| blob | e23be42c89f541ec96332f1ddf862e800ff8b21e |
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
139 #define obstack_chunk_alloc xmalloc
140 #define obstack_chunk_free free
143 /* EXIT_IGNORE_STACK should be nonzero if, when returning from a function,
144 the stack pointer does not matter. The value is tested only in
145 functions that have frame pointers.
146 No definition is equivalent to always zero. */
147 #ifndef EXIT_IGNORE_STACK
148 #define EXIT_IGNORE_STACK 0
149 #endif
152 /* The contents of the current function definition are allocated
153 in this obstack, and all are freed at the end of the function.
154 For top-level functions, this is temporary_obstack.
155 Separate obstacks are made for nested functions. */
159 /* Number of basic blocks in the current function. */
163 /* The basic block array. */
165 varray_type basic_block_info;
167 /* The special entry and exit blocks. */
170 {
171 {
183 },
184 {
196 }
197 };
199 /* Nonzero if the second flow pass has completed. */
202 /* Maximum register number used in this function, plus one. */
206 /* Indexed by n, giving various register information */
208 varray_type reg_n_info;
210 /* Size of the reg_n_info table. */
214 /* Element N is the next insn that uses (hard or pseudo) register number N
215 within the current basic block; or zero, if there is no such insn.
216 This is valid only during the final backward scan in propagate_block. */
220 /* Size of a regset for the current function,
221 in (1) bytes and (2) elements. */
226 /* Regset of regs live when calls to `setjmp'-like functions happen. */
227 /* ??? Does this exist only for the setjmp-clobbered warning message? */
229 regset regs_live_at_setjmp;
231 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
232 that have to go in the same hard reg.
233 The first two regs in the list are a pair, and the next two
234 are another pair, etc. */
235 rtx regs_may_share;
237 /* Depth within loops of basic block being scanned for lifetime analysis,
238 plus one. This is the weight attached to references to registers. */
242 /* During propagate_block, this is non-zero if the value of CC0 is live. */
246 /* During propagate_block, this contains a list of all the MEMs we are
247 tracking for dead store elimination.
249 ?!? Note we leak memory by not free-ing items on this list. We need to
250 write some generic routines to operate on memory lists since cse, gcse,
251 loop, sched, flow and possibly other passes all need to do basically the
252 same operations on these lists. */
256 /* Set of registers that may be eliminable. These are handled specially
257 in updating regs_ever_live. */
261 /* The basic block structure for every insn, indexed by uid. */
263 varray_type basic_block_for_insn;
265 /* The labels mentioned in non-jump rtl. Valid during find_basic_blocks. */
266 /* ??? Should probably be using LABEL_NUSES instead. It would take a
267 bit of surgery to be able to use or co-opt the routines in jump. */
271 /* INSN_VOLATILE (insn) is 1 if the insn refers to anything volatile. */
273 #define INSN_VOLATILE(INSN) bitmap_bit_p (uid_volatile, INSN_UID (INSN))
274 #define SET_INSN_VOLATILE(INSN) bitmap_set_bit (uid_volatile, INSN_UID (INSN))
277 /* Forward declarations */
302 basic_block));
304 basic_block));
327 #ifdef AUTO_INC_DEC
331 #endif
356 \f
357 /* Find basic blocks of the current function.
358 F is the first insn of the function and NREGS the number of register
359 numbers in use. */
361 void
363 rtx f;
367 {
370 /* Flush out existing data. */
372 {
377 /* Clear bb->aux on all extant basic blocks. We'll use this as a
378 tag for reuse during create_basic_block, just in case some pass
379 copies around basic block notes improperly. */
384 }
388 /* Size the basic block table. The actual structures will be allocated
389 by find_basic_blocks_1, since we want to keep the structure pointers
390 stable across calls to find_basic_blocks. */
391 /* ??? This whole issue would be much simpler if we called find_basic_blocks
392 exactly once, and thereafter we don't have a single long chain of
393 instructions at all until close to the end of compilation when we
394 actually lay them out. */
400 /* Record the block to which an insn belongs. */
401 /* ??? This should be done another way, by which (perhaps) a label is
402 tagged directly with the basic block that it starts. It is used for
403 more than that currently, but IMO that is the only valid use. */
406 #ifdef AUTO_INC_DEC
407 /* Leave space for insns life_analysis makes in some cases for auto-inc.
408 These cases are rare, so we don't need too much space. */
410 #endif
414 /* Discover the edges of our cfg. */
419 /* Delete unreachable blocks, then merge blocks when possible. */
422 {
427 }
429 /* Mark critical edges. */
433 /* Discover the loop depth at the start of each basic block to aid
434 register allocation. */
437 /* Kill the data we won't maintain. */
440 #ifdef ENABLE_CHECKING
442 #endif
443 }
445 /* Count the basic blocks of the function. */
447 static int
449 rtx f;
450 {
460 {
468 {
469 count++;
471 /* If the previous insn was a call that did not create an
472 abnormal edge, we want to add a nop so that the CALL_INSN
473 itself is not at basic_block_end. This allows us to
474 easily distinguish between normal calls and those which
475 create abnormal edges in the flow graph. */
478 {
481 }
482 }
484 /* Record whether this call created an edge. */
486 {
492 /* If there is a specified EH region, we have an edge. */
495 else
496 {
497 /* If there is a nonlocal goto label and the specified
498 region number isn't -1, we have an edge. (0 means
499 no throw, but might have a nonlocal goto). */
502 }
503 }
514 }
516 /* The rest of the compiler works a bit smoother when we don't have to
517 check for the edge case of do-nothing functions with no basic blocks. */
519 {
522 }
525 }
527 /* Find all basic blocks of the function whose first insn is F.
