| blob | f8ce8689d37011c37c82a64eb7b6aa5fd9174794 |
1 /* Data flow analysis for GNU compiler.
2 Copyright (C) 1987, 88, 92-97, 1998 Free Software Foundation, Inc.
4 This file is part of GNU CC.
6 GNU CC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
9 any later version.
11 GNU CC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU CC; see the file COPYING. If not, write to
18 the Free Software Foundation, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
22 /* This file contains the data flow analysis pass of the compiler.
23 It computes data flow information
24 which tells combine_instructions which insns to consider combining
25 and controls register allocation.
27 Additional data flow information that is too bulky to record
28 is generated during the analysis, and is used at that time to
29 create autoincrement and autodecrement addressing.
31 The first step is dividing the function into basic blocks.
32 find_basic_blocks does this. Then life_analysis determines
33 where each register is live and where it is dead.
35 ** find_basic_blocks **
37 find_basic_blocks divides the current function's rtl
38 into basic blocks. It records the beginnings and ends of the
39 basic blocks in the vectors basic_block_head and basic_block_end,
40 and the number of blocks in n_basic_blocks.
42 find_basic_blocks also finds any unreachable loops
43 and deletes them.
45 ** life_analysis **
47 life_analysis is called immediately after find_basic_blocks.
48 It uses the basic block information to determine where each
49 hard or pseudo register is live.
51 ** live-register info **
53 The information about where each register is live is in two parts:
54 the REG_NOTES of insns, and the vector basic_block_live_at_start.
56 basic_block_live_at_start has an element for each basic block,
57 and the element is a bit-vector with a bit for each hard or pseudo
58 register. The bit is 1 if the register is live at the beginning
59 of the basic block.
61 Two types of elements can be added to an insn's REG_NOTES.
62 A REG_DEAD note is added to an insn's REG_NOTES for any register
63 that meets both of two conditions: The value in the register is not
64 needed in subsequent insns and the insn does not replace the value in
65 the register (in the case of multi-word hard registers, the value in
66 each register must be replaced by the insn to avoid a REG_DEAD note).
68 In the vast majority of cases, an object in a REG_DEAD note will be
69 used somewhere in the insn. The (rare) exception to this is if an
70 insn uses a multi-word hard register and only some of the registers are
71 needed in subsequent insns. In that case, REG_DEAD notes will be
72 provided for those hard registers that are not subsequently needed.
73 Partial REG_DEAD notes of this type do not occur when an insn sets
74 only some of the hard registers used in such a multi-word operand;
75 omitting REG_DEAD notes for objects stored in an insn is optional and
76 the desire to do so does not justify the complexity of the partial
77 REG_DEAD notes.
79 REG_UNUSED notes are added for each register that is set by the insn
80 but is unused subsequently (if every register set by the insn is unused
81 and the insn does not reference memory or have some other side-effect,
82 the insn is deleted instead). If only part of a multi-word hard
83 register is used in a subsequent insn, REG_UNUSED notes are made for
84 the parts that will not be used.
86 To determine which registers are live after any insn, one can
87 start from the beginning of the basic block and scan insns, noting
88 which registers are set by each insn and which die there.
90 ** Other actions of life_analysis **
92 life_analysis sets up the LOG_LINKS fields of insns because the
93 information needed to do so is readily available.
95 life_analysis deletes insns whose only effect is to store a value
96 that is never used.
98 life_analysis notices cases where a reference to a register as
99 a memory address can be combined with a preceding or following
100 incrementation or decrementation of the register. The separate
101 instruction to increment or decrement is deleted and the address
102 is changed to a POST_INC or similar rtx.
104 Each time an incrementing or decrementing address is created,
105 a REG_INC element is added to the insn's REG_NOTES list.
107 life_analysis fills in certain vectors containing information about
108 register usage: reg_n_refs, reg_n_deaths, reg_n_sets, reg_live_length,
109 reg_n_calls_crosses and reg_basic_block. */
110 \f
124 #define obstack_chunk_alloc xmalloc
125 #define obstack_chunk_free free
127 /* The contents of the current function definition are allocated
128 in this obstack, and all are freed at the end of the function.
129 For top-level functions, this is temporary_obstack.
130 Separate obstacks are made for nested functions. */
134 /* List of labels that must never be deleted. */
137 /* Get the basic block number of an insn.
138 This info should not be expected to remain available
139 after the end of life_analysis. */
141 /* This is the limit of the allocated space in the following two arrays. */
145 #define BLOCK_NUM(INSN) uid_block_number[INSN_UID (INSN)]
147 /* This is where the BLOCK_NUM values are really stored.
148 This is set up by find_basic_blocks and used there and in life_analysis,
149 and then freed. */
153 /* INSN_VOLATILE (insn) is 1 if the insn refers to anything volatile. */
155 #define INSN_VOLATILE(INSN) uid_volatile[INSN_UID (INSN)]
158 /* Number of basic blocks in the current function. */
162 /* Maximum register number used in this function, plus one. */
166 /* Maximum number of SCRATCH rtx's used in any basic block of this
167 function. */
171 /* Number of SCRATCH rtx's in the current block. */
175 /* Indexed by n, giving various register information */
179 /* Size of the reg_n_info table. */
183 /* Element N is the next insn that uses (hard or pseudo) register number N
184 within the current basic block; or zero, if there is no such insn.
185 This is valid only during the final backward scan in propagate_block. */
189 /* Size of a regset for the current function,
190 in (1) bytes and (2) elements. */
195 /* Element N is first insn in basic block N.
196 This info lasts until we finish compiling the function. */
200 /* Element N is last insn in basic block N.
201 This info lasts until we finish compiling the function. */
205 /* Element N indicates whether basic block N can be reached through a
206 computed jump. */
210 /* Element N is a regset describing the registers live
211 at the start of basic block N.
212 This info lasts until we finish compiling the function. */
216 /* Regset of regs live when calls to `setjmp'-like functions happen. */
218 regset regs_live_at_setjmp;
220 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
221 that have to go in the same hard reg.
222 The first two regs in the list are a pair, and the next two
223 are another pair, etc. */
224 rtx regs_may_share;
226 /* Element N is nonzero if control can drop into basic block N
227 from the preceding basic block. Freed after life_analysis. */
231 /* Element N is depth within loops of the last insn in basic block number N.
232 Freed after life_analysis. */
236 /* Element N nonzero if basic block N can actually be reached.
237 Vector exists only during find_basic_blocks. */
241 /* Depth within loops of basic block being scanned for lifetime analysis,
242 plus one. This is the weight attached to references to registers. */
246 /* During propagate_block, this is non-zero if the value of CC0 is live. */
250 /* During propagate_block, this contains the last MEM stored into. It
251 is used to eliminate consecutive stores to the same location. */
255 /* Set of registers that may be eliminable. These are handled specially
256 in updating regs_ever_live. */
260 /* Forward declarations */
273 #ifdef AUTO_INC_DEC
277 #endif
287 \f
288 /* Find basic blocks of the current function.
289 F is the first insn of the function and NREGS the number of register numbers
290 in use.
