instruction is from the start of its block. We then use this
3249 data to restrict distance an expression can travel. */
3251 to_bb_head = XCNEWVEC (int, get_max_uid ());
3252 bb_size = XCNEWVEC (int, last_basic_block_for_fn (cfun));
3254 FOR_EACH_BB_FN (bb, cfun)
3256 rtx_insn *insn;
3257 int to_head;
3259 to_head = 0;
3260 FOR_BB_INSNS (bb, insn)
3262 /* Don't count debug instructions to avoid them affecting
3263 decision choices. */
3264 if (NONDEBUG_INSN_P (insn))
3265 to_bb_head[INSN_UID (insn)] = to_head++;
3268 bb_size[bb->index] = to_head;
3271 gcc_assert (EDGE_COUNT (ENTRY_BLOCK_PTR_FOR_FN (cfun)->succs) == 1
3272 && (EDGE_SUCC (ENTRY_BLOCK_PTR_FOR_FN (cfun), 0)->dest
3273 == ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb));
3275 from_bbs = BITMAP_ALLOC (NULL);
3276 if (flag_ira_hoist_pressure)
3277 hoisted_bbs = BITMAP_ALLOC (NULL);
3279 dom_tree_walk = get_all_dominated_blocks (CDI_DOMINATORS,
3280 ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb);
3282 /* Walk over each basic block looking for potentially hoistable
3283 expressions, nothing gets hoisted from the entry block. */
3284 FOR_EACH_VEC_ELT (dom_tree_walk, dom_tree_walk_index, bb)
3286 domby = get_dominated_to_depth (CDI_DOMINATORS, bb, MAX_HOIST_DEPTH);
3288 if (domby.length () == 0)
3289 continue;
3291 /* Examine each expression that is very busy at the exit of this
3292 block. These are the potentially hoistable expressions. */
3293 for (i = 0; i < SBITMAP_SIZE (hoist_vbeout[bb->index]); i++)
3295 if (bitmap_bit_p (hoist_vbeout[bb->index], i))
3297 int nregs = 0;
3298 enum reg_class pressure_class = NO_REGS;
3299 /* Current expression. */
3300 struct gcse_expr *expr = index_map[i];
3301 /* Number of occurrences of EXPR that can be hoisted to BB. */
3302 int hoistable = 0;
3303 /* Occurrences reachable from BB. */
3304 vec<occr_t> occrs_to_hoist = vNULL;
3305 /* We want to insert the expression into BB only once, so
3306 note when we've inserted it. */
3307 int insn_inserted_p;
3308 occr_t occr;
3310 /* If an expression is computed in BB and is available at end of
3311 BB, hoist all occurrences dominated by BB to BB. */
3312 if (bitmap_bit_p (comp[bb->index], i))
3314 occr = find_occr_in_bb (expr->antic_occr, bb);
3316 if (occr)
3318 /* An occurrence might've been already deleted
3319 while processing a dominator of BB. */
3320 if (!occr->deleted_p)
3322 gcc_assert (NONDEBUG_INSN_P (occr->insn));
3323 hoistable++;
3326 else
3327 hoistable++;
3330 /* We've found a potentially hoistable expression, now
3331 we look at every block BB dominates to see if it
3332 computes the expression. */
3333 FOR_EACH_VEC_ELT (domby, j, dominated)
3335 int max_distance;
3337 /* Ignore self dominance. */
3338 if (bb == dominated)
3339 continue;
3340 /* We've found a dominated block, now see if it computes
3341 the busy expression and whether or not moving that
3342 expression to the "beginning" of that block is safe. */
3343 if (!bitmap_bit_p (antloc[dominated->index], i))
3344 continue;
3346 occr = find_occr_in_bb (expr->antic_occr, dominated);
3347 gcc_assert (occr);
3349 /* An occurrence might've been already deleted
3350 while processing a dominator of BB. */
3351 if (occr->deleted_p)
3352 continue;
3353 gcc_assert (NONDEBUG_INSN_P (occr->insn));
3355 max_distance = expr->max_distance;
3356 if (max_distance > 0)
3357 /* Adjust MAX_DISTANCE to account for the fact that
3358 OCCR won't have to travel all of DOMINATED, but
3359 only part of it. */
3360 max_distance += (bb_size[dominated->index]
3361 - to_bb_head[INSN_UID (occr->insn)]);
3363 pressure_class = get_pressure_class_and_nregs (occr->insn,
3364 &nregs);
3366 /* Note if the expression should be hoisted from the dominated
3367 block to BB if it can reach DOMINATED unimpared.
