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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
138 #define obstack_chunk_alloc xmalloc
139 #define obstack_chunk_free free
142 /* EXIT_IGNORE_STACK should be nonzero if, when returning from a function,
143 the stack pointer does not matter. The value is tested only in
144 functions that have frame pointers.
145 No definition is equivalent to always zero. */
146 #ifndef EXIT_IGNORE_STACK
147 #define EXIT_IGNORE_STACK 0
148 #endif
151 /* The contents of the current function definition are allocated
152 in this obstack, and all are freed at the end of the function.
153 For top-level functions, this is temporary_obstack.
154 Separate obstacks are made for nested functions. */
158 /* Number of basic blocks in the current function. */
162 /* The basic block array. */
164 varray_type basic_block_info;
166 /* The special entry and exit blocks. */
169 {
170 {
181 },
182 {
193 }
194 };
196 /* Nonzero if the second flow pass has completed. */
199 /* Maximum register number used in this function, plus one. */
203 /* Indexed by n, giving various register information */
205 varray_type reg_n_info;
207 /* Size of the reg_n_info table. */
211 /* Element N is the next insn that uses (hard or pseudo) register number N
212 within the current basic block; or zero, if there is no such insn.
213 This is valid only during the final backward scan in propagate_block. */
217 /* Size of a regset for the current function,
218 in (1) bytes and (2) elements. */
223 /* Regset of regs live when calls to `setjmp'-like functions happen. */
224 /* ??? Does this exist only for the setjmp-clobbered warning message? */
226 regset regs_live_at_setjmp;
228 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
229 that have to go in the same hard reg.
230 The first two regs in the list are a pair, and the next two
231 are another pair, etc. */
232 rtx regs_may_share;
234 /* Depth within loops of basic block being scanned for lifetime analysis,
235 plus one. This is the weight attached to references to registers. */
239 /* During propagate_block, this is non-zero if the value of CC0 is live. */
243 /* During propagate_block, this contains a list of all the MEMs we are
244 tracking for dead store elimination.
246 ?!? Note we leak memory by not free-ing items on this list. We need to
247 write some generic routines to operate on memory lists since cse, gcse,
248 loop, sched, flow and possibly other passes all need to do basically the
249 same operations on these lists. */
253 /* Set of registers that may be eliminable. These are handled specially
254 in updating regs_ever_live. */
258 /* The basic block structure for every insn, indexed by uid. */
260 varray_type basic_block_for_insn;
262 /* The labels mentioned in non-jump rtl. Valid during find_basic_blocks. */
263 /* ??? Should probably be using LABEL_NUSES instead. It would take a
264 bit of surgery to be able to use or co-opt the routines in jump. */
268 /* INSN_VOLATILE (insn) is 1 if the insn refers to anything volatile. */
270 #define INSN_VOLATILE(INSN) bitmap_bit_p (uid_volatile, INSN_UID (INSN))
271 #define SET_INSN_VOLATILE(INSN) bitmap_set_bit (uid_volatile, INSN_UID (INSN))
274 /* Forward declarations */
316 #ifdef AUTO_INC_DEC
320 #endif
345 \f
346 /* Find basic blocks of the current function.
347 F is the first insn of the function and NREGS the number of register
348 numbers in use. */
350 void
352 rtx f;
356 {
360 /* Flush out existing data. */
362 {
367 /* Clear bb->aux on all extant basic blocks. We'll use this as a
368 tag for reuse during create_basic_block, just in case some pass
369 copies around basic block notes improperly. */
374 }
378 /* Size the basic block table. The actual structures will be allocated
379 by find_basic_blocks_1, since we want to keep the structure pointers
380 stable across calls to find_basic_blocks. */
381 /* ??? This whole issue would be much simpler if we called find_basic_blocks
382 exactly once, and thereafter we don't have a single long chain of
383 instructions at all until close to the end of compilation when we
384 actually lay them out. */
388 /* An array to record the active exception region at the end of each
389 basic block. It is filled in by find_basic_blocks_1 for make_edges. */
394 /* Record the block to which an insn belongs. */
395 /* ??? This should be done another way, by which (perhaps) a label is
396 tagged directly with the basic block that it starts. It is used for
397 more than that currently, but IMO that is the only valid use. */
400 #ifdef AUTO_INC_DEC
401 /* Leave space for insns life_analysis makes in some cases for auto-inc.
402 These cases are rare, so we don't need too much space. */
404 #endif
409 /* Discover the edges of our cfg. */
413 /* Delete unreachable blocks. */
418 /* Mark critical edges. */
422 /* Discover the loop depth at the start of each basic block to aid
423 register allocation. */
426 /* Kill the data we won't maintain. */
429 #ifdef ENABLE_CHECKING
431 #endif
432 }
434 /* Count the basic blocks of the function. */
436 static int
438 rtx f;
439 {
449 {
457 {
458 count++;
460 /* If the previous insn was a call that did not create an
461 abnormal edge, we want to add a nop so that the CALL_INSN
462 itself is not at basic_block_end. This allows us to
463 easily distinguish between normal calls and those which
464 create abnormal edges in the flow graph. */
467 {
470 }
471 }
473 /* Record whether this call created an edge. */
475 {
481 /* If there is a specified EH region, we have an edge. */
484 else
485 {
486 /* If there is a nonlocal goto label and the specified
487 region number isn't -1, we have an edge. (0 means
488 no throw, but might have a nonlocal goto). */
491 }
492 }
503 }
505 /* The rest of the compiler works a bit smoother when we don't have to
506 check for the edge case of do-nothing functions with no basic blocks. */
508 {
511 }
514 }
516 /* Find all basic blocks of the function whose first insn is F.
517 Store the correct data in the tables that describe the basic blocks,
518 set up the chains of references for each CODE_LABEL, and
519 delete any entire basic blocks that cannot be reached.
521 NONLOCAL_LABEL_LIST is a list of non-local labels in the function. Blocks
522 that are otherwise unreachable may be reachable with a non-local goto.
524 BB_EH_END is an array in which we record the list of exception regions
525 active at the end of every basic block. */
527 static rtx
529 rtx f;
531 {
541 /* We process the instructions in a slightly different way than we did
542 previously. This is so that we see a NOTE_BASIC_BLOCK after we have
543 closed out the previous block, so that it gets attached at the proper
544 place. Since this form should be equivalent to the previous,
545 find_basic_blocks_0 continues to use the old form as a check. */
548 {
554 {
555 /* Record whether this call created an edge. */
560 /* If there is an EH region, we have an edge. */
563 else
564 {
565 /* If there is a nonlocal goto label and the specified
566 region number isn't -1, we have an edge. (0 means
567 no throw, but might have a nonlocal goto). */
570 }
571 }
574 {
576 {
579 /* Keep a LIFO list of the currently active exception notes. */
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 }
618 }
623 /* A basic block ends at a jump. */
626 else
627 {
628 /* ??? Make a special check for table jumps. The way this
629 happens is truely and amazingly gross. We are about to
630 create a basic block that contains just a code label and
631 an addr*vec jump insn. Worse, an addr_diff_vec creates
632 its own natural loop.
634 Prevent this bit of brain damage, pasting things together
635 correctly in make_edges.
637 The correct solution involves emitting the table directly
638 on the tablejump instruction as a note, or JUMP_LABEL. */
642 {
644 n_basic_blocks--;
646 }
647 }
652 /* A basic block ends at a barrier. It may be that an unconditional
653 jump already closed the basic block -- no need to do it again. */
657 /* While we now have edge lists with which other portions of the
658 compiler might determine a call ending a basic block does not
659 imply an abnormal edge, it will be a bit before everything can
660 be updated. So continue to emit a noop at the end of such a
661 block. */
663 {
666 }
670 /* A basic block ends at a call that can either throw or
671 do a non-local goto. */
673 {
674 new_bb_inclusive:
679 new_bb_exclusive:
685 }
686 /* FALLTHRU */
690 {
694 }
696 }
699 {
700 rtx note;
702 /* Make a list of all labels referred to other than by jumps
703 (which just don't have the REG_LABEL notes).
705 Make a special exception for labels followed by an ADDR*VEC,
706 as this would be a part of the tablejump setup code.
708 Make a special exception for the eh_return_stub_label, which
709 we know isn't part of any otherwise visible control flow. */
713 {
717 ;
722 ;
723 else
724 label_value_list
726 label_value_list);
727 }
728 }
729 }
732 {
735 }
741 }
743 /* Create a new basic block consisting of the instructions between
744 HEAD and END inclusive. Reuses the note and basic block struct
745 in BB_NOTE, if any. */
747 static void
751 {
752 basic_block bb;
758 {
759 /* If we found an existing note, thread it back onto the chain. */
763 else
764 {
767 }
768 }
769 else
770 {
771 /* Otherwise we must create a note and a basic block structure.
772 Since we allow basic block structs in rtl, give the struct
773 the same lifetime by allocating it off the function obstack
774 rather than using malloc. */
781 else
782 {
785 }
787 }
789 /* Always include the bb note in the block. */
798 /* Tag the block so that we know it has been used when considering
799 other basic block notes. */
801 }
802 \f
803 /* Records the basic block struct in BB_FOR_INSN, for every instruction
804 indexed by INSN_UID. MAX is the size of the array. */
806 static void
808 varray_type bb_for_insn;
810 {
814 {
821 {
828 }
829 }
830 }
832 /* Free the memory associated with the edge structures. */
834 static void
836 {
841 {
845 {
848 }
852 }
855 {
858 }
862 }
864 /* Identify the edges between basic blocks.
866 NONLOCAL_LABEL_LIST is a list of non-local labels in the function. Blocks
867 that are otherwise unreachable may be reachable with a non-local goto.
869 BB_EH_END is an array indexed by basic block number in which we record
870 the list of exception regions active at the end of the basic block. */
872 static void
874 rtx label_value_list;
876 {
880 /* Assume no computed jump; revise as we create edges. */
883 /* By nature of the way these get numbered, block 0 is always the entry. */
887 {
893 /* If we have asynchronous exceptions, scan the notes for all exception
894 regions active in the block. In the normal case, we only need the
895 one active at the end of the block, which is bb_eh_end[i]. */
899 {
901 {
905 }
906 }
908 /* Now examine the last instruction of the block, and discover the
909 ways we can leave the block. */
914 /* A branch. */
916 {
917 rtx tmp;
919 /* ??? Recognize a tablejump and do the right thing. */
925 {
926 rtvec vec;
931 else
937 /* Some targets (eg, ARM) emit a conditional jump that also
938 contains the out-of-range target. Scan for these and
939 add an edge if necessary. */
946 #ifdef CASE_DROPS_THROUGH
947 /* Silly VAXen. The ADDR_VEC is going to be in the way of
948 us naturally detecting fallthru into the next block. */
950 #endif
951 }
953 /* If this is a computed jump, then mark it as reaching
954 everything on the label_value_list and forced_labels list. */
956 {
964 }
966 /* Returns create an exit out. */
970 /* Otherwise, we have a plain conditional or unconditional jump. */
971 else
972 {
976 }
977 }
979 /* If this is a CALL_INSN, then mark it as reaching the active EH
980 handler for this CALL_INSN. If we're handling asynchronous
981 exceptions then any insn can reach any of the active handlers.