291 LIVE_REACHABLE_P is non-zero if the caller needs all live blocks to
292 be reachable. This turns on a kludge that causes the control flow
293 information to be inaccurate and not suitable for passes like GCSE. */
295 void
297 rtx f;
301 {
307 /* Count the basic blocks. Also find maximum insn uid value used. */
309 {
317 {
319 /* Track when we are inside in LIBCALL block. */
334 i++;
349 }
350 }
354 #ifdef AUTO_INC_DEC
355 /* Leave space for insns life_analysis makes in some cases for auto-inc.
356 These cases are rare, so we don't need too much space. */
358 #endif
360 /* Allocate some tables that last till end of compiling this function
361 and some needed only in find_basic_blocks and life_analysis. */
368 uid_block_number
374 }
376 /* Find all basic blocks of the function whose first insn is F.
377 Store the correct data in the tables that describe the basic blocks,
378 set up the chains of references for each CODE_LABEL, and
379 delete any entire basic blocks that cannot be reached.
381 NONLOCAL_LABEL_LIST is a list of non-local labels in the function.
382 Blocks that are otherwise unreachable may be reachable with a non-local
383 goto.
384 LIVE_REACHABLE_P is non-zero if the caller needs all live blocks to
385 be reachable. This turns on a kludge that causes the control flow
386 information to be inaccurate and not suitable for passes like GCSE. */
388 static void
392 {
397 /* An array of CODE_LABELs, indexed by UID for the start of the active
398 EH handler for each insn in F. */
401 /* List of label_refs to all labels whose addresses are taken
402 and used as data. */
403 rtx label_value_list;
413 restart:
424 /* Initialize with just block 0 reachable and no blocks marked. */
428 /* Initialize the ref chain of each label to 0. Record where all the
429 blocks start and end and their depth in loops. For each insn, record
430 the block it is in. Also mark as reachable any blocks headed by labels
431 that must not be deleted. */
435 {
437 /* Track when we are inside in LIBCALL block. */
444 {
446 depth++;
448 depth--;
449 }
451 /* A basic block starts at label, or after something that can jump. */
459 {
465 {
467 /* Any label that cannot be deleted
468 is considered to start a reachable block. */
471 }
472 }
475 {
478 }
481 {
482 /* Make a list of all labels referred to other than by jumps. */
486 label_value_list);
487 }
489 /* Keep a lifo list of the currently active exception notes. */
491 {
493 {
497 else
501 }
504 }
505 /* If we encounter a CALL_INSN, note which exception handler it
506 might pass control to.
508 If doing asynchronous exceptions, record the active EH handler
509 for every insn, since most insns can throw. */
511 && (asynchronous_exceptions
524 }
526 /* During the second pass, `n_basic_blocks' is only an upper bound.
527 Only perform the sanity check for the first pass, and on the second
528 pass ensure `n_basic_blocks' is set to the correct value. */
533 /* Record which basic blocks control can drop in to. */
536 {
539 ;
542 }
544 /* Now find which basic blocks can actually be reached
545 and put all jump insns' LABEL_REFS onto the ref-chains
546 of their target labels. */
549 {
553 /* Pass over all blocks, marking each block that is reachable
554 and has not yet been marked.
555 Keep doing this until, in one pass, no blocks have been marked.
556 Then blocks_live and blocks_marked are identical and correct.
557 In addition, all jumps actually reachable have been marked. */
560 {
564 {
573 /* If we have any forced labels, mark them as potentially
574 reachable from this block. */
580 /* Now scan the insns for this block, we may need to make
581 edges for some of them to various non-obvious locations
582 (exception handlers, nonlocal labels, etc). */
586 {
588 {
590 /* References to labels in non-jumping insns have
591 REG_LABEL notes attached to them.
593 This can happen for computed gotos; we don't care
594 about them here since the values are also on the
595 label_value_list and will be marked live if we find
596 a live computed goto.
598 This can also happen when we take the address of
599 a label to pass as an argument to __throw. Note
600 throw only uses the value to determine what handler
601 should be called -- ie the label is not used as
602 a jump target, it just marks regions in the code.
604 In theory we should be able to ignore the REG_LABEL
605 notes, but we have to make sure that the label and
606 associated insns aren't marked dead, so we make
607 the block in question live and create an edge from
608 this insn to the label. This is not strictly
609 correct, but it is close enough for now. */
611 note;
613 {
615 {
620 }
621 }
623 /* If this is a computed jump, then mark it as
624 reaching everything on the label_value_list
625 and forced_labels list. */
627 {
630 {
636 }
639 {
645 }
646 }
648 /* If this is a CALL_INSN, then mark it as reaching
649 the active EH handler for this CALL_INSN. If
650 we're handling asynchronous exceptions mark every
651 insn as reaching the active EH handler.
653 Also mark the CALL_INSN as reaching any nonlocal
654 goto sites. */
658 NULL_RTX)))
659 {
661 {
667 {
672 }
673 }
675 {
677 x;
682 }
683 /* ??? This could be made smarter:
684 in some cases it's possible to tell that
685 certain calls will not do a nonlocal goto.
687 For example, if the nested functions that
688 do the nonlocal gotos do not have their
689 addresses taken, then only calls to those
690 functions or to other nested functions that
691 use them could possibly do nonlocal gotos. */
692 }
693 }
694 }
695 }
696 }
698 /* This should never happen. If it does that means we've computed an
699 incorrect flow graph, which can lead to aborts/crashes later in the
700 compiler or incorrect code generation.
702 We used to try and continue here, but that's just asking for trouble
703 later during the compile or at runtime. It's easier to debug the
704 problem here than later! */
711 /* Now delete the code for any basic blocks that can't be reached.
712 They can occur because jump_optimize does not recognize
713 unreachable loops as unreachable. */
718 {
719 deleted++;
721 /* Delete the insns in a (non-live) block. We physically delete
722 every non-note insn except the start and end (so
723 basic_block_head/end needn't be updated), we turn the latter
724 into NOTE_INSN_DELETED notes.
725 We use to "delete" the insns by turning them into notes, but
726 we may be deleting lots of insns that subsequent passes would
727 otherwise have to process. Secondly, lots of deleted blocks in
728 a row can really slow down propagate_block since it will
729 otherwise process insn-turned-notes multiple times when it
730 looks for loop begin/end notes. */
732 {
733 /* It would be quicker to delete all of these with a single
734 unchaining, rather than one at a time, but we need to keep
735 the NOTE's. */
738 {
743 else
745 }
746 }
749 {
750 /* Turn the head into a deleted insn note. */
754 /* If the head of this block is a CODE_LABEL, then it might
755 be the label for an exception handler which can't be
756 reached.
758 We need to remove the label from the exception_handler_label
759 list and remove the associated NOTE_EH_REGION_BEG and
760 NOTE_EH_REGION_END notes. */
762 {
766 {
768 {
769 /* Found a match, splice this label out of the
770 EH label list. */
775 /* Remove the handler from all regions */
779 }
781 }
782 }
787 }
790 {
791 /* Turn the tail into a deleted insn note. */
797 }
798 /* BARRIERs are between basic blocks, not part of one.
