| blob | a16d0ed5b2805caa18159c94b5e02ac5e15f6457 |
1 /* Data flow analysis for GNU compiler.
2 Copyright (C) 1987, 88, 92-98, 1999 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. It
23 computes data flow information which tells combine_instructions
24 which insns to consider combining and controls register allocation.
26 Additional data flow information that is too bulky to record is
27 generated during the analysis, and is used at that time to create
28 autoincrement and autodecrement addressing.
30 The first step is dividing the function into basic blocks.
31 find_basic_blocks does this. Then life_analysis determines
32 where each register is live and where it is dead.
34 ** find_basic_blocks **
36 find_basic_blocks divides the current function's rtl into basic
37 blocks and constructs the CFG. The blocks are recorded in the
38 basic_block_info array; the CFG exists in the edge structures
39 referenced by the blocks.
41 find_basic_blocks also finds any unreachable loops and deletes them.
43 ** life_analysis **
45 life_analysis is called immediately after find_basic_blocks.
46 It uses the basic block information to determine where each
47 hard or pseudo register is live.
49 ** live-register info **
51 The information about where each register is live is in two parts:
52 the REG_NOTES of insns, and the vector basic_block->global_live_at_start.
54 basic_block->global_live_at_start has an element for each basic
55 block, and the element is a bit-vector with a bit for each hard or
56 pseudo register. The bit is 1 if the register is live at the
57 beginning of the basic block.
59 Two types of elements can be added to an insn's REG_NOTES.
60 A REG_DEAD note is added to an insn's REG_NOTES for any register
61 that meets both of two conditions: The value in the register is not
62 needed in subsequent insns and the insn does not replace the value in
63 the register (in the case of multi-word hard registers, the value in
64 each register must be replaced by the insn to avoid a REG_DEAD note).
66 In the vast majority of cases, an object in a REG_DEAD note will be
67 used somewhere in the insn. The (rare) exception to this is if an
68 insn uses a multi-word hard register and only some of the registers are
69 needed in subsequent insns. In that case, REG_DEAD notes will be
70 provided for those hard registers that are not subsequently needed.
71 Partial REG_DEAD notes of this type do not occur when an insn sets
72 only some of the hard registers used in such a multi-word operand;
73 omitting REG_DEAD notes for objects stored in an insn is optional and
74 the desire to do so does not justify the complexity of the partial
75 REG_DEAD notes.
77 REG_UNUSED notes are added for each register that is set by the insn
78 but is unused subsequently (if every register set by the insn is unused
79 and the insn does not reference memory or have some other side-effect,
80 the insn is deleted instead). If only part of a multi-word hard
81 register is used in a subsequent insn, REG_UNUSED notes are made for
82 the parts that will not be used.
84 To determine which registers are live after any insn, one can
85 start from the beginning of the basic block and scan insns, noting
86 which registers are set by each insn and which die there.
88 ** Other actions of life_analysis **
90 life_analysis sets up the LOG_LINKS fields of insns because the
91 information needed to do so is readily available.
93 life_analysis deletes insns whose only effect is to store a value
94 that is never used.
96 life_analysis notices cases where a reference to a register as
97 a memory address can be combined with a preceding or following
98 incrementation or decrementation of the register. The separate
99 instruction to increment or decrement is deleted and the address
100 is changed to a POST_INC or similar rtx.
102 Each time an incrementing or decrementing address is created,
103 a REG_INC element is added to the insn's REG_NOTES list.
105 life_analysis fills in certain vectors containing information about
106 register usage: reg_n_refs, reg_n_deaths, reg_n_sets, reg_live_length,
107 reg_n_calls_crosses and reg_basic_block.
109 life_analysis sets current_function_sp_is_unchanging if the function
110 doesn't modify the stack pointer. */
112 /* TODO:
114 Split out from life_analysis:
115 - local property discovery (bb->local_live, bb->local_set)
116 - global property computation
117 - log links creation
118 - pre/post modify transformation
119 */
120 \f
140 #define obstack_chunk_alloc xmalloc
141 #define obstack_chunk_free free
144 /* EXIT_IGNORE_STACK should be nonzero if, when returning from a function,
145 the stack pointer does not matter. The value is tested only in
146 functions that have frame pointers.
147 No definition is equivalent to always zero. */
148 #ifndef EXIT_IGNORE_STACK
149 #define EXIT_IGNORE_STACK 0
150 #endif
152 #ifndef HAVE_epilogue
153 #define HAVE_epilogue 0
154 #endif
156 #ifndef HAVE_prologue
157 #define HAVE_prologue 0
158 #endif
160 /* The contents of the current function definition are allocated
161 in this obstack, and all are freed at the end of the function.
162 For top-level functions, this is temporary_obstack.
163 Separate obstacks are made for nested functions. */
167 /* Number of basic blocks in the current function. */
171 /* Number of edges in the current function. */
175 /* The basic block array. */
177 varray_type basic_block_info;
179 /* The special entry and exit blocks. */
182 {
183 {
195 },
196 {
208 }
209 };
211 /* Nonzero if the second flow pass has completed. */
214 /* Maximum register number used in this function, plus one. */
218 /* Indexed by n, giving various register information */
220 varray_type reg_n_info;
222 /* Size of the reg_n_info table. */
226 /* Element N is the next insn that uses (hard or pseudo) register number N
227 within the current basic block; or zero, if there is no such insn.
228 This is valid only during the final backward scan in propagate_block. */
232 /* Size of a regset for the current function,
233 in (1) bytes and (2) elements. */
238 /* Regset of regs live when calls to `setjmp'-like functions happen. */
239 /* ??? Does this exist only for the setjmp-clobbered warning message? */
241 regset regs_live_at_setjmp;
243 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
244 that have to go in the same hard reg.
245 The first two regs in the list are a pair, and the next two
246 are another pair, etc. */
247 rtx regs_may_share;
249 /* Depth within loops of basic block being scanned for lifetime analysis,
250 plus one. This is the weight attached to references to registers. */
254 /* During propagate_block, this is non-zero if the value of CC0 is live. */
258 /* During propagate_block, this contains a list of all the MEMs we are
259 tracking for dead store elimination. */
263 /* Set of registers that may be eliminable. These are handled specially
264 in updating regs_ever_live. */
268 /* The basic block structure for every insn, indexed by uid. */
270 varray_type basic_block_for_insn;
272 /* The labels mentioned in non-jump rtl. Valid during find_basic_blocks. */
273 /* ??? Should probably be using LABEL_NUSES instead. It would take a
274 bit of surgery to be able to use or co-opt the routines in jump. */
278 /* INSN_VOLATILE (insn) is 1 if the insn refers to anything volatile. */
280 #define INSN_VOLATILE(INSN) bitmap_bit_p (uid_volatile, INSN_UID (INSN))
281 #define SET_INSN_VOLATILE(INSN) bitmap_set_bit (uid_volatile, INSN_UID (INSN))
284 /* Forward declarations */
310 basic_block));
312 basic_block));
338 #ifdef AUTO_INC_DEC
342 #endif
355 /* This function is always defined so it can be called from the
356 debugger, and it is declared extern so we don't get warnings about
357 it being unused. */
360 \f
361 /* Find basic blocks of the current function.
362 F is the first insn of the function and NREGS the number of register
363 numbers in use. */
365 void
367 rtx f;
371 {
374 /* Flush out existing data. */
376 {
381 /* Clear bb->aux on all extant basic blocks. We'll use this as a
382 tag for reuse during create_basic_block, just in case some pass
383 copies around basic block notes improperly. */
388 }
392 /* Size the basic block table. The actual structures will be allocated
393 by find_basic_blocks_1, since we want to keep the structure pointers
394 stable across calls to find_basic_blocks. */
395 /* ??? This whole issue would be much simpler if we called find_basic_blocks
396 exactly once, and thereafter we don't have a single long chain of
397 instructions at all until close to the end of compilation when we
398 actually lay them out. */
404 /* Record the block to which an insn belongs. */
405 /* ??? This should be done another way, by which (perhaps) a label is
406 tagged directly with the basic block that it starts. It is used for
407 more than that currently, but IMO that is the only valid use. */
410 #ifdef AUTO_INC_DEC
411 /* Leave space for insns life_analysis makes in some cases for auto-inc.
412 These cases are rare, so we don't need too much space. */
414 #endif
418 /* Discover the edges of our cfg. */
423 /* Delete unreachable blocks, then merge blocks when possible. */
426 {
431 }
433 /* Mark critical edges. */
437 /* Discover the loop depth at the start of each basic block to aid
438 register allocation. */
441 /* Kill the data we won't maintain. */
444 #ifdef ENABLE_CHECKING
446 #endif
447 }
449 /* Count the basic blocks of the function. */
451 static int
453 rtx f;
454 {
464 {
472 {
473 count++;
474 }
476 /* Record whether this call created an edge. */
478 {
484 /* If there is a specified EH region, we have an edge. */
487 else
488 {
489 /* If there is a nonlocal goto label and the specified
490 region number isn't -1, we have an edge. (0 means
491 no throw, but might have a nonlocal goto). */
494 }
495 }
506 }
508 /* The rest of the compiler works a bit smoother when we don't have to
509 check for the edge case of do-nothing functions with no basic blocks. */
511 {
514 }
517 }
519 /* Find all basic blocks of the function whose first insn is F.
521 Collect and return a list of labels whose addresses are taken. This
522 will be used in make_edges for use with computed gotos. */
524 static rtx
526 rtx f;
527 {
537 /* We process the instructions in a slightly different way than we did
538 previously. This is so that we see a NOTE_BASIC_BLOCK after we have
539 closed out the previous block, so that it gets attached at the proper
540 place. Since this form should be equivalent to the previous,
541 count_basic_blocks continues to use the old form as a check. */
544 {
550 {
551 /* Record whether this call created an edge. */
556 /* If there is an EH region, we have an edge. */
559 else
560 {
561 /* If there is a nonlocal goto label and the specified
562 region number isn't -1, we have an edge. (0 means
563 no throw, but might have a nonlocal goto). */
566 }
567 }
570 {
572 {
575 /* Keep a LIFO list of the currently active exception notes. */
579 {
583 }
585 /* Look for basic block notes with which to keep the
586 basic_block_info pointers stable. Unthread the note now;
587 we'll put it back at the right place in create_basic_block.
588 Or not at all if we've already found a note in this block. */
590 {
594 }
597 }
600 /* A basic block starts at a label. If we've closed one off due
601 to a barrier or some such, no need to do it again. */
603 {
604 /* While we now have edge lists with which other portions of
605 the compiler might determine a call ending a basic block
606 does not imply an abnormal edge, it will be a bit before
607 everything can be updated. So continue to emit a noop at
608 the end of such a block. */
610 {
613 }
617 }
622 /* A basic block ends at a jump. */
625 else
626 {
627 /* ??? Make a special check for table jumps. The way this
628 happens is truly and amazingly gross. We are about to
629 create a basic block that contains just a code label and
630 an addr*vec jump insn. Worse, an addr_diff_vec creates
631 its own natural loop.
633 Prevent this bit of brain damage, pasting things together
634 correctly in make_edges.
636 The correct solution involves emitting the table directly
637 on the tablejump instruction as a note, or JUMP_LABEL. */
641 {
643 n_basic_blocks--;
645 }
646 }
651 /* A basic block ends at a barrier. It may be that an unconditional
652 jump already closed the basic block -- no need to do it again. */
656 /* While we now have edge lists with which other portions of the
657 compiler might determine a call ending a basic block does not
658 imply an abnormal edge, it will be a bit before everything can
659 be updated. So continue to emit a noop at the end of such a
660 block. */
662 {
665 }
669 /* A basic block ends at a call that can either throw or
670 do a non-local goto. */
672 {
673 new_bb_inclusive:
678 new_bb_exclusive:
683 }
684 /* FALLTHRU */
688 {
692 }
694 }
697 {
698 rtx note;
700 /* Make a list of all labels referred to other than by jumps
701 (which just don't have the REG_LABEL notes).