3369 Keep track of how many times this expression is hoistable
3370 from a dominated block into BB. */
3371 if (should_hoist_expr_to_dom (bb, expr, dominated, NULL,
3372 max_distance, bb_size,
3373 pressure_class, &nregs,
3374 hoisted_bbs, occr->insn))
3376 hoistable++;
3377 occrs_to_hoist.safe_push (occr);
3378 bitmap_set_bit (from_bbs, dominated->index);
3382 /* If we found more than one hoistable occurrence of this
3383 expression, then note it in the vector of expressions to
3384 hoist. It makes no sense to hoist things which are computed
3385 in only one BB, and doing so tends to pessimize register
3386 allocation. One could increase this value to try harder
3387 to avoid any possible code expansion due to register
3388 allocation issues; however experiments have shown that
3389 the vast majority of hoistable expressions are only movable
3390 from two successors, so raising this threshold is likely
3391 to nullify any benefit we get from code hoisting. */
3392 if (hoistable > 1 && dbg_cnt (hoist_insn))
3394 /* If (hoistable != vec::length), then there is
3395 an occurrence of EXPR in BB itself. Don't waste
3396 time looking for LCA in this case. */
3397 if ((unsigned) hoistable == occrs_to_hoist.length ())
3399 basic_block lca;
3401 lca = nearest_common_dominator_for_set (CDI_DOMINATORS,
3402 from_bbs);
3403 if (lca != bb)
3404 /* Punt, it's better to hoist these occurrences to
3405 LCA. */
3406 occrs_to_hoist.release ();
3409 else
3410 /* Punt, no point hoisting a single occurrence. */
3411 occrs_to_hoist.release ();
3413 if (flag_ira_hoist_pressure
3414 && !occrs_to_hoist.is_empty ())
3416 /* Increase register pressure of basic blocks to which
3417 expr is hoisted because of extended live range of
3418 output. */
3419 data = BB_DATA (bb);
3420 data->max_reg_pressure[pressure_class] += nregs;
3421 EXECUTE_IF_SET_IN_BITMAP (hoisted_bbs, 0, k, bi)
3423 data = BB_DATA (BASIC_BLOCK_FOR_FN (cfun, k));
3424 data->max_reg_pressure[pressure_class] += nregs;
3427 else if (flag_ira_hoist_pressure)
3429 /* Restore register pressure and live_in info for basic
3430 blocks recorded in hoisted_bbs when expr will not be
3431 hoisted. */
3432 EXECUTE_IF_SET_IN_BITMAP (hoisted_bbs, 0, k, bi)
3434 data = BB_DATA (BASIC_BLOCK_FOR_FN (cfun, k));
3435 bitmap_copy (data->live_in, data->backup);
3436 data->max_reg_pressure[pressure_class]
3437 = data->old_pressure;
3441 if (flag_ira_hoist_pressure)
3442 bitmap_clear (hoisted_bbs);
3444 insn_inserted_p = 0;
3446 /* Walk through occurrences of I'th expressions we want
3447 to hoist to BB and make the transformations. */
3448 FOR_EACH_VEC_ELT (occrs_to_hoist, j, occr)
3450 rtx_insn *insn;
3451 const_rtx set;
3453 gcc_assert (!occr->deleted_p);
3455 insn = occr->insn;
3456 set = single_set_gcse (insn);
3458 /* Create a pseudo-reg to store the result of reaching
3459 expressions into. Get the mode for the new pseudo
3460 from the mode of the original destination pseudo.