529 Collect and return a list of labels whose addresses are taken. This
530 will be used in make_edges for use with computed gotos. */
532 static rtx
534 rtx f;
535 {
545 /* We process the instructions in a slightly different way than we did
546 previously. This is so that we see a NOTE_BASIC_BLOCK after we have
547 closed out the previous block, so that it gets attached at the proper
548 place. Since this form should be equivalent to the previous,
549 count_basic_blocks continues to use the old form as a check. */
552 {
558 {
559 /* Record whether this call created an edge. */
564 /* If there is an EH region, we have an edge. */
567 else
568 {
569 /* If there is a nonlocal goto label and the specified
570 region number isn't -1, we have an edge. (0 means
571 no throw, but might have a nonlocal goto). */
574 }
575 }
578 {
580 {
583 /* Keep a LIFO list of the currently active exception notes. */
587 {
591 }
593 /* Look for basic block notes with which to keep the
594 basic_block_info pointers stable. Unthread the note now;
595 we'll put it back at the right place in create_basic_block.
596 Or not at all if we've already found a note in this block. */
598 {
602 }
605 }
608 /* A basic block starts at a label. If we've closed one off due
609 to a barrier or some such, no need to do it again. */
611 {
612 /* While we now have edge lists with which other portions of
613 the compiler might determine a call ending a basic block
614 does not imply an abnormal edge, it will be a bit before
615 everything can be updated. So continue to emit a noop at
616 the end of such a block. */
618 {
621 }
625 }
630 /* A basic block ends at a jump. */
633 else
634 {
635 /* ??? Make a special check for table jumps. The way this
636 happens is truely and amazingly gross. We are about to
637 create a basic block that contains just a code label and
638 an addr*vec jump insn. Worse, an addr_diff_vec creates
639 its own natural loop.
641 Prevent this bit of brain damage, pasting things together
642 correctly in make_edges.
644 The correct solution involves emitting the table directly
645 on the tablejump instruction as a note, or JUMP_LABEL. */
649 {
651 n_basic_blocks--;
653 }
654 }
659 /* A basic block ends at a barrier. It may be that an unconditional
660 jump already closed the basic block -- no need to do it again. */
664 /* While we now have edge lists with which other portions of the
665 compiler might determine a call ending a basic block does not
666 imply an abnormal edge, it will be a bit before everything can
667 be updated. So continue to emit a noop at the end of such a
668 block. */
670 {
673 }
677 /* A basic block ends at a call that can either throw or
678 do a non-local goto. */
680 {
681 new_bb_inclusive:
686 new_bb_exclusive:
691 }
692 /* FALLTHRU */
696 {
700 }
702 }
705 {
706 rtx note;
708 /* Make a list of all labels referred to other than by jumps
709 (which just don't have the REG_LABEL notes).
711 Make a special exception for labels followed by an ADDR*VEC,
712 as this would be a part of the tablejump setup code.
714 Make a special exception for the eh_return_stub_label, which
715 we know isn't part of any otherwise visible control flow. */
719 {
723 ;
728 ;
729 else
730 label_value_list
732 label_value_list);
733 }
734 }
735 }
744 }
746 /* Create a new basic block consisting of the instructions between
747 HEAD and END inclusive. Reuses the note and basic block struct
748 in BB_NOTE, if any. */
750 static void
754 {
755 basic_block bb;
761 {
762 /* If we found an existing note, thread it back onto the chain. */
766 else
767 {
770 }
771 }
772 else
773 {
774 /* Otherwise we must create a note and a basic block structure.
775 Since we allow basic block structs in rtl, give the struct
776 the same lifetime by allocating it off the function obstack
777 rather than using malloc. */
784 else
785 {
788 }
790 }
792 /* Always include the bb note in the block. */
801 /* Tag the block so that we know it has been used when considering
802 other basic block notes. */
804 }
805 \f
806 /* Records the basic block struct in BB_FOR_INSN, for every instruction
807 indexed by INSN_UID. MAX is the size of the array. */
809 void
812 {
818 {
825 {
832 }
833 }
834 }
836 /* Free the memory associated with the edge structures. */
838 static void
840 {
845 {
849 {
852 }
856 }
859 {
862 }
866 }
868 /* Identify the edges between basic blocks.
870 NONLOCAL_LABEL_LIST is a list of non-local labels in the function. Blocks
871 that are otherwise unreachable may be reachable with a non-local goto.
873 BB_EH_END is an array indexed by basic block number in which we record
874 the list of exception regions active at the end of the basic block. */
876 static void
878 rtx label_value_list;
879 {
883 /* Assume no computed jump; revise as we create edges. */
886 /* By nature of the way these get numbered, block 0 is always the entry. */
890 {
896 /* Examine the last instruction of the block, and discover the
897 ways we can leave the block. */
902 /* A branch. */
904 {
905 rtx tmp;
907 /* ??? Recognize a tablejump and do the right thing. */
913 {
914 rtvec vec;
919 else
925 /* Some targets (eg, ARM) emit a conditional jump that also
926 contains the out-of-range target. Scan for these and
927 add an edge if necessary. */
934 #ifdef CASE_DROPS_THROUGH
935 /* Silly VAXen. The ADDR_VEC is going to be in the way of
936 us naturally detecting fallthru into the next block. */
938 #endif
939 }
941 /* If this is a computed jump, then mark it as reaching
942 everything on the label_value_list and forced_labels list. */
944 {
952 }
954 /* Returns create an exit out. */
958 /* Otherwise, we have a plain conditional or unconditional jump. */
959 else
960 {
964 }
965 }
967 /* If this is a CALL_INSN, then mark it as reaching the active EH
968 handler for this CALL_INSN. If we're handling asynchronous
969 exceptions then any insn can reach any of the active handlers.