703 Make a special exception for labels followed by an ADDR*VEC,
704 as this would be a part of the tablejump setup code.
706 Make a special exception for the eh_return_stub_label, which
707 we know isn't part of any otherwise visible control flow. */
711 {
715 ;
720 ;
721 else
722 label_value_list
724 }
725 }
726 }
735 }
737 /* Create a new basic block consisting of the instructions between
738 HEAD and END inclusive. Reuses the note and basic block struct
739 in BB_NOTE, if any. */
741 static void
745 {
746 basic_block bb;
752 {
753 /* If we found an existing note, thread it back onto the chain. */
757 else
758 {
761 }
762 }
763 else
764 {
765 /* Otherwise we must create a note and a basic block structure.
766 Since we allow basic block structs in rtl, give the struct
767 the same lifetime by allocating it off the function obstack
768 rather than using malloc. */
775 else
776 {
779 }
781 }
783 /* Always include the bb note in the block. */
792 /* Tag the block so that we know it has been used when considering
793 other basic block notes. */
795 }
796 \f
797 /* Records the basic block struct in BB_FOR_INSN, for every instruction
798 indexed by INSN_UID. MAX is the size of the array. */
800 void
803 {
811 {
818 {
825 }
826 }
827 }
829 /* Free the memory associated with the edge structures. */
831 static void
833 {
838 {
842 {
845 }
849 }
852 {
855 }
861 }
863 /* Identify the edges between basic blocks.
865 NONLOCAL_LABEL_LIST is a list of non-local labels in the function. Blocks
866 that are otherwise unreachable may be reachable with a non-local goto.
868 BB_EH_END is an array indexed by basic block number in which we record
869 the list of exception regions active at the end of the basic block. */
871 static void
873 rtx label_value_list;
874 {
879 /* Assume no computed jump; revise as we create edges. */
882 /* Heavy use of computed goto in machine-generated code can lead to
883 nearly fully-connected CFGs. In that case we spend a significant
884 amount of time searching the edge lists for duplicates. */
886 {
889 }
891 /* By nature of the way these get numbered, block 0 is always the entry. */
895 {
901 /* Examine the last instruction of the block, and discover the
902 ways we can leave the block. */
907 /* A branch. */
909 {
910 rtx tmp;
912 /* ??? Recognize a tablejump and do the right thing. */
918 {
919 rtvec vec;
924 else
931 /* Some targets (eg, ARM) emit a conditional jump that also
932 contains the out-of-range target. Scan for these and
933 add an edge if necessary. */
941 #ifdef CASE_DROPS_THROUGH
942 /* Silly VAXen. The ADDR_VEC is going to be in the way of
943 us naturally detecting fallthru into the next block. */
945 #endif
946 }
948 /* If this is a computed jump, then mark it as reaching
949 everything on the label_value_list and forced_labels list. */
951 {
959 }
961 /* Returns create an exit out. */
965 /* Otherwise, we have a plain conditional or unconditional jump. */
966 else
967 {
971 }
972 }
974 /* If this is a CALL_INSN, then mark it as reaching the active EH
975 handler for this CALL_INSN. If we're handling asynchronous
976 exceptions then any insn can reach any of the active handlers.
978 Also mark the CALL_INSN as reaching any nonlocal goto handler. */
981 {
982 /* If there's an EH region active at the end of a block,
983 add the appropriate edges. */
987 /* If we have asynchronous exceptions, do the same for *all*
988 exception regions active in the block. */
991 {
1000 {
1004 }
1005 }
1008 {
1009 /* ??? This could be made smarter: in some cases it's possible
1010 to tell that certain calls will not do a nonlocal goto.
1012 For example, if the nested functions that do the nonlocal
1013 gotos do not have their addresses taken, then only calls to
1014 those functions or to other nested functions that use them
1015 could possibly do nonlocal gotos. */
1016 /* We do know that a REG_EH_REGION note with a value less
1017 than 0 is guaranteed not to perform a non-local goto. */
1023 }
1024 }
1026 /* We know something about the structure of the function __throw in
1027 libgcc2.c. It is the only function that ever contains eh_stub
1028 labels. It modifies its return address so that the last block
1029 returns to one of the eh_stub labels within it. So we have to
1030 make additional edges in the flow graph. */
1034 /* Find out if we can drop through to the next block. */
1039 {
1045 }
1046 }
1051 }
1053 /* Create an edge between two basic blocks. FLAGS are auxiliary information
1054 about the edge that is accumulated between calls. */
1056 static void
1061 {
1063 edge e;
1065 /* Don't bother with edge cache for ENTRY or EXIT; there aren't that
1066 many edges to them, and we didn't allocate memory for it. */
1067 use_edge_cache = (edge_cache
1071 /* Make sure we don't add duplicate edges. */
1075 {
1078 }
1081 n_edges++;
1094 }
1096 /* Create an edge from a basic block to a label. */
1098 static void
1101 basic_block src;
1102 rtx label;
1104 {
1108 /* If the label was never emitted, this insn is junk, but avoid a
1109 crash trying to refer to BLOCK_FOR_INSN (label). This can happen
1110 as a result of a syntax error and a diagnostic has already been
1111 printed. */
1117 }
1119 /* Create the edges generated by INSN in REGION. */
1121 static void
1125 basic_block src;
1126 rtx insn;
1128 {
1135 {
1138 }
1139 }
1141 /* EH_REGION notes appearing between basic blocks is ambiguous, and even
1142 dangerous if we intend to move basic blocks around. Move such notes
1143 into the following block. */
1145 static void
1147 {
1156 {
1161 {
1166 {
1167 /* Unlink from the insn chain. */
1171 /* Queue it. */
1174 }
1175 }
1180 /* Find where to insert these things. */
1186 {
1190 }
1191 }
1192 }
1194 /* Recompute eh_beg/eh_end for each basic block. */
1196 static void
1198 rtx f;
1199 {
1205 {
1210 {
1215 {
1219 }
1220 }
1223 {
1229 }
1230 }
1231 }
1233 /* Identify critical edges and set the bits appropriately. */
1235 static void
1237 {
1239 basic_block bb;
1241 /* We begin with the entry block. This is not terribly important now,
1242 but could be if a front end (Fortran) implemented alternate entry
1243 points. */
1248 {
1249 edge e;
1251 /* (1) Critical edges must have a source with multiple successors. */
1253 {
1255 {
1256 /* (2) Critical edges must have a destination with multiple
1257 predecessors. Note that we know there is at least one
1258 predecessor -- the edge we followed to get here. */
1261 else
1263 }
1264 }
1265 else
1266 {
1269 }
1274 }
1275 }
1276 \f
1277 /* Split a (typically critical) edge. Return the new block.
1278 Abort on abnormal edges.
1280 ??? The code generally expects to be called on critical edges.
1281 The case of a block ending in an unconditional jump to a
1282 block with multiple predecessors is not handled optimally. */
1284 basic_block
1286 edge edge_in;
1287 {
1289 edge edge_out;
1290 rtx bb_note;
1293 /* Abnormal edges cannot be split. */
1300 /* Remove the existing edge from the destination's pred list. */
1301 {
1307 }
1309 /* Create the new structures. */
1312 n_edges++;
1318 /* ??? This info is likely going to be out of date very soon. */
1320 {
1323 }
1324 else
1325 {
1328 }
1330 /* Wire them up. */
1346 /* Tricky case -- if there existed a fallthru into the successor
1347 (and we're not it) we must add a new unconditional jump around
1348 the new block we're actually interested in.
1350 Further, if that edge is critical, this means a second new basic
1351 block must be created to hold it. In order to simplify correct
1352 insn placement, do this before we touch the existing basic block
1353 ordering for the block we were really wanting. */
1355 {
1356 edge e;
1362 {
1363 basic_block jump_block;
1364 rtx pos;
1367 {
1368 /* Non critical -- we can simply add a jump to the end
1369 of the existing predecessor. */
1371 }
1372 else
1373 {
1374 /* We need a new block to hold the jump. The simplest
1375 way to do the bulk of the work here is to recursively
1376 call ourselves. */
1379 }
1381 /* Now add the jump insn ... */
1387 /* ... let jump know that label is in use, ... */
1391 /* ... and clear fallthru on the outgoing edge. */
1394 /* Continue splitting the interesting edge. */
1395 }
1396 }
1398 /* Place the new block just in front of the successor. */
1402 else
1405 {
1409 }
1413 /* Create the basic block note.
1415 Where we place the note can have a noticable impact on the generated
1416 code. Consider this cfg:
1419 E
1420 |
1421 0
1422 / \
1423 +->1-->2--->E
1424 | |
1425 +--+
1427 If we need to insert an insn on the edge from block 0 to block 1,
1428 we want to ensure the instructions we insert are outside of any
1429 loop notes that physically sit between block 0 and block 1. Otherwise
1430 we confuse the loop optimizer into thinking the loop is a phony. */
1439 else
1444 /* Not quite simple -- for non-fallthru edges, we must adjust the
1445 predecessor's jump instruction to target our new block. */
1447 {
1455 /* ??? Recognize a tablejump and adjust all matching cases. */
1461 {
1462 rtvec vec;
1467 else
1472 {
1476 }
1478 /* Handle casesi dispatch insns */
1484 {
1486 new_label);
1489 }
1490 }
1491 else
1492 {
1493 /* This would have indicated an abnormal edge. */
1497 /* A return instruction can't be redirected. */
1501 /* If the insn doesn't go where we think, we're confused. */
1506 }
1510 }
1513 }
1515 /* Queue instructions for insertion on an edge between two basic blocks.
1516 The new instructions and basic blocks (if any) will not appear in the
1517 CFG until commit_edge_insertions is called. */
1519 void
1521 rtx pattern;
1522 edge e;
1523 {
1524 /* We cannot insert instructions on an abnormal critical edge.
1525 It will be easier to find the culprit if we die now. */
1532 else
1539 }
1541 /* Update the CFG for the instructions queued on edge E. */
1543 static void
1545 edge e;
1546 {
1548 basic_block bb;
1550 /* Figure out where to put these things. If the destination has
1551 one predecessor, insert there. Except for the exit block. */
1554 {
1557 /* Get the location correct wrt a code label, and "nice" wrt
1558 a basic block note, and before everything else. */
1567 else
1569 }
1571 /* If the source has one successor and the edge is not abnormal,
1572 insert there. Except for the entry block. */
1576 {
1579 {
1580 /* ??? Is it possible to wind up with non-simple jumps? Perhaps
1581 a jump with delay slots already filled? */
1586 }
1587 else
1588 {
1589 /* We'd better be fallthru, or we've lost track of what's what. */
1594 }
1595 }
1597 /* Otherwise we must split the edge. */
1598 else
1599 {
1602 }
1604 /* Now that we've found the spot, do the insertion. */
1608 /* Set the new block number for these insns, if structure is allocated. */
1610 {
1611 rtx i;
1614 }
1617 {
1621 }
1622 else
1623 {
1627 }
1628 }
1630 /* Update the CFG for all queued instructions. */
1632 void
1634 {
1636 basic_block bb;
1641 {
1645 {
1649 }
1654 }
1655 }
1656 \f
1657 /* Delete all unreachable basic blocks. */
1659 static void
1661 {
1664 edge e;
1670 /* Use basic_block->aux as a marker. Clear them all. */
1675 /* Add our starting points to the worklist. Almost always there will
1676 be only one. It isn't inconcievable that we might one day directly
1677 support Fortran alternate entry points. */
1680 {
1683 /* Mark the block with a handy non-null value. */
1685 }
1687 /* Iterate: find everything reachable from what we've already seen. */
1690 {
1695 {
1698 }
1699 }
1701 /* Delete all unreachable basic blocks. Count down so that we don't
1702 interfere with the block renumbering that happens in delete_block. */
1707 {
1711 /* This block was found. Tidy up the mark. */
1713 else
1715 }
1717 /* Fix up edges that now fall through, or rather should now fall through
1718 but previously required a jump around now deleted blocks. Simplify
1719 the search by only examining blocks numerically adjacent, since this
1720 is how find_basic_blocks created them. */
1723 {
1726 edge s;
1728 /* We care about simple conditional or unconditional jumps with
1729 a single successor.