3462 It is important to use new pseudos whenever we
3463 emit a set. This will allow reload to use
3464 rematerialization for such registers. */
3465 if (!insn_inserted_p)
3466 expr->reaching_reg
3467 = gen_reg_rtx_and_attrs (SET_DEST (set));
3469 gcse_emit_move_after (SET_DEST (set), expr->reaching_reg,
3470 insn);
3471 delete_insn (insn);
3472 occr->deleted_p = 1;
3473 changed = 1;
3474 gcse_subst_count++;
3476 if (!insn_inserted_p)
3478 insert_insn_end_basic_block (expr, bb);
3479 insn_inserted_p = 1;
3483 occrs_to_hoist.release ();
3484 bitmap_clear (from_bbs);
3487 domby.release ();
3490 dom_tree_walk.release ();
3491 BITMAP_FREE (from_bbs);
3492 if (flag_ira_hoist_pressure)
3493 BITMAP_FREE (hoisted_bbs);
3495 free (bb_size);
3496 free (to_bb_head);
3497 free (index_map);
3499 return changed;
3502 /* Return pressure class and number of needed hard registers (through
3503 *NREGS) of register REGNO. */
3504 static enum reg_class
3505 get_regno_pressure_class (int regno, int *nregs)
3507 if (regno >= FIRST_PSEUDO_REGISTER)
3509 enum reg_class pressure_class;
3511 pressure_class = reg_allocno_class (regno);
3512 pressure_class = ira_pressure_class_translate[pressure_class];
3513 *nregs
3514 = ira_reg_class_max_nregs[pressure_class][PSEUDO_REGNO_MODE (regno)];
3515 return pressure_class;
3517 else if (! TEST_HARD_REG_BIT (ira_no_alloc_regs, regno)
3518 && ! TEST_HARD_REG_BIT (eliminable_regset, regno))
3520 *nregs = 1;
3521 return ira_pressure_class_translate[REGNO_REG_CLASS (regno)];
3523 else
3525 *nregs = 0;
3526 return NO_REGS;
3530 /* Return pressure class and number of hard registers (through *NREGS)
3531 for destination of INSN. */
3532 static enum reg_class
3533 get_pressure_class_and_nregs (rtx_insn *insn, int *nregs)
3535 rtx reg;
3536 enum reg_class pressure_class;
3537 const_rtx set = single_set_gcse (insn);
3539 reg = SET_DEST (set);
3540 if (GET_CODE (reg) == SUBREG)
3541 reg = SUBREG_REG (reg);
3542 if (MEM_P (reg))
3544 *nregs = 0;
3545 pressure_class = NO_REGS;
3547 else
3549 gcc_assert (REG_P (reg));
3550 pressure_class = reg_allocno_class (REGNO (reg));
3551 pressure_class = ira_pressure_class_translate[pressure_class];
3552 *nregs
3553 = ira_reg_class_max_nregs[pressure_class][GET_MODE (SET_SRC (set))];
3555 return pressure_class;
3558 /* Increase (if INCR_P) or decrease current register pressure for
3559 register REGNO. */
3560 static void
3561 change_pressure (int regno, bool incr_p)
3563 int nregs;
3564 enum reg_class pressure_class;
3566 pressure_class = get_regno_pressure_class (regno, &nregs);
3567 if (! incr_p)
3568 curr_reg_pressure[pressure_class] -= nregs;
3569 else
3571 curr_reg_pressure[pressure_class] += nregs;
3572 if (BB_DATA (curr_bb)->max_reg_pressure[pressure_class]
3573 < curr_reg_pressure[pressure_class])
3574 BB_DATA (curr_bb)->max_reg_pressure[pressure_class]
3575 = curr_reg_pressure[pressure_class];
3579 /* Calculate register pressure for each basic block by walking insns
3580 from last to first. */
3581 static void
3582 calculate_bb_reg_pressure (void)
3584 int i;
3585 unsigned int j;
3586 rtx_insn *insn;
3587 basic_block bb;
3588 bitmap curr_regs_live;
3589 bitmap_iterator bi;
3592 ira_setup_eliminable_regset ();
3593 curr_regs_live = BITMAP_ALLOC (&reg_obstack);
3594 FOR_EACH_BB_FN (bb, cfun)
3596 curr_bb = bb;
3597 BB_DATA (bb)->live_in = BITMAP_ALLOC (NULL);
3598 BB_DATA (bb)->backup = BITMAP_ALLOC (NULL);
3599 bitmap_copy (BB_DATA (bb)->live_in, df_get_live_in (bb));
3600 bitmap_copy (curr_regs_live, df_get_live_out (bb));
3601 for (i = 0; i < ira_pressure_classes_num; i++)
3602 curr_reg_pressure[ira_pressure_classes[i]] = 0;
3603 EXECUTE_IF_SET_IN_BITMAP (curr_regs_live, 0, j, bi)