983 Also mark the CALL_INSN as reaching any nonlocal goto handler. */
986 {
998 {
1001 }
1004 {
1005 /* ??? This could be made smarter: in some cases it's possible
1006 to tell that certain calls will not do a nonlocal goto.
1008 For example, if the nested functions that do the nonlocal
1009 gotos do not have their addresses taken, then only calls to
1010 those functions or to other nested functions that use them
1011 could possibly do nonlocal gotos. */
1012 /* We do know that a REG_EH_REGION note with a value less
1013 than 0 is guaranteed not to perform a non-local goto. */
1019 }
1020 }
1022 /* We know something about the structure of the function __throw in
1023 libgcc2.c. It is the only function that ever contains eh_stub
1024 labels. It modifies its return address so that the last block
1025 returns to one of the eh_stub labels within it. So we have to
1026 make additional edges in the flow graph. */
1030 /* Find out if we can drop through to the next block. */
1035 {
1041 }
1042 }
1044 }
1046 /* Create an edge between two basic blocks. FLAGS are auxiliary information
1047 about the edge that is accumulated between calls. */
1049 static void
1053 {
1054 edge e;
1056 /* Make sure we don't add duplicate edges. */
1060 {
1063 }
1075 }
1077 /* Create an edge from a basic block to a label. */
1079 static void
1081 basic_block src;
1082 rtx label;
1084 {
1088 /* If the label was never emitted, this insn is junk, but avoid a
1089 crash trying to refer to BLOCK_FOR_INSN (label). This can happen
1090 as a result of a syntax error and a diagnostic has already been
1091 printed. */
1097 }
1099 /* Identify critical edges and set the bits appropriately. */
1100 static void
1102 {
1104 basic_block bb;
1106 /* We begin with the entry block. This is not terribly important now,
1107 but could be if a front end (Fortran) implemented alternate entry
1108 points. */
1113 {
1114 edge e;
1116 /* (1) Critical edges must have a source with multiple successors. */
1118 {
1120 {
1121 /* (2) Critical edges must have a destination with multiple
1122 predecessors. Note that we know there is at least one
1123 predecessor -- the edge we followed to get here. */
1126 else
1128 }
1129 }
1130 else
1131 {
1134 }
1139 }
1140 }
1141 \f
1142 /* Split a (typically critical) edge. Return the new block.
1143 Abort on abnormal edges.
1145 ??? The code generally expects to be called on critical edges.
1146 The case of a block ending in an unconditional jump to a
1147 block with multiple predecessors is not handled optimally. */
1149 basic_block
1151 edge edge_in;
1152 {
1154 edge edge_out;
1155 rtx bb_note;
1158 /* Abnormal edges cannot be split. */
1165 /* Remove the existing edge from the destination's pred list. */
1166 {
1172 }
1174 /* Create the new structures. */
1183 /* ??? This info is likely going to be out of date very soon. */
1186 {
1189 }
1190 else
1191 {
1194 }
1196 /* Wire them up. */
1212 /* Tricky case -- if there existed a fallthru into the successor
1213 (and we're not it) we must add a new unconditional jump around
1214 the new block we're actually interested in.
1216 Further, if that edge is critical, this means a second new basic
1217 block must be created to hold it. In order to simplify correct
1218 insn placement, do this before we touch the existing basic block
1219 ordering for the block we were really wanting. */
1221 {
1222 edge e;
1228 {
1229 basic_block jump_block;
1230 rtx pos;
1233 {
1234 /* Non critical -- we can simply add a jump to the end
1235 of the existing predecessor. */
1237 }
1238 else
1239 {
1240 /* We need a new block to hold the jump. The simplest
1241 way to do the bulk of the work here is to recursively
1242 call ourselves. */
1245 }
1247 /* Now add the jump insn ... */
1253 /* ... let jump know that label is in use, ... */
1257 /* ... and clear fallthru on the outgoing edge. */
1260 /* Continue splitting the interesting edge. */
1261 }
1262 }
1264 /* Place the new block just in front of the successor. */
1267 {
1271 }
1275 /* Create the basic block note. */
1280 /* Not quite simple -- for non-fallthru edges, we must adjust the
1281 predecessor's jump instruction to target our new block. */
1283 {
1291 /* ??? Recognize a tablejump and adjust all matching cases. */
1297 {
1298 rtvec vec;
1303 else
1308 {
1312 }
1313 }
1314 else
1315 {
1316 /* This would have indicated an abnormal edge. */
1320 /* A return instruction can't be redirected. */
1324 /* If the insn doesn't go where we think, we're confused. */
1329 }
1333 }
1336 }
1338 /* Queue instructions for insertion on an edge between two basic blocks.
1339 The new instructions and basic blocks (if any) will not appear in the
1340 CFG until commit_edge_insertions is called. */
1342 void
1344 rtx pattern;
1345 edge e;
1346 {
1347 /* We cannot insert instructions on an abnormal critical edge.
1348 It will be easier to find the culprit if we die now. */
1355 else
1362 }
1364 /* Update the CFG for the instructions queued on edge E. */
1366 static void
1368 edge e;
1369 {
1371 basic_block bb;
1373 /* Figure out where to put these things. If the destination has
1374 one predecessor, insert there. Except for the exit block. */
1377 {
1380 /* Get the location correct wrt a code label, and "nice" wrt
1381 a basic block note, and before everything else. */
1390 else
1392 }
1394 /* If the source has one successor and the edge is not abnormal,
1395 insert there. Except for the entry block. */
1399 {
1402 {
1403 /* ??? Is it possible to wind up with non-simple jumps? Perhaps
1404 a jump with delay slots already filled? */
1409 }
1410 else
1411 {
1412 /* We'd better be fallthru, or we've lost track of what's what. */
1417 }
1418 }
1420 /* Otherwise we must split the edge. */
1421 else
1422 {
1425 }
1427 /* Now that we've found the spot, do the insertion. */
1431 /* Set the new block number for these insns, if structure is allocated. */
1433 {
1434 rtx i;
1437 }
1440 {
1444 }
1445 else
1446 {
1450 }
1451 }
1453 /* Update the CFG for all queued instructions. */
1455 void
1457 {
1459 basic_block bb;
1464 {
1468 {
1472 }
1477 }
1478 }
1479 \f
1480 /* Delete all unreachable basic blocks. */
1482 static void
1484 {
1487 edge e;
1493 /* Use basic_block->aux as a marker. Clear them all. */
1498 /* Add our starting points to the worklist. Almost always there will
1499 be only one. It isn't inconcievable that we might one day directly
1500 support Fortran alternate entry points. */
1503 {
1506 /* Mark the block with a handy non-null value. */
1508 }
1510 /* Iterate: find everything reachable from what we've already seen. */
1513 {
1518 {
1521 }
1522 }
1524 /* Delete all unreachable basic blocks. Count down so that we don't
1525 interfere with the block renumbering that happens in delete_block. */
1530 {
1534 /* This block was found. Tidy up the mark. */
1536 else
1538 }
1540 /* Fix up edges that now fall through, or rather should now fall through
1541 but previously required a jump around now deleted blocks. Simplify
1542 the search by only examining blocks numerically adjacent, since this
1543 is how find_basic_blocks created them. */
1546 {
1549 edge s;
1551 /* We care about simple conditional or unconditional jumps with
1552 a single successor.
1554 If we had a conditional branch to the next instruction when
1555 find_basic_blocks was called, then there will only be one
1556 out edge for the block which ended with the conditional
1557 branch (since we do not create duplicate edges).
1559 Furthermore, the edge will be marked as a fallthru because we
1560 merge the flags for the duplicate edges. So we do not want to
1561 check that the edge is not a FALLTHRU edge. */
1565 /* If the jump insn has side effects, we can't tidy the edge. */
1569 }
1571 /* Attempt to merge blocks as made possible by edge removal. If a block
1572 has only one successor, and the successor has only one predecessor,
1573 they may be combined. */
1576 {
1578 edge s;
1580 /* A loop because chains of blocks might be combineable. */
1586 /* If the jump insn has side effects, we can't kill the edge. */
1592 /* Don't get confused by the index shift caused by deleting blocks. */
1594 }
1596 /* If we deleted an exception handler, we may have EH region begin/end
1597 blocks to remove as well. */
1600 }
1602 /* Find EH regions for which there is no longer a handler, and delete them. */
1604 static void
1606 {
1607 rtx insn;
1613 {
1616 {
1618 /* A NULL handler indicates a region is no longer needed,
1619 as long as it isn't the target of a rethrow. */
1621 {
1624 }
1625 }
1626 }
1627 }
1629 /* Return true if NOTE is not one of the ones that must be kept paired,
1630 so that we may simply delete them. */
1632 static int
1634 rtx note;
1635 {
1638 }
1640 /* Unlink a chain of insns between START and FINISH, leaving notes
1641 that must be paired. */
1643 static void
1646 {
1647 /* Unchain the insns one by one. It would be quicker to delete all
1648 of these with a single unchaining, rather than one at a time, but
1649 we need to keep the NOTE's. */
1651 rtx next;
1654 {
1657 ;
1659 ;
1660 else
1666 }
1667 }
1669 /* Delete the insns in a (non-live) block. We physically delete every
1670 non-deleted-note insn, and update the flow graph appropriately.
1672 Return nonzero if we deleted an exception handler. */
1674 /* ??? Preserving all such notes strikes me as wrong. It would be nice
1675 to post-process the stream to remove empty blocks, loops, ranges, etc. */
1677 static int
1679 basic_block b;
1680 {
1684 /* If the head of this block is a CODE_LABEL, then it might be the
1685 label for an exception handler which can't be reached.
1687 We need to remove the label from the exception_handler_label list
1688 and remove the associated NOTE_INSN_EH_REGION_BEG and
1689 NOTE_INSN_EH_REGION_END notes. */
1696 {
1700 {
1702 {
1703 /* Found a match, splice this label out of the EH label list. */
1708 /* Remove the handler from all regions */
1712 }
1714 }
1716 /* This label may be referenced by code solely for its value, or
1717 referenced by static data, or something. We have determined
1718 that it is not reachable, but cannot delete the label itself.
