| blob | 8021b4e2c89432e637641a08d6bfda7ea592a0a4 |
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
123 #define obstack_chunk_alloc xmalloc
124 #define obstack_chunk_free free
126 /* The contents of the current function definition are allocated
127 in this obstack, and all are freed at the end of the function.
128 For top-level functions, this is temporary_obstack.
129 Separate obstacks are made for nested functions. */
133 /* List of labels that must never be deleted. */
136 /* Get the basic block number of an insn.
137 This info should not be expected to remain available
138 after the end of life_analysis. */
140 /* This is the limit of the allocated space in the following two arrays. */
144 #define BLOCK_NUM(INSN) uid_block_number[INSN_UID (INSN)]
146 /* This is where the BLOCK_NUM values are really stored.
147 This is set up by find_basic_blocks and used there and in life_analysis,
148 and then freed. */
152 /* INSN_VOLATILE (insn) is 1 if the insn refers to anything volatile. */
154 #define INSN_VOLATILE(INSN) uid_volatile[INSN_UID (INSN)]
157 /* Number of basic blocks in the current function. */
161 /* Maximum register number used in this function, plus one. */
165 /* Maximum number of SCRATCH rtx's used in any basic block of this
166 function. */
170 /* Number of SCRATCH rtx's in the current block. */
174 /* Indexed by n, giving various register information */
178 /* Size of the reg_n_info table. */
182 /* Element N is the next insn that uses (hard or pseudo) register number N
183 within the current basic block; or zero, if there is no such insn.
184 This is valid only during the final backward scan in propagate_block. */
188 /* Size of a regset for the current function,
189 in (1) bytes and (2) elements. */
194 /* Element N is first insn in basic block N.
195 This info lasts until we finish compiling the function. */
199 /* Element N is last insn in basic block N.
200 This info lasts until we finish compiling the function. */
204 /* Element N indicates whether basic block N can be reached through a
205 computed jump. */
209 /* Element N is a regset describing the registers live
210 at the start of basic block N.
211 This info lasts until we finish compiling the function. */
215 /* Regset of regs live when calls to `setjmp'-like functions happen. */
217 regset regs_live_at_setjmp;
219 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
220 that have to go in the same hard reg.
221 The first two regs in the list are a pair, and the next two
222 are another pair, etc. */
223 rtx regs_may_share;
225 /* Element N is nonzero if control can drop into basic block N
226 from the preceding basic block. Freed after life_analysis. */
230 /* Element N is depth within loops of the last insn in basic block number N.
231 Freed after life_analysis. */
235 /* Element N nonzero if basic block N can actually be reached.
236 Vector exists only during find_basic_blocks. */
240 /* Depth within loops of basic block being scanned for lifetime analysis,
241 plus one. This is the weight attached to references to registers. */
245 /* During propagate_block, this is non-zero if the value of CC0 is live. */
249 /* During propagate_block, this contains the last MEM stored into. It
250 is used to eliminate consecutive stores to the same location. */
254 /* Set of registers that may be eliminable. These are handled specially
255 in updating regs_ever_live. */
259 /* Forward declarations */
274 #ifdef AUTO_INC_DEC
278 #endif
286 \f
287 /* Find basic blocks of the current function.
288 F is the first insn of the function and NREGS the number of register numbers
289 in use.
290 LIVE_REACHABLE_P is non-zero if the caller needs all live blocks to
291 be reachable. This turns on a kludge that causes the control flow
292 information to be inaccurate and not suitable for passes like GCSE. */
294 void
296 rtx f;
300 {
306 /* Count the basic blocks. Also find maximum insn uid value used. */
308 {
316 {
318 /* Track when we are inside in LIBCALL block. */
333 i++;
348 }
349 }
353 #ifdef AUTO_INC_DEC
354 /* Leave space for insns life_analysis makes in some cases for auto-inc.
355 These cases are rare, so we don't need too much space. */
357 #endif
359 /* Allocate some tables that last till end of compiling this function
360 and some needed only in find_basic_blocks and life_analysis. */
367 uid_block_number
373 }
375 /* Find all basic blocks of the function whose first insn is F.
376 Store the correct data in the tables that describe the basic blocks,
377 set up the chains of references for each CODE_LABEL, and
378 delete any entire basic blocks that cannot be reached.
380 NONLOCAL_LABEL_LIST is a list of non-local labels in the function.
381 Blocks that are otherwise unreachable may be reachable with a non-local
382 goto.
383 LIVE_REACHABLE_P is non-zero if the caller needs all live blocks to
384 be reachable. This turns on a kludge that causes the control flow
385 information to be inaccurate and not suitable for passes like GCSE. */
387 static void
391 {
396 /* An array of CODE_LABELs, indexed by UID for the start of the active
397 EH handler for each insn in F. */
400 /* List of label_refs to all labels whose addresses are taken
401 and used as data. */
402 rtx label_value_list;
412 restart:
423 /* Initialize with just block 0 reachable and no blocks marked. */
427 /* Initialize the ref chain of each label to 0. Record where all the
428 blocks start and end and their depth in loops. For each insn, record
429 the block it is in. Also mark as reachable any blocks headed by labels
430 that must not be deleted. */
434 {
436 /* Track when we are inside in LIBCALL block. */
443 {
445 depth++;
447 depth--;
448 }
450 /* A basic block starts at label, or after something that can jump. */
458 {
464 {
466 /* Any label that cannot be deleted
467 is considered to start a reachable block. */
470 }
471 }
474 {
477 }
480 {
481 /* Make a list of all labels referred to other than by jumps. */
485 label_value_list);
486 }
488 /* Keep a lifo list of the currently active exception notes. */
490 {
492 {
496 else
500 }
503 }
504 /* If we encounter a CALL_INSN, note which exception handler it
505 might pass control to.
507 If doing asynchronous exceptions, record the active EH handler
508 for every insn, since most insns can throw. */
510 && (asynchronous_exceptions
523 }
525 /* During the second pass, `n_basic_blocks' is only an upper bound.
526 Only perform the sanity check for the first pass, and on the second
527 pass ensure `n_basic_blocks' is set to the correct value. */
532 /* Record which basic blocks control can drop in to. */
535 {
538 ;
541 }
543 /* Now find which basic blocks can actually be reached
544 and put all jump insns' LABEL_REFS onto the ref-chains
545 of their target labels. */
548 {
552 /* Pass over all blocks, marking each block that is reachable
553 and has not yet been marked.