3604 change_pressure (j, true);
3606 FOR_BB_INSNS_REVERSE (bb, insn)
3608 rtx dreg;
3609 int regno;
3610 df_ref def, use;
3612 if (! NONDEBUG_INSN_P (insn))
3613 continue;
3615 FOR_EACH_INSN_DEF (def, insn)
3617 dreg = DF_REF_REAL_REG (def);
3618 gcc_assert (REG_P (dreg));
3619 regno = REGNO (dreg);
3620 if (!(DF_REF_FLAGS (def)
3621 & (DF_REF_PARTIAL | DF_REF_CONDITIONAL)))
3623 if (bitmap_clear_bit (curr_regs_live, regno))
3624 change_pressure (regno, false);
3628 FOR_EACH_INSN_USE (use, insn)
3630 dreg = DF_REF_REAL_REG (use);
3631 gcc_assert (REG_P (dreg));
3632 regno = REGNO (dreg);
3633 if (bitmap_set_bit (curr_regs_live, regno))
3634 change_pressure (regno, true);
3638 BITMAP_FREE (curr_regs_live);
3640 if (dump_file == NULL)
3641 return;
3643 fprintf (dump_file, "\nRegister Pressure: \n");
3644 FOR_EACH_BB_FN (bb, cfun)
3646 fprintf (dump_file, " Basic block %d: \n", bb->index);
3647 for (i = 0; (int) i < ira_pressure_classes_num; i++)
3649 enum reg_class pressure_class;
3651 pressure_class = ira_pressure_classes[i];
3652 if (BB_DATA (bb)->max_reg_pressure[pressure_class] == 0)
3653 continue;
3655 fprintf (dump_file, " %s=%d\n", reg_class_names[pressure_class],
3656 BB_DATA (bb)->max_reg_pressure[pressure_class]);
3659 fprintf (dump_file, "\n");
3662 /* Top level routine to perform one code hoisting (aka unification) pass
3664 Return nonzero if a change was made. */
3666 static int
3667 one_code_hoisting_pass (void)
3669 int changed = 0;
3671 gcse_subst_count = 0;
3672 gcse_create_count = 0;
3674 /* Return if there's nothing to do, or it is too expensive. */
3675 if (n_basic_blocks_for_fn (cfun) <= NUM_FIXED_BLOCKS + 1
3676 || is_too_expensive (_("GCSE disabled")))
3677 return 0;
3679 doing_code_hoisting_p = true;
3681 /* Calculate register pressure for each basic block. */
3682 if (flag_ira_hoist_pressure)
3684 regstat_init_n_sets_and_refs ();
3685 ira_set_pseudo_classes (false, dump_file);
3686 alloc_aux_for_blocks (sizeof (struct bb_data));
3687 calculate_bb_reg_pressure ();
3688 regstat_free_n_sets_and_refs ();
3691 /* We need alias. */
3692 init_alias_analysis ();
3694 bytes_used = 0;
3695 gcc_obstack_init (&gcse_obstack);
3696 alloc_gcse_mem ();
3698 alloc_hash_table (&expr_hash_table);
3699 compute_hash_table (&expr_hash_table);
3700 if (dump_file)
3701 dump_hash_table (dump_file, "Code Hosting Expressions", &expr_hash_table);
3703 if (expr_hash_table.n_elems > 0)
3705 alloc_code_hoist_mem (last_basic_block_for_fn (cfun),
3706 expr_hash_table.n_elems);
3707 compute_code_hoist_data ();
3708 changed = hoist_code ();
3709 free_code_hoist_mem ();
3712 if (flag_ira_hoist_pressure)
3714 free_aux_for_blocks ();
3715 free_reg_info ();
3717 free_hash_table (&expr_hash_table);
3718 free_gcse_mem ();
3719 obstack_free (&gcse_obstack, NULL);
3721 /* We are finished with alias. */
3722 end_alias_analysis ();
3724 if (dump_file)
3726 fprintf (dump_file, "HOIST of %s, %d basic blocks, %d bytes needed, ",
3727 current_function_name (), n_basic_blocks_for_fn (cfun),
3728 bytes_used);
3729 fprintf (dump_file, "%d substs, %d insns created\n",
3730 gcse_subst_count, gcse_create_count);
3733 doing_code_hoisting_p = false;
3735 return changed;
3738 /* Here we provide the things required to do store motion towards the exit.
3739 In order for this to be effective, gcse also needed to be taught how to
3740 move a load when it is killed only by a store to itself.
3742 int i;
3743 float a[10];
3745 void foo(float scale)
3747 for (i=0; i<10; i++)
3748 a[i] *= scale;
3751 'i' is both loaded and stored to in the loop. Normally, gcse cannot move
3752 the load out since its live around the loop, and stored at the bottom
3753 of the loop.