971 Also mark the CALL_INSN as reaching any nonlocal goto handler. */
974 {
975 /* If there's an EH region active at the end of a block,
976 add the appropriate edges. */
980 /* If we have asynchronous exceptions, do the same for *all*
981 exception regions active in the block. */
984 {
992 {
995 }
996 }
999 {
1000 /* ??? This could be made smarter: in some cases it's possible
1001 to tell that certain calls will not do a nonlocal goto.
1003 For example, if the nested functions that do the nonlocal
1004 gotos do not have their addresses taken, then only calls to
1005 those functions or to other nested functions that use them
1006 could possibly do nonlocal gotos. */
1007 /* We do know that a REG_EH_REGION note with a value less
1008 than 0 is guaranteed not to perform a non-local goto. */
1014 }
1015 }
1017 /* We know something about the structure of the function __throw in
1018 libgcc2.c. It is the only function that ever contains eh_stub
1019 labels. It modifies its return address so that the last block
1020 returns to one of the eh_stub labels within it. So we have to
1021 make additional edges in the flow graph. */
1025 /* Find out if we can drop through to the next block. */
1030 {
1036 }
1037 }
1039 }
1041 /* Create an edge between two basic blocks. FLAGS are auxiliary information
1042 about the edge that is accumulated between calls. */
1044 static void
1048 {
1049 edge e;
1051 /* Make sure we don't add duplicate edges. */
1055 {
1058 }
1070 }
1072 /* Create an edge from a basic block to a label. */
1074 static void
1076 basic_block src;
1077 rtx label;
1079 {
1083 /* If the label was never emitted, this insn is junk, but avoid a
1084 crash trying to refer to BLOCK_FOR_INSN (label). This can happen
1085 as a result of a syntax error and a diagnostic has already been
1086 printed. */
1092 }
1094 /* Create the edges generated by INSN in REGION. */
1096 static void
1099 basic_block src;
1100 rtx insn;
1102 {
1109 {
1112 }
1113 }
1115 /* EH_REGION notes appearing between basic blocks is ambiguous, and even
1116 dangerous if we intend to move basic blocks around. Move such notes
1117 into the following block. */
1119 static void
1121 {
1130 {
1135 {
1140 {
1141 /* Unlink from the insn chain. */
1145 /* Queue it. */
1148 }
1149 }
1154 /* Find where to insert these things. */
1160 {
1164 }
1165 }
1166 }
1168 /* Recompute eh_beg/eh_end for each basic block. */
1170 static void
1172 rtx f;
1173 {
1179 {
1184 {
1189 {
1193 }
1194 }
1197 {
1203 }
1204 }
1205 }
1207 /* Identify critical edges and set the bits appropriately. */
1209 static void
1211 {
1213 basic_block bb;
1215 /* We begin with the entry block. This is not terribly important now,
1216 but could be if a front end (Fortran) implemented alternate entry
1217 points. */
1222 {
1223 edge e;
1225 /* (1) Critical edges must have a source with multiple successors. */
1227 {
1229 {
1230 /* (2) Critical edges must have a destination with multiple
1231 predecessors. Note that we know there is at least one
1232 predecessor -- the edge we followed to get here. */
1235 else
1237 }
1238 }
1239 else
1240 {
1243 }
1248 }
1249 }
1250 \f
1251 /* Split a (typically critical) edge. Return the new block.
1252 Abort on abnormal edges.
1254 ??? The code generally expects to be called on critical edges.
1255 The case of a block ending in an unconditional jump to a
1256 block with multiple predecessors is not handled optimally. */
1258 basic_block
1260 edge edge_in;
1261 {
1263 edge edge_out;
1264 rtx bb_note;
1267 /* Abnormal edges cannot be split. */
1274 /* Remove the existing edge from the destination's pred list. */
1275 {
1281 }
1283 /* Create the new structures. */
1292 /* ??? This info is likely going to be out of date very soon. */
1295 {
1298 }
1299 else
1300 {
1303 }
1305 /* Wire them up. */
1321 /* Tricky case -- if there existed a fallthru into the successor
1322 (and we're not it) we must add a new unconditional jump around
1323 the new block we're actually interested in.
1325 Further, if that edge is critical, this means a second new basic
1326 block must be created to hold it. In order to simplify correct
1327 insn placement, do this before we touch the existing basic block
1328 ordering for the block we were really wanting. */
1330 {
1331 edge e;
1337 {
1338 basic_block jump_block;
1339 rtx pos;
1342 {
1343 /* Non critical -- we can simply add a jump to the end
1344 of the existing predecessor. */
1346 }
1347 else
1348 {
1349 /* We need a new block to hold the jump. The simplest
1350 way to do the bulk of the work here is to recursively
1351 call ourselves. */
1354 }
1356 /* Now add the jump insn ... */
1362 /* ... let jump know that label is in use, ... */
1366 /* ... and clear fallthru on the outgoing edge. */
1369 /* Continue splitting the interesting edge. */
1370 }
1371 }
1373 /* Place the new block just in front of the successor. */
1377 else
1380 {
1384 }
1388 /* Create the basic block note. */
1391 else
1396 /* Not quite simple -- for non-fallthru edges, we must adjust the
1397 predecessor's jump instruction to target our new block. */
1399 {
1407 /* ??? Recognize a tablejump and adjust all matching cases. */
1413 {
1414 rtvec vec;
1419 else
1424 {
1428 }
1429 }
1430 else
1431 {
1432 /* This would have indicated an abnormal edge. */
1436 /* A return instruction can't be redirected. */
1440 /* If the insn doesn't go where we think, we're confused. */
1445 }
1449 }
1452 }
1454 /* Queue instructions for insertion on an edge between two basic blocks.