1731 If we had a conditional branch to the next instruction when
1732 find_basic_blocks was called, then there will only be one
1733 out edge for the block which ended with the conditional
1734 branch (since we do not create duplicate edges).
1736 Furthermore, the edge will be marked as a fallthru because we
1737 merge the flags for the duplicate edges. So we do not want to
1738 check that the edge is not a FALLTHRU edge. */
1742 /* If the jump insn has side effects, we can't tidy the edge. */
1746 }
1748 /* If we deleted an exception handler, we may have EH region begin/end
1749 blocks to remove as well. */
1754 }
1756 /* Find EH regions for which there is no longer a handler, and delete them. */
1758 static void
1760 {
1761 rtx insn;
1767 {
1770 {
1772 /* A NULL handler indicates a region is no longer needed,
1773 as long as it isn't the target of a rethrow. */
1775 {
1778 }
1779 }
1780 }
1781 }
1783 /* Return true if NOTE is not one of the ones that must be kept paired,
1784 so that we may simply delete them. */
1786 static int
1788 rtx note;
1789 {
1792 }
1794 /* Unlink a chain of insns between START and FINISH, leaving notes
1795 that must be paired. */
1797 void
1800 {
1801 /* Unchain the insns one by one. It would be quicker to delete all
1802 of these with a single unchaining, rather than one at a time, but
1803 we need to keep the NOTE's. */
1805 rtx next;
1808 {
1811 ;
1813 ;
1814 else
1820 }
1821 }
1823 /* Delete the insns in a (non-live) block. We physically delete every
1824 non-deleted-note insn, and update the flow graph appropriately.
1826 Return nonzero if we deleted an exception handler. */
1828 /* ??? Preserving all such notes strikes me as wrong. It would be nice
1829 to post-process the stream to remove empty blocks, loops, ranges, etc. */
1831 static int
1833 basic_block b;
1834 {
1838 /* If the head of this block is a CODE_LABEL, then it might be the
1839 label for an exception handler which can't be reached.
1841 We need to remove the label from the exception_handler_label list
1842 and remove the associated NOTE_INSN_EH_REGION_BEG and
1843 NOTE_INSN_EH_REGION_END notes. */
1850 {
1854 {
1856 {
1857 /* Found a match, splice this label out of the EH label list. */
1862 /* Remove the handler from all regions */
1866 }
1868 }
1870 /* This label may be referenced by code solely for its value, or
1871 referenced by static data, or something. We have determined
1872 that it is not reachable, but cannot delete the label itself.
1873 Save code space and continue to delete the balance of the block,
1874 along with properly updating the cfg. */
1876 {
1877 /* If we've only got one of these, skip the whole deleting
1878 insns thing. */
1882 }
1883 }
1885 /* Selectively unlink the insn chain. Include any BARRIER that may
1886 follow the basic block. */
1892 no_delete_insns:
1894 /* Remove the edges into and out of this block. Note that there may
1895 indeed be edges in, if we are removing an unreachable loop. */
1896 {
1900 {
1905 n_edges--;
1907 }
1909 {
1914 n_edges--;
1916 }
1920 }
1922 /* Remove the basic block from the array, and compact behind it. */
1926 }
1928 /* Remove block B from the basic block array and compact behind it. */
1930 static void
1932 basic_block b;
1933 {
1937 {
1941 }
1944 n_basic_blocks--;
1945 }
1947 /* Delete INSN by patching it out. Return the next insn. */
1949 static rtx
1951 rtx insn;
1952 {
1963 else
1969 /* If deleting a jump, decrement the use count of the label. Deleting
1970 the label itself should happen in the normal course of block merging. */
1975 }
1977 /* True if a given label can be deleted. */
1979 static int
1981 rtx label;
1982 {
1983 rtx x;
1998 /* User declared labels must be preserved. */
2003 }
2005 /* Blocks A and B are to be merged into a single block. A has no incoming
2006 fallthru edge, so it can be moved before B without adding or modifying
2007 any jumps (aside from the jump from A to B). */
2009 static int
2012 {
2019 /* We want to delete the BARRIER after the end of the insns we are
2020 going to move. If we don't find a BARRIER, then do nothing. This
2021 can happen in some cases if we have labels we can not delete.
2023 Similarly, do nothing if we can not delete the label at the start
2024 of the target block. */
2030 else
2033 /* Move block and loop notes out of the chain so that we do not
2034 disturb their order.
2036 ??? A better solution would be to squeeze out all the non-nested notes
2037 and adjust the block trees appropriately. Even better would be to have
2038 a tighter connection between block trees and rtl so that this is not
2039 necessary. */
2042 /* Scramble the insn chain. */
2047 {
2050 }
2052 /* Swap the records for the two blocks around. Although we are deleting B,
2053 A is now where B was and we want to compact the BB array from where
2054 A used to be. */
2061 /* Now blocks A and B are contiguous. Merge them. */
2065 }
2067 /* Blocks A and B are to be merged into a single block. B has no outgoing
2068 fallthru edge, so it can be moved after A without adding or modifying
2069 any jumps (aside from the jump from A to B). */
2071 static int
2074 {
2080 /* We want to delete the BARRIER after the end of the insns we are
2081 going to move. If we don't find a BARRIER, then do nothing. This
2082 can happen in some cases if we have labels we can not delete.
2084 Similarly, do nothing if we can not delete the label at the start
2085 of the target block. */
2091 else
2094 /* Move block and loop notes out of the chain so that we do not
2095 disturb their order.
2097 ??? A better solution would be to squeeze out all the non-nested notes
2098 and adjust the block trees appropriately. Even better would be to have
2099 a tighter connection between block trees and rtl so that this is not
2100 necessary. */
2103 /* Scramble the insn chain. */
2106 /* Now blocks A and B are contiguous. Merge them. */
2110 {
2113 }
2116 }
2118 /* Blocks A and B are to be merged into a single block. The insns
2119 are already contiguous, hence `nomove'. */
2121 static void
2124 {
2125 edge e;
2129 /* If there was a CODE_LABEL beginning B, delete it. */
2133 {
2134 /* Detect basic blocks with nothing but a label. This can happen
2135 in particular at the end of a function. */
2139 }
2141 /* Delete the basic block note. */
2144 {
2148 }
2150 /* If there was a jump out of A, delete it. */
2153 {
2154 rtx prev;
2160 #ifdef HAVE_cc0
2161 /* If this was a conditional jump, we need to also delete
2162 the insn that set cc0. */
2165 {
2171 }
2172 #endif
2174 /* Note that a->head != a->end, since we should have at least a
2175 bb note plus the jump, so prev != insn. */
2178 }
2180 /* By definition, there should only be one successor of A, and that is
2181 B. Free that edge struct. */
2182 n_edges--;
2185 /* Adjust the edges out of B for the new owner. */
2190 /* Reassociate the insns of B with A. */
2192 {
2195 {
2198 }
2200 }
2203 /* Compact the basic block array. */
2205 }
2207 /* Attempt to merge basic blocks that are potentially non-adjacent.
2208 Return true iff the attempt succeeded. */
2210 static int
2212 edge e;
2214 {
2215 /* If B has a fallthru edge to C, no need to move anything. */
2217 {
2218 /* If a label still appears somewhere and we cannot delete the label,
2219 then we cannot merge the blocks. The edge was tidied already. */
2229 {
2232 }
2235 }
2236 else
2237 {
2238 edge tmp_edge;
2239 basic_block d;
2243 /* We must make sure to not munge nesting of exception regions,
2244 lexical blocks, and loop notes.
2246 The first is taken care of by requiring that the active eh
2247 region at the end of one block always matches the active eh
2248 region at the beginning of the next block.
2250 The later two are taken care of by squeezing out all the notes. */
2252 /* ??? A throw/catch edge (or any abnormal edge) should be rarely
2253 executed and we may want to treat blocks which have two out
2254 edges, one normal, one abnormal as only having one edge for
2255 block merging purposes. */
2267 /* If B does not have an incoming fallthru, and the exception regions
2268 match, then it can be moved immediately before C without introducing
2269 or modifying jumps.
2271 C can not be the first block, so we do not have to worry about
2272 accessing a non-existent block. */
2279 /* Otherwise, we're going to try to move C after B. Make sure the
2280 exception regions match.
2282 If B is the last basic block, then we must not try to access the
2283 block structure for block B + 1. Luckily in that case we do not
2284 need to worry about matching exception regions. */
2288 {
2289 /* If C does not have an outgoing fallthru, then it can be moved
2290 immediately after B without introducing or modifying jumps. */
2294 /* Otherwise, we'll need to insert an extra jump, and possibly
2295 a new block to contain it. */
2296 /* ??? Not implemented yet. */
2297 }
2300 }
2301 }
2303 /* Top level driver for merge_blocks. */
2305 static void
2307 {
2310 /* Attempt to merge blocks as made possible by edge removal. If a block
2311 has only one successor, and the successor has only one predecessor,
2312 they may be combined. */
2315 {
2317 edge s;
2319 /* A loop because chains of blocks might be combineable. */
2325 /* If the jump insn has side effects, we can't kill the edge. */
2331 /* Don't get confused by the index shift caused by deleting blocks. */
2333 }
2334 }
2336 /* The given edge should potentially a fallthru edge. If that is in
2337 fact true, delete the unconditional jump and barriers that are in
2338 the way. */
2340 static void
2342 edge e;
2344 {
2345 rtx q;
2347 /* ??? In a late-running flow pass, other folks may have deleted basic
2348 blocks by nopping out blocks, leaving multiple BARRIERs between here
2349 and the target label. They ought to be chastized and fixed.
2351 We can also wind up with a sequence of undeletable labels between
2352 one block and the next.
2354 So search through a sequence of barriers, labels, and notes for
2355 the head of block C and assert that we really do fall through. */
2360 /* Remove what will soon cease being the jump insn from the source block.
2361 If block B consisted only of this single jump, turn it into a deleted
2362 note. */
2365 {
2366 #ifdef HAVE_cc0
2367 /* If this was a conditional jump, we need to also delete
2368 the insn that set cc0. */
2371 #endif
2374 {
2378 }
2379 else
2381 }
2383 /* Selectively unlink the sequence. */
2388 }
2390 /* Discover and record the loop depth at the head of each basic block. */
2392 static void
2394 rtx insns;
2395 {
2396 basic_block bb;
2397 rtx insn;
2402 {
2404 {
2409 }
2412 {
2414 depth++;
2416 depth--;
2418 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error. */
2421 }
2422 }
2423 }
2424 \f
2425 /* Perform data flow analysis.
2426 F is the first insn of the function and NREGS the number of register numbers
2427 in use. */
2429 void
2431 rtx f;
2435 {
2436 #ifdef ELIMINABLE_REGS
2439 #endif
2442 /* Record which registers will be eliminated. We use this in
2443 mark_used_regs. */
2447 #ifdef ELIMINABLE_REGS
2450 #else
2452 #endif
2454 /* Allocate a bitmap to be filled in by record_volatile_insns. */
2457 /* We want alias analysis information for local dead store elimination. */
2475 }
2477 /* A subroutine of verify_wide_reg, called through for_each_rtx.