799 Delete a BARRIER if the preceding jump is deleted.
800 We cannot alter a BARRIER into a NOTE
801 because it is too short; but we can really delete
802 it because it is not part of a basic block. */
807 /* Each time we delete some basic blocks,
808 see if there is a jump around them that is
809 being turned into a no-op. If so, delete it. */
812 {
816 {
817 rtx label;
820 /* An unconditional jump is the only possibility
821 we must check for, since a conditional one
822 would make these blocks live. */
827 {
830 /* The deleted blocks still show up in the cfg,
831 so we must set basic_block_drops_in for blocks
832 I to J inclusive to keep the cfg accurate. */
842 }
844 }
845 }
846 }
847 /* If we deleted an exception handler, we may have EH region
848 begin/end blocks to remove as well. */
852 {
855 {
857 /* A NULL handler indicates a region is no longer needed */
859 {
862 }
863 }
864 }
866 /* There are pathological cases where one function calling hundreds of
867 nested inline functions can generate lots and lots of unreachable
868 blocks that jump can't delete. Since we don't use sparse matrices
869 a lot of memory will be needed to compile such functions.
870 Implementing sparse matrices is a fair bit of work and it is not
871 clear that they win more than they lose (we don't want to
872 unnecessarily slow down compilation of normal code). By making
873 another pass for the pathological case, we can greatly speed up
874 their compilation without hurting normal code. This works because
875 all the insns in the unreachable blocks have either been deleted or
876 turned into notes.
877 Note that we're talking about reducing memory usage by 10's of
878 megabytes and reducing compilation time by several minutes. */
879 /* ??? The choice of when to make another pass is a bit arbitrary,
880 and was derived from empirical data. */
883 {
884 pass++;
886 /* `n_basic_blocks' may not be correct at this point: two previously
887 separate blocks may now be merged. That's ok though as we
888 recalculate it during the second pass. It certainly can't be
889 any larger than the current value. */
891 }
892 }
893 }
895 /* Record INSN's block number as BB. */
897 void
899 rtx insn;
901 {
903 {
904 /* Add one-eighth the size so we don't keep calling xrealloc. */
908 }
910 }
912 \f
913 /* Subroutines of find_basic_blocks. */
915 /* Check expression X for label references;
916 if one is found, add INSN to the label's chain of references.
918 CHECKDUP means check for and avoid creating duplicate references
919 from the same insn. Such duplicates do no serious harm but
920 can slow life analysis. CHECKDUP is set only when duplicates
921 are likely. */
923 static void
927 {
932 /* We can be called with NULL when scanning label_value_list. */
938 {
943 /* If the label was never emitted, this insn is junk,
944 but avoid a crash trying to refer to BLOCK_NUM (label).
945 This can happen as a result of a syntax error
946 and a diagnostic has already been printed. */
950 /* if CHECKDUP is set, check for duplicate ref from same insn
951 and don't insert. */
960 }
964 {
968 {
972 }
973 }
974 }
976 /* Delete INSN by patching it out.
977 Return the next insn. */
979 static rtx
981 rtx insn;
982 {
983 /* ??? For the moment we assume we don't have to watch for NULLs here
984 since the start/end of basic blocks aren't deleted like this. */
988 }
989 \f
990 /* Perform data flow analysis.
991 F is the first insn of the function and NREGS the number of register numbers
992 in use. */
994 void
996 rtx f;
999 {
1000 #ifdef ELIMINABLE_REGS
1003 #endif
1005 /* Record which registers will be eliminated. We use this in
1006 mark_used_regs. */
1010 #ifdef ELIMINABLE_REGS
1013 #else
1015 #endif
1022 }
1024 /* Free the variables allocated by find_basic_blocks.
1026 KEEP_HEAD_END_P is non-zero if basic_block_head and basic_block_end
1027 are not to be freed. */
1029 void
1032 {
1034 {
1036 /* Tell dump_flow_info this isn't available anymore. */
1038 }
1040 {
1043 }
1045 {
1048 }
1050 {
1053 }
1056 {
1061 }
1062 }
1064 /* Determine which registers are live at the start of each
1065 basic block of the function whose first insn is F.
1066 NREGS is the number of registers used in F.
1067 We allocate the vector basic_block_live_at_start
1068 and the regsets that it points to, and fill them with the data.
1069 regset_size and regset_bytes are also set here. */
1071 static void
1073 rtx f;
1075 {
1078 /* For each basic block, a bitmask of regs
1079 live on exit from the block. */
1081 /* For each basic block, a bitmask of regs
1082 live on entry to a successor-block of this block.
1083 If this does not match basic_block_live_at_end,
1084 that must be updated, and the block must be rescanned. */
1086 /* For each basic block, a bitmask of regs
1087 whose liveness at the end of the basic block
1088 can make a difference in which regs are live on entry to the block.
1089 These are the regs that are set within the basic block,
1090 possibly excluding those that are used after they are set. */
1093 rtx insn;
1103 /* Allocate and zero out many data structures
1104 that will record the data from lifetime analysis. */
1111 /* Set up several regset-vectors used internally within this function.
1112 Their meanings are documented above, with their declarations. */
1114 basic_block_live_at_end
1117 /* Don't use alloca since that leads to a crash rather than an error message
1118 if there isn't enough space.
1119 Don't use oballoc since we may need to allocate other things during
1120 this function on the temporary obstack. */
1123 basic_block_new_live_at_end
1128 basic_block_significant
1132 /* Record which insns refer to any volatile memory
1133 or for any reason can't be deleted just because they are dead stores.
1134 Also, delete any insns that copy a register to itself. */
1137 {
1142 {
1143 /* Delete (in effect) any obvious no-op moves. */
1149 /* Insns carrying these notes are useful later on. */
1151 {
1155 }
1156 /* Delete (in effect) any obvious no-op moves. */
1166 /* Insns carrying these notes are useful later on. */
1168 {
1172 }
1174 {
1175 /* If nothing but SETs of registers to themselves,
1176 this insn can also be deleted. */
1178 {
1190 }
1193 /* Insns carrying these notes are useful later on. */
1195 {
1199 }
1200 else
1202 }
1205 /* A SET that makes space on the stack cannot be dead.
1206 (Such SETs occur only for allocating variable-size data,
1207 so they will always have a PLUS or MINUS according to the
1208 direction of stack growth.)
1209 Even if this function never uses this stack pointer value,
1210 signal handlers do! */
1213 #ifdef STACK_GROWS_DOWNWARD
1215 #else
1217 #endif
1220 }
1221 }
1224 #ifdef EXIT_IGNORE_STACK
1226 || (! FRAME_POINTER_REQUIRED
1227 && ! current_function_calls_alloca
1229 #endif
1230 {
1231 /* If exiting needs the right stack value,
1232 consider the stack pointer live at the end of the function. */
1234 STACK_POINTER_REGNUM);
1236 STACK_POINTER_REGNUM);
1237 }
1239 /* Mark the frame pointer is needed at the end of the function. If
1240 we end up eliminating it, it will be removed from the live list
1241 of each basic block by reload. */
1244 {
1246 FRAME_POINTER_REGNUM);
1248 FRAME_POINTER_REGNUM);
1249 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1250 /* If they are different, also mark the hard frame pointer as live */
1252 HARD_FRAME_POINTER_REGNUM);
1254 HARD_FRAME_POINTER_REGNUM);
1255 #endif
1256 }
1258 /* Mark all global registers and all registers used by the epilogue
1259 as being live at the end of the function since they may be
1260 referenced by our caller. */
1265 #ifdef EPILOGUE_USES
1267 #endif
1268 )
1269 {
1272 }
1274 /* Propagate life info through the basic blocks
1275 around the graph of basic blocks.