1719 Save code space and continue to delete the balance of the block,
1720 along with properly updating the cfg. */
1722 {
1723 /* If we've only got one of these, skip the whole deleting
1724 insns thing. */
1728 }
1729 }
1731 /* Selectively unlink the insn chain. Include any BARRIER that may
1732 follow the basic block. */
1738 no_delete_insns:
1740 /* Remove the edges into and out of this block. Note that there may
1741 indeed be edges in, if we are removing an unreachable loop. */
1742 {
1746 {
1752 }
1754 {
1760 }
1764 }
1766 /* Remove the basic block from the array, and compact behind it. */
1770 }
1772 /* Remove block B from the basic block array and compact behind it. */
1774 static void
1776 basic_block b;
1777 {
1781 {
1785 }
1788 n_basic_blocks--;
1789 }
1791 /* Delete INSN by patching it out. Return the next insn. */
1793 static rtx
1795 rtx insn;
1796 {
1807 else
1813 /* If deleting a jump, decrement the use count of the label. Deleting
1814 the label itself should happen in the normal course of block merging. */
1819 }
1821 /* True if a given label can be deleted. */
1823 static int
1825 rtx label;
1826 {
1827 rtx x;
1842 /* User declared labels must be preserved. */
1847 }
1849 /* Blocks A and B are to be merged into a single block. The insns
1850 are already contiguous, hence `nomove'. */
1852 static void
1855 {
1856 edge e;
1860 /* If there was a CODE_LABEL beginning B, delete it. */
1864 {
1865 /* Detect basic blocks with nothing but a label. This can happen
1866 in particular at the end of a function. */
1870 }
1872 /* Delete the basic block note. */
1875 {
1879 }
1881 /* If there was a jump out of A, delete it. */
1884 {
1885 rtx prev;
1891 #ifdef HAVE_cc0
1892 /* If this was a conditional jump, we need to also delete
1893 the insn that set cc0. */
1896 {
1902 }
1903 #endif
1905 /* Note that a->head != a->end, since we should have at least a
1906 bb note plus the jump, so prev != insn. */
1909 }
1911 /* By definition, there should only be one successor of A, and that is
1912 B. Free that edge struct. */
1915 /* Adjust the edges out of B for the new owner. */
1920 /* Reassociate the insns of B with A. */
1922 {
1925 {
1928 }
1930 }
1933 /* Compact the basic block array. */
1935 }
1937 /* Attempt to merge basic blocks that are potentially non-adjacent.
1938 Return true iff the attempt succeeded. */
1940 static int
1942 edge e;
1944 {
1945 /* If B has a fallthru edge to C, no need to move anything. */
1947 {
1948 /* ??? From here on out we must make sure to not munge nesting
1949 of exception regions and lexical blocks. Need to think about
1950 these cases before this gets implemented. */
1953 /* If C has an outgoing fallthru, and B does not have an incoming
1954 fallthru, move B before C. The later clause is somewhat arbitrary,
1955 but avoids modifying blocks other than the two we've been given. */
1957 /* Otherwise, move C after B. If C had a fallthru, which doesn't
1958 happen to be the physical successor to B, insert an unconditional
1959 branch. If C already ended with a conditional branch, the new
1960 jump must go in a new basic block D. */
1961 }
1963 /* If a label still appears somewhere and we cannot delete the label,
1964 then we cannot merge the blocks. The edge was tidied already. */
1965 {
1970 }
1974 }
1976 /* The given edge should potentially a fallthru edge. If that is in
1977 fact true, delete the unconditional jump and barriers that are in
1978 the way. */
1980 static void
1982 edge e;
1984 {
1985 rtx q;
1987 /* ??? In a late-running flow pass, other folks may have deleted basic
1988 blocks by nopping out blocks, leaving multiple BARRIERs between here
1989 and the target label. They ought to be chastized and fixed.
1991 We can also wind up with a sequence of undeletable labels between
1992 one block and the next.
1994 So search through a sequence of barriers, labels, and notes for
1995 the head of block C and assert that we really do fall through. */
2000 /* Remove what will soon cease being the jump insn from the source block.
2001 If block B consisted only of this single jump, turn it into a deleted
2002 note. */
2005 {
2006 #ifdef HAVE_cc0
2007 /* If this was a conditional jump, we need to also delete
2008 the insn that set cc0. */
2011 #endif
2014 {
2018 }
2019 else
2021 }
2023 /* Selectively unlink the sequence. */
2028 }
2030 /* Discover and record the loop depth at the head of each basic block. */
2032 static void
2034 rtx insns;
2035 {
2036 basic_block bb;
2037 rtx insn;
2042 {
2044 {
2049 }
2052 {
2054 depth++;
2056 depth--;
2058 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error. */
2061 }
2062 }
2063 }
2064 \f
2065 /* Perform data flow analysis.
2066 F is the first insn of the function and NREGS the number of register numbers
2067 in use. */
2069 void
2071 rtx f;
2075 {
2076 #ifdef ELIMINABLE_REGS
2079 #endif
2081 /* Record which registers will be eliminated. We use this in
2082 mark_used_regs. */
2086 #ifdef ELIMINABLE_REGS
2089 #else
2091 #endif
2093 /* Allocate a bitmap to be filled in by record_volatile_insns. */
2096 /* We want alias analysis information for local dead store elimination. */
2111 }
2113 /* Free the variables allocated by find_basic_blocks.
2115 KEEP_HEAD_END_P is non-zero if basic_block_info is not to be freed. */
2117 void
2120 {
2122 {
2125 }
2128 {
2137 }
2138 }
2140 /* Return nonzero if the destination of SET equals the source. */
2141 static int
2143 rtx set;
2144 {
2159 }
2161 /* Return nonzero if an insn consists only of SETs, each of which only sets a
2162 value to itself. */
2163 static int
2165 rtx insn;
2166 {
2169 /* Insns carrying these notes are useful later on. */
2177 {
2179 /* If nothing but SETs of registers to themselves,
2180 this insn can also be deleted. */
2182 {
2191 }
2194 }
2196 }
2198 static void
2200 rtx x;
2201 rtx pat ATTRIBUTE_UNUSED;
2202 {
2204 /* The stack pointer is only modified indirectly as the result
2205 of a push until later in flow. See the comments in rtl.texi
2206 regarding Embedded Side-Effects on Addresses. */
2214 }
2216 /* Record which insns refer to any volatile memory
2217 or for any reason can't be deleted just because they are dead stores.
2218 Also, delete any insns that copy a register to itself.
2219 And see if the stack pointer is modified. */
2220 static void
2222 rtx f;
2223 {
2224 rtx insn;
2226 {
2231 {
2236 /* A SET that makes space on the stack cannot be dead.
2237 (Such SETs occur only for allocating variable-size data,
2238 so they will always have a PLUS or MINUS according to the
2239 direction of stack growth.)
2240 Even if this function never uses this stack pointer value,
2241 signal handlers do! */
2244 #ifdef STACK_GROWS_DOWNWARD
2246 #else
2248 #endif
2252 /* Delete (in effect) any obvious no-op moves. */
2254 {
2258 }
2259 }
2261 /* Check if insn modifies the stack pointer. */
2265 }
2266 }
2268 /* Mark those regs which are needed at the end of the function as live
2269 at the end of the last basic block. */
2270 static void
2272 regset set;
2273 {
2276 /* If exiting needs the right stack value, consider the stack pointer
2277 live at the end of the function. */
2279 || (! FRAME_POINTER_REQUIRED
2280 && ! current_function_calls_alloca
2283 {
2285 }
2287 /* Mark the frame pointer if needed at the end of the function. If
2288 we end up eliminating it, it will be removed from the live list
2289 of each basic block by reload. */
2292 {
2294 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2295 /* If they are different, also mark the hard frame pointer as live */
2297 #endif
2298 }
2300 /* Mark all global registers, and all registers used by the epilogue
2301 as being live at the end of the function since they may be
2302 referenced by our caller. */
2305 #ifdef EPILOGUE_USES
2307 #endif
2308 )
2311 /* ??? Mark function return value here rather than as uses. */
2312 }
2314 /* Determine which registers are live at the start of each
2315 basic block of the function whose first insn is F.
2316 NREGS is the number of registers used in F.
2317 We allocate the vector basic_block_live_at_start
2318 and the regsets that it points to, and fill them with the data.
2319 regset_size and regset_bytes are also set here. */
2321 static void
2323 rtx f;
2326 {
2339 /* Allocate and zero out many data structures
2340 that will record the data from lifetime analysis. */
2348 /* Set up regset-vectors used internally within this function.
2349 Their meanings are documented above, with their declarations. */
2354 /* Stick these vectors into the AUX field of the basic block, so that
2355 we don't have to keep going through the index. */
2361 /* Assume that the stack pointer is unchanging if alloca hasn't been used.
2362 This will be cleared by record_volatile_insns if it encounters an insn
2363 which modifies the stack pointer. */
2369 {
2370 regset theend;
2376 /* Propogate this exit data to each of EXIT's predecessors. */
2378 {
2381 }
2382 }
2384 /* The post-reload life analysis have (on a global basis) the same registers
2385 live as was computed by reload itself.
2387 Otherwise elimination offsets and such may be incorrect.
2389 Reload will make some registers as live even though they do not appear
2390 in the rtl. */
2395 /* Propagate life info through the basic blocks
2396 around the graph of basic blocks.
2398 This is a relaxation process: each time a new register
2399 is live at the end of the basic block, we must scan the block
2400 to determine which registers are, as a consequence, live at the beginning
2401 of that block. These registers must then be marked live at the ends
2402 of all the blocks that can transfer control to that block.
2403 The process continues until it reaches a fixed point. */
2408 {
2411 {
2418 {
2419 /* Set CONSIDER if this block needs thinking about at all
2420 (that is, if the regs live now at the end of it
2421 are not the same as were live at the end of it when
2422 we last thought about it).