2478 Search for REGNO. If found, abort if it is not wider than word_mode. */
2480 static int
2484 {
2489 {
2493 }
2495 }
2497 /* A subroutine of verify_local_live_at_start. Search through insns
2498 between HEAD and END looking for register REGNO. */
2500 static void
2504 {
2506 {
2513 }
2515 /* We didn't find the register at all. Something's way screwy. */
2517 }
2519 /* A subroutine of update_life_info. Verify that there are no untoward
2520 changes in live_at_start during a local update. */
2522 static void
2524 regset new_live_at_start;
2525 basic_block bb;
2526 {
2528 {
2529 /* After reload, there are no pseudos, nor subregs of multi-word
2530 registers. The regsets should exactly match. */
2533 }
2534 else
2535 {
2538 /* Find the set of changed registers. */
2542 {
2543 /* No registers should die. */
2546 /* Verify that the now-live register is wider than word_mode. */
2548 });
2549 }
2550 }
2552 /* Updates death notes starting with the basic blocks set in BLOCKS.
2554 If LOCAL_ONLY, such as after splitting or peepholeing, we are only
2555 expecting local modifications to basic blocks. If we find extra
2556 registers live at the beginning of a block, then we either killed
2557 useful data, or we have a broken split that wants data not provided.
2558 If we find registers removed from live_at_start, that means we have
2559 a broken peephole that is killing a register it shouldn't.
2561 ??? This is not true in one situation -- when a pre-reload splitter
2562 generates subregs of a multi-word pseudo, current life analysis will
2563 lose the kill. So we _can_ have a pseudo go live. How irritating.
2565 BLOCK_FOR_INSN is assumed to be correct.
2567 ??? PROP_FLAGS should not contain PROP_LOG_LINKS. Need to set up
2568 reg_next_use for that. Including PROP_REG_INFO does not refresh
2569 regs_ever_live unless the caller resets it to zero. */
2571 void
2573 sbitmap blocks;
2576 {
2577 regset tmp;
2582 /* For a global update, we go through the relaxation process again. */
2584 {
2588 /* If asked, remove notes from the blocks we'll update. */
2591 }
2594 {
2599 prop_flags);
2603 });
2606 }
2608 /* Free the variables allocated by find_basic_blocks.
2610 KEEP_HEAD_END_P is non-zero if basic_block_info is not to be freed. */
2612 void
2615 {
2617 {
2620 }
2623 {
2632 }
2633 }
2635 /* Return nonzero if the destination of SET equals the source. */
2636 static int
2638 rtx set;
2639 {
2654 }
2656 /* Return nonzero if an insn consists only of SETs, each of which only sets a
2657 value to itself. */
2658 static int
2660 rtx insn;
2661 {
2664 /* Insns carrying these notes are useful later on. */
2672 {
2674 /* If nothing but SETs of registers to themselves,
2675 this insn can also be deleted. */
2677 {
2686 }
2689 }
2691 }
2693 static void
2695 rtx x;
2696 rtx pat ATTRIBUTE_UNUSED;
2698 {
2700 /* The stack pointer is only modified indirectly as the result
2701 of a push until later in flow. See the comments in rtl.texi
2702 regarding Embedded Side-Effects on Addresses. */
2710 }
2712 /* Record which insns refer to any volatile memory
2713 or for any reason can't be deleted just because they are dead stores.
2714 Also, delete any insns that copy a register to itself.
2715 And see if the stack pointer is modified. */
2716 static void
2718 rtx f;
2719 {
2720 rtx insn;
2722 {
2727 {
2732 /* A SET that makes space on the stack cannot be dead.
2733 (Such SETs occur only for allocating variable-size data,
2734 so they will always have a PLUS or MINUS according to the
2735 direction of stack growth.)
2736 Even if this function never uses this stack pointer value,
2737 signal handlers do! */
2740 #ifdef STACK_GROWS_DOWNWARD
2742 #else
2744 #endif
2748 /* Delete (in effect) any obvious no-op moves. */
2750 {
2754 }
2755 }
2757 /* Check if insn modifies the stack pointer. */
2761 notice_stack_pointer_modification,
2762 NULL);
2763 }
2764 }
2766 /* Mark a register in SET. Hard registers in large modes get all
2767 of their component registers set as well. */
2768 static void
2770 regset set;
2771 rtx reg;
2772 {
2777 {
2781 }
2782 }
2784 /* Mark those regs which are needed at the end of the function as live
2785 at the end of the last basic block. */
2786 static void
2788 regset set;
2789 {
2790 tree type;
2793 /* If exiting needs the right stack value, consider the stack pointer
2794 live at the end of the function. */
2796 || ! EXIT_IGNORE_STACK
2797 || (! FRAME_POINTER_REQUIRED
2798 && ! current_function_calls_alloca
2801 {
2803 }
2805 /* Mark the frame pointer if needed at the end of the function. If
2806 we end up eliminating it, it will be removed from the live list
2807 of each basic block by reload. */
2810 {
2812 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2813 /* If they are different, also mark the hard frame pointer as live */
2815 #endif
2816 }
2818 #ifdef PIC_OFFSET_TABLE_REGNUM
2819 #ifndef PIC_OFFSET_TABLE_REG_CALL_CLOBBERED
2820 /* Many architectures have a GP register even without flag_pic.
2821 Assume the pic register is not in use, or will be handled by
2822 other means, if it is not fixed. */
2825 #endif
2826 #endif
2828 /* Mark all global registers, and all registers used by the epilogue
2829 as being live at the end of the function since they may be
2830 referenced by our caller. */
2833 #ifdef EPILOGUE_USES
2835 #endif
2836 )
2839 /* Mark all call-saved registers that we actaully used. */
2841 {
2845 }
2847 /* Mark function return value. */
2848 /* ??? Only do this after reload. Consider a non-void function that
2849 omits a return statement. Across that edge we'll have the return
2850 register live, and no set for it. Thus the return register will
2851 be live back through the CFG to the entry, and thus we die. A
2852 possible solution is to emit a clobber at exits without returns. */
2857 {
2858 rtx outgoing;
2864 #ifdef FUNCTION_OUTGOING_VALUE
2866 #else
2868 #endif
2873 {
2876 /* Check for a NULL entry, used to indicate that the parameter
2877 goes on the stack and in registers. */
2881 {
2885 }
2886 }
2887 else
2889 }
2890 }
2892 /* Determine which registers are live at the start of each
2893 basic block of the function whose first insn is F.
2894 NREGS is the number of registers used in F.
2895 We allocate the vector basic_block_live_at_start
2896 and the regsets that it points to, and fill them with the data.
2897 regset_size and regset_bytes are also set here. */
2899 static void
2901 rtx f;
2904 {
2910 /* Allocate and zero out many data structures
2911 that will record the data from lifetime analysis. */
2918 /* Assume that the stack pointer is unchanging if alloca hasn't been used.
2919 This will be cleared by record_volatile_insns if it encounters an insn
2920 which modifies the stack pointer. */
2924 /* Find the set of registers live on function exit. Do this before
2925 zeroing regs_ever_live, as we use that data post-reload. */
2928 /* The post-reload life analysis have (on a global basis) the same
2929 registers live as was computed by reload itself. elimination
2930 Otherwise offsets and such may be incorrect.
2932 Reload will make some registers as live even though they do not
2933 appear in the rtl. */
2938 /* Compute register life at block boundaries. It'd be nice to
2939 begin with just the exit and noreturn blocks, but that set
2940 is not immediately handy. */
2941 {
2942 sbitmap blocks;
2947 }
2949 /* The only pseudos that are live at the beginning of the function are
2950 those that were not set anywhere in the function. local-alloc doesn't
2951 know how to handle these correctly, so mark them as not local to any
2952 one basic block. */
2958 /* Now the life information is accurate. Make one more pass over each
2959 basic block to delete dead stores, create autoincrement addressing
2960 and record how many times each register is used, is set, or dies. */
2961 {
2962 regset tmp;
2966 {
2971 }
2974 }
2976 /* We have a problem with any pseudoreg that lives across the setjmp.
2977 ANSI says that if a user variable does not change in value between
2978 the setjmp and the longjmp, then the longjmp preserves it. This
2979 includes longjmp from a place where the pseudo appears dead.
2980 (In principle, the value still exists if it is in scope.)
2981 If the pseudo goes in a hard reg, some other value may occupy
2982 that hard reg where this pseudo is dead, thus clobbering the pseudo.
2983 Conclusion: such a pseudo must not go in a hard reg. */
2986 {
2988 {
2991 }
2992 });
2994 /* Restore regs_ever_live that was provided by reload. */
2998 /* Clean up. */
3001 }
3003 /* Propagate global life info around the graph of basic blocks. Begin
3004 considering blocks with their corresponding bit set in BLOCKS_IN.
3005 BLOCKS_OUT is set for every block that was changed. */
3007 static void
3011 {
3019 /* Create a worklist. Allocate an extra slot for ENTRY_BLOCK, and one
3020 because the `head == tail' style test for an empty queue doesn't
3021 work with a full queue. */
3026 /* Clear out the garbage that might be hanging out in bb->aux. */
3030 /* Queue the blocks set in the initial mask. Do this in reverse block
3031 number order so that we are more likely for the first round to do
3032 useful work. We use AUX non-null to flag that the block is queued. */
3034 {
3038 });
3043 {
3045 basic_block bb;
3046 edge e;
3053 /* Begin by propogating live_at_start from the successor blocks. */
3056 {
3059 }
3062 {
3065 }
3067 /* On our first pass through this block, we'll go ahead and continue.
3068 Recognize first pass by local_set NULL. On subsequent passes, we
3069 get to skip out early if live_at_end wouldn't have changed. */
3072 {
3075 }
3076 else
3077 {
3078 /* If any bits were removed from live_at_end, we'll have to
3079 rescan the block. This wouldn't be necessary if we had
3080 precalculated local_live, however with PROP_SCAN_DEAD_CODE
3081 local_live is really dependant on live_at_end. */
3087 {
3088 /* Find the set of changed bits. Take this opportunity
3089 to notice that this set is empty and early out. */
3096 /* If any of the changed bits overlap with local_set,
3097 we'll have to rescan the block. Detect overlap by
3098 the AND with ~local_set turning off bits. */
3100 BITMAP_AND_COMPL);
3101 }
3102 }
3104 /* Let our caller know that BB changed enough to require its
3105 death notes updated. */
3109 {
3110 /* Add to live_at_start the set of all registers in
3111 new_live_at_end that aren't in the old live_at_end. */
3114 BITMAP_AND_COMPL);
3122 }
3123 else
3124 {
3127 /* Rescan the block insn by insn to turn (a copy of) live_at_end
3128 into live_at_start. */
3132 /* If live_at start didn't change, no need to go farther. */
3137 }
3139 /* Queue all predecessors of BB so that we may re-examine
3140 their live_at_end. */
3142 {
3145 {
3150 }
3151 }
3152 }
3158 {
3161 });
3164 }
3165 \f
3166 /* Subroutines of life analysis. */
3168 /* Allocate the permanent data structures that represent the results
3169 of life analysis. Not static since used also for stupid life analysis. */
3171 void
3173 {
3177 {
3182 }
3184 ENTRY_BLOCK_PTR->global_live_at_end
3186 EXIT_BLOCK_PTR->global_live_at_start
3190 }
3192 void
3194 {
3197 /* Recalculate the register space, in case it has grown. Old style
3198 vector oriented regsets would set regset_{size,bytes} here also. */
3201 /* Reset all the data we'll collect in propagate_block and its
3202 subroutines. */
3204 {
3211 }
3212 }
3214 /* Compute the registers live at the beginning of a basic block
3215 from those live at the end.
3217 When called, OLD contains those live at the end.
3218 On return, it contains those live at the beginning.
3219 FIRST and LAST are the first and last insns of the basic block.
3221 FINAL is nonzero if we are doing the final pass which is not
3222 for computing the life info (since that has already been done)
3223 but for acting on it. On this pass, we delete dead stores,
3224 set up the logical links and dead-variables lists of instructions,
3225 and merge instructions for autoincrement and autodecrement addresses.