1455 The new instructions and basic blocks (if any) will not appear in the
1456 CFG until commit_edge_insertions is called. */
1458 void
1460 rtx pattern;
1461 edge e;
1462 {
1463 /* We cannot insert instructions on an abnormal critical edge.
1464 It will be easier to find the culprit if we die now. */
1471 else
1478 }
1480 /* Update the CFG for the instructions queued on edge E. */
1482 static void
1484 edge e;
1485 {
1487 basic_block bb;
1489 /* Figure out where to put these things. If the destination has
1490 one predecessor, insert there. Except for the exit block. */
1493 {
1496 /* Get the location correct wrt a code label, and "nice" wrt
1497 a basic block note, and before everything else. */
1506 else
1508 }
1510 /* If the source has one successor and the edge is not abnormal,
1511 insert there. Except for the entry block. */
1515 {
1518 {
1519 /* ??? Is it possible to wind up with non-simple jumps? Perhaps
1520 a jump with delay slots already filled? */
1525 }
1526 else
1527 {
1528 /* We'd better be fallthru, or we've lost track of what's what. */
1533 }
1534 }
1536 /* Otherwise we must split the edge. */
1537 else
1538 {
1541 }
1543 /* Now that we've found the spot, do the insertion. */
1547 /* Set the new block number for these insns, if structure is allocated. */
1549 {
1550 rtx i;
1553 }
1556 {
1560 }
1561 else
1562 {
1566 }
1567 }
1569 /* Update the CFG for all queued instructions. */
1571 void
1573 {
1575 basic_block bb;
1580 {
1584 {
1588 }
1593 }
1594 }
1595 \f
1596 /* Delete all unreachable basic blocks. */
1598 static void
1600 {
1603 edge e;
1609 /* Use basic_block->aux as a marker. Clear them all. */
1614 /* Add our starting points to the worklist. Almost always there will
1615 be only one. It isn't inconcievable that we might one day directly
1616 support Fortran alternate entry points. */
1619 {
1622 /* Mark the block with a handy non-null value. */
1624 }
1626 /* Iterate: find everything reachable from what we've already seen. */
1629 {
1634 {
1637 }
1638 }
1640 /* Delete all unreachable basic blocks. Count down so that we don't
1641 interfere with the block renumbering that happens in delete_block. */
1646 {
1650 /* This block was found. Tidy up the mark. */
1652 else
1654 }
1656 /* Fix up edges that now fall through, or rather should now fall through
1657 but previously required a jump around now deleted blocks. Simplify
1658 the search by only examining blocks numerically adjacent, since this
1659 is how find_basic_blocks created them. */
1662 {
1665 edge s;
1667 /* We care about simple conditional or unconditional jumps with
1668 a single successor.
1670 If we had a conditional branch to the next instruction when
1671 find_basic_blocks was called, then there will only be one
1672 out edge for the block which ended with the conditional
1673 branch (since we do not create duplicate edges).
1675 Furthermore, the edge will be marked as a fallthru because we
1676 merge the flags for the duplicate edges. So we do not want to
1677 check that the edge is not a FALLTHRU edge. */
1681 /* If the jump insn has side effects, we can't tidy the edge. */
1685 }
1687 /* If we deleted an exception handler, we may have EH region begin/end
1688 blocks to remove as well. */
1691 }
1693 /* Find EH regions for which there is no longer a handler, and delete them. */
1695 static void
1697 {
1698 rtx insn;
1704 {
1707 {
1709 /* A NULL handler indicates a region is no longer needed,
1710 as long as it isn't the target of a rethrow. */
1712 {
1715 }
1716 }
1717 }
1718 }
1720 /* Return true if NOTE is not one of the ones that must be kept paired,
1721 so that we may simply delete them. */
1723 static int
1725 rtx note;
1726 {
1729 }
1731 /* Unlink a chain of insns between START and FINISH, leaving notes
1732 that must be paired. */
1734 static void
1737 {
1738 /* Unchain the insns one by one. It would be quicker to delete all
1739 of these with a single unchaining, rather than one at a time, but
1740 we need to keep the NOTE's. */
1742 rtx next;
1745 {
1748 ;
1750 ;
1751 else
1757 }
1758 }
1760 /* Delete the insns in a (non-live) block. We physically delete every
1761 non-deleted-note insn, and update the flow graph appropriately.
1763 Return nonzero if we deleted an exception handler. */
1765 /* ??? Preserving all such notes strikes me as wrong. It would be nice
1766 to post-process the stream to remove empty blocks, loops, ranges, etc. */
1768 static int
1770 basic_block b;
1771 {
1775 /* If the head of this block is a CODE_LABEL, then it might be the
1776 label for an exception handler which can't be reached.