1277 This is a relaxation process: each time a new register
1278 is live at the end of the basic block, we must scan the block
1279 to determine which registers are, as a consequence, live at the beginning
1280 of that block. These registers must then be marked live at the ends
1281 of all the blocks that can transfer control to that block.
1282 The process continues until it reaches a fixed point. */
1287 {
1290 {
1296 {
1297 /* Set CONSIDER if this block needs thinking about at all
1298 (that is, if the regs live now at the end of it
1299 are not the same as were live at the end of it when
1300 we last thought about it).
1301 Set must_rescan if it needs to be thought about
1302 instruction by instruction (that is, if any additional
1303 reg that is live at the end now but was not live there before
1304 is one of the significant regs of this basic block). */
1306 EXECUTE_IF_AND_COMPL_IN_REG_SET
1309 {
1312 {
1315 }
1316 });
1317 done:
1320 }
1322 /* The live_at_start of this block may be changing,
1323 so another pass will be required after this one. */
1327 {
1328 /* No complete rescan needed;
1329 just record those variables newly known live at end
1330 as live at start as well. */
1338 }
1339 else
1340 {
1341 /* Update the basic_block_live_at_start
1342 by propagation backwards through the block. */
1351 i);
1352 }
1354 {
1357 /* Update the basic_block_new_live_at_end's of the block
1358 that falls through into this one (if any). */
1364 /* Update the basic_block_new_live_at_end's of
1365 all the blocks that jump to this one. */
1370 {
1374 }
1375 }
1376 #ifdef USE_C_ALLOCA
1378 #endif
1379 }
1381 }
1383 /* The only pseudos that are live at the beginning of the function are
1384 those that were not set anywhere in the function. local-alloc doesn't
1385 know how to handle these correctly, so mark them as not local to any
1386 one basic block. */
1391 {
1393 });
1395 /* Now the life information is accurate.
1396 Make one more pass over each basic block
1397 to delete dead stores, create autoincrement addressing
1398 and record how many times each register is used, is set, or dies.
1400 To save time, we operate directly in basic_block_live_at_end[i],
1401 thus destroying it (in fact, converting it into a copy of
1402 basic_block_live_at_start[i]). This is ok now because
1403 basic_block_live_at_end[i] is no longer used past this point. */
1408 {
1412 #ifdef USE_C_ALLOCA
1414 #endif
1415 }
1417 #if 0
1418 /* Something live during a setjmp should not be put in a register
1419 on certain machines which restore regs from stack frames
1420 rather than from the jmpbuf.
1421 But we don't need to do this for the user's variables, since
1422 ANSI says only volatile variables need this. */
1423 #ifdef LONGJMP_RESTORE_FROM_STACK
1426 {
1429 {
1432 }
1433 });
1434 #endif
1435 #endif
1437 /* We have a problem with any pseudoreg that
1438 lives across the setjmp. ANSI says that if a
1439 user variable does not change in value
1440 between the setjmp and the longjmp, then the longjmp preserves it.
1441 This includes longjmp from a place where the pseudo appears dead.
1442 (In principle, the value still exists if it is in scope.)
1443 If the pseudo goes in a hard reg, some other value may occupy
1444 that hard reg where this pseudo is dead, thus clobbering the pseudo.
1445 Conclusion: such a pseudo must not go in a hard reg. */
1448 {
1450 {
1453 }
1454 });
1465 }
1466 \f
1467 /* Subroutines of life analysis. */
1469 /* Allocate the permanent data structures that represent the results
1470 of life analysis. Not static since used also for stupid life analysis. */
1472 void
1474 {
1477 /* Recalculate the register space, in case it has grown. Old style
1478 vector oriented regsets would set regset_{size,bytes} here also. */
1481 /* Because both reg_scan and flow_analysis want to set up the REG_N_SETS
1482 information, explicitly reset it here. The allocation should have
1483 already happened on the previous reg_scan pass. Make sure in case
1484 some more registers were allocated. */
1488 basic_block_live_at_start
1491 function_obstack);
1495 }
1497 /* Make each element of VECTOR point at a regset. The vector has
1498 NELTS elements, and space is allocated from the ALLOC_OBSTACK
1499 obstack. */
1501 static void
1506 {
1510 {
1513 }
1514 }
1516 /* Release any additional space allocated for each element of VECTOR point
1517 other than the regset header itself. The vector has NELTS elements. */
1519 void
1523 {
1528 }
1530 /* Compute the registers live at the beginning of a basic block
1531 from those live at the end.
1533 When called, OLD contains those live at the end.
1534 On return, it contains those live at the beginning.
1535 FIRST and LAST are the first and last insns of the basic block.
1537 FINAL is nonzero if we are doing the final pass which is not
1538 for computing the life info (since that has already been done)
1539 but for acting on it. On this pass, we delete dead stores,
1540 set up the logical links and dead-variables lists of instructions,
1541 and merge instructions for autoincrement and autodecrement addresses.
1543 SIGNIFICANT is nonzero only the first time for each basic block.
1544 If it is nonzero, it points to a regset in which we store
1545 a 1 for each register that is set within the block.
1547 BNUM is the number of the basic block. */
1549 static void
1552 rtx first;
1553 rtx last;
1555 regset significant;
1557 {
1559 rtx prev;
1560 regset live;
1561 regset dead;
1563 /* The following variables are used only if FINAL is nonzero. */
1564 /* This vector gets one element for each reg that has been live
1565 at any point in the basic block that has been scanned so far.
1566 SOMETIMES_MAX says how many elements are in use so far. */
1569 /* This regset has 1 for each reg that we have seen live so far.
1570 It and REGS_SOMETIMES_LIVE are updated together. */
1571 regset maxlive;
1573 /* The loop depth may change in the middle of a basic block. Since we
1574 scan from end to beginning, we start with the depth at the end of the
1575 current basic block, and adjust as we pass ends and starts of loops. */
1584 /* Include any notes at the end of the block in the scan.
1585 This is in case the block ends with a call to setjmp. */
1588 {
1589 /* Look for loop boundaries, we are going forward here. */
1592 loop_depth++;
1594 loop_depth--;
1595 }
1598 {
1606 /* Process the regs live at the end of the block.
1607 Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
1608 Also mark them as not local to any one basic block. */
1610 {
1613 sometimes_max++;
1614 });
1615 }
1617 /* Scan the block an insn at a time from end to beginning. */
1620 {
1624 {
1625 /* Look for loop boundaries, remembering that we are going
1626 backwards. */
1628 loop_depth++;
1630 loop_depth--;
1632 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
1633 Abort now rather than setting register status incorrectly. */
1637 /* If this is a call to `setjmp' et al,
1638 warn if any non-volatile datum is live. */
1642 }
1644 /* Update the life-status of regs for this insn.
1645 First DEAD gets which regs are set in this insn
1646 then LIVE gets which regs are used in this insn.