2423 Set must_rescan if it needs to be thought about
2424 instruction by instruction (that is, if any additional
2425 reg that is live at the end now but was not live there before
2426 is one of the significant regs of this basic block). */
2428 EXECUTE_IF_AND_COMPL_IN_REG_SET
2430 {
2433 {
2436 }
2437 });
2438 done:
2441 }
2443 /* The live_at_start of this block may be changing,
2444 so another pass will be required after this one. */
2448 {
2449 /* No complete rescan needed;
2450 just record those variables newly known live at end
2451 as live at start as well. */
2459 }
2460 else
2461 {
2462 /* Update the basic_block_live_at_start
2463 by propagation backwards through the block. */
2471 }
2473 /* Update the new_live_at_end's of the block's predecessors. */
2474 {
2479 }
2481 #ifdef USE_C_ALLOCA
2483 #endif
2484 }
2486 }
2488 /* The only pseudos that are live at the beginning of the function are
2489 those that were not set anywhere in the function. local-alloc doesn't
2490 know how to handle these correctly, so mark them as not local to any
2491 one basic block. */
2496 {
2498 });
2500 /* Now the life information is accurate. Make one more pass over each
2501 basic block to delete dead stores, create autoincrement addressing
2502 and record how many times each register is used, is set, or dies. */
2505 {
2508 /* We start with global_live_at_end to determine which stores are
2509 dead. This process is destructive, and we wish to preserve the
2510 contents of global_live_at_end for posterity. Fortunately,
2511 new_live_at_end, due to the way we converged on a solution,
2512 contains a duplicate of global_live_at_end that we can kill. */
2515 #ifdef USE_C_ALLOCA
2517 #endif
2518 }
2520 /* We have a problem with any pseudoreg that lives across the setjmp.
2521 ANSI says that if a user variable does not change in value between
2522 the setjmp and the longjmp, then the longjmp preserves it. This
2523 includes longjmp from a place where the pseudo appears dead.
2524 (In principle, the value still exists if it is in scope.)
2525 If the pseudo goes in a hard reg, some other value may occupy
2526 that hard reg where this pseudo is dead, thus clobbering the pseudo.
2527 Conclusion: such a pseudo must not go in a hard reg. */
2530 {
2532 {
2535 }
2536 });
2538 /* Restore regs_ever_live that was provided by reload. */
2548 }
2549 \f
2550 /* Subroutines of life analysis. */
2552 /* Allocate the permanent data structures that represent the results
2553 of life analysis. Not static since used also for stupid life analysis. */
2555 void
2557 {
2561 {
2567 }
2569 ENTRY_BLOCK_PTR->global_live_at_end
2571 EXIT_BLOCK_PTR->global_live_at_start
2575 }
2577 void
2579 {
2582 /* Recalculate the register space, in case it has grown. Old style
2583 vector oriented regsets would set regset_{size,bytes} here also. */
2586 /* Because both reg_scan and flow_analysis want to set up the REG_N_SETS
2587 information, explicitly reset it here. The allocation should have
2588 already happened on the previous reg_scan pass. Make sure in case
2589 some more registers were allocated. */
2592 }
2594 /* Make each element of VECTOR point at a regset. The vector has
2595 NELTS elements, and space is allocated from the ALLOC_OBSTACK
2596 obstack. */
2598 static void
2603 {
2607 {
2610 }
2611 }
2613 /* Release any additional space allocated for each element of VECTOR point
2614 other than the regset header itself. The vector has NELTS elements. */
2616 void
2620 {
2625 }
2627 /* Compute the registers live at the beginning of a basic block
2628 from those live at the end.
2630 When called, OLD contains those live at the end.
2631 On return, it contains those live at the beginning.
2632 FIRST and LAST are the first and last insns of the basic block.
2634 FINAL is nonzero if we are doing the final pass which is not
2635 for computing the life info (since that has already been done)
2636 but for acting on it. On this pass, we delete dead stores,
2637 set up the logical links and dead-variables lists of instructions,
2638 and merge instructions for autoincrement and autodecrement addresses.
2640 SIGNIFICANT is nonzero only the first time for each basic block.
2641 If it is nonzero, it points to a regset in which we store
2642 a 1 for each register that is set within the block.
2644 BNUM is the number of the basic block. */
2646 static void
2649 rtx first;
2650 rtx last;
2652 regset significant;
2655 {
2657 rtx prev;
2658 regset live;
2659 regset dead;
2661 /* Find the loop depth for this block. Ignore loop level changes in the
2662 middle of the basic block -- for register allocation purposes, the
2663 important uses will be in the blocks wholely contained within the loop
2664 not in the loop pre-header or post-trailer. */
2674 {
2677 /* Process the regs live at the end of the block.
2678 Mark them as not local to any one basic block. */
2680 {
2682 });
2683 }
2685 /* Scan the block an insn at a time from end to beginning. */
2688 {
2692 {
2693 /* If this is a call to `setjmp' et al,
2694 warn if any non-volatile datum is live. */
2698 }
2700 /* Update the life-status of regs for this insn.
2701 First DEAD gets which regs are set in this insn
2702 then LIVE gets which regs are used in this insn.
2703 Then the regs live before the insn
2704 are those live after, with DEAD regs turned off,
2705 and then LIVE regs turned on. */
2708 {
2715 {
2717 /* Don't delete something that refers to volatile storage! */
2721 }
2723 /* If an instruction consists of just dead store(s) on final pass,
2724 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
2725 We could really delete it with delete_insn, but that
2726 can cause trouble for first or last insn in a basic block. */
2728 {
2733 /* CC0 is now known to be dead. Either this insn used it,
2734 in which case it doesn't anymore, or clobbered it,
2735 so the next insn can't use it. */
2738 /* If this insn is copying the return value from a library call,
2739 delete the entire library call. */
2741 {
2747 {
2752 }
2753 }
2755 }
2760 /* See if this is an increment or decrement that can be
2761 merged into a following memory address. */
2762 #ifdef AUTO_INC_DEC
2763 {
2766 /* Does this instruction increment or decrement a register? */
2774 /* Ok, look for a following memory ref we can combine with.
2775 If one is found, change the memory ref to a PRE_INC
2776 or PRE_DEC, cancel this insn, and return 1.
2777 Return 0 if nothing has been done. */
2780 }
2783 /* If this is not the final pass, and this insn is copying the
2784 value of a library call and it's dead, don't scan the
2785 insns that perform the library call, so that the call's
2786 arguments are not marked live. */
2788 {
2789 /* Mark the dest reg as `significant'. */
2794 }
2800 /* We have an insn to pop a constant amount off the stack.
2801 (Such insns use PLUS regardless of the direction of the stack,
2802 and any insn to adjust the stack by a constant is always a pop.)
2803 These insns, if not dead stores, have no effect on life. */
2804 ;
2805 else
2806 {
2807 /* Any regs live at the time of a call instruction
2808 must not go in a register clobbered by calls.
2809 Find all regs now live and record this for them. */
2813 {
2815 });
2817 /* LIVE gets the regs used in INSN;
2818 DEAD gets those set by it. Dead insns don't make anything
2819 live. */
2824 /* If an insn doesn't use CC0, it becomes dead since we
2825 assume that every insn clobbers it. So show it dead here;
2826 mark_used_regs will set it live if it is referenced. */
2832 /* Sometimes we may have inserted something before INSN (such as
2833 a move) when we make an auto-inc. So ensure we will scan
2834 those insns. */
2835 #ifdef AUTO_INC_DEC
2837 #endif
2840 {
2843 rtx note;
2846 note;
2852 /* Each call clobbers all call-clobbered regs that are not
2853 global or fixed. Note that the function-value reg is a
2854 call-clobbered reg, and mark_set_regs has already had
2855 a chance to handle it. */
2862 /* The stack ptr is used (honorarily) by a CALL insn. */
2865 /* Calls may also reference any of the global registers,
2866 so they are made live. */
2873 /* Calls also clobber memory. */
2875 }
2877 /* Update OLD for the registers used or set. */
2881 }
2883 /* On final pass, update counts of how many insns each reg is live
2884 at. */
2888 }
2889 flushed: ;
2892 }
2896 }
2897 \f
2898 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
2899 (SET expressions whose destinations are registers dead after the insn).
2900 NEEDED is the regset that says which regs are alive after the insn.
2902 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL.
2904 If X is the entire body of an insn, NOTES contains the reg notes
2905 pertaining to the insn. */
2907 static int
2909 rtx x;
2910 regset needed;
2912 rtx notes ATTRIBUTE_UNUSED;
2913 {
2916 #ifdef AUTO_INC_DEC
2917 /* If flow is invoked after reload, we must take existing AUTO_INC
2918 expresions into account. */
2920 {
2922 {
2924 {
2927 /* Don't delete insns to set global regs. */
2931 }
2932 }
2933 }
2934 #endif
2936 /* If setting something that's a reg or part of one,
2937 see if that register's altered value will be live. */
2940 {
2943 /* A SET that is a subroutine call cannot be dead. */
2947 #ifdef HAVE_cc0
2950 #endif
2953 {
2954 rtx temp;
2955 /* Walk the set of memory locations we are currently tracking
2956 and see if one is an identical match to this memory location.
2957 If so, this memory write is dead (remember, we're walking
2958 backwards from the end of the block to the start. */
2961 {
2965 }
2966 }
2973 {
2976 /* Don't delete insns to set global regs. */
2978 /* Make sure insns to set frame pointer aren't deleted. */
2981 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2984 #endif
2985 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2986 /* Make sure insns to set arg pointer are never deleted
2987 (if the arg pointer isn't fixed, there will be a USE for
2988 it, so we can treat it normally). */
2990 #endif
2994 /* If this is a hard register, verify that subsequent words are
2995 not needed. */
2997 {
3003 }
3006 }
3007 }
3009 /* If performing several activities,
3010 insn is dead if each activity is individually dead.
3011 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
3012 that's inside a PARALLEL doesn't make the insn worth keeping. */
3014 {
3024 }
3026 /* A CLOBBER of a pseudo-register that is dead serves no purpose. That
3027 is not necessarily true for hard registers. */
3033 /* We do not check other CLOBBER or USE here. An insn consisting of just
3034 a CLOBBER or just a USE should not be deleted. */
3036 }
3038 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
3039 return 1 if the entire library call is dead.
3040 This is true if X copies a register (hard or pseudo)
3041 and if the hard return reg of the call insn is dead.
3042 (The caller should have tested the destination of X already for death.)
3044 If this insn doesn't just copy a register, then we don't
3045 have an ordinary libcall. In that case, cse could not have
3046 managed to substitute the source for the dest later on,
3047 so we can assume the libcall is dead.
3049 NEEDED is the bit vector of pseudoregs live before this insn.
3050 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
3052 static int
3054 rtx x;
3055 regset needed;
3056 rtx note;
3057 rtx insn;
3058 {
3062 {
3065 {
3067 rtx call_pat;
3070 /* Find the call insn. */
3074 /* If there is none, do nothing special,
3075 since ordinary death handling can understand these insns. */
3079 /* See if the hard reg holding the value is dead.