1778 We need to remove the label from the exception_handler_label list
1779 and remove the associated NOTE_INSN_EH_REGION_BEG and
1780 NOTE_INSN_EH_REGION_END notes. */
1787 {
1791 {
1793 {
1794 /* Found a match, splice this label out of the EH label list. */
1799 /* Remove the handler from all regions */
1803 }
1805 }
1807 /* This label may be referenced by code solely for its value, or
1808 referenced by static data, or something. We have determined
1809 that it is not reachable, but cannot delete the label itself.
1810 Save code space and continue to delete the balance of the block,
1811 along with properly updating the cfg. */
1813 {
1814 /* If we've only got one of these, skip the whole deleting
1815 insns thing. */
1819 }
1820 }
1822 /* Selectively unlink the insn chain. Include any BARRIER that may
1823 follow the basic block. */
1829 no_delete_insns:
1831 /* Remove the edges into and out of this block. Note that there may
1832 indeed be edges in, if we are removing an unreachable loop. */
1833 {
1837 {
1843 }
1845 {
1851 }
1855 }
1857 /* Remove the basic block from the array, and compact behind it. */
1861 }
1863 /* Remove block B from the basic block array and compact behind it. */
1865 static void
1867 basic_block b;
1868 {
1872 {
1876 }
1879 n_basic_blocks--;
1880 }
1882 /* Delete INSN by patching it out. Return the next insn. */
1884 static rtx
1886 rtx insn;
1887 {
1898 else
1904 /* If deleting a jump, decrement the use count of the label. Deleting
1905 the label itself should happen in the normal course of block merging. */
1910 }
1912 /* True if a given label can be deleted. */
1914 static int
1916 rtx label;
1917 {
1918 rtx x;
1933 /* User declared labels must be preserved. */
1938 }
1940 /* Blocks A and B are to be merged into a single block. A has no incoming
1941 fallthru edge, so it can be moved before B without adding or modifying
1942 any jumps (aside from the jump from A to B). */
1944 static int
1947 {
1954 /* We want to delete the BARRIER after the end of the insns we are
1955 going to move. If we don't find a BARRIER, then do nothing. This
1956 can happen in some cases if we have labels we can not delete.
1958 Similarly, do nothing if we can not delete the label at the start
1959 of the target block. */
1965 else
1968 /* Move block and loop notes out of the chain so that we do not
1969 disturb their order.
1971 ??? A better solution would be to squeeze out all the non-nested notes
1972 and adjust the block trees appropriately. Even better would be to have
1973 a tighter connection between block trees and rtl so that this is not
1974 necessary. */
1977 /* Scramble the insn chain. */
1980 /* Now blocks A and B are contiguous. Merge them. */
1984 {
1987 }
1990 }
1992 /* Blocks A and B are to be merged into a single block. B has no outgoing
1993 fallthru edge, so it can be moved after A without adding or modifying
1994 any jumps (aside from the jump from A to B). */
1996 static int
1999 {
2006 /* We want to delete the BARRIER after the end of the insns we are
2007 going to move. If we don't find a BARRIER, then do nothing. This
2008 can happen in some cases if we have labels we can not delete.
2010 Similarly, do nothing if we can not delete the label at the start
2011 of the target block. */
2017 else
2020 /* Move block and loop notes out of the chain so that we do not
2021 disturb their order.
2023 ??? A better solution would be to squeeze out all the non-nested notes
2024 and adjust the block trees appropriately. Even better would be to have
2025 a tighter connection between block trees and rtl so that this is not
2026 necessary. */
2029 /* Scramble the insn chain. */
2032 /* Now blocks A and B are contiguous. Merge them. */
2036 {
2039 }
2042 }
2044 /* Blocks A and B are to be merged into a single block. The insns
2045 are already contiguous, hence `nomove'. */
2047 static void
2050 {
2051 edge e;
2055 /* If there was a CODE_LABEL beginning B, delete it. */
2059 {
2060 /* Detect basic blocks with nothing but a label. This can happen
2061 in particular at the end of a function. */
2065 }
2067 /* Delete the basic block note. */
2070 {
2074 }
2076 /* If there was a jump out of A, delete it. */
2079 {
2080 rtx prev;
2086 #ifdef HAVE_cc0
2087 /* If this was a conditional jump, we need to also delete
2088 the insn that set cc0. */
2091 {
2097 }
2098 #endif
2100 /* Note that a->head != a->end, since we should have at least a
2101 bb note plus the jump, so prev != insn. */
2104 }
2106 /* By definition, there should only be one successor of A, and that is
2107 B. Free that edge struct. */
2110 /* Adjust the edges out of B for the new owner. */
2115 /* Reassociate the insns of B with A. */
2117 {
2120 {
2123 }
2125 }
2128 /* Compact the basic block array. */
2130 }
2132 /* Attempt to merge basic blocks that are potentially non-adjacent.
2133 Return true iff the attempt succeeded. */
2135 static int
2137 edge e;
2139 {
2140 /* If B has a fallthru edge to C, no need to move anything. */
2142 {
2143 /* If a label still appears somewhere and we cannot delete the label,
2144 then we cannot merge the blocks. The edge was tidied already. */
2154 {
2157 }
2160 }
2161 else
2162 {
2163 edge tmp_edge;
2164 basic_block d;
2168 /* We must make sure to not munge nesting of exception regions,
2169 lexical blocks, and loop notes.
2171 The first is taken care of by requiring that the active eh
2172 region at the end of one block always matches the active eh
2173 region at the beginning of the next block.