1647 Then the regs live before the insn
1648 are those live after, with DEAD regs turned off,
1649 and then LIVE regs turned on. */
1652 {
1655 int insn_is_dead
1657 /* Don't delete something that refers to volatile storage! */
1659 int libcall_is_dead
1663 /* If an instruction consists of just dead store(s) on final pass,
1664 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1665 We could really delete it with delete_insn, but that
1666 can cause trouble for first or last insn in a basic block. */
1668 {
1673 /* CC0 is now known to be dead. Either this insn used it,
1674 in which case it doesn't anymore, or clobbered it,
1675 so the next insn can't use it. */
1678 /* If this insn is copying the return value from a library call,
1679 delete the entire library call. */
1681 {
1687 {
1692 }
1693 }
1695 }
1700 /* See if this is an increment or decrement that can be
1701 merged into a following memory address. */
1702 #ifdef AUTO_INC_DEC
1703 {
1706 /* Does this instruction increment or decrement a register? */
1713 /* Ok, look for a following memory ref we can combine with.
1714 If one is found, change the memory ref to a PRE_INC
1715 or PRE_DEC, cancel this insn, and return 1.
1716 Return 0 if nothing has been done. */
1719 }
1722 /* If this is not the final pass, and this insn is copying the
1723 value of a library call and it's dead, don't scan the
1724 insns that perform the library call, so that the call's
1725 arguments are not marked live. */
1727 {
1728 /* Mark the dest reg as `significant'. */
1733 }
1739 /* We have an insn to pop a constant amount off the stack.
1740 (Such insns use PLUS regardless of the direction of the stack,
1741 and any insn to adjust the stack by a constant is always a pop.)
1742 These insns, if not dead stores, have no effect on life. */
1743 ;
1744 else
1745 {
1746 /* LIVE gets the regs used in INSN;
1747 DEAD gets those set by it. Dead insns don't make anything
1748 live. */
1753 /* If an insn doesn't use CC0, it becomes dead since we
1754 assume that every insn clobbers it. So show it dead here;
1755 mark_used_regs will set it live if it is referenced. */
1761 /* Sometimes we may have inserted something before INSN (such as
1762 a move) when we make an auto-inc. So ensure we will scan
1763 those insns. */
1764 #ifdef AUTO_INC_DEC
1766 #endif
1769 {
1772 rtx note;
1775 note;
1781 /* Each call clobbers all call-clobbered regs that are not
1782 global or fixed. Note that the function-value reg is a
1783 call-clobbered reg, and mark_set_regs has already had
1784 a chance to handle it. */
1791 /* The stack ptr is used (honorarily) by a CALL insn. */
1794 /* Calls may also reference any of the global registers,
1795 so they are made live. */
1802 /* Calls also clobber memory. */
1804 }
1806 /* Update OLD for the registers used or set. */
1811 {
1812 /* Any regs live at the time of a call instruction
1813 must not go in a register clobbered by calls.
1814 Find all regs now live and record this for them. */
1821 }
1822 }
1824 /* On final pass, add any additional sometimes-live regs
1825 into MAXLIVE and REGS_SOMETIMES_LIVE.
1826 Also update counts of how many insns each reg is live at. */
1829 {
1833 EXECUTE_IF_AND_COMPL_IN_REG_SET
1835 {
1838 });
1842 {
1846 }
1847 }
1848 }
1849 flushed: ;
1852 }
1861 }
1862 \f
1863 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1864 (SET expressions whose destinations are registers dead after the insn).
1865 NEEDED is the regset that says which regs are alive after the insn.
1867 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL. */
1869 static int
1871 rtx x;
1872 regset needed;
1874 {
1877 /* If setting something that's a reg or part of one,
1878 see if that register's altered value will be live. */
1881 {
1884 /* A SET that is a subroutine call cannot be dead. */
1888 #ifdef HAVE_cc0
1891 #endif
1902 {
1905 /* Don't delete insns to set global regs. */
1907 /* Make sure insns to set frame pointer aren't deleted. */
1909 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1911 #endif
1912 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1913 /* Make sure insns to set arg pointer are never deleted
1914 (if the arg pointer isn't fixed, there will be a USE for
1915 it, so we can treat it normally). */
1917 #endif
1921 /* If this is a hard register, verify that subsequent words are
1922 not needed. */
1924 {
1930 }
1933 }
1934 }
1936 /* If performing several activities,
1937 insn is dead if each activity is individually dead.
1938 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1939 that's inside a PARALLEL doesn't make the insn worth keeping. */
1941 {
1951 }
1953 /* A CLOBBER of a pseudo-register that is dead serves no purpose. That
1954 is not necessarily true for hard registers. */
1960 /* We do not check other CLOBBER or USE here. An insn consisting of just
1961 a CLOBBER or just a USE should not be deleted. */
1963 }
1965 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
1966 return 1 if the entire library call is dead.
1967 This is true if X copies a register (hard or pseudo)
1968 and if the hard return reg of the call insn is dead.
1969 (The caller should have tested the destination of X already for death.)
1971 If this insn doesn't just copy a register, then we don't
1972 have an ordinary libcall. In that case, cse could not have
1973 managed to substitute the source for the dest later on,
1974 so we can assume the libcall is dead.
1976 NEEDED is the bit vector of pseudoregs live before this insn.
1977 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
1979 static int
1981 rtx x;
1982 regset needed;
1983 rtx note;
1984 rtx insn;
1985 {
1989 {
1992 {
1996 /* Find the call insn. */
2000 /* If there is none, do nothing special,
2001 since ordinary death handling can understand these insns. */
2005 /* See if the hard reg holding the value is dead.
2006 If this is a PARALLEL, find the call within it. */
2009 {
2015 /* This may be a library call that is returning a value
2016 via invisible pointer. Do nothing special, since
2017 ordinary death handling can understand these insns. */
2022 }
2025 }
2026 }
2028 }
2030 /* Return 1 if register REGNO was used before it was set.
2031 In other words, if it is live at function entry.
2032 Don't count global register variables or variables in registers
2033 that can be used for function arg passing, though. */
2035 int
2038 {
2045 }
2047 /* 1 if register REGNO was alive at a place where `setjmp' was called
2048 and was set more than once or is an argument.
2049 Such regs may be clobbered by `longjmp'. */
2051 int
2054 {
2061 }
2062 \f
2063 /* Process the registers that are set within X.
2064 Their bits are set to 1 in the regset DEAD,
2065 because they are dead prior to this insn.
2067 If INSN is nonzero, it is the insn being processed
2068 and the fact that it is nonzero implies this is the FINAL pass
2069 in propagate_block. In this case, various info about register
2070 usage is stored, LOG_LINKS fields of insns are set up. */
2072 static void
2074 regset needed;
2075 regset dead;
2076 rtx x;
2077 rtx insn;
2078 regset significant;
2079 {
2085 {
2088 {
2092 }
2093 }
2094 }
2096 /* Process a single SET rtx, X. */
2098 static void
2100 regset needed;
2101 regset dead;
2102 rtx x;
2103 rtx insn;
2104 regset significant;
2105 {
2109 /* Modifying just one hardware register of a multi-reg value
2110 or just a byte field of a register
2111 does not mean the value from before this insn is now dead.
2112 But it does mean liveness of that register at the end of the block
2113 is significant.