554 Keep doing this until, in one pass, no blocks have been marked.
555 Then blocks_live and blocks_marked are identical and correct.
556 In addition, all jumps actually reachable have been marked. */
559 {
563 {
572 /* If we have any forced labels, mark them as potentially
573 reachable from this block. */
579 /* Now scan the insns for this block, we may need to make
580 edges for some of them to various non-obvious locations
581 (exception handlers, nonlocal labels, etc). */
585 {
587 {
589 /* References to labels in non-jumping insns have
590 REG_LABEL notes attached to them.
592 This can happen for computed gotos; we don't care
593 about them here since the values are also on the
594 label_value_list and will be marked live if we find
595 a live computed goto.
597 This can also happen when we take the address of
598 a label to pass as an argument to __throw. Note
599 throw only uses the value to determine what handler
600 should be called -- ie the label is not used as
601 a jump target, it just marks regions in the code.
603 In theory we should be able to ignore the REG_LABEL
604 notes, but we have to make sure that the label and
605 associated insns aren't marked dead, so we make
606 the block in question live and create an edge from
607 this insn to the label. This is not strictly
608 correct, but it is close enough for now. */
610 note;
612 {
614 {
619 }
620 }
622 /* If this is a computed jump, then mark it as
623 reaching everything on the label_value_list
624 and forced_labels list. */
626 {
629 {
635 }
638 {
644 }
645 }
647 /* If this is a CALL_INSN, then mark it as reaching
648 the active EH handler for this CALL_INSN. If
649 we're handling asynchronous exceptions mark every
650 insn as reaching the active EH handler.
652 Also mark the CALL_INSN as reaching any nonlocal
653 goto sites. */
657 NULL_RTX)))
658 {
660 {
666 {
671 }
672 }
674 {
676 x;
681 }
682 /* ??? This could be made smarter:
683 in some cases it's possible to tell that
684 certain calls will not do a nonlocal goto.
686 For example, if the nested functions that
687 do the nonlocal gotos do not have their
688 addresses taken, then only calls to those
689 functions or to other nested functions that
690 use them could possibly do nonlocal gotos. */
691 }
692 }
693 }
694 }
695 }
697 /* This should never happen. If it does that means we've computed an
698 incorrect flow graph, which can lead to aborts/crashes later in the
699 compiler or incorrect code generation.
701 We used to try and continue here, but that's just asking for trouble
702 later during the compile or at runtime. It's easier to debug the
703 problem here than later! */
710 /* Now delete the code for any basic blocks that can't be reached.
711 They can occur because jump_optimize does not recognize
712 unreachable loops as unreachable. */
717 {
718 deleted++;
720 /* Delete the insns in a (non-live) block. We physically delete
721 every non-note insn except the start and end (so
722 basic_block_head/end needn't be updated), we turn the latter
723 into NOTE_INSN_DELETED notes.
724 We use to "delete" the insns by turning them into notes, but
725 we may be deleting lots of insns that subsequent passes would
726 otherwise have to process. Secondly, lots of deleted blocks in
727 a row can really slow down propagate_block since it will
728 otherwise process insn-turned-notes multiple times when it
729 looks for loop begin/end notes. */
731 {
732 /* It would be quicker to delete all of these with a single
733 unchaining, rather than one at a time, but we need to keep
734 the NOTE's. */
737 {
742 else
744 }
745 }
748 {
749 /* Turn the head into a deleted insn note. */
753 /* If the head of this block is a CODE_LABEL, then it might
754 be the label for an exception handler which can't be
755 reached.
757 We need to remove the label from the exception_handler_label
758 list and remove the associated NOTE_EH_REGION_BEG and
759 NOTE_EH_REGION_END notes. */
761 {
765 {
767 {
768 /* Found a match, splice this label out of the
769 EH label list. */
774 /* Remove the handler from all regions */
778 }
780 }
781 }
786 }
789 {
790 /* Turn the tail into a deleted insn note. */
796 }
797 /* BARRIERs are between basic blocks, not part of one.
798 Delete a BARRIER if the preceding jump is deleted.
799 We cannot alter a BARRIER into a NOTE
800 because it is too short; but we can really delete
801 it because it is not part of a basic block. */
806 /* Each time we delete some basic blocks,
807 see if there is a jump around them that is
808 being turned into a no-op. If so, delete it. */
811 {
815 {
816 rtx label;
819 /* An unconditional jump is the only possibility
820 we must check for, since a conditional one
821 would make these blocks live. */
826 {
829 /* The deleted blocks still show up in the cfg,
830 so we must set basic_block_drops_in for blocks
831 I to J inclusive to keep the cfg accurate. */
841 }
843 }
844 }
845 }
846 /* If we deleted an exception handler, we may have EH region
847 begin/end blocks to remove as well. */
851 {
854 {
856 /* A NULL handler indicates a region is no longer needed */
858 {
861 }
862 }
863 }
865 /* There are pathological cases where one function calling hundreds of
866 nested inline functions can generate lots and lots of unreachable
867 blocks that jump can't delete. Since we don't use sparse matrices
868 a lot of memory will be needed to compile such functions.
869 Implementing sparse matrices is a fair bit of work and it is not
870 clear that they win more than they lose (we don't want to
871 unnecessarily slow down compilation of normal code). By making
872 another pass for the pathological case, we can greatly speed up
873 their compilation without hurting normal code. This works because
874 all the insns in the unreachable blocks have either been deleted or
875 turned into notes.
876 Note that we're talking about reducing memory usage by 10's of
877 megabytes and reducing compilation time by several minutes. */
878 /* ??? The choice of when to make another pass is a bit arbitrary,
879 and was derived from empirical data. */
882 {
883 pass++;
885 /* `n_basic_blocks' may not be correct at this point: two previously
886 separate blocks may now be merged. That's ok though as we
887 recalculate it during the second pass. It certainly can't be
888 any larger than the current value. */
890 }
891 }
892 }
894 /* Record INSN's block number as BB. */
896 void
898 rtx insn;
900 {
902 {
903 /* Add one-eighth the size so we don't keep calling xrealloc. */
907 }
909 }
911 \f
912 /* Subroutines of find_basic_blocks. */
914 /* Check expression X for label references;
915 if one is found, add INSN to the label's chain of references.
917 CHECKDUP means check for and avoid creating duplicate references
918 from the same insn. Such duplicates do no serious harm but
919 can slow life analysis. CHECKDUP is set only when duplicates
920 are likely. */
922 static void
926 {
931 /* We can be called with NULL when scanning label_value_list. */
937 {
942 /* If the label was never emitted, this insn is junk,
943 but avoid a crash trying to refer to BLOCK_NUM (label).
944 This can happen as a result of a syntax error
945 and a diagnostic has already been printed. */
949 /* if CHECKDUP is set, check for duplicate ref from same insn
950 and don't insert. */
959 }
963 {
967 {
971 }
972 }
973 }
975 /* Delete INSN by patching it out.
976 Return the next insn. */
978 static rtx
980 rtx insn;
981 {
982 /* ??? For the moment we assume we don't have to watch for NULLs here
983 since the start/end of basic blocks aren't deleted like this. */
987 }
988 \f
989 /* Perform data flow analysis.