2175 The later two are taken care of by squeezing out all the notes. */
2177 /* ??? A throw/catch edge (or any abnormal edge) should be rarely
2178 executed and we may want to treat blocks which have two out
2179 edges, one normal, one abnormal as only having one edge for
2180 block merging purposes. */
2192 /* If B does not have an incoming fallthru, and the exception regions
2193 match, then it can be moved immediately before C without introducing
2194 or modifying jumps. */
2201 /* Otherwise, we're going to try to move C after B. Make sure the
2202 exception regions match. */
2206 {
2207 /* If C does not have an outgoing fallthru, then it can be moved
2208 immediately after B without introducing or modifying jumps. */
2212 /* Otherwise, we'll need to insert an extra jump, and possibly
2213 a new block to contain it. */
2214 /* ??? Not implemented yet. */
2215 }
2218 }
2219 }
2221 /* Top level driver for merge_blocks. */
2223 static void
2225 {
2228 /* Attempt to merge blocks as made possible by edge removal. If a block
2229 has only one successor, and the successor has only one predecessor,
2230 they may be combined. */
2233 {
2235 edge s;
2237 /* A loop because chains of blocks might be combineable. */
2243 /* If the jump insn has side effects, we can't kill the edge. */
2249 /* Don't get confused by the index shift caused by deleting blocks. */
2251 }
2252 }
2254 /* The given edge should potentially a fallthru edge. If that is in
2255 fact true, delete the unconditional jump and barriers that are in
2256 the way. */
2258 static void
2260 edge e;
2262 {
2263 rtx q;
2265 /* ??? In a late-running flow pass, other folks may have deleted basic
2266 blocks by nopping out blocks, leaving multiple BARRIERs between here
2267 and the target label. They ought to be chastized and fixed.
2269 We can also wind up with a sequence of undeletable labels between
2270 one block and the next.
2272 So search through a sequence of barriers, labels, and notes for
2273 the head of block C and assert that we really do fall through. */
2278 /* Remove what will soon cease being the jump insn from the source block.
2279 If block B consisted only of this single jump, turn it into a deleted
2280 note. */
2283 {
2284 #ifdef HAVE_cc0
2285 /* If this was a conditional jump, we need to also delete
2286 the insn that set cc0. */
2289 #endif
2292 {
2296 }
2297 else
2299 }
2301 /* Selectively unlink the sequence. */
2306 }
2308 /* Discover and record the loop depth at the head of each basic block. */
2310 static void
2312 rtx insns;
2313 {
2314 basic_block bb;
2315 rtx insn;
2320 {
2322 {
2327 }
2330 {
2332 depth++;
2334 depth--;
2336 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error. */
2339 }
2340 }
2341 }
2342 \f
2343 /* Perform data flow analysis.
2344 F is the first insn of the function and NREGS the number of register numbers
2345 in use. */
2347 void
2349 rtx f;
2353 {
2354 #ifdef ELIMINABLE_REGS
2357 #endif
2359 /* Record which registers will be eliminated. We use this in
2360 mark_used_regs. */
2364 #ifdef ELIMINABLE_REGS
2367 #else
2369 #endif
2371 /* Allocate a bitmap to be filled in by record_volatile_insns. */
2374 /* We want alias analysis information for local dead store elimination. */
2389 }
2391 /* Free the variables allocated by find_basic_blocks.
2393 KEEP_HEAD_END_P is non-zero if basic_block_info is not to be freed. */
2395 void
2398 {
2400 {
2403 }
2406 {
2415 }
2416 }
2418 /* Return nonzero if the destination of SET equals the source. */
2419 static int
2421 rtx set;
2422 {
2437 }
2439 /* Return nonzero if an insn consists only of SETs, each of which only sets a
2440 value to itself. */
2441 static int
2443 rtx insn;
2444 {
2447 /* Insns carrying these notes are useful later on. */
2455 {
2457 /* If nothing but SETs of registers to themselves,
2458 this insn can also be deleted. */
2460 {
2469 }
2472 }
2474 }
2476 static void
2478 rtx x;
2479 rtx pat ATTRIBUTE_UNUSED;
2480 {
2482 /* The stack pointer is only modified indirectly as the result
2483 of a push until later in flow. See the comments in rtl.texi
2484 regarding Embedded Side-Effects on Addresses. */
2492 }
2494 /* Record which insns refer to any volatile memory
2495 or for any reason can't be deleted just because they are dead stores.
2496 Also, delete any insns that copy a register to itself.
2497 And see if the stack pointer is modified. */
2498 static void
2500 rtx f;
2501 {
2502 rtx insn;
2504 {
2509 {
2514 /* A SET that makes space on the stack cannot be dead.
2515 (Such SETs occur only for allocating variable-size data,
2516 so they will always have a PLUS or MINUS according to the
2517 direction of stack growth.)