3755 The 'Load Motion' referred to and implemented in this file is
3756 an enhancement to gcse which when using edge based LCM, recognizes
3757 this situation and allows gcse to move the load out of the loop.
3759 Once gcse has hoisted the load, store motion can then push this
3760 load towards the exit, and we end up with no loads or stores of 'i'
3761 in the loop. */
3763 /* This will search the ldst list for a matching expression. If it
3764 doesn't find one, we create one and initialize it. */
3766 static struct ls_expr *
3767 ldst_entry (rtx x)
3769 int do_not_record_p = 0;
3770 struct ls_expr * ptr;
3771 unsigned int hash;
3772 ls_expr **slot;
3773 struct ls_expr e;
3775 hash = hash_rtx (x, GET_MODE (x), &do_not_record_p,
3776 NULL, /*have_reg_qty=*/false);
3778 e.pattern = x;
3779 slot = pre_ldst_table->find_slot_with_hash (&e, hash, INSERT);
3780 if (*slot)
3781 return *slot;
3783 ptr = XNEW (struct ls_expr);
3785 ptr->next = pre_ldst_mems;
3786 ptr->expr = NULL;
3787 ptr->pattern = x;
3788 ptr->pattern_regs = NULL_RTX;
3789 ptr->loads = NULL;
3790 ptr->stores = NULL;
3791 ptr->reaching_reg = NULL_RTX;
3792 ptr->invalid = 0;
3793 ptr->index = 0;
3794 ptr->hash_index = hash;
3795 pre_ldst_mems = ptr;
3796 *slot = ptr;
3798 return ptr;
3801 /* Free up an individual ldst entry. */
3803 static void
3804 free_ldst_entry (struct ls_expr * ptr)
3806 free_INSN_LIST_list (& ptr->loads);
3807 free_INSN_LIST_list (& ptr->stores);
3809 free (ptr);
3812 /* Free up all memory associated with the ldst list. */
3814 static void
3815 free_ld_motion_mems (void)
3817 delete pre_ldst_table;
3818 pre_ldst_table = NULL;
3820 while (pre_ldst_mems)
3822 struct ls_expr * tmp = pre_ldst_mems;
3824 pre_ldst_mems = pre_ldst_mems->next;
3826 free_ldst_entry (tmp);
3829 pre_ldst_mems = NULL;
3832 /* Dump debugging info about the ldst list. */
3834 static void
3835 print_ldst_list (FILE * file)
3837 struct ls_expr * ptr;
3839 fprintf (file, "LDST list: \n");
3841 for (ptr = pre_ldst_mems; ptr != NULL; ptr = ptr->next)
3843 fprintf (file, " Pattern (%3d): ", ptr->index);
3845 print_rtl (file, ptr->pattern);
3847 fprintf (file, "\n Loads : ");
3849 if (ptr->loads)
3850 print_rtl (file, ptr->loads);
3851 else
3852 fprintf (file, "(nil)");
3854 fprintf (file, "\n Stores : ");
3856 if (ptr->stores)
3857 print_rtl (file, ptr->stores);
3858 else
3859 fprintf (file, "(nil)");
3861 fprintf (file, "\n\n");
3864 fprintf (file, "\n");
3867 /* Returns 1 if X is in the list of ldst only expressions. */
3869 static struct ls_expr *
3870 find_rtx_in_ldst (rtx x)
3872 struct ls_expr e;
3873 ls_expr **slot;
3874 if (!pre_ldst_table)
3875 return NULL;
3876 e.pattern = x;
3877 slot = pre_ldst_table->find_slot (&e, NO_INSERT);
3878 if (!slot || (*slot)->invalid)
3879 return NULL;
3880 return *slot;
3883 /* Load Motion for loads which only kill themselves. */
3885 /* Return true if x, a MEM, is a simple access with no side effects.
3886 These are the types of loads we consider for the ld_motion list,
3887 otherwise we let the usual aliasing take care of it. */
3889 static int
3890 simple_mem (const_rtx x)
3892 if (MEM_VOLATILE_P (x))
3893 return 0;
3895 if (GET_MODE (x) == BLKmode)
3896 return 0;
3898 /* If we are handling exceptions, we must be careful with memory references
3899 that may trap. If we are not, the behavior is undefined, so we may just
3900 continue. */
3901 if (cfun->can_throw_non_call_exceptions && may_trap_p (x))
3902 return 0;
3904 if (side_effects_p (x))
3905 return 0;
3907 /* Do not consider function arguments passed on stack. */
3908 if (reg_mentioned_p (stack_pointer_rtx, x))
3909 return 0;
3911 if (flag_float_store && FLOAT_MODE_P (GET_MODE (x)))
3912 return 0;
3914 return 1;
3917 /* Make sure there isn't a buried reference in this pattern anywhere.