3227 SIGNIFICANT is nonzero only the first time for each basic block.
3228 If it is nonzero, it points to a regset in which we store
3229 a 1 for each register that is set within the block.
3231 BNUM is the number of the basic block. */
3233 static void
3236 rtx first;
3237 rtx last;
3238 regset significant;
3241 {
3243 rtx prev;
3244 regset live;
3245 regset dead;
3247 /* Find the loop depth for this block. Ignore loop level changes in the
3248 middle of the basic block -- for register allocation purposes, the
3249 important uses will be in the blocks wholely contained within the loop
3250 not in the loop pre-header or post-trailer. */
3259 {
3262 /* Process the regs live at the end of the block.
3263 Mark them as not local to any one basic block. */
3265 {
3267 });
3268 }
3270 /* Scan the block an insn at a time from end to beginning. */
3273 {
3277 {
3278 /* If this is a call to `setjmp' et al,
3279 warn if any non-volatile datum is live. */
3284 }
3286 /* Update the life-status of regs for this insn.
3287 First DEAD gets which regs are set in this insn
3288 then LIVE gets which regs are used in this insn.
3289 Then the regs live before the insn
3290 are those live after, with DEAD regs turned off,
3291 and then LIVE regs turned on. */
3294 {
3301 {
3303 /* Don't delete something that refers to volatile storage! */
3307 }
3309 /* We almost certainly don't want to delete prologue or epilogue
3310 instructions. Warn about probable compiler losage. */
3312 && insn_is_dead
3313 && reload_completed
3316 {
3320 }
3322 /* If an instruction consists of just dead store(s) on final pass,
3323 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
3324 We could really delete it with delete_insn, but that
3325 can cause trouble for first or last insn in a basic block. */
3327 {
3328 rtx inote;
3329 /* If the insn referred to a label, note that the label is
3330 now less used. */
3332 {
3334 {
3336 rtx next;
3339 /* If this label was attached to an ADDR_VEC, it's
3340 safe to delete the ADDR_VEC. In fact, it's pretty much
3341 mandatory to delete it, because the ADDR_VEC may
3342 be referencing labels that no longer exist. */
3348 {
3358 }
3359 }
3360 }
3366 /* CC0 is now known to be dead. Either this insn used it,
3367 in which case it doesn't anymore, or clobbered it,
3368 so the next insn can't use it. */
3371 /* If this insn is copying the return value from a library call,
3372 delete the entire library call. */
3374 {
3380 {
3385 }
3386 }
3388 }
3393 /* See if this is an increment or decrement that can be
3394 merged into a following memory address. */
3395 #ifdef AUTO_INC_DEC
3396 {
3399 /* Does this instruction increment or decrement a register? */
3408 /* Ok, look for a following memory ref we can combine with.
3409 If one is found, change the memory ref to a PRE_INC
3410 or PRE_DEC, cancel this insn, and return 1.
3411 Return 0 if nothing has been done. */
3414 }
3417 /* If this is not the final pass, and this insn is copying the
3418 value of a library call and it's dead, don't scan the
3419 insns that perform the library call, so that the call's
3420 arguments are not marked live. */
3422 {
3423 /* Mark the dest reg as `significant'. */
3429 }
3435 /* We have an insn to pop a constant amount off the stack.
3436 (Such insns use PLUS regardless of the direction of the stack,
3437 and any insn to adjust the stack by a constant is always a pop.)
3438 These insns, if not dead stores, have no effect on life. */
3439 ;
3440 else
3441 {
3442 /* Any regs live at the time of a call instruction
3443 must not go in a register clobbered by calls.
3444 Find all regs now live and record this for them. */
3449 {
3451 });
3453 /* LIVE gets the regs used in INSN;
3454 DEAD gets those set by it. Dead insns don't make anything
3455 live. */
3460 /* If an insn doesn't use CC0, it becomes dead since we
3461 assume that every insn clobbers it. So show it dead here;
3462 mark_used_regs will set it live if it is referenced. */
3468 /* Sometimes we may have inserted something before INSN (such as
3469 a move) when we make an auto-inc. So ensure we will scan
3470 those insns. */
3471 #ifdef AUTO_INC_DEC
3473 #endif
3476 {
3479 rtx note;
3482 note;
3488 /* Each call clobbers all call-clobbered regs that are not
3489 global or fixed. Note that the function-value reg is a
3490 call-clobbered reg, and mark_set_regs has already had
3491 a chance to handle it. */
3496 {
3500 }
3502 /* The stack ptr is used (honorarily) by a CALL insn. */
3505 /* Calls may also reference any of the global registers,
3506 so they are made live. */
3513 /* Calls also clobber memory. */
3515 }
3517 /* Update OLD for the registers used or set. */
3521 }
3523 /* On final pass, update counts of how many insns each reg is live
3524 at. */
3528 }
3529 flushed: ;
3532 }
3537 }
3538 \f
3539 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
3540 (SET expressions whose destinations are registers dead after the insn).
3541 NEEDED is the regset that says which regs are alive after the insn.
3543 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL.
3545 If X is the entire body of an insn, NOTES contains the reg notes
3546 pertaining to the insn. */
3548 static int
3550 rtx x;
3551 regset needed;
3553 rtx notes ATTRIBUTE_UNUSED;
3554 {
3557 #ifdef AUTO_INC_DEC
3558 /* If flow is invoked after reload, we must take existing AUTO_INC
3559 expresions into account. */
3561 {
3563 {
3565 {
3568 /* Don't delete insns to set global regs. */
3572 }
3573 }
3574 }
3575 #endif
3577 /* If setting something that's a reg or part of one,
3578 see if that register's altered value will be live. */
3581 {
3584 /* A SET that is a subroutine call cannot be dead. */
3588 #ifdef HAVE_cc0
3591 #endif
3594 {
3595 rtx temp;
3596 /* Walk the set of memory locations we are currently tracking
3597 and see if one is an identical match to this memory location.
3598 If so, this memory write is dead (remember, we're walking
3599 backwards from the end of the block to the start. */
3602 {
3606 }
3607 }
3614 {
3617 /* Don't delete insns to set global regs. */
3619 /* Make sure insns to set frame pointer aren't deleted. */
3622 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
3625 #endif
3626 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
3627 /* Make sure insns to set arg pointer are never deleted
3628 (if the arg pointer isn't fixed, there will be a USE for
3629 it, so we can treat it normally). */
3631 #endif
3635 /* If this is a hard register, verify that subsequent words are
3636 not needed. */
3638 {
3644 }
3647 }
3648 }
3650 /* If performing several activities,
3651 insn is dead if each activity is individually dead.
3652 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
3653 that's inside a PARALLEL doesn't make the insn worth keeping. */
3655 {
3665 }
3667 /* A CLOBBER of a pseudo-register that is dead serves no purpose. That
3668 is not necessarily true for hard registers. */
3674 /* We do not check other CLOBBER or USE here. An insn consisting of just
3675 a CLOBBER or just a USE should not be deleted. */
3677 }
3679 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
3680 return 1 if the entire library call is dead.
3681 This is true if X copies a register (hard or pseudo)
3682 and if the hard return reg of the call insn is dead.
3683 (The caller should have tested the destination of X already for death.)
3685 If this insn doesn't just copy a register, then we don't
3686 have an ordinary libcall. In that case, cse could not have
3687 managed to substitute the source for the dest later on,
3688 so we can assume the libcall is dead.
3690 NEEDED is the bit vector of pseudoregs live before this insn.
3691 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
3693 static int
3695 rtx x;
3696 regset needed;
3697 rtx note;
3698 rtx insn;
3699 {
3703 {
3706 {
3708 rtx call_pat;
3711 /* Find the call insn. */
3715 /* If there is none, do nothing special,
3716 since ordinary death handling can understand these insns. */
3720 /* See if the hard reg holding the value is dead.
3721 If this is a PARALLEL, find the call within it. */
3724 {
3730 /* This may be a library call that is returning a value
3731 via invisible pointer. Do nothing special, since
3732 ordinary death handling can understand these insns. */
3737 }
3740 }
3741 }
3743 }
3745 /* Return 1 if register REGNO was used before it was set, i.e. if it is
3746 live at function entry. Don't count global register variables, variables
3747 in registers that can be used for function arg passing, or variables in
3748 fixed hard registers. */
3750 int
3753 {
3762 }
3764 /* 1 if register REGNO was alive at a place where `setjmp' was called
3765 and was set more than once or is an argument.
3766 Such regs may be clobbered by `longjmp'. */
3768 int
3771 {
3778 }
3779 \f
3780 /* INSN references memory, possibly using autoincrement addressing modes.
3781 Find any entries on the mem_set_list that need to be invalidated due
3782 to an address change. */
3783 static void
3785 rtx insn;
3786 {
3789 {
3791 {
3794 rtx next;
3797 {
3800 {
3801 /* Splice temp out of list. */
3804 else
3807 }
3808 else
3811 }
3812 }
3813 }
3814 }
3816 /* Process the registers that are set within X. Their bits are set to
3817 1 in the regset DEAD, because they are dead prior to this insn.
3819 If INSN is nonzero, it is the insn being processed.
3821 FLAGS is the set of operations to perform. */
3823 static void
3825 regset needed;
3826 regset dead;
3827 rtx x;
3828 rtx insn;
3829 regset significant;
3831 {
3837 {
3840 {
3845 }
3846 }
3847 }
3849 /* Process a single SET rtx, X. */
3851 static void
3853 regset needed;
3854 regset dead;
3855 rtx x;
3856 rtx insn;
3857 regset significant;
3859 {
3863 /* Some targets place small structures in registers for
3864 return values of functions. We have to detect this
3865 case specially here to get correct flow information. */
3868 {
3875 }
3877 /* Modifying just one hardware register of a multi-reg value
3878 or just a byte field of a register
3879 does not mean the value from before this insn is now dead.
3880 But it does mean liveness of that register at the end of the block
3881 is significant.
3883 Within mark_set_1, however, we treat it as if the register is
3884 indeed modified. mark_used_regs will, however, also treat this
3885 register as being used. Thus, we treat these insns as setting a
3886 new value for the register as a function of its old value. This
3887 cases LOG_LINKS to be made appropriately and this will help combine. */
3894 /* If this set is a MEM, then it kills any aliased writes.
3895 If this set is a REG, then it kills any MEMs which use the reg. */
3897 {
3900 {
3903 rtx next;
3906 {
3912 {
3913 /* Splice this entry out of the list. */
3916 else
3919 }
3920 else
3923 }
3924 }
3926 /* If the memory reference had embedded side effects (autoincrement
3927 address modes. Then we may need to kill some entries on the
3928 memory set list. */
3933 /* We do not know the size of a BLKmode store, so we do not track
3934 them for redundant store elimination. */
3936 /* There are no REG_INC notes for SP, so we can't assume we'll see
3937 everything that invalidates it. To be safe, don't eliminate any
3938 stores though SP; none of them should be redundant anyway. */
3941 }
3947 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
3950 #endif
3951 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
3953 #endif
3955 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
3956 {
3960 /* Mark it as a significant register for this basic block. */
3964 /* Mark it as dead before this insn. */
3967 /* A hard reg in a wide mode may really be multiple registers.
3968 If so, mark all of them just like the first. */
3970 {
3973 /* Nothing below is needed for the stack pointer; get out asap.