3080 If this is a PARALLEL, find the call within it. */
3083 {
3089 /* This may be a library call that is returning a value
3090 via invisible pointer. Do nothing special, since
3091 ordinary death handling can understand these insns. */
3096 }
3099 }
3100 }
3102 }
3104 /* Return 1 if register REGNO was used before it was set, i.e. if it is
3105 live at function entry. Don't count global register variables, variables
3106 in registers that can be used for function arg passing, or variables in
3107 fixed hard registers. */
3109 int
3112 {
3121 }
3123 /* 1 if register REGNO was alive at a place where `setjmp' was called
3124 and was set more than once or is an argument.
3125 Such regs may be clobbered by `longjmp'. */
3127 int
3130 {
3137 }
3138 \f
3139 /* INSN references memory, possibly using autoincrement addressing modes.
3140 Find any entries on the mem_set_list that need to be invalidated due
3141 to an address change. */
3142 static void
3144 rtx insn;
3145 {
3148 {
3150 {
3155 {
3157 {
3158 /* Splice temp out of list. */
3161 else
3163 }
3164 else
3167 }
3168 }
3169 }
3170 }
3172 /* Process the registers that are set within X.
3173 Their bits are set to 1 in the regset DEAD,
3174 because they are dead prior to this insn.
3176 If INSN is nonzero, it is the insn being processed
3177 and the fact that it is nonzero implies this is the FINAL pass
3178 in propagate_block. In this case, various info about register
3179 usage is stored, LOG_LINKS fields of insns are set up. */
3181 static void
3183 regset needed;
3184 regset dead;
3185 rtx x;
3186 rtx insn;
3187 regset significant;
3188 {
3194 {
3197 {
3201 }
3202 }
3203 }
3205 /* Process a single SET rtx, X. */
3207 static void
3209 regset needed;
3210 regset dead;
3211 rtx x;
3212 rtx insn;
3213 regset significant;
3214 {
3218 /* Some targets place small structures in registers for
3219 return values of functions. We have to detect this
3220 case specially here to get correct flow information. */
3223 {
3229 }
3231 /* Modifying just one hardware register of a multi-reg value
3232 or just a byte field of a register
3233 does not mean the value from before this insn is now dead.
3234 But it does mean liveness of that register at the end of the block
3235 is significant.
3237 Within mark_set_1, however, we treat it as if the register is
3238 indeed modified. mark_used_regs will, however, also treat this
3239 register as being used. Thus, we treat these insns as setting a
3240 new value for the register as a function of its old value. This
3241 cases LOG_LINKS to be made appropriately and this will help combine. */
3248 /* If this set is a MEM, then it kills any aliased writes.
3249 If this set is a REG, then it kills any MEMs which use the reg. */
3252 {
3257 {
3262 {
3263 /* Splice this entry out of the list. */
3266 else
3268 }
3269 else
3272 }
3273 }
3275 /* If the memory reference had embedded side effects (autoincrement
3276 address modes. Then we may need to kill some entries on the
3277 memory set list. */
3282 /* We do not know the size of a BLKmode store, so we do not track
3283 them for redundant store elimination. */
3285 /* There are no REG_INC notes for SP, so we can't assume we'll see
3286 everything that invalidates it. To be safe, don't eliminate any
3287 stores though SP; none of them should be redundant anyway. */
3294 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
3297 #endif
3298 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
3300 #endif
3302 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
3303 {
3307 /* Mark it as a significant register for this basic block. */
3311 /* Mark it as dead before this insn. */
3314 /* A hard reg in a wide mode may really be multiple registers.
3315 If so, mark all of them just like the first. */
3317 {
3320 /* Nothing below is needed for the stack pointer; get out asap.
3321 Eg, log links aren't needed, since combine won't use them. */
3327 {
3336 }
3337 }
3338 /* Additional data to record if this is the final pass. */
3340 {
3344 /* If this is a hard reg, record this function uses the reg. */
3347 {
3352 {
3353 /* The next use is no longer "next", since a store
3354 intervenes. */
3359 }
3360 }
3361 else
3362 {
3363 /* The next use is no longer "next", since a store
3364 intervenes. */
3367 /* Keep track of which basic blocks each reg appears in. */
3374 /* Count (weighted) references, stores, etc. This counts a
3375 register twice if it is modified, but that is correct. */
3380 /* The insns where a reg is live are normally counted
3381 elsewhere, but we want the count to include the insn
3382 where the reg is set, and the normal counting mechanism
3383 would not count it. */
3385 }
3388 {
3389 /* Make a logical link from the next following insn
3390 that uses this register, back to this insn.
3391 The following insns have already been processed.
3393 We don't build a LOG_LINK for hard registers containing
3394 in ASM_OPERANDs. If these registers get replaced,
3395 we might wind up changing the semantics of the insn,
3396 even if reload can make what appear to be valid assignments
3397 later. */
3403 }
3405 {
3406 /* Note that dead stores have already been deleted when possible
3407 If we get here, we have found a dead store that cannot
3408 be eliminated (because the same insn does something useful).
3409 Indicate this by marking the reg being set as dying here. */
3413 }
3414 else
3415 {
3416 /* This is a case where we have a multi-word hard register
3417 and some, but not all, of the words of the register are
3418 needed in subsequent insns. Write REG_UNUSED notes
3419 for those parts that were not needed. This case should
3420 be rare. */
3432 }
3433 }
3434 }
3438 /* If this is the last pass and this is a SCRATCH, show it will be dying
3439 here and count it. */
3441 {
3444 }
3445 }
3446 \f
3447 #ifdef AUTO_INC_DEC
3449 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
3450 reference. */
3452 static void
3454 regset needed;
3455 rtx x;
3456 rtx insn;
3457 {
3460 rtx set;
3462 /* Here we detect use of an index register which might be good for
3463 postincrement, postdecrement, preincrement, or predecrement. */
3469 {
3472 rtx use;
3473 rtx incr;
3476 /* Is the next use an increment that might make auto-increment? */
3481 /* Can't add side effects to jumps; if reg is spilled and
3482 reloaded, there's no way to store back the altered value. */
3487 && ((HAVE_POST_INCREMENT
3489 || (HAVE_POST_DECREMENT
3491 || (HAVE_PRE_INCREMENT
3493 || (HAVE_PRE_DECREMENT
3495 /* Make sure this reg appears only once in this insn. */
3498 {
3505 {
3506 /* This is the simple case. Try to make the auto-inc. If
3507 we can't, we are done. Otherwise, we will do any
3508 needed updates below. */
3513 }
3515 /* PREV_INSN used here to check the semi-open interval
3516 [insn,incr). */
3518 /* We must also check for sets of q as q may be
3519 a call clobbered hard register and there may
3520 be a call between PREV_INSN (insn) and incr. */
3522 {
3523 /* We have *p followed sometime later by q = p+size.
3524 Both p and q must be live afterward,
3525 and q is not used between INSN and its assignment.
3526 Change it to q = p, ...*q..., q = q+size.
3527 Then fall into the usual case. */
3529 basic_block bb;
3540 /* If we can't make the auto-inc, or can't make the
3541 replacement into Y, exit. There's no point in making
3542 the change below if we can't do the auto-inc and doing
3543 so is not correct in the pre-inc case. */
3552 /* We now know we'll be doing this change, so emit the
3553 new insn(s) and do the updates. */
3559 /* INCR will become a NOTE and INSN won't contain a
3560 use of ADDR. If a use of ADDR was just placed in
3561 the insn before INSN, make that the next use.
3562 Otherwise, invalidate it. */
3567 else
3573 /* REGNO is now used in INCR which is below INSN, but
3574 it previously wasn't live here. If we don't mark
3575 it as needed, we'll put a REG_DEAD note for it
3576 on this insn, which is incorrect. */
3579 /* If there are any calls between INSN and INCR, show
3580 that REGNO now crosses them. */
3584 }
3585 else
3588 /* If we haven't returned, it means we were able to make the
3589 auto-inc, so update the status. First, record that this insn
3590 has an implicit side effect. */
3595 /* Modify the old increment-insn to simply copy
3596 the already-incremented value of our register. */
3600 /* If that makes it a no-op (copying the register into itself) delete
3601 it so it won't appear to be a "use" and a "set" of this
3602 register. */
3604 {
3608 }
3611 {
3612 /* Count an extra reference to the reg. When a reg is
3613 incremented, spilling it is worse, so we want to make
3614 that less likely. */
3617 /* Count the increment as a setting of the register,
3618 even though it isn't a SET in rtl. */
3620 }
3621 }
3622 }
3623 }
3625 \f
3626 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
3627 This is done assuming the registers needed from X
3628 are those that have 1-bits in NEEDED.
3630 On the final pass, FINAL is 1. This means try for autoincrement
3631 and count the uses and deaths of each pseudo-reg.
3633 INSN is the containing instruction. If INSN is dead, this function is not
3634 called. */
3636 static void
3638 regset needed;
3639 regset live;
3640 rtx x;
3642 rtx insn;
3643 {
3648 retry:
3651 {
3662 #ifdef HAVE_cc0
3666 #endif
3669 /* If we are clobbering a MEM, mark any registers inside the address
3670 as being used. */
3676 /* Invalidate the data for the last MEM stored, but only if MEM is
3677 something that can be stored into. */
3681 else
3682 {
3687 {
3689 {
3690 /* Splice temp out of the list. */
3693 else
3695 }
3696 else
3699 }
3700 }
3702 /* If the memory reference had embedded side effects (autoincrement
3703 address modes. Then we may need to kill some entries on the
3704 memory set list. */
3708 #ifdef AUTO_INC_DEC
3711 #endif
3721 /* While we're here, optimize this case. */
3724 /* In case the SUBREG is not of a register, don't optimize */
3726 {
3729 }
3731 /* ... fall through ... */
3734 /* See a register other than being set
3735 => mark it as needed. */
3738 {
3744 /* A hard reg in a wide mode may really be multiple registers.
3745 If so, mark all of them just like the first. */
3747 {
3750 /* For stack ptr or fixed arg pointer,
3751 nothing below can be necessary, so waste no more time. */
3753 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
3756 #endif
3757 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
3759 #endif
3762 {
3763 /* If this is a register we are going to try to eliminate,
3764 don't mark it live here. If we are successful in
3765 eliminating it, it need not be live unless it is used for
3766 pseudos, in which case it will have been set live when
3767 it was allocated to the pseudos. If the register will not
3768 be eliminated, reload will set it live at that point. */
3773 }
3774 /* No death notes for global register variables;
3775 their values are live after this function exits. */
3777 {
3781 }
3785 {
3792 }
3793 }
3795 {
3796 /* Record where each reg is used, so when the reg
3797 is set we know the next insn that uses it. */
3802 {
3803 /* If a hard reg is being used,
3804 record that this function does use it. */
3809 do
3812 }
3813 else
3814 {
3815 /* Keep track of which basic block each reg appears in. */
3824 /* Count (weighted) number of uses of each reg. */
3827 }
3829 /* Record and count the insns in which a reg dies.