990 F is the first insn of the function and NREGS the number of register numbers
991 in use. */
993 void
995 rtx f;
998 {
999 #ifdef ELIMINABLE_REGS
1002 #endif
1004 /* Record which registers will be eliminated. We use this in
1005 mark_used_regs. */
1009 #ifdef ELIMINABLE_REGS
1012 #else
1014 #endif
1021 }
1023 /* Free the variables allocated by find_basic_blocks.
1025 KEEP_HEAD_END_P is non-zero if basic_block_head and basic_block_end
1026 are not to be freed. */
1028 void
1031 {
1033 {
1035 /* Tell dump_flow_info this isn't available anymore. */
1037 }
1039 {
1042 }
1044 {
1047 }
1049 {
1052 }
1055 {
1060 }
1061 }
1063 /* Determine which registers are live at the start of each
1064 basic block of the function whose first insn is F.
1065 NREGS is the number of registers used in F.
1066 We allocate the vector basic_block_live_at_start
1067 and the regsets that it points to, and fill them with the data.
1068 regset_size and regset_bytes are also set here. */
1070 static void
1072 rtx f;
1074 {
1077 /* For each basic block, a bitmask of regs
1078 live on exit from the block. */
1080 /* For each basic block, a bitmask of regs
1081 live on entry to a successor-block of this block.
1082 If this does not match basic_block_live_at_end,
1083 that must be updated, and the block must be rescanned. */
1085 /* For each basic block, a bitmask of regs
1086 whose liveness at the end of the basic block
1087 can make a difference in which regs are live on entry to the block.
1088 These are the regs that are set within the basic block,
1089 possibly excluding those that are used after they are set. */
1092 rtx insn;
1102 /* Allocate and zero out many data structures
1103 that will record the data from lifetime analysis. */
1110 /* Set up several regset-vectors used internally within this function.
1111 Their meanings are documented above, with their declarations. */
1113 basic_block_live_at_end
1116 /* Don't use alloca since that leads to a crash rather than an error message
1117 if there isn't enough space.
1118 Don't use oballoc since we may need to allocate other things during
1119 this function on the temporary obstack. */
1122 basic_block_new_live_at_end
1127 basic_block_significant
1131 /* Record which insns refer to any volatile memory
1132 or for any reason can't be deleted just because they are dead stores.
1133 Also, delete any insns that copy a register to itself. */
1136 {
1141 {
1142 /* Delete (in effect) any obvious no-op moves. */
1148 /* Insns carrying these notes are useful later on. */
1150 {
1154 }
1155 /* Delete (in effect) any obvious no-op moves. */
1165 /* Insns carrying these notes are useful later on. */
1167 {
1171 }
1173 {
1174 /* If nothing but SETs of registers to themselves,
1175 this insn can also be deleted. */
1177 {
1189 }
1192 /* Insns carrying these notes are useful later on. */
1194 {
1198 }
1199 else
1201 }
1204 /* A SET that makes space on the stack cannot be dead.
1205 (Such SETs occur only for allocating variable-size data,
1206 so they will always have a PLUS or MINUS according to the
1207 direction of stack growth.)
1208 Even if this function never uses this stack pointer value,
1209 signal handlers do! */
1212 #ifdef STACK_GROWS_DOWNWARD
1214 #else
1216 #endif
1219 }
1220 }
1223 #ifdef EXIT_IGNORE_STACK
1225 || (! FRAME_POINTER_REQUIRED
1226 && ! current_function_calls_alloca
1228 #endif
1229 {
1230 /* If exiting needs the right stack value,
1231 consider the stack pointer live at the end of the function. */
1233 STACK_POINTER_REGNUM);
1235 STACK_POINTER_REGNUM);
1236 }
1238 /* Mark the frame pointer is needed at the end of the function. If
1239 we end up eliminating it, it will be removed from the live list
1240 of each basic block by reload. */
1243 {
1245 FRAME_POINTER_REGNUM);
1247 FRAME_POINTER_REGNUM);
1248 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1249 /* If they are different, also mark the hard frame pointer as live */
1251 HARD_FRAME_POINTER_REGNUM);
1253 HARD_FRAME_POINTER_REGNUM);
1254 #endif
1255 }
1257 /* Mark all global registers and all registers used by the epilogue
1258 as being live at the end of the function since they may be
1259 referenced by our caller. */
1264 #ifdef EPILOGUE_USES
1266 #endif
1267 )
1268 {
1271 }
1273 /* Propagate life info through the basic blocks
1274 around the graph of basic blocks.
1276 This is a relaxation process: each time a new register
1277 is live at the end of the basic block, we must scan the block
1278 to determine which registers are, as a consequence, live at the beginning
1279 of that block. These registers must then be marked live at the ends
1280 of all the blocks that can transfer control to that block.
1281 The process continues until it reaches a fixed point. */
1286 {
1289 {
1295 {
1296 /* Set CONSIDER if this block needs thinking about at all
1297 (that is, if the regs live now at the end of it
1298 are not the same as were live at the end of it when
1299 we last thought about it).
1300 Set must_rescan if it needs to be thought about
1301 instruction by instruction (that is, if any additional
1302 reg that is live at the end now but was not live there before
1303 is one of the significant regs of this basic block). */
1305 EXECUTE_IF_AND_COMPL_IN_REG_SET
1308 {
1311 {
1314 }
1315 });
1316 done:
1319 }
1321 /* The live_at_start of this block may be changing,
1322 so another pass will be required after this one. */
1326 {
1327 /* No complete rescan needed;
1328 just record those variables newly known live at end
1329 as live at start as well. */
1337 }
1338 else
1339 {
1340 /* Update the basic_block_live_at_start
1341 by propagation backwards through the block. */
1350 i);
1351 }
1353 {
1356 /* Update the basic_block_new_live_at_end's of the block
1357 that falls through into this one (if any). */
1363 /* Update the basic_block_new_live_at_end's of
1364 all the blocks that jump to this one. */
1369 {
1373 }
1374 }
1375 #ifdef USE_C_ALLOCA
1377 #endif
1378 }
1380 }
1382 /* The only pseudos that are live at the beginning of the function are
1383 those that were not set anywhere in the function. local-alloc doesn't
1384 know how to handle these correctly, so mark them as not local to any
1385 one basic block. */
1390 {
1392 });
1394 /* Now the life information is accurate.
1395 Make one more pass over each basic block
1396 to delete dead stores, create autoincrement addressing
1397 and record how many times each register is used, is set, or dies.