3974 Eg, log links aren't needed, since combine won't use them. */
3980 {
3989 }
3990 }
3992 /* Additional data to record if this is the final pass. */
3995 {
4003 /* If this is a hard reg, record this function uses the reg. */
4006 {
4012 {
4013 /* The next use is no longer "next", since a store
4014 intervenes. */
4016 }
4020 {
4023 }
4024 }
4025 else
4026 {
4027 /* The next use is no longer "next", since a store
4028 intervenes. */
4032 /* Keep track of which basic blocks each reg appears in. */
4035 {
4041 /* Count (weighted) references, stores, etc. This counts a
4042 register twice if it is modified, but that is correct. */
4046 /* The insns where a reg is live are normally counted
4047 elsewhere, but we want the count to include the insn
4048 where the reg is set, and the normal counting mechanism
4049 would not count it. */
4051 }
4052 }
4055 {
4057 {
4058 /* Make a logical link from the next following insn
4059 that uses this register, back to this insn.
4060 The following insns have already been processed.
4062 We don't build a LOG_LINK for hard registers containing
4063 in ASM_OPERANDs. If these registers get replaced,
4064 we might wind up changing the semantics of the insn,
4065 even if reload can make what appear to be valid
4066 assignments later. */
4071 }
4072 }
4074 {
4079 {
4080 /* Note that dead stores have already been deleted
4081 when possible. If we get here, we have found a
4082 dead store that cannot be eliminated (because the
4083 same insn does something useful). Indicate this
4084 by marking the reg being set as dying here. */
4087 }
4088 }
4089 else
4090 {
4092 {
4093 /* This is a case where we have a multi-word hard register
4094 and some, but not all, of the words of the register are
4095 needed in subsequent insns. Write REG_UNUSED notes
4096 for those parts that were not needed. This case should
4097 be rare. */
4105 = (alloc_EXPR_LIST
4109 }
4110 }
4111 }
4112 }
4114 {
4117 }
4119 /* If this is the last pass and this is a SCRATCH, show it will be dying
4120 here and count it. */
4122 {
4126 }
4127 }
4128 \f
4129 #ifdef AUTO_INC_DEC
4131 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
4132 reference. */
4134 static void
4136 regset needed;
4137 rtx x;
4138 rtx insn;
4139 {
4142 rtx set;
4144 /* Here we detect use of an index register which might be good for
4145 postincrement, postdecrement, preincrement, or predecrement. */
4151 {
4154 rtx use;
4155 rtx incr;
4158 /* Is the next use an increment that might make auto-increment? */
4163 /* Can't add side effects to jumps; if reg is spilled and
4164 reloaded, there's no way to store back the altered value. */
4169 && ((HAVE_POST_INCREMENT
4171 || (HAVE_POST_DECREMENT
4173 || (HAVE_PRE_INCREMENT
4175 || (HAVE_PRE_DECREMENT
4177 /* Make sure this reg appears only once in this insn. */
4180 {
4187 {
4188 /* This is the simple case. Try to make the auto-inc. If
4189 we can't, we are done. Otherwise, we will do any
4190 needed updates below. */
4195 }
4197 /* PREV_INSN used here to check the semi-open interval
4198 [insn,incr). */
4200 /* We must also check for sets of q as q may be
4201 a call clobbered hard register and there may
4202 be a call between PREV_INSN (insn) and incr. */
4204 {
4205 /* We have *p followed sometime later by q = p+size.
4206 Both p and q must be live afterward,
4207 and q is not used between INSN and its assignment.
4208 Change it to q = p, ...*q..., q = q+size.
4209 Then fall into the usual case. */
4211 basic_block bb;
4222 /* If we can't make the auto-inc, or can't make the
4223 replacement into Y, exit. There's no point in making
4224 the change below if we can't do the auto-inc and doing
4225 so is not correct in the pre-inc case. */
4234 /* We now know we'll be doing this change, so emit the
4235 new insn(s) and do the updates. */
4241 /* INCR will become a NOTE and INSN won't contain a
4242 use of ADDR. If a use of ADDR was just placed in
4243 the insn before INSN, make that the next use.
4244 Otherwise, invalidate it. */
4249 else
4255 /* REGNO is now used in INCR which is below INSN, but
4256 it previously wasn't live here. If we don't mark
4257 it as needed, we'll put a REG_DEAD note for it
4258 on this insn, which is incorrect. */
4261 /* If there are any calls between INSN and INCR, show
4262 that REGNO now crosses them. */
4266 }
4267 else
4270 /* If we haven't returned, it means we were able to make the
4271 auto-inc, so update the status. First, record that this insn
4272 has an implicit side effect. */
4277 /* Modify the old increment-insn to simply copy
4278 the already-incremented value of our register. */
4282 /* If that makes it a no-op (copying the register into itself) delete
4283 it so it won't appear to be a "use" and a "set" of this
4284 register. */
4286 {
4290 }
4293 {
4294 /* Count an extra reference to the reg. When a reg is
4295 incremented, spilling it is worse, so we want to make
4296 that less likely. */
4299 /* Count the increment as a setting of the register,
4300 even though it isn't a SET in rtl. */
4302 }
4303 }
4304 }
4305 }
4307 \f
4308 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
4309 This is done assuming the registers needed from X
4310 are those that have 1-bits in NEEDED.
4312 FLAGS is the set of enabled operations.
4314 INSN is the containing instruction. If INSN is dead, this function is not
4315 called. */
4317 static void
4319 regset needed;
4320 regset live;
4321 rtx x;
4323 rtx insn;
4324 {
4329 retry:
4332 {
4343 #ifdef HAVE_cc0
4347 #endif
4350 /* If we are clobbering a MEM, mark any registers inside the address
4351 as being used. */
4357 /* Don't bother watching stores to mems if this is not the
4358 final pass. We'll not be deleting dead stores this round. */
4360 {
4361 /* Invalidate the data for the last MEM stored, but only if MEM is
4362 something that can be stored into. */
4366 else
4367 {
4370 rtx next;
4373 {
4376 {
4377 /* Splice temp out of the list. */
4380 else
4383 }
4384 else
4387 }
4388 }
4390 /* If the memory reference had embedded side effects (autoincrement
4391 address modes. Then we may need to kill some entries on the
4392 memory set list. */
4395 }
4397 #ifdef AUTO_INC_DEC
4400 #endif
4410 /* While we're here, optimize this case. */
4413 /* In case the SUBREG is not of a register, don't optimize */
4415 {
4418 }
4420 /* ... fall through ... */
4423 /* See a register other than being set
4424 => mark it as needed. */
4427 {
4433 /* A hard reg in a wide mode may really be multiple registers.
4434 If so, mark all of them just like the first. */
4436 {
4439 /* For stack ptr or fixed arg pointer,
4440 nothing below can be necessary, so waste no more time. */
4442 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
4445 #endif
4446 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
4448 #endif
4451 {
4452 /* If this is a register we are going to try to eliminate,
4453 don't mark it live here. If we are successful in
4454 eliminating it, it need not be live unless it is used for
4455 pseudos, in which case it will have been set live when
4456 it was allocated to the pseudos. If the register will not
4457 be eliminated, reload will set it live at that point. */
4462 }
4463 /* No death notes for global register variables;
4464 their values are live after this function exits. */
4466 {
4470 }
4474 {
4481 }
4482 }
4485 {
4486 /* Record where each reg is used, so when the reg
4487 is set we know the next insn that uses it. */
4490 }
4492 {
4494 {
4495 /* If a hard reg is being used,
4496 record that this function does use it. */
4501 do
4504 }
4505 else
4506 {
4507 /* Keep track of which basic block each reg appears in. */
4516 /* Count (weighted) number of uses of each reg. */
4519 }
4520 }
4522 /* Record and count the insns in which a reg dies.
4523 If it is used in this insn and was dead below the insn
4524 then it dies in this insn. If it was set in this insn,
4525 we do not make a REG_DEAD note; likewise if we already
4526 made such a note. */
4529 {
4532 #if 0
4534 #endif
4535 )
4536 {
4537 /* Check for the case where the register dying partially
4538 overlaps the register set by this insn. */
4541 {
4545 }
4547 /* If none of the words in X is needed, make a REG_DEAD
4548 note. Otherwise, we must make partial REG_DEAD notes. */
4550 {
4554 }
4555 else
4556 {
4559 /* Don't make a REG_DEAD note for a part of a register
4560 that is set in the insn. */
4567 = (alloc_EXPR_LIST
4571 }
4572 }
4573 }
4574 }
4578 {
4582 /* If storing into MEM, don't show it as being used. But do
4583 show the address as being used. */
4585 {
4586 #ifdef AUTO_INC_DEC
4589 #endif
4593 }
4595 /* Storing in STRICT_LOW_PART is like storing in a reg
4596 in that this SET might be dead, so ignore it in TESTREG.
4597 but in some other ways it is like using the reg.
4599 Storing in a SUBREG or a bit field is like storing the entire
4600 register in that if the register's value is not used
4601 then this SET is not needed. */
4606 {
4614 /* Modifying a single register in an alternate mode
4615 does not use any of the old value. But these other
4616 ways of storing in a register do use the old value. */
4619 ;
4620 else
4624 }
4626 /* If this is a store into a register,
4627 recursively scan the value being stored. */
4634 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
4637 #endif
4638 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
4640 #endif
4641 ))
4642 /* We used to exclude global_regs here, but that seems wrong.
4643 Storing in them is like storing in mem. */
4644 {
4649 }
4650 }
4654 /* ??? This info should have been gotten from mark_regs_live_at_end,
4655 as applied to the EXIT block, and propagated along the edge that
4656 connects this block to the EXIT. */
4663 {
4664 /* Traditional and volatile asm instructions must be considered to use
4665 and clobber all hard registers, all pseudo-registers and all of
4666 memory. So must TRAP_IF and UNSPEC_VOLATILE operations.
4668 Consider for instance a volatile asm that changes the fpu rounding
4669 mode. An insn should not be moved across this even if it only uses
4670 pseudo-regs because it might give an incorrectly rounded result.
4672 ?!? Unfortunately, marking all hard registers as live causes massive
4673 problems for the register allocator and marking all pseudos as live
4674 creates mountains of uninitialized variable warnings.
4676 So for now, just clear the memory set list and mark any regs
4677 we can find in ASM_OPERANDS as used. */
4681 /* For all ASM_OPERANDS, we must traverse the vector of input operands.
4682 We can not just fall through here since then we would be confused
4683 by the ASM_INPUT rtx inside ASM_OPERANDS, which do not indicate
4684 traditional asms unlike their normal usage. */
4686 {
4692 }
4694 }
4699 }
4701 /* Recursively scan the operands of this expression. */
4703 {
4708 {
4710 {
4711 /* Tail recursive case: save a function call level. */
4713 {
4716 }
4718 }
4720 {
4724 }
4725 }
4726 }
4727 }
4728 \f
4729 #ifdef AUTO_INC_DEC
4731 static int
4733 rtx insn;
4734 {
4735 /* Find the next use of this reg. If in same basic block,
4736 make it do pre-increment or pre-decrement if appropriate. */
4744 /* Don't do this if the reg dies, or gets set in y; a standard addressing
4745 mode would be better. */
4748 {
4749 /* We have found a suitable auto-increment
4750 and already changed insn Y to do it.
4751 So flush this increment-instruction. */
4755 /* Count a reference to this reg for the increment
4756 insn we are deleting. When a reg is incremented.
4757 spilling it is worse, so we want to make that
4758 less likely. */
4760 {
4763 }
4765 }
4767 }
4769 /* Try to change INSN so that it does pre-increment or pre-decrement
4770 addressing on register REG in order to add AMOUNT to REG.
4771 AMOUNT is negative for pre-decrement.
4772 Returns 1 if the change could be made.
4773 This checks all about the validity of the result of modifying INSN. */
4775 static int
4778 HOST_WIDE_INT amount;
4779 {
4782 /* Nonzero if we can try to make a pre-increment or pre-decrement.
4783 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
4785 /* Nonzero if we can try to make a post-increment or post-decrement.