2518 Even if this function never uses this stack pointer value,
2519 signal handlers do! */
2522 #ifdef STACK_GROWS_DOWNWARD
2524 #else
2526 #endif
2530 /* Delete (in effect) any obvious no-op moves. */
2532 {
2536 }
2537 }
2539 /* Check if insn modifies the stack pointer. */
2543 }
2544 }
2546 /* Mark those regs which are needed at the end of the function as live
2547 at the end of the last basic block. */
2548 static void
2550 regset set;
2551 {
2554 /* If exiting needs the right stack value, consider the stack pointer
2555 live at the end of the function. */
2557 || (! FRAME_POINTER_REQUIRED
2558 && ! current_function_calls_alloca
2561 {
2563 }
2565 /* Mark the frame pointer if needed at the end of the function. If
2566 we end up eliminating it, it will be removed from the live list
2567 of each basic block by reload. */
2570 {
2572 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2573 /* If they are different, also mark the hard frame pointer as live */
2575 #endif
2576 }
2578 /* Mark all global registers, and all registers used by the epilogue
2579 as being live at the end of the function since they may be
2580 referenced by our caller. */
2583 #ifdef EPILOGUE_USES
2585 #endif
2586 )
2589 /* ??? Mark function return value here rather than as uses. */
2590 }
2592 /* Determine which registers are live at the start of each
2593 basic block of the function whose first insn is F.
2594 NREGS is the number of registers used in F.
2595 We allocate the vector basic_block_live_at_start
2596 and the regsets that it points to, and fill them with the data.
2597 regset_size and regset_bytes are also set here. */
2599 static void
2601 rtx f;
2604 {
2617 /* Allocate and zero out many data structures
2618 that will record the data from lifetime analysis. */
2626 /* Set up regset-vectors used internally within this function.
2627 Their meanings are documented above, with their declarations. */
2632 /* Stick these vectors into the AUX field of the basic block, so that
2633 we don't have to keep going through the index. */
2639 /* Assume that the stack pointer is unchanging if alloca hasn't been used.
2640 This will be cleared by record_volatile_insns if it encounters an insn
2641 which modifies the stack pointer. */
2647 {
2648 regset theend;
2654 /* Propogate this exit data to each of EXIT's predecessors. */
2656 {
2659 }
2660 }
2662 /* The post-reload life analysis have (on a global basis) the same registers
2663 live as was computed by reload itself.
2665 Otherwise elimination offsets and such may be incorrect.
2667 Reload will make some registers as live even though they do not appear
2668 in the rtl. */
2673 /* Propagate life info through the basic blocks
2674 around the graph of basic blocks.
2676 This is a relaxation process: each time a new register
2677 is live at the end of the basic block, we must scan the block
2678 to determine which registers are, as a consequence, live at the beginning
2679 of that block. These registers must then be marked live at the ends
2680 of all the blocks that can transfer control to that block.
2681 The process continues until it reaches a fixed point. */
2686 {
2689 {
2696 {
2697 /* Set CONSIDER if this block needs thinking about at all
2698 (that is, if the regs live now at the end of it
2699 are not the same as were live at the end of it when
2700 we last thought about it).
2701 Set must_rescan if it needs to be thought about
2702 instruction by instruction (that is, if any additional
2703 reg that is live at the end now but was not live there before
2704 is one of the significant regs of this basic block). */
2706 EXECUTE_IF_AND_COMPL_IN_REG_SET
2708 {
2711 {
2714 }
2715 });
2716 done:
2719 }
2721 /* The live_at_start of this block may be changing,
2722 so another pass will be required after this one. */
2726 {
2727 /* No complete rescan needed;
2728 just record those variables newly known live at end
2729 as live at start as well. */
2737 }
2738 else
2739 {
2740 /* Update the basic_block_live_at_start
2741 by propagation backwards through the block. */
2749 }
2751 /* Update the new_live_at_end's of the block's predecessors. */
2752 {
2757 }
2759 #ifdef USE_C_ALLOCA
2761 #endif
2762 }
2764 }
2766 /* The only pseudos that are live at the beginning of the function are
2767 those that were not set anywhere in the function. local-alloc doesn't
2768 know how to handle these correctly, so mark them as not local to any
2769 one basic block. */
2774 {
2776 });
2778 /* Now the life information is accurate. Make one more pass over each
2779 basic block to delete dead stores, create autoincrement addressing
2780 and record how many times each register is used, is set, or dies. */
2783 {
2786 /* We start with global_live_at_end to determine which stores are
2787 dead. This process is destructive, and we wish to preserve the
2788 contents of global_live_at_end for posterity. Fortunately,
2789 new_live_at_end, due to the way we converged on a solution,
2790 contains a duplicate of global_live_at_end that we can kill. */
2793 #ifdef USE_C_ALLOCA
2795 #endif
2796 }
2798 /* We have a problem with any pseudoreg that lives across the setjmp.
2799 ANSI says that if a user variable does not change in value between
2800 the setjmp and the longjmp, then the longjmp preserves it. This
2801 includes longjmp from a place where the pseudo appears dead.
2802 (In principle, the value still exists if it is in scope.)
2803 If the pseudo goes in a hard reg, some other value may occupy
2804 that hard reg where this pseudo is dead, thus clobbering the pseudo.
2805 Conclusion: such a pseudo must not go in a hard reg. */
2808 {
2810 {
2813 }
2814 });
2816 /* Restore regs_ever_live that was provided by reload. */
2826 }
2827 \f
2828 /* Subroutines of life analysis. */
2830 /* Allocate the permanent data structures that represent the results
2831 of life analysis. Not static since used also for stupid life analysis. */
2833 void
2835 {
2839 {
2845 }
2847 ENTRY_BLOCK_PTR->global_live_at_end
2849 EXIT_BLOCK_PTR->global_live_at_start
2853 }
2855 void
2857 {
2860 /* Recalculate the register space, in case it has grown. Old style
2861 vector oriented regsets would set regset_{size,bytes} here also. */
2864 /* Because both reg_scan and flow_analysis want to set up the REG_N_SETS
2865 information, explicitly reset it here. The allocation should have
2866 already happened on the previous reg_scan pass. Make sure in case
2867 some more registers were allocated. */
2870 }
2872 /* Make each element of VECTOR point at a regset. The vector has
2873 NELTS elements, and space is allocated from the ALLOC_OBSTACK
2874 obstack. */
2876 static void
2881 {
2885 {
2888 }
2889 }
2891 /* Release any additional space allocated for each element of VECTOR point
2892 other than the regset header itself. The vector has NELTS elements. */
2894 void
2898 {
2903 }
2905 /* Compute the registers live at the beginning of a basic block
2906 from those live at the end.