1399 To save time, we operate directly in basic_block_live_at_end[i],
1400 thus destroying it (in fact, converting it into a copy of
1401 basic_block_live_at_start[i]). This is ok now because
1402 basic_block_live_at_end[i] is no longer used past this point. */
1407 {
1411 #ifdef USE_C_ALLOCA
1413 #endif
1414 }
1416 #if 0
1417 /* Something live during a setjmp should not be put in a register
1418 on certain machines which restore regs from stack frames
1419 rather than from the jmpbuf.
1420 But we don't need to do this for the user's variables, since
1421 ANSI says only volatile variables need this. */
1422 #ifdef LONGJMP_RESTORE_FROM_STACK
1425 {
1428 {
1431 }
1432 });
1433 #endif
1434 #endif
1436 /* We have a problem with any pseudoreg that
1437 lives across the setjmp. ANSI says that if a
1438 user variable does not change in value
1439 between the setjmp and the longjmp, then the longjmp preserves it.
1440 This includes longjmp from a place where the pseudo appears dead.
1441 (In principle, the value still exists if it is in scope.)
1442 If the pseudo goes in a hard reg, some other value may occupy
1443 that hard reg where this pseudo is dead, thus clobbering the pseudo.
1444 Conclusion: such a pseudo must not go in a hard reg. */
1447 {
1449 {
1452 }
1453 });
1464 }
1465 \f
1466 /* Subroutines of life analysis. */
1468 /* Allocate the permanent data structures that represent the results
1469 of life analysis. Not static since used also for stupid life analysis. */
1471 void
1473 {
1476 /* Recalculate the register space, in case it has grown. Old style
1477 vector oriented regsets would set regset_{size,bytes} here also. */
1480 /* Because both reg_scan and flow_analysis want to set up the REG_N_SETS
1481 information, explicitly reset it here. The allocation should have
1482 already happened on the previous reg_scan pass. Make sure in case
1483 some more registers were allocated. */
1487 basic_block_live_at_start
1490 function_obstack);
1494 }
1496 /* Make each element of VECTOR point at a regset. The vector has
1497 NELTS elements, and space is allocated from the ALLOC_OBSTACK
1498 obstack. */
1500 void
1505 {
1509 {
1512 }
1513 }
1515 /* Release any additional space allocated for each element of VECTOR point
1516 other than the regset header itself. The vector has NELTS elements. */
1518 void
1522 {
1527 }
1529 /* Compute the registers live at the beginning of a basic block
1530 from those live at the end.
1532 When called, OLD contains those live at the end.
1533 On return, it contains those live at the beginning.
1534 FIRST and LAST are the first and last insns of the basic block.
1536 FINAL is nonzero if we are doing the final pass which is not
1537 for computing the life info (since that has already been done)
1538 but for acting on it. On this pass, we delete dead stores,
1539 set up the logical links and dead-variables lists of instructions,
1540 and merge instructions for autoincrement and autodecrement addresses.
1542 SIGNIFICANT is nonzero only the first time for each basic block.
1543 If it is nonzero, it points to a regset in which we store
1544 a 1 for each register that is set within the block.
1546 BNUM is the number of the basic block. */
1548 static void
1551 rtx first;
1552 rtx last;
1554 regset significant;
1556 {
1558 rtx prev;
1559 regset live;
1560 regset dead;
1562 /* The following variables are used only if FINAL is nonzero. */
1563 /* This vector gets one element for each reg that has been live
1564 at any point in the basic block that has been scanned so far.
1565 SOMETIMES_MAX says how many elements are in use so far. */
1568 /* This regset has 1 for each reg that we have seen live so far.
1569 It and REGS_SOMETIMES_LIVE are updated together. */
1570 regset maxlive;
1572 /* The loop depth may change in the middle of a basic block. Since we
1573 scan from end to beginning, we start with the depth at the end of the
1574 current basic block, and adjust as we pass ends and starts of loops. */
1583 /* Include any notes at the end of the block in the scan.
1584 This is in case the block ends with a call to setjmp. */
1587 {
1588 /* Look for loop boundaries, we are going forward here. */
1591 loop_depth++;
1593 loop_depth--;
1594 }
1597 {
1605 /* Process the regs live at the end of the block.
1606 Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
1607 Also mark them as not local to any one basic block. */
1609 {
1612 sometimes_max++;
1613 });
1614 }
1616 /* Scan the block an insn at a time from end to beginning. */
1619 {
1623 {
1624 /* Look for loop boundaries, remembering that we are going
1625 backwards. */
1627 loop_depth++;
1629 loop_depth--;
1631 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
1632 Abort now rather than setting register status incorrectly. */
1636 /* If this is a call to `setjmp' et al,
1637 warn if any non-volatile datum is live. */
1641 }
1643 /* Update the life-status of regs for this insn.
1644 First DEAD gets which regs are set in this insn
1645 then LIVE gets which regs are used in this insn.
1646 Then the regs live before the insn
1647 are those live after, with DEAD regs turned off,
1648 and then LIVE regs turned on. */
1651 {
1654 int insn_is_dead
1656 /* Don't delete something that refers to volatile storage! */
1658 int libcall_is_dead
1662 /* If an instruction consists of just dead store(s) on final pass,
1663 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1664 We could really delete it with delete_insn, but that
1665 can cause trouble for first or last insn in a basic block. */
1667 {
1672 /* CC0 is now known to be dead. Either this insn used it,
1673 in which case it doesn't anymore, or clobbered it,
1674 so the next insn can't use it. */
1677 /* If this insn is copying the return value from a library call,
1678 delete the entire library call. */
1680 {
1686 {
1691 }
1692 }
1694 }
1699 /* See if this is an increment or decrement that can be
1700 merged into a following memory address. */
1701 #ifdef AUTO_INC_DEC
1702 {
1705 /* Does this instruction increment or decrement a register? */
1712 /* Ok, look for a following memory ref we can combine with.
1713 If one is found, change the memory ref to a PRE_INC
1714 or PRE_DEC, cancel this insn, and return 1.
1715 Return 0 if nothing has been done. */
1718 }
1721 /* If this is not the final pass, and this insn is copying the
1722 value of a library call and it's dead, don't scan the
1723 insns that perform the library call, so that the call's
1724 arguments are not marked live. */
1726 {
1727 /* Mark the dest reg as `significant'. */
1732 }
1738 /* We have an insn to pop a constant amount off the stack.
1739 (Such insns use PLUS regardless of the direction of the stack,
1740 and any insn to adjust the stack by a constant is always a pop.)