3830 If it is used in this insn and was dead below the insn
3831 then it dies in this insn. If it was set in this insn,
3832 we do not make a REG_DEAD note; likewise if we already
3833 made such a note. */
3837 #if 0
3839 #endif
3840 )
3841 {
3842 /* Check for the case where the register dying partially
3843 overlaps the register set by this insn. */
3846 {
3850 }
3852 /* If none of the words in X is needed, make a REG_DEAD
3853 note. Otherwise, we must make partial REG_DEAD notes. */
3855 {
3859 }
3860 else
3861 {
3864 /* Don't make a REG_DEAD note for a part of a register
3865 that is set in the insn. */
3876 }
3877 }
3878 }
3879 }
3883 {
3887 /* If storing into MEM, don't show it as being used. But do
3888 show the address as being used. */
3890 {
3891 #ifdef AUTO_INC_DEC
3894 #endif
3898 }
3900 /* Storing in STRICT_LOW_PART is like storing in a reg
3901 in that this SET might be dead, so ignore it in TESTREG.
3902 but in some other ways it is like using the reg.
3904 Storing in a SUBREG or a bit field is like storing the entire
3905 register in that if the register's value is not used
3906 then this SET is not needed. */
3911 {
3919 /* Modifying a single register in an alternate mode
3920 does not use any of the old value. But these other
3921 ways of storing in a register do use the old value. */
3924 ;
3925 else
3929 }
3931 /* If this is a store into a register,
3932 recursively scan the value being stored. */
3939 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
3942 #endif
3943 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
3945 #endif
3946 ))
3947 /* We used to exclude global_regs here, but that seems wrong.
3948 Storing in them is like storing in mem. */
3949 {
3954 }
3955 }
3959 /* If exiting needs the right stack value, consider this insn as
3960 using the stack pointer. In any event, consider it as using
3961 all global registers and all registers used by return. */
3963 || (! FRAME_POINTER_REQUIRED
3964 && ! current_function_calls_alloca
3971 #ifdef EPILOGUE_USES
3973 #endif
3974 )
3982 {
3983 /* Traditional and volatile asm instructions must be considered to use
3984 and clobber all hard registers, all pseudo-registers and all of
3985 memory. So must TRAP_IF and UNSPEC_VOLATILE operations.
3987 Consider for instance a volatile asm that changes the fpu rounding
3988 mode. An insn should not be moved across this even if it only uses
3989 pseudo-regs because it might give an incorrectly rounded result.
3991 ?!? Unfortunately, marking all hard registers as live causes massive
3992 problems for the register allocator and marking all pseudos as live
3993 creates mountains of uninitialized variable warnings.
3995 So for now, just clear the memory set list and mark any regs
3996 we can find in ASM_OPERANDS as used. */
4000 /* For all ASM_OPERANDS, we must traverse the vector of input operands.
4001 We can not just fall through here since then we would be confused
4002 by the ASM_INPUT rtx inside ASM_OPERANDS, which do not indicate
4003 traditional asms unlike their normal usage. */
4005 {
4011 }
4013 }
4018 }
4020 /* Recursively scan the operands of this expression. */
4022 {
4027 {
4029 {
4030 /* Tail recursive case: save a function call level. */
4032 {
4035 }
4037 }
4039 {
4043 }
4044 }
4045 }
4046 }
4047 \f
4048 #ifdef AUTO_INC_DEC
4050 static int
4052 rtx insn;
4053 {
4054 /* Find the next use of this reg. If in same basic block,
4055 make it do pre-increment or pre-decrement if appropriate. */
4063 /* Don't do this if the reg dies, or gets set in y; a standard addressing
4064 mode would be better. */
4067 {
4068 /* We have found a suitable auto-increment
4069 and already changed insn Y to do it.
4070 So flush this increment-instruction. */
4074 /* Count a reference to this reg for the increment
4075 insn we are deleting. When a reg is incremented.
4076 spilling it is worse, so we want to make that
4077 less likely. */
4079 {
4082 }
4084 }
4086 }
4088 /* Try to change INSN so that it does pre-increment or pre-decrement
4089 addressing on register REG in order to add AMOUNT to REG.
4090 AMOUNT is negative for pre-decrement.
4091 Returns 1 if the change could be made.
4092 This checks all about the validity of the result of modifying INSN. */
4094 static int
4097 HOST_WIDE_INT amount;
4098 {
4101 /* Nonzero if we can try to make a pre-increment or pre-decrement.
4102 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
4104 /* Nonzero if we can try to make a post-increment or post-decrement.
4105 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
4106 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
4107 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
4110 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
4113 /* From the sign of increment, see which possibilities are conceivable
4114 on this target machine. */
4128 /* It is not safe to add a side effect to a jump insn
4129 because if the incremented register is spilled and must be reloaded
4130 there would be no way to store the incremented value back in memory. */
4139 {
4142 }
4150 /* See if this combination of instruction and addressing mode exists. */
4158 /* Record that this insn now has an implicit side effect on X. */
4161 }
4164 \f
4165 /* Find the place in the rtx X where REG is used as a memory address.
4166 Return the MEM rtx that so uses it.
4167 If PLUSCONST is nonzero, search instead for a memory address equivalent to
4168 (plus REG (const_int PLUSCONST)).
4170 If such an address does not appear, return 0.
4171 If REG appears more than once, or is used other than in such an address,
4172 return (rtx)1. */
4174 rtx
4177 rtx reg;
4178 HOST_WIDE_INT plusconst;
4179 {
4196 {
4197 /* If REG occurs inside a MEM used in a bit-field reference,
4198 that is unacceptable. */
4201 }
4207 {
4209 {
4215 }
4217 {
4220 {
4226 }
4227 }
4228 }
4231 }
4232 \f
4233 /* Write information about registers and basic blocks into FILE.
4234 This is part of making a debugging dump. */
4236 void
4239 {
4246 {
4268 {
4273 else
4277 }
4281 }
4285 {
4303 {
4307 }
4308 else
4313 {
4317 }
4318 else
4322 }
4325 }
4327 static void
4330 edge e;
4332 {
4339 else
4343 {
4346 };
4354 {
4361 else
4364 }
4366 }
4367 }
4369 \f
4370 /* Like print_rtl, but also print out live information for the start of each
4371 basic block. */
4373 void
4376 rtx rtx_first;
4377 {
4382 else
4383 {
4399 {
4401 rtx x;
4406 {
4414 }
4415 }
4418 {
4420 basic_block bb;
4423 {
4428 {
4433 });
4435 }
4452 }
4453 }
4454 }
4456 \f
4457 /* Integer list support. */
4459 /* Allocate a node from list *HEAD_PTR. */
4461 static int_list_ptr
4464 {
4468 {
4473 }
4477 }
4479 /* Pointer to head of predecessor/successor block list. */
4482 /* Add a new node to integer list LIST with value VAL.
4483 LIST is a pointer to a list object to allow for different implementations.
4484 If *LIST is initially NULL, the list is empty.
4485 The caller must not care whether the element is added to the front or
4486 to the end of the list (to allow for different implementations). */
4488 static int_list_ptr
4493 {
4500 }
4502 /* Free the blocks of lists at BLK_LIST. */
4504 void
4507 {
4511 {
4514 }
4516 /* Mark list as empty for the next function we compile. */
4518 }
4519 \f
4520 /* Predecessor/successor computation. */
4522 /* Mark PRED_BB a precessor of SUCC_BB,
4523 and conversely SUCC_BB a successor of PRED_BB. */
4525 static void
4533 {
4535 {
4538 }
4540 {
4543 }
4544 }
4546 /* Convert edge lists into pred/succ lists for backward compatibility. */
4548 void
4554 {
4556 edge e;
4564 {
4570 }
4575 }
4577 void
4583 {
4585 int_list_ptr p;
4589 {
4594 {
4598 else
4600 }
4604 {
4608 else
4610 }
4612 {
4619 }
4621 }
4623 }
4625 /* Free basic block data storage. */
4627 void
4629 {
4631 }
4633 /* Compute dominator relationships. */
4634 void
4640 {
4658 {
4661 {
4674 }
4675 passes++;
4676 }
4679 }
4681 /* Compute dominator relationships using new flow graph structures. */
4682 void
4686 {
4704 {
4707 {
4718 }
4719 passes++;
4720 }
4723 }
4725 /* Given DOMINATORS, compute the immediate dominators into IDOM. */
4727 void
4731 {
4737 /* Begin with tmp(n) = dom(n) - { n }. */
4739 {
4742 }
4744 /* Subtract out all of our dominator's dominators. */
4746 {
4753 }
4755 /* Find the one bit set in the bitmap and put it in the output array. */
4757 {
4760 }
4763 }
4765 /* Count for a single SET rtx, X. */
4767 static void
4769 rtx x;
4770 {
4774 /* Find the register that's set/clobbered. */
4782 {
4787 }
4790 {
4793 {
4794 /* Count (weighted) references, stores, etc. This counts a
4795 register twice if it is modified, but that is correct. */
4799 }
4800 }
4801 }
4803 /* Increment REG_N_SETS for each SET or CLOBBER found in X; also increment
4804 REG_N_REFS by the current loop depth for each SET or CLOBBER found. */
4806 static void
4808 rtx x;
4809 {
4815 {
4818 {
4822 }
4823 }
4824 }
4826 /* Increment REG_N_REFS by the current loop depth each register reference
4827 found in X. */
4829 static void
4831 rtx x;
4832 {
4835 retry:
4838 {
4850 #ifdef HAVE_cc0
4853 #endif
4856 /* If we are clobbering a MEM, mark any registers inside the address
4857 as being used. */
4863 /* While we're here, optimize this case. */
4866 /* In case the SUBREG is not of a register, don't optimize */
4868 {
4871 }
4873 /* ... fall through ... */
4881 {
4885 /* If storing into MEM, don't show it as being used. But do
4886 show the address as being used. */
4888 {
4892 }
4894 /* Storing in STRICT_LOW_PART is like storing in a reg
4895 in that this SET might be dead, so ignore it in TESTREG.
4896 but in some other ways it is like using the reg.