2115 Within mark_set_1, however, we treat it as if the register is
2116 indeed modified. mark_used_regs will, however, also treat this
2117 register as being used. Thus, we treat these insns as setting a
2118 new value for the register as a function of its old value. This
2119 cases LOG_LINKS to be made appropriately and this will help combine. */
2126 /* If we are writing into memory or into a register mentioned in the
2127 address of the last thing stored into memory, show we don't know
2128 what the last store was. If we are writing memory, save the address
2129 unless it is volatile. */
2136 /* There are no REG_INC notes for SP, so we can't assume we'll see
2137 everything that invalidates it. To be safe, don't eliminate any
2138 stores though SP; none of them should be redundant anyway. */
2144 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2146 #endif
2147 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2149 #endif
2151 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
2152 {
2156 /* Mark it as a significant register for this basic block. */
2160 /* Mark it as dead before this insn. */
2163 /* A hard reg in a wide mode may really be multiple registers.
2164 If so, mark all of them just like the first. */
2166 {
2169 /* Nothing below is needed for the stack pointer; get out asap.
2170 Eg, log links aren't needed, since combine won't use them. */
2176 {
2185 }
2186 }
2187 /* Additional data to record if this is the final pass. */
2189 {
2193 /* If this is a hard reg, record this function uses the reg. */
2196 {
2201 {
2202 /* The next use is no longer "next", since a store
2203 intervenes. */
2208 }
2209 }
2210 else
2211 {
2212 /* The next use is no longer "next", since a store
2213 intervenes. */
2216 /* Keep track of which basic blocks each reg appears in. */
2223 /* Count (weighted) references, stores, etc. This counts a
2224 register twice if it is modified, but that is correct. */
2229 /* The insns where a reg is live are normally counted
2230 elsewhere, but we want the count to include the insn
2231 where the reg is set, and the normal counting mechanism
2232 would not count it. */
2234 }
2237 {
2238 /* Make a logical link from the next following insn
2239 that uses this register, back to this insn.
2240 The following insns have already been processed.
2242 We don't build a LOG_LINK for hard registers containing
2243 in ASM_OPERANDs. If these registers get replaced,
2244 we might wind up changing the semantics of the insn,
2245 even if reload can make what appear to be valid assignments
2246 later. */
2252 }
2254 {
2255 /* Note that dead stores have already been deleted when possible
2256 If we get here, we have found a dead store that cannot
2257 be eliminated (because the same insn does something useful).
2258 Indicate this by marking the reg being set as dying here. */
2262 }
2263 else
2264 {
2265 /* This is a case where we have a multi-word hard register
2266 and some, but not all, of the words of the register are
2267 needed in subsequent insns. Write REG_UNUSED notes
2268 for those parts that were not needed. This case should
2269 be rare. */
2281 }
2282 }
2283 }
2287 /* If this is the last pass and this is a SCRATCH, show it will be dying
2288 here and count it. */
2290 {
2293 num_scratch++;
2294 }
2295 }
2296 \f
2297 #ifdef AUTO_INC_DEC
2299 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
2300 reference. */
2302 static void
2304 regset needed;
2305 rtx x;
2306 rtx insn;
2307 {
2310 rtx set;
2312 /* Here we detect use of an index register which might be good for
2313 postincrement, postdecrement, preincrement, or predecrement. */
2319 {
2322 rtx use;
2323 rtx incr;
2326 /* Is the next use an increment that might make auto-increment? */
2331 /* Can't add side effects to jumps; if reg is spilled and
2332 reloaded, there's no way to store back the altered value. */
2338 #ifdef HAVE_POST_INCREMENT
2340 #endif
2341 #ifdef HAVE_POST_DECREMENT
2343 #endif
2344 #ifdef HAVE_PRE_INCREMENT
2346 #endif
2347 #ifdef HAVE_PRE_DECREMENT
2349 #endif
2350 )
2351 /* Make sure this reg appears only once in this insn. */
2354 {
2361 {
2362 /* This is the simple case. Try to make the auto-inc. If
2363 we can't, we are done. Otherwise, we will do any
2364 needed updates below. */
2369 }
2371 /* PREV_INSN used here to check the semi-open interval
2372 [insn,incr). */
2374 /* We must also check for sets of q as q may be
2375 a call clobbered hard register and there may
2376 be a call between PREV_INSN (insn) and incr. */
2378 {
2379 /* We have *p followed sometime later by q = p+size.
2380 Both p and q must be live afterward,
2381 and q is not used between INSN and it's assignment.
2382 Change it to q = p, ...*q..., q = q+size.
2383 Then fall into the usual case. */
2391 /* If anything in INSNS have UID's that don't fit within the
2392 extra space we allocate earlier, we can't make this auto-inc.
2393 This should never happen. */
2395 {
2399 }
2401 /* If we can't make the auto-inc, or can't make the
2402 replacement into Y, exit. There's no point in making
2403 the change below if we can't do the auto-inc and doing
2404 so is not correct in the pre-inc case. */
2413 /* We now know we'll be doing this change, so emit the
2414 new insn(s) and do the updates. */
2420 /* INCR will become a NOTE and INSN won't contain a
2421 use of ADDR. If a use of ADDR was just placed in
2422 the insn before INSN, make that the next use.
2423 Otherwise, invalidate it. */
2428 else
2434 /* REGNO is now used in INCR which is below INSN, but
2435 it previously wasn't live here. If we don't mark
2436 it as needed, we'll put a REG_DEAD note for it
2437 on this insn, which is incorrect. */
2440 /* If there are any calls between INSN and INCR, show
2441 that REGNO now crosses them. */
2445 }
2446 else
2449 /* If we haven't returned, it means we were able to make the
2450 auto-inc, so update the status. First, record that this insn
2451 has an implicit side effect. */
2456 /* Modify the old increment-insn to simply copy
2457 the already-incremented value of our register. */
2461 /* If that makes it a no-op (copying the register into itself) delete
2462 it so it won't appear to be a "use" and a "set" of this
2463 register. */
2465 {
2469 }
2472 {
2473 /* Count an extra reference to the reg. When a reg is
2474 incremented, spilling it is worse, so we want to make
2475 that less likely. */
2478 /* Count the increment as a setting of the register,
2479 even though it isn't a SET in rtl. */
2481 }
2482 }
2483 }
2484 }
2486 \f
2487 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
2488 This is done assuming the registers needed from X
2489 are those that have 1-bits in NEEDED.
2491 On the final pass, FINAL is 1. This means try for autoincrement
2492 and count the uses and deaths of each pseudo-reg.
2494 INSN is the containing instruction. If INSN is dead, this function is not
2495 called. */
2497 static void
2499 regset needed;
2500 regset live;
2501 rtx x;
2503 rtx insn;
2504 {
2509 retry:
2512 {
2524 #ifdef HAVE_cc0
2528 #endif
2531 /* If we are clobbering a MEM, mark any registers inside the address
2532 as being used. */
2538 /* Invalidate the data for the last MEM stored, but only if MEM is
2539 something that can be stored into. */
2543 else
2546 #ifdef AUTO_INC_DEC
2549 #endif
2559 /* While we're here, optimize this case. */
2562 /* In case the SUBREG is not of a register, don't optimize */
2564 {
2567 }
2569 /* ... fall through ... */
2572 /* See a register other than being set
2573 => mark it as needed. */
2576 {
2582 /* A hard reg in a wide mode may really be multiple registers.