4786 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
4787 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
4788 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
4791 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
4794 /* From the sign of increment, see which possibilities are conceivable
4795 on this target machine. */
4809 /* It is not safe to add a side effect to a jump insn
4810 because if the incremented register is spilled and must be reloaded
4811 there would be no way to store the incremented value back in memory. */
4820 {
4823 }
4831 /* See if this combination of instruction and addressing mode exists. */
4839 /* Record that this insn now has an implicit side effect on X. */
4842 }
4845 \f
4846 /* Find the place in the rtx X where REG is used as a memory address.
4847 Return the MEM rtx that so uses it.
4848 If PLUSCONST is nonzero, search instead for a memory address equivalent to
4849 (plus REG (const_int PLUSCONST)).
4851 If such an address does not appear, return 0.
4852 If REG appears more than once, or is used other than in such an address,
4853 return (rtx)1. */
4855 rtx
4858 rtx reg;
4859 HOST_WIDE_INT plusconst;
4860 {
4877 {
4878 /* If REG occurs inside a MEM used in a bit-field reference,
4879 that is unacceptable. */
4882 }
4888 {
4890 {
4896 }
4898 {
4901 {
4907 }
4908 }
4909 }
4912 }
4913 \f
4914 /* Write information about registers and basic blocks into FILE.
4915 This is part of making a debugging dump. */
4917 void
4920 {
4927 {
4949 {
4954 else
4958 }
4962 }
4966 {
4984 {
4988 }
4989 else
4994 {
4998 }
4999 else
5003 }
5006 }
5008 void
5010 {
5012 }
5014 static void
5017 edge e;
5019 {
5026 else
5030 {
5033 };
5041 {
5048 else
5051 }
5053 }
5054 }
5056 \f
5057 /* Like print_rtl, but also print out live information for the start of each
5058 basic block. */
5060 void
5063 rtx rtx_first;
5064 {
5069 else
5070 {
5082 {
5084 rtx x;
5089 {
5097 }
5098 }
5101 {
5103 basic_block bb;
5106 {
5111 {
5116 });
5118 }
5135 }
5140 }
5143 {
5148 }
5149 }
5151 /* Compute dominator relationships using new flow graph structures. */
5152 void
5156 {
5159 edge e;
5162 /* Allocate a worklist array/queue. Entries are only added to the
5163 list if they were not already on the list. So the size is
5164 bounded by the number of basic blocks. */
5172 {
5173 /* The optimistic setting of dominators requires us to put every
5174 block on the work list initially. */
5176 {
5179 }
5181 /* We want a maximal solution, so initially assume everything dominates
5182 everything else. */
5185 /* Mark successors of the entry block so we can identify them below. */
5189 /* Iterate until the worklist is empty. */
5191 {
5192 /* Take the first entry off the worklist. */
5196 /* Compute the intersection of the dominators of all the
5197 predecessor blocks.
5199 If one of the predecessor blocks is the ENTRY block, then the
5200 intersection of the dominators of the predecessor blocks is
5201 defined as the null set. We can identify such blocks by the
5202 special value in the AUX field in the block structure. */
5204 {
5205 /* Do not clear the aux field for blocks which are
5206 successors of the ENTRY block. That way we we never
5207 add them to the worklist again.
5209 The intersect of dominators of the preds of this block is
5210 defined as the null set. */
5212 }
5213 else
5214 {
5215 /* Clear the aux field of this block so it can be added to
5216 the worklist again if necessary. */
5219 }
5221 /* Make sure each block always dominates itself. */
5224 /* If the out state of this block changed, then we need to
5225 add the successors of this block to the worklist if they
5226 are not already on the worklist. */
5228 {
5230 {
5232 {
5235 }
5236 }
5237 }
5238 }
5239 }
5242 {
5243 /* The optimistic setting of dominators requires us to put every
5244 block on the work list initially. */
5246 {
5249 }
5251 /* We want a maximal solution, so initially assume everything post
5252 dominates everything else. */
5255 /* Mark predecessors of the exit block so we can identify them below. */
5259 /* Iterate until the worklist is empty. */
5261 {
5262 /* Take the first entry off the worklist. */
5266 /* Compute the intersection of the post dominators of all the
5267 successor blocks.
5269 If one of the successor blocks is the EXIT block, then the
5270 intersection of the dominators of the successor blocks is
5271 defined as the null set. We can identify such blocks by the
5272 special value in the AUX field in the block structure. */
5274 {
5275 /* Do not clear the aux field for blocks which are
5276 predecessors of the EXIT block. That way we we never
5277 add them to the worklist again.
5279 The intersect of dominators of the succs of this block is
5280 defined as the null set. */
5282 }
5283 else
5284 {
5285 /* Clear the aux field of this block so it can be added to
5286 the worklist again if necessary. */
5290 }
5292 /* Make sure each block always post dominates itself. */
5295 /* If the out state of this block changed, then we need to
5296 add the successors of this block to the worklist if they
5297 are not already on the worklist. */
5301 {
5303 {
5305 {
5308 }
5309 }
5310 }
5311 }
5312 }
5314 }
5316 /* Given DOMINATORS, compute the immediate dominators into IDOM. */
5318 void
5322 {
5328 /* Begin with tmp(n) = dom(n) - { n }. */
5330 {
5333 }
5335 /* Subtract out all of our dominator's dominators. */
5337 {
5344 }
5346 /* Find the one bit set in the bitmap and put it in the output array. */
5348 {
5351 }
5354 }
5356 /* Count for a single SET rtx, X. */
5358 static void
5360 rtx x;
5361 {
5365 /* Find the register that's set/clobbered. */
5373 {
5378 }
5381 {
5384 {
5385 /* Count (weighted) references, stores, etc. This counts a
5386 register twice if it is modified, but that is correct. */
5390 }
5391 }
5392 }
5394 /* Increment REG_N_SETS for each SET or CLOBBER found in X; also increment
5395 REG_N_REFS by the current loop depth for each SET or CLOBBER found. */
5397 static void
5399 rtx x;
5400 {
5406 {
5409 {
5413 }
5414 }
5415 }
5417 /* Increment REG_N_REFS by the current loop depth each register reference
5418 found in X. */
5420 static void
5422 rtx x;
5423 {
5426 retry:
5429 {
5441 #ifdef HAVE_cc0
5444 #endif
5447 /* If we are clobbering a MEM, mark any registers inside the address
5448 as being used. */
5454 /* While we're here, optimize this case. */
5457 /* In case the SUBREG is not of a register, don't optimize */
5459 {
5462 }
5464 /* ... fall through ... */
5472 {
5476 /* If storing into MEM, don't show it as being used. But do
5477 show the address as being used. */
5479 {
5483 }
5485 /* Storing in STRICT_LOW_PART is like storing in a reg
5486 in that this SET might be dead, so ignore it in TESTREG.
5487 but in some other ways it is like using the reg.
5489 Storing in a SUBREG or a bit field is like storing the entire
5490 register in that if the register's value is not used
5491 then this SET is not needed. */
5496 {
5497 /* Modifying a single register in an alternate mode
5498 does not use any of the old value. But these other
5499 ways of storing in a register do use the old value. */
5502 ;
5503 else
5507 }
5509 /* If this is a store into a register,
5510 recursively scan the value being stored. */
5515 {
5520 }
5521 }
5526 }
5528 /* Recursively scan the operands of this expression. */
5530 {
5535 {
5537 {
5538 /* Tail recursive case: save a function call level. */
5540 {
5543 }
5545 }
5547 {
5551 }
5552 }
5553 }
5554 }
5556 /* Recompute register set/reference counts immediately prior to register
5557 allocation.
5559 This avoids problems with set/reference counts changing to/from values
5560 which have special meanings to the register allocators.
5562 Additionally, the reference counts are the primary component used by the
5563 register allocators to prioritize pseudos for allocation to hard regs.
5564 More accurate reference counts generally lead to better register allocation.
5566 F is the first insn to be scanned.
5567 LOOP_STEP denotes how much loop_depth should be incremented per
5568 loop nesting level in order to increase the ref count more for references
5569 in a loop.
5571 It might be worthwhile to update REG_LIVE_LENGTH, REG_BASIC_BLOCK and
5572 possibly other information which is used by the register allocators. */
5574 void
5576 rtx f;
5578 {
5579 rtx insn;
5583 /* Clear out the old data. */
5586 {
5589 }
5591 /* Scan each insn in the chain and count how many times each register is
5592 set/used. */
5595 {
5599 {
5601 {
5602 rtx links;
5604 /* This call will increment REG_N_SETS for each SET or CLOBBER
5605 of a register in INSN. It will also increment REG_N_REFS
5606 by the loop depth for each set of a register in INSN. */
5609 /* count_reg_sets does not detect autoincrement address modes, so
5610 detect them here by looking at the notes attached to INSN. */
5612 {
5614 /* Count (weighted) references, stores, etc. This counts a
5615 register twice if it is modified, but that is correct. */
5617 }
5619 /* This call will increment REG_N_REFS by the current loop depth for
5620 each reference to a register in INSN. */
5623 /* count_reg_references will not include counts for arguments to
5624 function calls, so detect them here by examining the
5625 CALL_INSN_FUNCTION_USAGE data. */
5627 {
5628 rtx note;
5631 note;
5635 }
5636 }
5639 }
5640 }
5641 }
5643 /* Optionally removes all the REG_DEAD and REG_UNUSED notes from a set of
5644 blocks. If BLOCKS is NULL, assume the universal set. Returns a count
5645 of the number of registers that died. */
5647 int
5649 sbitmap blocks;
5651 {
5655 {
5656 basic_block bb;
5657 rtx insn;
5665 {
5667 {
5672 {
5674 {
5677 {
5683 else
5686 }
5687 /* FALLTHRU */
5691 {
5696 }
5697 /* FALLTHRU */
5703 }
5704 }
5705 }
5709 }
5710 }
5713 }
5715 /* Record INSN's block as BB. */
5717 void
5719 rtx insn;
5720 basic_block bb;
5721 {
5724 {
5727 /* Add one-eighth the size so we don't keep calling xrealloc. */
5731 }
5733 }
5735 /* Record INSN's block number as BB. */
5736 /* ??? This has got to go. */
5738 void
5740 rtx insn;
5742 {
5744 }
5745 \f
5746 /* Verify the CFG consistency. This function check some CFG invariants and
5747 aborts when something is wrong. Hope that this function will help to
5748 convert many optimization passes to preserve CFG consistent.
5750 Currently it does following checks:
5752 - test head/end pointers
5753 - overlapping of basic blocks
5754 - edge list corectness
5755 - headers of basic blocks (the NOTE_INSN_BASIC_BLOCK note)
5756 - tails of basic blocks (ensure that boundary is necesary)
5757 - scans body of the basic block for JUMP_INSN, CODE_LABEL
5758 and NOTE_INSN_BASIC_BLOCK
5759 - check that all insns are in the basic blocks
5760 (except the switch handling code, barriers and notes)
5762 In future it can be extended check a lot of other stuff as well
5763 (reachability of basic blocks, life information, etc. etc.). */
5765 void
5767 {
5771 rtx x;
5776 /* First pass check head/end pointers and set bb_info array used by
5777 later passes. */
5779 {
5782 /* Check the head pointer and make sure that it is pointing into
5783 insn list. */
5788 {
5792 }
5794 /* Check the end pointer and make sure that it is pointing into
5795 insn list. */
5797 {
5799 {
5803 }
5808 }
5810 {
5814 }
5815 }
5817 /* Now check the basic blocks (boundaries etc.) */
5819 {
5821 /* Check corectness of edge lists */
5822 edge e;
5826 {
5828 {
5837 }
5839 {
5844 {
5847 }
5848 }
5850 }
5854 {
5856 {
5864 }
5866 {
5871 {
5874 }
5875 }
5877 }
5879 /* OK pointers are correct. Now check the header of basic
5880 block. It ought to contain optional CODE_LABEL followed
5881 by NOTE_BASIC_BLOCK. */
5884 {
5886 {
5890 }
5892 }
5896 {
5900 }
5903 {
5904 /* Do checks for empty blocks here */
5905 }
5906 else
5907 {
5910 {
5913 {
5917 }
5925 {
5928 }
5931 }
5932 }
5933 }
5937 {
5939 {
5941 {
5947 /* An addr_vec is placed outside any block block. */
5952 {
5954 }
5956 /* But in any case, non-deletable labels can appear anywhere. */
5961 }
5962 }
5965 }
5970 /* Clean up. */
5972 }
5973 \f
5974 /* Functions to access an edge list with a vector representation.