4898 Storing in a SUBREG or a bit field is like storing the entire
4899 register in that if the register's value is not used
4900 then this SET is not needed. */
4905 {
4906 /* Modifying a single register in an alternate mode
4907 does not use any of the old value. But these other
4908 ways of storing in a register do use the old value. */
4911 ;
4912 else
4916 }
4918 /* If this is a store into a register,
4919 recursively scan the value being stored. */
4924 {
4929 }
4930 }
4935 }
4937 /* Recursively scan the operands of this expression. */
4939 {
4944 {
4946 {
4947 /* Tail recursive case: save a function call level. */
4949 {
4952 }
4954 }
4956 {
4960 }
4961 }
4962 }
4963 }
4965 /* Recompute register set/reference counts immediately prior to register
4966 allocation.
4968 This avoids problems with set/reference counts changing to/from values
4969 which have special meanings to the register allocators.
4971 Additionally, the reference counts are the primary component used by the
4972 register allocators to prioritize pseudos for allocation to hard regs.
4973 More accurate reference counts generally lead to better register allocation.
4975 F is the first insn to be scanned.
4976 LOOP_STEP denotes how much loop_depth should be incremented per
4977 loop nesting level in order to increase the ref count more for references
4978 in a loop.
4980 It might be worthwhile to update REG_LIVE_LENGTH, REG_BASIC_BLOCK and
4981 possibly other information which is used by the register allocators. */
4983 void
4985 rtx f;
4987 {
4988 rtx insn;
4991 /* Clear out the old data. */
4994 {
4997 }
4999 /* Scan each insn in the chain and count how many times each register is
5000 set/used. */
5003 {
5004 /* Keep track of loop depth. */
5006 {
5007 /* Look for loop boundaries. */
5013 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
5014 Abort now rather than setting register status incorrectly. */
5017 }
5019 {
5020 rtx links;
5022 /* This call will increment REG_N_SETS for each SET or CLOBBER
5023 of a register in INSN. It will also increment REG_N_REFS
5024 by the loop depth for each set of a register in INSN. */
5027 /* count_reg_sets does not detect autoincrement address modes, so
5028 detect them here by looking at the notes attached to INSN. */
5030 {
5032 /* Count (weighted) references, stores, etc. This counts a
5033 register twice if it is modified, but that is correct. */
5035 }
5037 /* This call will increment REG_N_REFS by the current loop depth for
5038 each reference to a register in INSN. */
5041 /* count_reg_references will not include counts for arguments to
5042 function calls, so detect them here by examining the
5043 CALL_INSN_FUNCTION_USAGE data. */
5045 {
5046 rtx note;
5049 note;
5053 }
5054 }
5055 }
5056 }
5058 /* Record INSN's block as BB. */
5060 void
5062 rtx insn;
5063 basic_block bb;
5064 {
5067 {
5070 /* Add one-eighth the size so we don't keep calling xrealloc. */
5074 }
5076 }
5078 /* Record INSN's block number as BB. */
5079 /* ??? This has got to go. */
5081 void
5083 rtx insn;
5085 {
5087 }
5088 \f
5089 /* Unlink a chain of insns between START and FINISH inclusive, leaving notes
5090 that must be paired, and return the new chain. */
5092 rtx
5095 {
5099 /* Unchain the insns one by one. It would be quicker to delete all
5100 of these with a single unchaining, rather than one at a time, but
5101 we need to keep the NOTE's. */
5104 {
5109 /* ??? Despite the fact that we're patching out the insn, it's
5110 still referenced in LOG_LINKS. Rather than try and track
5111 them all down and remove them, just mark the insn deleted. */
5115 {
5118 }
5119 else
5120 {
5122 {
5126 }
5127 else
5128 {
5132 }
5133 }
5138 }
5144 }
5146 /* Subroutine of update_life_info. Determines whether multiple
5147 REG_NOTEs need to be distributed for the hard register mentioned in
5148 NOTE. This can happen if a reference to a hard register in the
5149 original insns was split into several smaller hard register
5150 references in the new insns. */
5152 static void
5155 {
5157 rtx insn;
5166 {
5170 }
5175 {
5178 /* Check for references to new_reg in the split insns. */
5180 {
5183 {
5184 /* Create a new reg dead note here. */
5191 /* If killed multiple registers here, then add in the excess. */
5195 }
5196 /* It isn't mentioned anywhere, so no new reg note is needed for
5197 this register. */
5200 }
5201 }
5202 }
5204 /* SET_INSN kills REG; add a REG_DEAD note mentioning REG to the last
5205 use of REG in the insns after SET_INSN and before or including
5206 LAST, if necessary.
5208 A non-zero value is returned if we added a REG_DEAD note, or if we
5209 determined that a REG_DEAD note because of this particular SET
5210 wasn't necessary. */
5212 static int
5215 {
5216 rtx insn;
5219 {
5220 rtx set;
5225 {
5235 {
5236 /* Use the same scheme as combine.c, don't put both REG_DEAD
5237 and REG_UNUSED notes on the same insn. */
5240 {
5246 }
5248 }
5250 {
5251 /* We found an instruction that both uses the register and
5252 sets it, so no new REG_NOTE is needed for the previous
5253 set. */
5255 }
5256 }
5257 }
5259 }
5261 static int
5264 {
5265 rtx set;
5267 /* We need to add a REG_DEAD note to the last place DEST is
5268 referenced. */
5273 {
5283 {
5284 /* Use the same scheme as combine.c, don't put both REG_DEAD
5285 and REG_UNUSED notes on the same insn. */
5288 {
5294 }
5296 }
5297 }
5299 }
5301 /* Find the first insn in the set of insns from FIRST to LAST inclusive
5302 that contains the note NOTE. */
5303 rtx
5306 {
5307 rtx insn;
5310 {
5313 {
5315 }
5317 {
5319 }
5320 }
5322 }
5324 /* Subroutine of update_life_info. Determines whether a SET or
5325 CLOBBER in an insn created by splitting needs a REG_DEAD or
5326 REG_UNUSED note added. */
5328 static void
5331 {
5345 {
5346 /* If the original insns already used this register, we may not
5347 add new notes for it. One example for a replacement that
5348 needs this test is when a multi-word memory access with
5349 register-indirect addressing is changed into multiple memory
5350 accesses with auto-increment and one adjusting add
5351 instruction for the address register.
5353 However, there is a problem with this code. We're assuming
5354 that any registers that are set in the new insns are either
5355 set/referenced in the old insns (and thus "inherit" the
5356 liveness of the old insns), or are registers that are dead
5357 before we enter this part of the stream (and thus should be
5358 dead when we leave).
5360 To do this absolutely correctly, we must determine the actual
5361 liveness of the registers before we go randomly adding
5362 REG_DEAD notes. This can probably be accurately done by
5363 calling mark_referenced_resources() on the old stream before
5364 replacing the old insns. */
5367 {
5373 }
5374 /* So it's a new register, presumably only used within this
5375 group of insns. Find the last insn in the set of new insns
5376 that DEST is referenced in, and add a dead note to it. */
5378 {
5379 /* If this is a set, it must die somewhere, unless it is the
5380 dest of the original insn, and thus is live after the
5381 original insn. Abort if it isn't supposed to be live after
5382 the original insn.
5384 If this is a clobber, then just add a REG_UNUSED note. */
5386 {
5393 }
5394 else
5395 {
5397 rtx curr;
5403 {
5410 }
5412 /* In case reg was not used later, it is dead store.
5413 add REG_UNUSED note. */
5415 {
5422 }
5423 }
5424 }
5426 {
5428 /* If this is a set, scan backwards for a previous
5429 reference, and attach a REG_DEAD note to it. But we don't
5430 want to do it if the insn is both using and setting the
5431 register.
5433 Global registers are always live. */
5437 {
5440 {
5445 }
5446 }
5447 }
5448 }
5449 }
5451 /* Subroutine of update_life_info. Update the value of reg_n_sets for all
5452 registers modified by X. INC is -1 if the containing insn is being deleted,
5453 and is 1 if the containing insn is a newly generated insn. */
5455 static void
5457 rtx x;
5459 {
5467 {
5471 {
5477 }
5478 else
5480 }
5481 }
5483 /* Scan INSN for a SET that sets REG. If it sets REG via a SUBREG,
5484 then return 2. If it sets REG directly, return 1. Otherwise, return
5485 0. */
5490 static void
5493 {
5495 {
5500 }
5501 }
5503 static int
5505 rtx insn;
5506 rtx reg;
5507 {
5515 }
5517 /* If a replaced SET_INSN (which is part of the insns between
5518 OLD_FIRST_INSN and OLD_LAST_INSN inclusive) is modifying a multiple
5519 register target, and the original dest is now set in the new insns
5520 (between FIRST_INSN and LAST_INSN inclusive) by one or more subreg
5521 sets, then the new insns no longer kill the destination of the
5522 original insn.
5524 We may also be directly using the register in the new insns before
5525 setting it.
5527 In either case, if there exists an instruction in the same basic
5528 block before the replaced insns which uses the original dest (and
5529 contains a corresponding REG_DEAD note), then we must remove this
5530 REG_DEAD note.
5532 SET_INSN is the insn that contains the SET; it may be a PARALLEL
5533 containing the SET insn.
5535 SET is the actual SET insn proper. */
5537 static void
5543 {
5544 rtx insn;
5547 rtx set_dest;
5548 rtx set_pattern;
5556 {
5560 {
5564 }
5566 }
5569 {
5571 }
5576 {
5578 }
5580 /* We have a set of a REG. First we need to determine if this set is
5581 both using and setting the register. (FIXME: if this is in a
5582 PARALLEL, we will have to check the other exprs as well.) */
5584 {
5586 }
5588 /* Now determine if we used or set the register in the old insns
5589 previous to this one. */
5592 {
5594 {
5596 }
5597 }
5599 /* Now determine if we're setting it in the new insns, or using
5600 it. */
5602 {
5605 {
5607 }
5609 {
5610 /* Is the reg now used in this new insn? -- This is probably an
5611 error. */
5614 }
5615 }
5617 {
5618 /* The register is being set via a SUBREG or is being used in
5619 some other way, so it's no longer dead.
5621 Search backwards from first_insn, looking for the first insn
5622 that uses the original dest. Stop if we pass a CODE_LABEL or
5623 a JUMP_INSN.
5625 If we find such an insn and it has a REG_DEAD note referring
5626 to the original dest, then delete the note. */
5629 {
5635 {
5638 {
5640 }
5641 /* ??? -- Is this right? */
5643 }
5644 }
5645 }
5647 {
5648 /* The reg is not being set or used in the new insns at all. */
5651 /* Should never reach here for a pseudo reg. */
5655 /* This can happen for a hard register, if the new insns do not
5656 contain instructions which would be no-ops referring to the
5657 old registers.