1741 These insns, if not dead stores, have no effect on life. */
1742 ;
1743 else
1744 {
1745 /* LIVE gets the regs used in INSN;
1746 DEAD gets those set by it. Dead insns don't make anything
1747 live. */
1752 /* If an insn doesn't use CC0, it becomes dead since we
1753 assume that every insn clobbers it. So show it dead here;
1754 mark_used_regs will set it live if it is referenced. */
1760 /* Sometimes we may have inserted something before INSN (such as
1761 a move) when we make an auto-inc. So ensure we will scan
1762 those insns. */
1763 #ifdef AUTO_INC_DEC
1765 #endif
1768 {
1771 rtx note;
1774 note;
1780 /* Each call clobbers all call-clobbered regs that are not
1781 global or fixed. Note that the function-value reg is a
1782 call-clobbered reg, and mark_set_regs has already had
1783 a chance to handle it. */
1790 /* The stack ptr is used (honorarily) by a CALL insn. */
1793 /* Calls may also reference any of the global registers,
1794 so they are made live. */
1801 /* Calls also clobber memory. */
1803 }
1805 /* Update OLD for the registers used or set. */
1810 {
1811 /* Any regs live at the time of a call instruction
1812 must not go in a register clobbered by calls.
1813 Find all regs now live and record this for them. */
1820 }
1821 }
1823 /* On final pass, add any additional sometimes-live regs
1824 into MAXLIVE and REGS_SOMETIMES_LIVE.
1825 Also update counts of how many insns each reg is live at. */
1828 {
1832 EXECUTE_IF_AND_COMPL_IN_REG_SET
1834 {
1837 });
1841 {
1845 }
1846 }
1847 }
1848 flushed: ;
1851 }
1860 }
1861 \f
1862 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1863 (SET expressions whose destinations are registers dead after the insn).
1864 NEEDED is the regset that says which regs are alive after the insn.
1866 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL. */
1868 static int
1870 rtx x;
1871 regset needed;
1873 {
1876 /* If setting something that's a reg or part of one,
1877 see if that register's altered value will be live. */
1880 {
1883 /* A SET that is a subroutine call cannot be dead. */
1887 #ifdef HAVE_cc0
1890 #endif
1901 {
1904 /* Don't delete insns to set global regs. */
1906 /* Make sure insns to set frame pointer aren't deleted. */
1908 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1910 #endif
1911 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1912 /* Make sure insns to set arg pointer are never deleted
1913 (if the arg pointer isn't fixed, there will be a USE for
1914 it, so we can treat it normally). */
1916 #endif
1920 /* If this is a hard register, verify that subsequent words are
1921 not needed. */
1923 {
1929 }
1932 }
1933 }
1935 /* If performing several activities,
1936 insn is dead if each activity is individually dead.
1937 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1938 that's inside a PARALLEL doesn't make the insn worth keeping. */
1940 {
1950 }
1952 /* A CLOBBER of a pseudo-register that is dead serves no purpose. That
1953 is not necessarily true for hard registers. */
1959 /* We do not check other CLOBBER or USE here. An insn consisting of just
1960 a CLOBBER or just a USE should not be deleted. */
1962 }
1964 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
1965 return 1 if the entire library call is dead.
1966 This is true if X copies a register (hard or pseudo)
1967 and if the hard return reg of the call insn is dead.
1968 (The caller should have tested the destination of X already for death.)
1970 If this insn doesn't just copy a register, then we don't
1971 have an ordinary libcall. In that case, cse could not have
1972 managed to substitute the source for the dest later on,
1973 so we can assume the libcall is dead.
1975 NEEDED is the bit vector of pseudoregs live before this insn.
1976 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
1978 static int
1980 rtx x;
1981 regset needed;
1982 rtx note;
1983 rtx insn;
1984 {
1988 {
1991 {
1995 /* Find the call insn. */
1999 /* If there is none, do nothing special,
2000 since ordinary death handling can understand these insns. */
2004 /* See if the hard reg holding the value is dead.
2005 If this is a PARALLEL, find the call within it. */
2008 {
2014 /* This may be a library call that is returning a value
2015 via invisible pointer. Do nothing special, since
2016 ordinary death handling can understand these insns. */
2021 }
2024 }
2025 }
2027 }
2029 /* Return 1 if register REGNO was used before it was set.
2030 In other words, if it is live at function entry.
2031 Don't count global register variables or variables in registers
2032 that can be used for function arg passing, though. */
2034 int
2037 {
2044 }
2046 /* 1 if register REGNO was alive at a place where `setjmp' was called
2047 and was set more than once or is an argument.
2048 Such regs may be clobbered by `longjmp'. */
2050 int
2053 {
2060 }
2061 \f
2062 /* Process the registers that are set within X.
2063 Their bits are set to 1 in the regset DEAD,
2064 because they are dead prior to this insn.
2066 If INSN is nonzero, it is the insn being processed
2067 and the fact that it is nonzero implies this is the FINAL pass
2068 in propagate_block. In this case, various info about register
2069 usage is stored, LOG_LINKS fields of insns are set up. */
2071 static void
2073 regset needed;
2074 regset dead;
2075 rtx x;
2076 rtx insn;
2077 regset significant;
2078 {
2084 {
2087 {
2091 }
2092 }
2093 }
2095 /* Process a single SET rtx, X. */
2097 static void
2099 regset needed;
2100 regset dead;
2101 rtx x;
2102 rtx insn;
2103 regset significant;
2104 {
2108 /* Modifying just one hardware register of a multi-reg value
2109 or just a byte field of a register
2110 does not mean the value from before this insn is now dead.
2111 But it does mean liveness of that register at the end of the block
2112 is significant.
2114 Within mark_set_1, however, we treat it as if the register is
2115 indeed modified. mark_used_regs will, however, also treat this
2116 register as being used. Thus, we treat these insns as setting a
2117 new value for the register as a function of its old value. This
2118 cases LOG_LINKS to be made appropriately and this will help combine. */
2125 /* If we are writing into memory or into a register mentioned in the
2126 address of the last thing stored into memory, show we don't know
2127 what the last store was. If we are writing memory, save the address
2128 unless it is volatile. */
2135 /* There are no REG_INC notes for SP, so we can't assume we'll see
2136 everything that invalidates it. To be safe, don't eliminate any
2137 stores though SP; none of them should be redundant anyway. */
2143 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2145 #endif
2146 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2148 #endif
2150 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
2151 {
2155 /* Mark it as a significant register for this basic block. */
2159 /* Mark it as dead before this insn. */
2162 /* A hard reg in a wide mode may really be multiple registers.
2163 If so, mark all of them just like the first. */
2165 {
2168 /* Nothing below is needed for the stack pointer; get out asap.
2169 Eg, log links aren't needed, since combine won't use them. */
2175 {
2184 }
2185 }
2186 /* Additional data to record if this is the final pass. */
2188 {
2192 /* If this is a hard reg, record this function uses the reg. */
2195 {
2200 {
2201 /* The next use is no longer "next", since a store
2202 intervenes. */
2207 }
2208 }
2209 else
2210 {
2211 /* The next use is no longer "next", since a store
2212 intervenes. */
2215 /* Keep track of which basic blocks each reg appears in. */
2222 /* Count (weighted) references, stores, etc. This counts a
2223 register twice if it is modified, but that is correct. */
2228 /* The insns where a reg is live are normally counted
2229 elsewhere, but we want the count to include the insn
2230 where the reg is set, and the normal counting mechanism
2231 would not count it. */
2233 }
2236 {
2237 /* Make a logical link from the next following insn
2238 that uses this register, back to this insn.