5975 Enough data is kept such that given an index number, the
5976 pred and succ that edge reprsents can be determined, or
5977 given a pred and a succ, it's index number can be returned.
5978 This allows algorithms which comsume a lot of memory to
5979 represent the normally full matrix of edge (pred,succ) with a
5980 single indexed vector, edge (EDGE_INDEX (pred, succ)), with no
5981 wasted space in the client code due to sparse flow graphs. */
5983 /* This functions initializes the edge list. Basically the entire
5984 flowgraph is processed, and all edges are assigned a number,
5985 and the data structure is filed in. */
5988 {
5990 edge e;
5999 /* Determine the number of edges in the flow graph by counting successor
6000 edges on each basic block. */
6002 {
6006 num_edges++;
6007 }
6008 /* Don't forget successors of the entry block. */
6010 num_edges++;
6019 /* Follow successors of the entry block, and register these edges. */
6021 {
6023 num_edges++;
6024 }
6027 {
6030 /* Follow all successors of blocks, and register these edges. */
6032 {
6034 num_edges++;
6035 }
6036 }
6038 }
6040 /* This function free's memory associated with an edge list. */
6041 void
6044 {
6046 {
6049 }
6050 }
6052 /* This function provides debug output showing an edge list. */
6053 void
6057 {
6063 {
6067 else
6072 else
6074 }
6075 }
6077 /* This function provides an internal consistancy check of an edge list,
6078 verifying that all edges are present, and that there are no
6079 extra edges. */
6080 void
6084 {
6086 edge e;
6089 {
6093 {
6098 {
6101 }
6108 }
6109 }
6111 {
6116 {
6119 }
6126 }
6127 /* We've verified that all the edges are in the list, no lets make sure
6128 there are no spurious edges in the list. */
6132 {
6140 {
6143 }
6146 {
6149 }
6159 }
6161 {
6169 {
6172 }
6175 {
6178 }
6182 succ);
6188 }
6190 {
6198 {
6201 }
6204 {
6207 }
6211 pred);
6216 EXIT_BLOCK_PTR));
6217 }
6218 }
6220 /* This routine will determine what, if any, edge there is between
6221 a specified predecessor and successor. */
6223 int
6227 {
6230 {
6234 }
6236 }
6238 /* This function will remove an edge from the flow graph. */
6239 static void
6241 edge e;
6242 {
6245 edge tmp;
6256 else
6266 else
6269 n_edges--;
6271 }
6273 /* This routine will remove any fake successor edges for a basic block.
6274 When the edge is removed, it is also removed from whatever predecessor
6275 list it is in. */
6276 static void
6278 basic_block bb;
6279 {
6280 edge e;
6282 {
6287 }
6288 }
6290 /* This routine will remove all fake edges from the flow graph. If
6291 we remove all fake successors, it will automatically remove all
6292 fake predecessors. */
6293 void
6295 {
6301 /* We've handled all successors except the entry block's. */
6303 }
6305 /* This functions will add a fake edge between any block which has no
6306 successors, and the exit block. Some data flow equations require these
6307 edges to exist. */
6308 void
6310 {
6316 }
6317 \f
6318 /* Dump the list of basic blocks in the bitmap NODES. */
6319 static void
6324 {
6330 }
6333 /* Dump the list of exiting edges in the array EDGES. */
6334 static void
6340 {
6347 }
6350 /* Dump loop related CFG information. */
6351 static void
6355 {
6362 {
6363 edge succ;
6369 }
6372 /* Dump the DFS node order. */
6374 {
6379 }
6380 }
6383 /* Return non-zero if the nodes of LOOP are a subset of OUTER. */
6384 int
6388 {
6390 }
6393 /* Dump the loop information specified by LOOPS to the stream FILE. */
6394 void
6399 {
6410 {
6413 fprintf (file, ";; loop %d (%d to %d):\n;; header %d, latch %d, pre-header %d, depth %d, level %d, outer %ld\n",
6425 {
6429 {
6433 {
6439 /* If the union of LOOP and OLOOP is different than
6440 the larger of LOOP and OLOOP then LOOP and OLOOP
6441 must be disjoint. */
6447 }
6448 }
6449 }
6452 {
6453 /* Print diagnostics to compare our concept of a loop with
6454 what the loop notes say. */
6465 }
6466 }
6470 }
6473 /* Free all the memory allocated for LOOPS. */
6474 void
6477 {
6479 {
6485 /* Free the loop descriptors. */
6487 {
6494 }
6504 }
6505 }
6508 /* Find the exits from the loop using the bitmap of loop nodes NODES
6509 and store in EXITS array. Return the number of exits from the
6510 loop. */
6511 static int
6515 {
6516 edge e;
6522 /* Check all nodes within the loop to see if there are any
6523 successors not in the loop. Note that a node may have multiple
6524 exiting edges. */
6528 {
6532 num_exits++;
6533 }
6534 });
6541 /* Store all exiting edges into an array. */
6545 {
6550 }
6551 });
6554 }
6557 /* Find the nodes contained within the loop with header HEADER and
6558 latch LATCH and store in NODES. Return the number of nodes within
6559 the loop. */
6560 static int
6562 basic_block header;
6563 basic_block latch;
6564 sbitmap nodes;
6565 {
6573 /* Start with only the loop header in the set of loop nodes. */
6576 num_nodes++;
6578 /* Push the loop latch on to the stack. */
6580 {
6582 num_nodes++;
6584 }
6587 {
6588 basic_block node;
6589 edge e;
6593 {
6596 /* If each ancestor not marked as part of loop, add to set of
6597 loop nodes and push on to stack. */
6600 {
6602 num_nodes++;
6604 }
6605 }
6606 }
6609 }
6612 /* Compute the depth first search order and store in the array
6613 DFS_ORDER, marking the nodes visited in VISITED. Returns the
6614 number of nodes visited. */
6615 static int
6618 {
6619 edge e;
6623 sbitmap visited;
6625 /* Allocate stack for back-tracking up CFG. */
6629 /* Allocate bitmap to track nodes that have been visited. */
6632 /* None of the nodes in the CFG have been visited yet. */
6635 /* Start with the first successor edge from the entry block. */
6638 {
6642 /* Mark that we have visited this node. */
6646 /* If this node has not been visited before, push the current
6647 edge on to the stack and proceed with the first successor
6648 edge of this node. */
6651 {
6654 }
6655 else
6656 {
6659 {
6660 /* DEST has no successors (for example, a non-returning
6661 function is called) so do not push the current edge
6662 but carry on with its next successor. */
6665 }
6668 {
6671 /* Pop edge off stack. */
6674 }
6676 }
6677 }
6681 /* The number of nodes visited should not be greater than
6682 n_basic_blocks. */
6686 /* There are some nodes left in the CFG that are unreachable. */
6690 }
6693 /* Return the block for the pre-header of the loop with header
6694 HEADER where DOM specifies the dominator information. Return NULL if
6695 there is no pre-header. */
6696 static basic_block
6698 basic_block header;
6700 {
6701 basic_block pre_header;
6702 edge e;
6704 /* If block p is a predecessor of the header and is the only block
6705 that the header does not dominate, then it is the pre-header. */
6708 {
6713 {
6716 else
6717 {
6718 /* There are multiple edges into the header from outside
6719 the loop so there is no pre-header block. */
6722 }
6723 }
6724 }
6726 }
6729 /* Add LOOP to the loop hierarchy tree so that it is a sibling or a
6730 descendant of ROOT. */
6731 static void
6735 {
6742 {
6744 {
6746 {
6747 /* Add LOOP as a sibling or descendent of OUTER->INNER. */
6749 }
6750 else
6751 {
6752 /* Add LOOP as child of OUTER. */
6756 }
6758 }
6759 }
6760 /* Add LOOP as a sibling of ROOT. */
6764 }
6767 /* Build the loop hierarchy tree for LOOPS. */
6768 static void
6771 {
6779 /* Root the loop hierarchy tree with the first loop found.
6780 Since we used a depth first search this should be the
6781 outermost loop. */
6785 /* Add the remaining loops to the tree. */
6788 }
6791 /* Helper function to compute loop nesting depth and enclosed loop level
6792 for the natural loop specified by LOOP at the loop depth DEPTH.
6793 Returns the loop level. */
6794 static int
6798 {
6805 /* Traverse loop tree assigning depth and computing level as the
6806 maximum level of all the inner loops of this loop. The loop
6807 level is equivalent to the height of the loop in the loop tree
6808 and corresponds to the number of enclosed loop levels. */
6810 {
6817 }
6821 }
6824 /* Compute the loop nesting depth and enclosed loop level for the loop
6825 hierarchy tree specfied by LOOPS. Return the maximum enclosed loop
6826 level. */
6827 static int
6830 {
6832 }
6835 /* Find all the natural loops in the function and save in LOOPS structure.
6836 Return the number of natural loops found. */
6837 int
6840 {
6844 edge e;
6845 sbitmap headers;
6854 /* Taking care of this degenerate case makes the rest of
6855 this code simpler. */
6859 /* Compute the dominators. */
6863 /* Count the number of loop edges (back edges). This should be the
6864 same as the number of natural loops. */
6867 {
6869 {
6872 /* Look for back edges where a predecessor is dominated
6873 by this block. A natural loop has a single entry
6874 node (header) that dominates all the nodes in the
6875 loop. It also has single back edge to the header
6876 from a latch node. Note that multiple natural loops
6877 may share the same header. */
6879 num_loops++;
6880 }
6881 }
6884 {
6885 /* Compute depth first search order of the CFG so that outer
6886 natural loops will be found before inner natural loops. */
6890 /* Allocate loop structures. */
6900 /* Find and record information about all the natural loops
6901 in the CFG. */
6904 {
6905 basic_block header;
6907 /* Search the nodes of the CFG in DFS order that we can find
6908 outer loops first. */
6911 /* Look for all the possible latch blocks for this header. */
6913 {
6916 /* Look for back edges where a predecessor is dominated
6917 by this block. A natural loop has a single entry
6918 node (header) that dominates all the nodes in the
6919 loop. It also has single back edge to the header
6920 from a latch node. Note that multiple natural loops
6921 may share the same header. */
6924 {
6932 /* Keep track of blocks that are loop headers so
6933 that we can tell which loops should be merged. */
6938 /* Find nodes contained within the loop. */
6943 /* Find edges which exit the loop. Note that a node
6944 may have several exit edges. */
6945 loop->num_exits
6948 /* Look to see if the loop has a pre-header node. */
6949 loop->pre_header
6952 num_loops++;
6953 }
6954 }
6955 }
6957 /* Natural loops with shared headers may either be disjoint or
6958 nested. Disjoint loops with shared headers cannot be inner
6959 loops and should be merged. For now just mark loops that share
6960 headers. */
6966 }
6970 /* Save CFG derived information to avoid recomputing it. */
6974 /* Build the loop hierarchy tree. */
6977 /* Assign the loop nesting depth and enclosed loop level for each
6978 loop. */
6982 }
6985 /* Return non-zero if edge E enters header of LOOP from outside of LOOP. */
6986 int
6989 edge e;
6990 {
6995 }