5659 We try to verify that this is the case by checking to see if
5660 the original instruction uses all of the registers that it
5661 set. This case is OK, because deleting a no-op can not affect
5662 REG_DEAD notes on other insns. If this is not the case, then
5663 abort. */
5668 {
5670 NULL_PTR))
5672 }
5675 }
5676 }
5678 /* Updates all flow-analysis related quantities (including REG_NOTES) for
5679 the insns from FIRST to LAST inclusive that were created by replacing
5680 the insns from ORIG_INSN_FIRST to ORIG_INSN_LAST inclusive. NOTES
5681 are the original REG_NOTES. */
5683 void
5685 rtx notes;
5688 {
5690 rtx next;
5692 rtx orig_insn;
5693 rtx tem;
5695 /* Get and save the destination set by the original insn, if there
5696 was only one insn replaced. */
5699 {
5704 }
5705 else
5706 {
5709 }
5711 /* Move REG_NOTES from the original insns to where they now belong. */
5714 {
5717 {
5720 /* Move these notes from the original insn to the last new
5721 insn where the register is mentioned. */
5724 {
5727 {
5728 /* Sometimes need to convert REG_UNUSED notes to
5729 REG_DEAD notes. */
5733 {
5735 }
5737 /* The reg only dies in one insn, the last one that uses
5738 it. */
5740 }
5741 /* It must die somewhere, fail if we couldn't find where it died.
5743 We abort because otherwise the register will be live
5744 longer than it should, and we'll probably take an
5745 abort later. What we should do instead is search back
5746 and find the appropriate places to insert the note. */
5748 {
5750 {
5752 }
5754 }
5755 }
5759 {
5760 rtx note_dest;
5762 /* If the insn that set the register to 0 was deleted, this
5763 note cannot be relied on any longer. The destination might
5764 even have been moved to memory.
5765 This was observed for SH4 with execute/920501-6.c compilation,
5766 -O2 -fomit-frame-pointer -finline-functions . */
5772 {
5774 }
5775 else
5776 {
5779 {
5782 {
5784 }
5785 }
5786 }
5787 /* This note applies to the dest of the original insn. Find the
5788 first new insn that now has the same dest, and move the note
5789 there. */
5795 {
5799 {
5802 /* The reg is only zero before one insn, the first that
5803 uses it. */
5805 }
5806 /* If this note refers to a multiple word hard
5807 register, it may have been split into several smaller
5808 hard register references. We could split the notes,
5809 but simply dropping them is good enough. */
5815 /* It must be set somewhere; fail if we couldn't find
5816 where it was set. */
5819 }
5820 }
5825 /* A REG_EQUIV or REG_EQUAL note on an insn with more than one
5826 set is meaningless. Just drop the note. */
5831 /* These notes apply to the dest of the original insn. Find the last
5832 new insn that now has the same dest, and move the note there.
5834 If we are replacing multiple insns, just drop the note. */
5843 {
5847 {
5850 /* Only put this note on one of the new insns. */
5852 }
5854 /* The original dest must still be set someplace. Abort if we
5855 couldn't find it. */
5857 {
5858 /* However, if this note refers to a multiple word hard
5859 register, it may have been split into several smaller
5860 hard register references. We could split the notes,
5861 but simply dropping them is good enough. */
5867 /* Likewise for multi-word memory references. */
5872 }
5873 }
5877 /* Move a REG_LIBCALL note to the first insn created, and update
5878 the corresponding REG_RETVAL note. */
5889 /* Move a REG_EXEC_COUNT note to the first insn created. */
5895 /* Move a REG_RETVAL note to the last insn created, and update
5896 the corresponding REG_LIBCALL note. */
5908 /* This should be moved to whichever instruction is a JUMP_INSN. */
5911 {
5913 {
5916 /* Only put this note on one of the new insns. */
5918 }
5919 /* Fail if we couldn't find a JUMP_INSN. */
5922 }
5926 /* reload sometimes leaves obsolete REG_INC notes around. */
5929 /* This should be moved to whichever instruction now has the
5930 increment operation. */
5934 /* Should be moved to the new insn(s) which use the label. */
5945 /* These two notes will never appear until after reorg, so we don't
5946 have to handle them here. */
5949 }
5950 }
5952 /* Each new insn created has a new set. If the destination is a
5953 register, then this reg is now live across several insns, whereas
5954 previously the dest reg was born and died within the same insn.
5955 To reflect this, we now need a REG_DEAD note on the insn where
5956 this dest reg dies.
5958 Similarly, the new insns may have clobbers that need REG_UNUSED
5959 notes. */
5962 {
5963 rtx pat;
5971 {
5973 {
5976 {
5981 }
5982 }
5983 }
5985 {
5987 }
5988 }
5990 /* Check to see if we have any REG_DEAD notes on insns previous to
5991 the new ones that are now incorrect and need to be removed. */
5994 {
6000 }
6002 /* Update reg_n_sets. This is necessary to prevent local alloc from
6003 converting REG_EQUAL notes to REG_EQUIV when the new insns are setting
6004 a reg multiple times instead of once. */
6007 {
6008 rtx x;
6009 RTX_CODE code;
6019 {
6022 {
6026 }
6027 }
6030 }
6033 {
6040 {
6043 {
6047 }
6048 }
6052 }
6053 }
6054 \f
6055 /* Prepends the set of REG_NOTES in NEW to NOTES, and returns NEW. */
6056 static rtx
6059 {
6060 rtx end;
6063 {
6065 }
6067 {
6069 }
6072 {
6074 }
6077 }
6078 \f
6079 /* Replace the insns from FIRST to LAST inclusive with the set of insns in
6080 NEW, and update the life analysis info accordingly. */
6081 void
6084 {
6086 rtx last_new;
6092 {
6094 {
6096 }
6097 }
6099 {
6104 }
6108 {
6110 {
6112 }
6114 {
6116 }
6117 }
6118 /* This is probably bogus. */
6120 {
6122 {
6125 }
6126 }
6128 }
6129 \f
6130 /* Verify the CFG consistency. This function check some CFG invariants and
6131 aborts when something is wrong. Hope that this function will help to
6132 convert many optimization passes to preserve CFG consistent.
6134 Currently it does following checks:
6136 - test head/end pointers
6137 - overlapping of basic blocks
6138 - edge list corectness
6139 - headers of basic blocks (the NOTE_INSN_BASIC_BLOCK note)
6140 - tails of basic blocks (ensure that boundary is necesary)
6141 - scans body of the basic block for JUMP_INSN, CODE_LABEL
6142 and NOTE_INSN_BASIC_BLOCK
6143 - check that all insns are in the basic blocks
6144 (except the switch handling code, barriers and notes)
6146 In future it can be extended check a lot of other stuff as well
6147 (reachability of basic blocks, life information, etc. etc.). */
6149 void
6151 {
6155 rtx x;
6161 /* First pass check head/end pointers and set bb_info array used by
6162 later passes. */
6164 {
6167 /* Check the head pointer and make sure that it is pointing into
6168 insn list. */
6173 {
6176 }
6178 /* Check the end pointer and make sure that it is pointing into
6179 insn list. */
6181 {
6183 {
6186 }
6191 }
6193 {
6196 }
6197 }
6199 /* Now check the basic blocks (boundaries etc.) */
6201 {
6203 /* Check corectness of edge lists */
6204 edge e;
6208 {
6210 {
6219 }
6221 {
6226 {
6229 }
6230 }
6232 }
6236 {
6238 {
6247 }
6249 {
6254 {
6257 }
6258 }
6260 }
6262 /* OK pointers are correct. Now check the header of basic
6263 block. It ought to contain optional CODE_LABEL followed
6264 by NOTE_BASIC_BLOCK. */
6267 {
6269 {
6270 fatal ("verify_flow_info: Basic block contains only CODE_LABEL and no NOTE_INSN_BASIC_BLOCK note\n");
6271 }
6273 }
6277 {
6280 }
6283 {
6284 /* Do checks for empty blocks here */
6285 }
6286 else
6287 {
6290 {
6293 {
6296 }
6304 {
6307 }
6310 }
6311 }
6312 }
6316 {
6318 {
6320 {
6326 /* An addr_vec is placed outside any block block. */
6331 {
6333 }
6335 /* But in any case, non-deletable labels can appear anywhere. */
6340 }
6341 }
6344 }
6345 }
6346 \f
6347 /* Functions to access an edge list with a vector representation.
6348 Enough data is kept such that given an index number, the
6349 pred and succ that edge reprsents can be determined, or
6350 given a pred and a succ, it's index number can be returned.
6351 This allows algorithms which comsume a lot of memory to
6352 represent the normally full matrix of edge (pred,succ) with a
6353 single indexed vector, edge (EDGE_INDEX (pred, succ)), with no
6354 wasted space in the client code due to sparse flow graphs. */
6356 /* This functions initializes the edge list. Basically the entire
6357 flowgraph is processed, and all edges are assigned a number,
6358 and the data structure is filed in. */
6361 {
6363 edge e;
6366 int_list_ptr ptr;
6373 /* Determine the number of edges in the flow graph by counting successor
6374 edges on each basic block. */
6376 {
6380 num_edges++;
6381 }
6382 /* Don't forget successors of the entry block. */
6384 num_edges++;
6393 /* Follow successors of the entry block, and register these edges. */
6395 {
6397 num_edges++;
6398 }
6401 {
6404 /* Follow all successors of blocks, and register these edges. */
6406 {
6408 num_edges++;
6409 }
6410 }
6412 }
6414 /* This function free's memory associated with an edge list. */
6415 void
6418 {
6420 {
6423 }
6424 }
6426 /* This function provides debug output showing an edge list. */
6427 void
6431 {
6437 {
6441 else
6446 else
6448 }
6449 }
6451 /* This function provides an internal consistancy check of an edge list,
6452 verifying that all edges are present, and that there are no
6453 extra edges. */
6454 void
6458 {
6460 int_list_ptr ptr;
6462 edge e;
6465 {
6469 {
6474 {
6477 }
6484 }
6485 }
6487 {
6492 {
6495 }
6502 }
6503 /* We've verified that all the edges are in the list, no lets make sure
6504 there are no spurious edges in the list. */
6508 {
6516 {
6519 }
6522 {
6525 }
6534 }
6536 {
6544 {
6547 }
6550 {
6553 }
6557 succ);
6562 }
6564 {
6572 {
6575 }
6578 {
6581 }
6585 pred);
6590 }
6591 }
6593 /* This routine will determine what, if any, edge there is between
6594 a specified predecessor and successor. */
6596 int
6600 {
6603 {
6607 }
6609 }