2239 The following insns have already been processed.
2241 We don't build a LOG_LINK for hard registers containing
2242 in ASM_OPERANDs. If these registers get replaced,
2243 we might wind up changing the semantics of the insn,
2244 even if reload can make what appear to be valid assignments
2245 later. */
2251 }
2253 {
2254 /* Note that dead stores have already been deleted when possible
2255 If we get here, we have found a dead store that cannot
2256 be eliminated (because the same insn does something useful).
2257 Indicate this by marking the reg being set as dying here. */
2261 }
2262 else
2263 {
2264 /* This is a case where we have a multi-word hard register
2265 and some, but not all, of the words of the register are
2266 needed in subsequent insns. Write REG_UNUSED notes
2267 for those parts that were not needed. This case should
2268 be rare. */
2280 }
2281 }
2282 }
2286 /* If this is the last pass and this is a SCRATCH, show it will be dying
2287 here and count it. */
2289 {
2292 num_scratch++;
2293 }
2294 }
2295 \f
2296 #ifdef AUTO_INC_DEC
2298 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
2299 reference. */
2301 static void
2303 regset needed;
2304 rtx x;
2305 rtx insn;
2306 {
2309 rtx set;
2311 /* Here we detect use of an index register which might be good for
2312 postincrement, postdecrement, preincrement, or predecrement. */
2318 {
2321 rtx use;
2322 rtx incr;
2325 /* Is the next use an increment that might make auto-increment? */
2330 /* Can't add side effects to jumps; if reg is spilled and
2331 reloaded, there's no way to store back the altered value. */
2337 #ifdef HAVE_POST_INCREMENT
2339 #endif
2340 #ifdef HAVE_POST_DECREMENT
2342 #endif
2343 #ifdef HAVE_PRE_INCREMENT
2345 #endif
2346 #ifdef HAVE_PRE_DECREMENT
2348 #endif
2349 )
2350 /* Make sure this reg appears only once in this insn. */
2353 {
2360 {
2361 /* This is the simple case. Try to make the auto-inc. If
2362 we can't, we are done. Otherwise, we will do any
2363 needed updates below. */
2368 }
2370 /* PREV_INSN used here to check the semi-open interval
2371 [insn,incr). */
2373 /* We must also check for sets of q as q may be
2374 a call clobbered hard register and there may
2375 be a call between PREV_INSN (insn) and incr. */
2377 {
2378 /* We have *p followed sometime later by q = p+size.
2379 Both p and q must be live afterward,
2380 and q is not used between INSN and it's assignment.
2381 Change it to q = p, ...*q..., q = q+size.
2382 Then fall into the usual case. */
2390 /* If anything in INSNS have UID's that don't fit within the
2391 extra space we allocate earlier, we can't make this auto-inc.
2392 This should never happen. */
2394 {
2398 }
2400 /* If we can't make the auto-inc, or can't make the
2401 replacement into Y, exit. There's no point in making
2402 the change below if we can't do the auto-inc and doing
2403 so is not correct in the pre-inc case. */
2412 /* We now know we'll be doing this change, so emit the
2413 new insn(s) and do the updates. */
2419 /* INCR will become a NOTE and INSN won't contain a
2420 use of ADDR. If a use of ADDR was just placed in
2421 the insn before INSN, make that the next use.
2422 Otherwise, invalidate it. */
2427 else
2433 /* REGNO is now used in INCR which is below INSN, but
2434 it previously wasn't live here. If we don't mark
2435 it as needed, we'll put a REG_DEAD note for it
2436 on this insn, which is incorrect. */
2439 /* If there are any calls between INSN and INCR, show
2440 that REGNO now crosses them. */
2444 }
2445 else
2448 /* If we haven't returned, it means we were able to make the
2449 auto-inc, so update the status. First, record that this insn
2450 has an implicit side effect. */
2455 /* Modify the old increment-insn to simply copy
2456 the already-incremented value of our register. */
2460 /* If that makes it a no-op (copying the register into itself) delete
2461 it so it won't appear to be a "use" and a "set" of this
2462 register. */
2464 {
2468 }
2471 {
2472 /* Count an extra reference to the reg. When a reg is
2473 incremented, spilling it is worse, so we want to make
2474 that less likely. */
2477 /* Count the increment as a setting of the register,
2478 even though it isn't a SET in rtl. */
2480 }
2481 }
2482 }
2483 }
2485 \f
2486 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
2487 This is done assuming the registers needed from X
2488 are those that have 1-bits in NEEDED.
2490 On the final pass, FINAL is 1. This means try for autoincrement
2491 and count the uses and deaths of each pseudo-reg.
2493 INSN is the containing instruction. If INSN is dead, this function is not
2494 called. */
2496 static void
2498 regset needed;
2499 regset live;
2500 rtx x;
2502 rtx insn;
2503 {
2508 retry:
2511 {
2523 #ifdef HAVE_cc0
2527 #endif
2530 /* If we are clobbering a MEM, mark any registers inside the address
2531 as being used. */
2537 /* Invalidate the data for the last MEM stored, but only if MEM is
2538 something that can be stored into. */
2542 else
2545 #ifdef AUTO_INC_DEC
2548 #endif
2558 /* While we're here, optimize this case. */
2561 /* In case the SUBREG is not of a register, don't optimize */
2563 {
2566 }
2568 /* ... fall through ... */
2571 /* See a register other than being set
2572 => mark it as needed. */
2575 {
2581 /* A hard reg in a wide mode may really be multiple registers.
2582 If so, mark all of them just like the first. */
2584 {
2587 /* For stack ptr or fixed arg pointer,
2588 nothing below can be necessary, so waste no more time. */
2590 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2592 #endif
2593 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2595 #endif
2597 {
2598 /* If this is a register we are going to try to eliminate,
2599 don't mark it live here. If we are successful in
2600 eliminating it, it need not be live unless it is used for
2601 pseudos, in which case it will have been set live when
2602 it was allocated to the pseudos. If the register will not
2603 be eliminated, reload will set it live at that point. */
2608 }
2609 /* No death notes for global register variables;
2610 their values are live after this function exits. */
2612 {
2616 }
2620 {
2627 }
2628 }
2630 {
2631 /* Record where each reg is used, so when the reg
2632 is set we know the next insn that uses it. */
2637 {
2638 /* If a hard reg is being used,
2639 record that this function does use it. */
2644 do
2647 }
2648 else
2649 {
2650 /* Keep track of which basic block each reg appears in. */
2659 /* Count (weighted) number of uses of each reg. */
2662 }
2664 /* Record and count the insns in which a reg dies.