3918 If there is, invalidate the entry for it since we're not capable
3919 of fixing it up just yet.. We have to be sure we know about ALL
3920 loads since the aliasing code will allow all entries in the
3921 ld_motion list to not-alias itself. If we miss a load, we will get
3922 the wrong value since gcse might common it and we won't know to
3923 fix it up. */
3925 static void
3926 invalidate_any_buried_refs (rtx x)
3928 const char * fmt;
3929 int i, j;
3930 struct ls_expr * ptr;
3932 /* Invalidate it in the list. */
3933 if (MEM_P (x) && simple_mem (x))
3935 ptr = ldst_entry (x);
3936 ptr->invalid = 1;
3939 /* Recursively process the insn. */
3940 fmt = GET_RTX_FORMAT (GET_CODE (x));
3942 for (i = GET_RTX_LENGTH (GET_CODE (x)) - 1; i >= 0; i--)
3944 if (fmt[i] == 'e')
3945 invalidate_any_buried_refs (XEXP (x, i));
3946 else if (fmt[i] == 'E')
3947 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
3948 invalidate_any_buried_refs (XVECEXP (x, i, j));
3952 /* Find all the 'simple' MEMs which are used in LOADs and STORES. Simple
3953 being defined as MEM loads and stores to symbols, with no side effects
3954 and no registers in the expression. For a MEM destination, we also
3955 check that the insn is still valid if we replace the destination with a
3956 REG, as is done in update_ld_motion_stores. If there are any uses/defs
3957 which don't match this criteria, they are invalidated and trimmed out
3958 later. */
3960 static void
3961 compute_ld_motion_mems (void)
3963 struct ls_expr * ptr;
3964 basic_block bb;
3965 rtx_insn *insn;
3967 pre_ldst_mems = NULL;
3968 pre_ldst_table = new hash_table<pre_ldst_expr_hasher> (13);
3970 FOR_EACH_BB_FN (bb, cfun)
3972 FOR_BB_INSNS (bb, insn)
3974 if (NONDEBUG_INSN_P (insn))
3976 if (GET_CODE (PATTERN (insn)) == SET)
3978 rtx src = SET_SRC (PATTERN (insn));
3979 rtx dest = SET_DEST (PATTERN (insn));
3980 rtx note = find_reg_equal_equiv_note (insn);
3981 rtx src_eq;
3983 /* Check for a simple LOAD... */
3984 if (MEM_P (src) && simple_mem (src))
3986 ptr = ldst_entry (src);
3987 if (REG_P (dest))
3988 ptr->loads = alloc_INSN_LIST (insn, ptr->loads);
3989 else
3990 ptr->invalid = 1;
3992 else
3994 /* Make sure there isn't a buried load somewhere. */
3995 invalidate_any_buried_refs (src);
3998 if (note != 0 && REG_NOTE_KIND (note) == REG_EQUAL)
3999 src_eq = XEXP (note, 0);
4000 else
4001 src_eq = NULL_RTX;
4003 if (src_eq != NULL_RTX
4004 && !(MEM_P (src_eq) && simple_mem (src_eq)))
4005 invalidate_any_buried_refs (src_eq);
4007 /* Check for stores. Don't worry about aliased ones, they
4008 will block any movement we might do later. We only care
4009 about this exact pattern since those are the only
4010 circumstance that we will ignore the aliasing info. */
4011 if (MEM_P (dest) && simple_mem (dest))
4013 ptr = ldst_entry (dest);
4015 if (! MEM_P (src)
4016 && GET_CODE (src) != ASM_OPERANDS
4017 /* Check for REG manually since want_to_gcse_p
4018 returns 0 for all REGs. */
4019 && can_assign_to_reg_without_clobbers_p (src))
4020 ptr->stores = alloc_INSN_LIST (insn, ptr->stores);
4021 else
4022 ptr->invalid = 1;
4025 else
4026 invalidate_any_buried_refs (PATTERN (insn));
4032 /* Remove any references that have been either invalidated or are not in the