2583 If so, mark all of them just like the first. */
2585 {
2588 /* For stack ptr or fixed arg pointer,
2589 nothing below can be necessary, so waste no more time. */
2591 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2593 #endif
2594 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2596 #endif
2598 {
2599 /* If this is a register we are going to try to eliminate,
2600 don't mark it live here. If we are successful in
2601 eliminating it, it need not be live unless it is used for
2602 pseudos, in which case it will have been set live when
2603 it was allocated to the pseudos. If the register will not
2604 be eliminated, reload will set it live at that point. */
2609 }
2610 /* No death notes for global register variables;
2611 their values are live after this function exits. */
2613 {
2617 }
2621 {
2628 }
2629 }
2631 {
2632 /* Record where each reg is used, so when the reg
2633 is set we know the next insn that uses it. */
2638 {
2639 /* If a hard reg is being used,
2640 record that this function does use it. */
2645 do
2648 }
2649 else
2650 {
2651 /* Keep track of which basic block each reg appears in. */
2660 /* Count (weighted) number of uses of each reg. */
2663 }
2665 /* Record and count the insns in which a reg dies.
2666 If it is used in this insn and was dead below the insn
2667 then it dies in this insn. If it was set in this insn,
2668 we do not make a REG_DEAD note; likewise if we already
2669 made such a note. */
2673 #if 0
2675 #endif
2676 )
2677 {
2678 /* Check for the case where the register dying partially
2679 overlaps the register set by this insn. */
2682 {
2686 }
2688 /* If none of the words in X is needed, make a REG_DEAD
2689 note. Otherwise, we must make partial REG_DEAD notes. */
2691 {
2695 }
2696 else
2697 {
2700 /* Don't make a REG_DEAD note for a part of a register
2701 that is set in the insn. */
2712 }
2713 }
2714 }
2715 }
2719 {
2723 /* If storing into MEM, don't show it as being used. But do
2724 show the address as being used. */
2726 {
2727 #ifdef AUTO_INC_DEC
2730 #endif
2734 }
2736 /* Storing in STRICT_LOW_PART is like storing in a reg
2737 in that this SET might be dead, so ignore it in TESTREG.
2738 but in some other ways it is like using the reg.
2740 Storing in a SUBREG or a bit field is like storing the entire
2741 register in that if the register's value is not used
2742 then this SET is not needed. */
2747 {
2755 /* Modifying a single register in an alternate mode
2756 does not use any of the old value. But these other
2757 ways of storing in a register do use the old value. */
2760 ;
2761 else
2765 }
2767 /* If this is a store into a register,
2768 recursively scan the value being stored. */
2772 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2774 #endif
2775 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2777 #endif
2778 )
2779 /* We used to exclude global_regs here, but that seems wrong.
2780 Storing in them is like storing in mem. */
2781 {
2786 }
2787 }
2791 /* If exiting needs the right stack value, consider this insn as
2792 using the stack pointer. In any event, consider it as using
2793 all global registers and all registers used by return. */
2795 #ifdef EXIT_IGNORE_STACK
2797 || (! FRAME_POINTER_REQUIRED
2798 && ! current_function_calls_alloca
2800 #endif
2805 #ifdef EPILOGUE_USES
2807 #endif
2808 )
2814 }
2816 /* Recursively scan the operands of this expression. */
2818 {
2823 {
2825 {
2826 /* Tail recursive case: save a function call level. */
2828 {
2831 }
2833 }
2835 {
2839 }
2840 }
2841 }
2842 }
2843 \f
2844 #ifdef AUTO_INC_DEC
2846 static int
2848 rtx insn;
2849 {
2850 /* Find the next use of this reg. If in same basic block,
2851 make it do pre-increment or pre-decrement if appropriate. */
2859 /* Don't do this if the reg dies, or gets set in y; a standard addressing
2860 mode would be better. */
2863 {
2864 /* We have found a suitable auto-increment
2865 and already changed insn Y to do it.
2866 So flush this increment-instruction. */
2870 /* Count a reference to this reg for the increment
2871 insn we are deleting. When a reg is incremented.
2872 spilling it is worse, so we want to make that
2873 less likely. */
2875 {
2878 }
2880 }
2882 }
2884 /* Try to change INSN so that it does pre-increment or pre-decrement
2885 addressing on register REG in order to add AMOUNT to REG.
2886 AMOUNT is negative for pre-decrement.
2887 Returns 1 if the change could be made.
2888 This checks all about the validity of the result of modifying INSN. */
2890 static int
2893 HOST_WIDE_INT amount;
2894 {
2897 /* Nonzero if we can try to make a pre-increment or pre-decrement.
2898 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
2900 /* Nonzero if we can try to make a post-increment or post-decrement.
2901 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
2902 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
2903 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
2906 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
2909 /* From the sign of increment, see which possibilities are conceivable
2910 on this target machine. */
2911 #ifdef HAVE_PRE_INCREMENT
2914 #endif
2915 #ifdef HAVE_POST_INCREMENT
2918 #endif
2920 #ifdef HAVE_PRE_DECREMENT
2923 #endif
2924 #ifdef HAVE_POST_DECREMENT
2927 #endif
2932 /* It is not safe to add a side effect to a jump insn
2933 because if the incremented register is spilled and must be reloaded
2934 there would be no way to store the incremented value back in memory. */
2943 {
2946 }
2954 /* See if this combination of instruction and addressing mode exists. */
2962 /* Record that this insn now has an implicit side effect on X. */
2965 }
2968 \f
2969 /* Find the place in the rtx X where REG is used as a memory address.
2970 Return the MEM rtx that so uses it.
2971 If PLUSCONST is nonzero, search instead for a memory address equivalent to
2972 (plus REG (const_int PLUSCONST)).
2974 If such an address does not appear, return 0.
2975 If REG appears more than once, or is used other than in such an address,
2976 return (rtx)1. */
2978 rtx
2981 rtx reg;
2982 HOST_WIDE_INT plusconst;
2983 {
3000 {
3001 /* If REG occurs inside a MEM used in a bit-field reference,
3002 that is unacceptable. */
3005 }
3011 {
3013 {
3019 }
3021 {
3024 {
3030 }
3031 }
3032 }
3035 }
3036 \f
3037 /* Write information about registers and basic blocks into FILE.
3038 This is part of making a debugging dump. */
3040 void
3043 {
3051 {
3073 {
3078 else
3082 }
3086 }
3089 {
3093 i,
3096 /* The control flow graph's storage is freed
3097 now when flow_analysis returns.
3098 Don't try to print it if it is gone. */
3100 {
3107 {
3110 }
3113 }
3119 }
3121 }
3123 \f
3124 /* Like print_rtl, but also print out live information for the start of each
3125 basic block. */
3127 void
3130 rtx rtx_first;
3131 {
3137 else
3138 {
3147 {
3150 }
3153 {
3154 rtx x;
3158 {
3164 }
3165 }
3168 {
3170 {
3172 bb);
3175 {
3180 });
3182 }
3197 }
3198 }
3199 }
3201 \f
3202 /* Integer list support. */
3204 /* Allocate a node from list *HEAD_PTR. */
3206 static int_list_ptr
3209 {
3213 {
3218 }
3222 }
3224 /* Pointer to head of predecessor/successor block list. */
3227 /* Add a new node to integer list LIST with value VAL.