2665 If it is used in this insn and was dead below the insn
2666 then it dies in this insn. If it was set in this insn,
2667 we do not make a REG_DEAD note; likewise if we already
2668 made such a note. */
2672 #if 0
2674 #endif
2675 )
2676 {
2677 /* Check for the case where the register dying partially
2678 overlaps the register set by this insn. */
2681 {
2685 }
2687 /* If none of the words in X is needed, make a REG_DEAD
2688 note. Otherwise, we must make partial REG_DEAD notes. */
2690 {
2694 }
2695 else
2696 {
2699 /* Don't make a REG_DEAD note for a part of a register
2700 that is set in the insn. */
2711 }
2712 }
2713 }
2714 }
2718 {
2722 /* If storing into MEM, don't show it as being used. But do
2723 show the address as being used. */
2725 {
2726 #ifdef AUTO_INC_DEC
2729 #endif
2733 }
2735 /* Storing in STRICT_LOW_PART is like storing in a reg
2736 in that this SET might be dead, so ignore it in TESTREG.
2737 but in some other ways it is like using the reg.
2739 Storing in a SUBREG or a bit field is like storing the entire
2740 register in that if the register's value is not used
2741 then this SET is not needed. */
2746 {
2754 /* Modifying a single register in an alternate mode
2755 does not use any of the old value. But these other
2756 ways of storing in a register do use the old value. */
2759 ;
2760 else
2764 }
2766 /* If this is a store into a register,
2767 recursively scan the value being stored. */
2771 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2773 #endif
2774 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2776 #endif
2777 )
2778 /* We used to exclude global_regs here, but that seems wrong.
2779 Storing in them is like storing in mem. */
2780 {
2785 }
2786 }
2790 /* If exiting needs the right stack value, consider this insn as
2791 using the stack pointer. In any event, consider it as using
2792 all global registers and all registers used by return. */
2794 #ifdef EXIT_IGNORE_STACK
2796 || (! FRAME_POINTER_REQUIRED
2797 && ! current_function_calls_alloca
2799 #endif
2804 #ifdef EPILOGUE_USES
2806 #endif
2807 )
2813 }
2815 /* Recursively scan the operands of this expression. */
2817 {
2822 {
2824 {
2825 /* Tail recursive case: save a function call level. */
2827 {
2830 }
2832 }
2834 {
2838 }
2839 }
2840 }
2841 }
2842 \f
2843 #ifdef AUTO_INC_DEC
2845 static int
2847 rtx insn;
2848 {
2849 /* Find the next use of this reg. If in same basic block,
2850 make it do pre-increment or pre-decrement if appropriate. */
2858 /* Don't do this if the reg dies, or gets set in y; a standard addressing
2859 mode would be better. */
2862 {
2863 /* We have found a suitable auto-increment
2864 and already changed insn Y to do it.
2865 So flush this increment-instruction. */
2869 /* Count a reference to this reg for the increment
2870 insn we are deleting. When a reg is incremented.
2871 spilling it is worse, so we want to make that
2872 less likely. */
2874 {
2877 }
2879 }
2881 }
2883 /* Try to change INSN so that it does pre-increment or pre-decrement
2884 addressing on register REG in order to add AMOUNT to REG.
2885 AMOUNT is negative for pre-decrement.
2886 Returns 1 if the change could be made.
2887 This checks all about the validity of the result of modifying INSN. */
2889 static int
2892 HOST_WIDE_INT amount;
2893 {
2896 /* Nonzero if we can try to make a pre-increment or pre-decrement.
2897 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
2899 /* Nonzero if we can try to make a post-increment or post-decrement.
2900 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
2901 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
2902 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
2905 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
2908 /* From the sign of increment, see which possibilities are conceivable
2909 on this target machine. */
2910 #ifdef HAVE_PRE_INCREMENT
2913 #endif
2914 #ifdef HAVE_POST_INCREMENT
2917 #endif
2919 #ifdef HAVE_PRE_DECREMENT
2922 #endif
2923 #ifdef HAVE_POST_DECREMENT
2926 #endif
2931 /* It is not safe to add a side effect to a jump insn
2932 because if the incremented register is spilled and must be reloaded
2933 there would be no way to store the incremented value back in memory. */
2942 {
2945 }
2953 /* See if this combination of instruction and addressing mode exists. */
2961 /* Record that this insn now has an implicit side effect on X. */
2964 }
2967 \f
2968 /* Find the place in the rtx X where REG is used as a memory address.
2969 Return the MEM rtx that so uses it.
2970 If PLUSCONST is nonzero, search instead for a memory address equivalent to
2971 (plus REG (const_int PLUSCONST)).
2973 If such an address does not appear, return 0.
2974 If REG appears more than once, or is used other than in such an address,
2975 return (rtx)1. */
2977 rtx
2980 rtx reg;
2981 HOST_WIDE_INT plusconst;
2982 {
2999 {
3000 /* If REG occurs inside a MEM used in a bit-field reference,
3001 that is unacceptable. */
3004 }
3010 {
3012 {
3018 }
3020 {
3023 {
3029 }
3030 }
3031 }
3034 }
3035 \f
3036 /* Write information about registers and basic blocks into FILE.
3037 This is part of making a debugging dump. */
3039 void
3042 {
3050 {
3072 {
3077 else
3081 }
3085 }
3088 {
3092 i,
3095 /* The control flow graph's storage is freed
3096 now when flow_analysis returns.
3097 Don't try to print it if it is gone. */
3099 {
3106 {
3109 }
3112 }
3118 }
3120 }
3122 \f
3123 /* Like print_rtl, but also print out live information for the start of each
3124 basic block. */
3126 void
3129 rtx rtx_first;
3130 {
3136 else
3137 {
3146 {
3149 }
3152 {
3153 rtx x;
3157 {
3163 }
3164 }
3167 {
3169 {
3171 bb);
3174 {
3179 });
3181 }
3196 }
3197 }
3198 }
3200 \f
3201 /* Integer list support. */
3203 /* Allocate a node from list *HEAD_PTR. */
3205 static int_list_ptr
3208 {
3212 {
3217 }
3221 }
3223 /* Pointer to head of predecessor/successor block list. */
3226 /* Add a new node to integer list LIST with value VAL.