4033 expression list for pre gcse. */
4035 static void
4036 trim_ld_motion_mems (void)
4038 struct ls_expr * * last = & pre_ldst_mems;
4039 struct ls_expr * ptr = pre_ldst_mems;
4041 while (ptr != NULL)
4043 struct gcse_expr * expr;
4045 /* Delete if entry has been made invalid. */
4046 if (! ptr->invalid)
4048 /* Delete if we cannot find this mem in the expression list. */
4049 unsigned int hash = ptr->hash_index % expr_hash_table.size;
4051 for (expr = expr_hash_table.table[hash];
4052 expr != NULL;
4053 expr = expr->next_same_hash)
4054 if (expr_equiv_p (expr->expr, ptr->pattern))
4055 break;
4057 else
4058 expr = (struct gcse_expr *) 0;
4060 if (expr)
4062 /* Set the expression field if we are keeping it. */
4063 ptr->expr = expr;
4064 last = & ptr->next;
4065 ptr = ptr->next;
4067 else
4069 *last = ptr->next;
4070 pre_ldst_table->remove_elt_with_hash (ptr, ptr->hash_index);
4071 free_ldst_entry (ptr);
4072 ptr = * last;
4076 /* Show the world what we've found. */
4077 if (dump_file && pre_ldst_mems != NULL)
4078 print_ldst_list (dump_file);
4081 /* This routine will take an expression which we are replacing with
4082 a reaching register, and update any stores that are needed if
4083 that expression is in the ld_motion list. Stores are updated by
4084 copying their SRC to the reaching register, and then storing
4085 the reaching register into the store location. These keeps the
4086 correct value in the reaching register for the loads. */
4088 static void
4089 update_ld_motion_stores (struct gcse_expr * expr)
4091 struct ls_expr * mem_ptr;
4093 if ((mem_ptr = find_rtx_in_ldst (expr->expr)))
4095 /* We can try to find just the REACHED stores, but is shouldn't
4096 matter to set the reaching reg everywhere... some might be
4097 dead and should be eliminated later. */
4099 /* We replace (set mem expr) with (set reg expr) (set mem reg)
4100 where reg is the reaching reg used in the load. We checked in
4101 compute_ld_motion_mems that we can replace (set mem expr) with
4102 (set reg expr) in that insn. */
4103 rtx list = mem_ptr->stores;
4105 for ( ; list != NULL_RTX; list = XEXP (list, 1))
4107 rtx_insn *insn = as_a <rtx_insn *> (XEXP (list, 0));
4108 rtx pat = PATTERN (insn);
4109 rtx src = SET_SRC (pat);
4110 rtx reg = expr->reaching_reg;
4111 rtx copy;
4113 /* If we've already copied it, continue. */
4114 if (expr->reaching_reg == src)
4115 continue;
4117 if (dump_file)
4119 fprintf (dump_file, "PRE: store updated with reaching reg ");
4120 print_rtl (dump_file, reg);
4121 fprintf (dump_file, ":\n ");
4122 print_inline_rtx (dump_file, insn, 8);
4123 fprintf (dump_file, "\n");
4126 copy = gen_move_insn (reg, copy_rtx (SET_SRC (pat)));
4127 emit_insn_before (copy, insn);
4128 SET_SRC (pat) = reg;
4129 df_insn_rescan (insn);
4131 /* un-recognize this pattern since it's probably different now. */
4132 INSN_CODE (insn) = -1;
4133 gcse_create_count++;
4138 /* Return true if the graph is too expensive to optimize. PASS is the
4139 optimization about to be performed. */
4141 static bool
4142 is_too_expensive (const char *pass)
4144 /* Trying to perform global optimizations on flow graphs which have
4145 a high connectivity will take a long time and is unlikely to be
4146 particularly useful.