3228 LIST is a pointer to a list object to allow for different implementations.
3229 If *LIST is initially NULL, the list is empty.
3230 The caller must not care whether the element is added to the front or
3231 to the end of the list (to allow for different implementations). */
3233 static int_list_ptr
3238 {
3245 }
3247 /* Free the blocks of lists at BLK_LIST. */
3249 void
3252 {
3256 {
3259 }
3261 /* Mark list as empty for the next function we compile. */
3263 }
3264 \f
3265 /* Predecessor/successor computation. */
3267 /* Mark PRED_BB a precessor of SUCC_BB,
3268 and conversely SUCC_BB a successor of PRED_BB. */
3270 static void
3278 {
3280 {
3283 }
3285 {
3288 }
3289 }
3291 /* Compute the predecessors and successors for each block. */
3292 void
3298 {
3306 /* This routine can be called after life analysis; in that case
3307 basic_block_drops_in and uid_block_number will not be available
3308 and we must recompute their values. */
3310 {
3318 /* Scan each basic block setting basic_block_drops_in and
3319 uid_block_number as needed. */
3321 {
3326 else
3329 /* Look backwards from the start of this block. Stop if we
3330 hit the start of the function or the end of a previous
3331 block. Don't walk backwards through blocks that are just
3332 deleted insns! */
3336 ;
3338 /* Never set basic_block_drops_in for the first block. It is
3339 implicit.
3341 If we stopped on anything other than a BARRIER, then this
3342 block drops in. */
3348 {
3353 }
3354 }
3355 }
3358 {
3359 rtx head;
3360 rtx jump;
3368 {
3375 }
3378 /* If this is a RETURN insn or a conditional jump in the last
3379 basic block, or a non-jump insn in the last basic block, then
3380 this block reaches the exit block. */
3390 }
3395 /* If we allocated any variables in temporary storage, clear out the
3396 pointer to the local storage to avoid dangling pointers. */
3398 {
3402 }
3403 }
3405 void
3410 {
3412 int_list_ptr p;
3416 {
3421 {
3425 else
3427 }
3431 {
3435 else
3437 }
3439 }
3441 }
3443 void
3446 sbitmap bmap;
3447 {
3454 {
3456 {
3460 }
3461 }
3463 }
3465 void
3471 {
3476 {
3479 }
3481 }
3483 /* Free basic block data storage. */
3485 void
3487 {
3489 }
3490 \f
3491 /* Bitmap manipulation routines. */
3493 /* Allocate a simple bitmap of N_ELMS bits. */
3495 sbitmap
3498 {
3500 sbitmap bmap;
3511 }
3513 /* Allocate a vector of N_VECS bitmaps of N_ELMS bits. */
3515 sbitmap *
3518 {
3528 /* Round up `vector_bytes' to account for the alignment requirements
3529 of an sbitmap. One could allocate the vector-table and set of sbitmaps
3530 separately, but that requires maintaining two pointers or creating
3531 a cover struct to hold both pointers (so our result is still just
3532 one pointer). Neither is a bad idea, but this is simpler for now. */
3533 {
3534 /* Based on DEFAULT_ALIGNMENT computation in obstack.c. */
3538 }
3546 {
3552 }
3555 }
3557 /* Copy sbitmap SRC to DST. */
3559 void
3562 {
3570 }
3572 /* Zero all elements in a bitmap. */
3574 void
3576 sbitmap bmap;
3577 {
3579 }
3581 /* Set to ones all elements in a bitmap. */
3583 void
3585 sbitmap bmap;
3586 {
3588 }
3590 /* Zero a vector of N_VECS bitmaps. */
3592 void
3596 {
3601 }
3603 /* Set to ones a vector of N_VECS bitmaps. */
3605 void
3609 {
3614 }
3616 /* Set DST to be A union (B - C).
3617 DST = A | (B & ~C).
3618 Return non-zero if any change is made. */
3620 int
3623 {
3633 {
3639 }
3641 }
3643 /* Set bitmap DST to the bitwise negation of the bitmap SRC. */
3645 void
3648 {
3655 {
3659 }
3660 }
3662 /* Set the bits in DST to be the difference between the bits
3663 in A and the bits in B. i.e. dst = a - b.
3664 The - operator is implemented as a & (~b). */
3666 void
3669 {
3678 }
3680 /* Set DST to be (A and B)).
3681 Return non-zero if any change is made. */
3683 int
3686 {
3695 {
3701 }
3703 }
3704 /* Set DST to be (A or B)).
3705 Return non-zero if any change is made. */
3707 int
3710 {
3719 {
3725 }
3727 }
3729 /* Set DST to be (A or (B and C)).
3730 Return non-zero if any change is made. */
3732 int
3735 {
3745 {
3751 }
3753 }
3755 /* Set DST to be (A ann (B or C)).
3756 Return non-zero if any change is made. */
3758 int
3761 {
3771 {
3777 }
3779 }
3781 /* Set the bitmap DST to the intersection of SRC of all predecessors or
3782 successors of block number BB (PRED_SUCC says which). */
3784 void
3786 sbitmap dst;
3790 {
3791 int_list_ptr ps;
3797 /* It is possible that there are no predecessors(/successors).
3798 This can happen for example in unreachable code. */
3801 {
3802 /* In APL-speak this is the `and' reduction of the empty set and thus
3803 the result is the identity for `and'. */
3806 }
3808 /* Set result to first predecessor/successor. */
3811 {
3816 /* Break out since we're only doing first predecessor. */
3818 }
3822 /* Now do the remaining predecessors/successors. */
3825 {
3838 }
3839 }
3841 /* Set the bitmap DST to the intersection of SRC of all predecessors
3842 of block number BB. */
3844 void
3846 sbitmap dst;
3850 {
3852 }
3854 /* Set the bitmap DST to the intersection of SRC of all successors
3855 of block number BB. */
3857 void
3859 sbitmap dst;
3863 {
3865 }
3867 /* Set the bitmap DST to the union of SRC of all predecessors/successors of
3868 block number BB. */
3870 void
3872 sbitmap dst;
3876 {
3877 int_list_ptr ps;
3883 /* It is possible that there are no predecessors(/successors).
3884 This can happen for example in unreachable code. */
3887 {
3888 /* In APL-speak this is the `or' reduction of the empty set and thus
3889 the result is the identity for `or'. */
3892 }
3894 /* Set result to first predecessor/successor. */
3897 {
3902 /* Break out since we're only doing first predecessor. */
3904 }
3908 /* Now do the remaining predecessors/successors. */
3911 {
3924 }
3925 }
3927 /* Set the bitmap DST to the union of SRC of all predecessors of
3928 block number BB. */
3930 void
3932 sbitmap dst;
3936 {
3938 }
3940 /* Set the bitmap DST to the union of SRC of all predecessors of
3941 block number BB. */
3943 void
3945 sbitmap dst;
3949 {
3951 }
3953 /* Compute dominator relationships. */
3954 void
3960 {
3978 {
3981 {
3994 }
3995 passes++;
3996 }
3999 }