3227 LIST is a pointer to a list object to allow for different implementations.
3228 If *LIST is initially NULL, the list is empty.
3229 The caller must not care whether the element is added to the front or
3230 to the end of the list (to allow for different implementations). */
3232 static int_list_ptr
3237 {
3244 }
3246 /* Free the blocks of lists at BLK_LIST. */
3248 void
3251 {
3255 {
3258 }
3260 /* Mark list as empty for the next function we compile. */
3262 }
3263 \f
3264 /* Predecessor/successor computation. */
3266 /* Mark PRED_BB a precessor of SUCC_BB,
3267 and conversely SUCC_BB a successor of PRED_BB. */
3269 static void
3277 {
3279 {
3282 }
3284 {
3287 }
3288 }
3290 /* Compute the predecessors and successors for each block. */
3291 void
3297 {
3305 /* This routine can be called after life analysis; in that case
3306 basic_block_drops_in and uid_block_number will not be available
3307 and we must recompute their values. */
3309 {
3317 /* Scan each basic block setting basic_block_drops_in and
3318 uid_block_number as needed. */
3320 {
3325 else
3328 /* Look backwards from the start of this block. Stop if we
3329 hit the start of the function or the end of a previous
3330 block. Don't walk backwards through blocks that are just
3331 deleted insns! */
3335 ;
3337 /* Never set basic_block_drops_in for the first block. It is
3338 implicit.
3340 If we stopped on anything other than a BARRIER, then this
3341 block drops in. */
3347 {
3352 }
3353 }
3354 }
3357 {
3358 rtx head;
3359 rtx jump;
3367 {
3374 }
3377 /* If this is a RETURN insn or a conditional jump in the last
3378 basic block, or a non-jump insn in the last basic block, then
3379 this block reaches the exit block. */
3389 }
3394 /* If we allocated any variables in temporary storage, clear out the
3395 pointer to the local storage to avoid dangling pointers. */
3397 {
3401 }
3402 }
3404 void
3409 {
3411 int_list_ptr p;
3415 {
3420 {
3424 else
3426 }
3430 {
3434 else
3436 }
3438 }
3440 }
3442 void
3445 sbitmap bmap;
3446 {
3453 {
3455 {
3459 }
3460 }
3462 }
3464 void
3470 {
3475 {
3478 }
3480 }
3482 /* Free basic block data storage. */
3484 void
3486 {
3488 }
3489 \f
3490 /* Bitmap manipulation routines. */
3492 /* Allocate a simple bitmap of N_ELMS bits. */
3494 sbitmap
3497 {
3499 sbitmap bmap;
3510 }
3512 /* Allocate a vector of N_VECS bitmaps of N_ELMS bits. */
3514 sbitmap *
3517 {
3527 /* Round up `vector_bytes' to account for the alignment requirements
3528 of an sbitmap. One could allocate the vector-table and set of sbitmaps
3529 separately, but that requires maintaining two pointers or creating
3530 a cover struct to hold both pointers (so our result is still just
3531 one pointer). Neither is a bad idea, but this is simpler for now. */
3532 {
3533 /* Based on DEFAULT_ALIGNMENT computation in obstack.c. */
3537 }
3545 {
3551 }
3554 }
3556 /* Copy sbitmap SRC to DST. */
3558 void
3561 {
3569 }
3571 /* Zero all elements in a bitmap. */
3573 void
3575 sbitmap bmap;
3576 {
3578 }
3580 /* Set to ones all elements in a bitmap. */
3582 void
3584 sbitmap bmap;
3585 {
3587 }
3589 /* Zero a vector of N_VECS bitmaps. */
3591 void
3595 {
3600 }
3602 /* Set to ones a vector of N_VECS bitmaps. */
3604 void
3608 {
3613 }
3615 /* Set DST to be A union (B - C).
3616 DST = A | (B & ~C).
3617 Return non-zero if any change is made. */
3619 int
3622 {
3632 {
3638 }
3640 }
3642 /* Set bitmap DST to the bitwise negation of the bitmap SRC. */
3644 void
3647 {
3654 {
3658 }
3659 }
3661 /* Set the bits in DST to be the difference between the bits
3662 in A and the bits in B. i.e. dst = a - b.
3663 The - operator is implemented as a & (~b). */
3665 void
3668 {
3677 }
3679 /* Set DST to be (A and B)).
3680 Return non-zero if any change is made. */
3682 int
3685 {
3694 {
3700 }
3702 }
3703 /* Set DST to be (A or B)).
3704 Return non-zero if any change is made. */
3706 int
3709 {
3718 {
3724 }
3726 }
3728 /* Set DST to be (A or (B and C)).
3729 Return non-zero if any change is made. */
3731 int
3734 {
3744 {
3750 }
3752 }
3754 /* Set DST to be (A ann (B or C)).
3755 Return non-zero if any change is made. */
3757 int
3760 {
3770 {
3776 }
3778 }
3780 /* Set the bitmap DST to the intersection of SRC of all predecessors or
3781 successors of block number BB (PRED_SUCC says which). */
3783 void
3785 sbitmap dst;
3789 {
3790 int_list_ptr ps;
3796 /* It is possible that there are no predecessors(/successors).
3797 This can happen for example in unreachable code. */
3800 {
3801 /* In APL-speak this is the `and' reduction of the empty set and thus
3802 the result is the identity for `and'. */
3805 }
3807 /* Set result to first predecessor/successor. */
3810 {
3815 /* Break out since we're only doing first predecessor. */
3817 }
3821 /* Now do the remaining predecessors/successors. */
3824 {
3837 }
3838 }
3840 /* Set the bitmap DST to the intersection of SRC of all predecessors
3841 of block number BB. */
3843 void
3845 sbitmap dst;
3849 {
3851 }
3853 /* Set the bitmap DST to the intersection of SRC of all successors
3854 of block number BB. */
3856 void
3858 sbitmap dst;
3862 {
3864 }
3866 /* Set the bitmap DST to the union of SRC of all predecessors/successors of
3867 block number BB. */
3869 void
3871 sbitmap dst;
3875 {
3876 int_list_ptr ps;
3882 /* It is possible that there are no predecessors(/successors).
3883 This can happen for example in unreachable code. */
3886 {
3887 /* In APL-speak this is the `or' reduction of the empty set and thus
3888 the result is the identity for `or'. */
3891 }
3893 /* Set result to first predecessor/successor. */
3896 {
3901 /* Break out since we're only doing first predecessor. */
3903 }
3907 /* Now do the remaining predecessors/successors. */
3910 {
3923 }
3924 }
3926 /* Set the bitmap DST to the union of SRC of all predecessors of
3927 block number BB. */
3929 void
3931 sbitmap dst;
3935 {
3937 }
3939 /* Set the bitmap DST to the union of SRC of all predecessors of
3940 block number BB. */
3942 void
3944 sbitmap dst;
3948 {
3950 }
3952 /* Compute dominator relationships. */
3953 void
3959 {
3977 {
3980 {
3993 }
3994 passes++;
3995 }
3998 }