4148 In normal circumstances a cfg should have about twice as many
4149 edges as blocks. But we do not want to punish small functions
4150 which have a couple switch statements. Rather than simply
4151 threshold the number of blocks, uses something with a more
4152 graceful degradation. */
4153 if (n_edges_for_fn (cfun) > 20000 + n_basic_blocks_for_fn (cfun) * 4)
4155 warning (OPT_Wdisabled_optimization,
4156 "%s: %d basic blocks and %d edges/basic block",
4157 pass, n_basic_blocks_for_fn (cfun),
4158 n_edges_for_fn (cfun) / n_basic_blocks_for_fn (cfun));
4160 return true;
4163 /* If allocating memory for the dataflow bitmaps would take up too much
4164 storage it's better just to disable the optimization. */
4165 if ((n_basic_blocks_for_fn (cfun)
4166 * SBITMAP_SET_SIZE (max_reg_num ())
4167 * sizeof (SBITMAP_ELT_TYPE)) > MAX_GCSE_MEMORY)
4169 warning (OPT_Wdisabled_optimization,
4170 "%s: %d basic blocks and %d registers",
4171 pass, n_basic_blocks_for_fn (cfun), max_reg_num ());
4173 return true;
4176 return false;
4179 static unsigned int
4180 execute_rtl_pre (void)
4182 int changed;
4183 delete_unreachable_blocks ();
4184 df_analyze ();
4185 changed = one_pre_gcse_pass ();
4186 flag_rerun_cse_after_global_opts |= changed;
4187 if (changed)
4188 cleanup_cfg (0);
4189 return 0;
4192 static unsigned int
4193 execute_rtl_hoist (void)
4195 int changed;
4196 delete_unreachable_blocks ();
4197 df_analyze ();
4198 changed = one_code_hoisting_pass ();
4199 flag_rerun_cse_after_global_opts |= changed;
4200 if (changed)
4201 cleanup_cfg (0);
4202 return 0;
4205 namespace {
4207 const pass_data pass_data_rtl_pre =
4209 RTL_PASS, /* type */
4210 "rtl pre", /* name */
4211 OPTGROUP_NONE, /* optinfo_flags */
4212 TV_PRE, /* tv_id */
4213 PROP_cfglayout, /* properties_required */
4214 0, /* properties_provided */
4215 0, /* properties_destroyed */
4216 0, /* todo_flags_start */
4217 TODO_df_finish, /* todo_flags_finish */
4220 class pass_rtl_pre : public rtl_opt_pass
4222 public:
4223 pass_rtl_pre (gcc::context *ctxt)
4224 : rtl_opt_pass (pass_data_rtl_pre, ctxt)
4227 /* opt_pass methods: */
4228 virtual bool gate (function *);
4229 virtual unsigned int execute (function *) { return execute_rtl_pre (); }
4231 }; // class pass_rtl_pre
4233 /* We do not construct an accurate cfg in functions which call
4234 setjmp, so none of these passes runs if the function calls
4235 setjmp.
4236 FIXME: Should just handle setjmp via REG_SETJMP notes. */
4238 bool
4239 pass_rtl_pre::gate (function *fun)
4241 return optimize > 0 && flag_gcse
4242 && !fun->calls_setjmp
4243 && optimize_function_for_speed_p (fun)
4244 && dbg_cnt (pre);
4247 } // anon namespace
4249 rtl_opt_pass *
4250 make_pass_rtl_pre (gcc::context *ctxt)
4252 return new pass_rtl_pre (ctxt);
4255 namespace {
4257 const pass_data pass_data_rtl_hoist =
4259 RTL_PASS, /* type */
4260 "hoist", /* name */
4261 OPTGROUP_NONE, /* optinfo_flags */
4262 TV_HOIST, /* tv_id */
4263 PROP_cfglayout, /* properties_required */
4264 0, /* properties_provided */
4265 0, /* properties_destroyed */
4266 0, /* todo_flags_start */
4267 TODO_df_finish, /* todo_flags_finish */
4270 class pass_rtl_hoist : public rtl_opt_pass
4272 public:
4273 pass_rtl_hoist (gcc::context *ctxt)
4274 : rtl_opt_pass (pass_data_rtl_hoist, ctxt)
4277 /* opt_pass methods: */
4278 virtual bool gate (function *);
4279 virtual unsigned int execute (function *) { return execute_rtl_hoist (); }
4281 }; // class pass_rtl_hoist
4283 bool
4284 pass_rtl_hoist::gate (function *)
4286 return optimize > 0 && flag_gcse
4287 && !cfun->calls_setjmp
4288 /* It does not make sense to run code hoisting unless we are optimizing
4289 for code size -- it rarely makes programs faster, and can make then
4290 bigger if we did PRE (when optimizing for space, we don't run PRE). */
4291 && optimize_function_for_size_p (cfun)
4292 && dbg_cnt (hoist);
4295 } // anon namespace
4297 rtl_opt_pass *
4298 make_pass_rtl_hoist (gcc::context *ctxt)
4300 return new pass_rtl_hoist (ctxt);
4303 /* Reset all state within gcse.c so that we can rerun the compiler
4304 within the same process. For use by toplev::finalize. */
4306 void
4307 gcse_c_finalize (void)
4309 test_insn = NULL;
4312 #include "gt-gcse.h"