2908 When called, OLD contains those live at the end.
2909 On return, it contains those live at the beginning.
2910 FIRST and LAST are the first and last insns of the basic block.
2912 FINAL is nonzero if we are doing the final pass which is not
2913 for computing the life info (since that has already been done)
2914 but for acting on it. On this pass, we delete dead stores,
2915 set up the logical links and dead-variables lists of instructions,
2916 and merge instructions for autoincrement and autodecrement addresses.
2918 SIGNIFICANT is nonzero only the first time for each basic block.
2919 If it is nonzero, it points to a regset in which we store
2920 a 1 for each register that is set within the block.
2922 BNUM is the number of the basic block. */
2924 static void
2927 rtx first;
2928 rtx last;
2930 regset significant;
2933 {
2935 rtx prev;
2936 regset live;
2937 regset dead;
2939 /* Find the loop depth for this block. Ignore loop level changes in the
2940 middle of the basic block -- for register allocation purposes, the
2941 important uses will be in the blocks wholely contained within the loop
2942 not in the loop pre-header or post-trailer. */
2952 {
2955 /* Process the regs live at the end of the block.
2956 Mark them as not local to any one basic block. */
2958 {
2960 });
2961 }
2963 /* Scan the block an insn at a time from end to beginning. */
2966 {
2970 {
2971 /* If this is a call to `setjmp' et al,
2972 warn if any non-volatile datum is live. */
2976 }
2978 /* Update the life-status of regs for this insn.
2979 First DEAD gets which regs are set in this insn
2980 then LIVE gets which regs are used in this insn.
2981 Then the regs live before the insn
2982 are those live after, with DEAD regs turned off,
2983 and then LIVE regs turned on. */
2986 {
2993 {
2995 /* Don't delete something that refers to volatile storage! */
2999 }
3001 /* If an instruction consists of just dead store(s) on final pass,
3002 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
3003 We could really delete it with delete_insn, but that
3004 can cause trouble for first or last insn in a basic block. */
3006 {
3011 /* CC0 is now known to be dead. Either this insn used it,
3012 in which case it doesn't anymore, or clobbered it,
3013 so the next insn can't use it. */
3016 /* If this insn is copying the return value from a library call,
3017 delete the entire library call. */
3019 {
3025 {
3030 }
3031 }
3033 }
3038 /* See if this is an increment or decrement that can be
3039 merged into a following memory address. */
3040 #ifdef AUTO_INC_DEC
3041 {
3044 /* Does this instruction increment or decrement a register? */
3052 /* Ok, look for a following memory ref we can combine with.
3053 If one is found, change the memory ref to a PRE_INC
3054 or PRE_DEC, cancel this insn, and return 1.
3055 Return 0 if nothing has been done. */
3058 }
3061 /* If this is not the final pass, and this insn is copying the
3062 value of a library call and it's dead, don't scan the
3063 insns that perform the library call, so that the call's
3064 arguments are not marked live. */
3066 {
3067 /* Mark the dest reg as `significant'. */
3072 }
3078 /* We have an insn to pop a constant amount off the stack.
3079 (Such insns use PLUS regardless of the direction of the stack,
3080 and any insn to adjust the stack by a constant is always a pop.)
3081 These insns, if not dead stores, have no effect on life. */
3082 ;
3083 else
3084 {
3085 /* Any regs live at the time of a call instruction
3086 must not go in a register clobbered by calls.
3087 Find all regs now live and record this for them. */
3091 {
3093 });
3095 /* LIVE gets the regs used in INSN;
3096 DEAD gets those set by it. Dead insns don't make anything
3097 live. */
3102 /* If an insn doesn't use CC0, it becomes dead since we
3103 assume that every insn clobbers it. So show it dead here;
3104 mark_used_regs will set it live if it is referenced. */
3110 /* Sometimes we may have inserted something before INSN (such as
3111 a move) when we make an auto-inc. So ensure we will scan
3112 those insns. */
3113 #ifdef AUTO_INC_DEC
3115 #endif
3118 {
3121 rtx note;
3124 note;
3130 /* Each call clobbers all call-clobbered regs that are not
3131 global or fixed. Note that the function-value reg is a
3132 call-clobbered reg, and mark_set_regs has already had
3133 a chance to handle it. */
3140 /* The stack ptr is used (honorarily) by a CALL insn. */
3143 /* Calls may also reference any of the global registers,
3144 so they are made live. */
3151 /* Calls also clobber memory. */
3153 }
3155 /* Update OLD for the registers used or set. */
3159 }
3161 /* On final pass, update counts of how many insns each reg is live
3162 at. */
3166 }
3167 flushed: ;
3170 }
3174 }
3175 \f
3176 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
3177 (SET expressions whose destinations are registers dead after the insn).
3178 NEEDED is the regset that says which regs are alive after the insn.
3180 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL.
3182 If X is the entire body of an insn, NOTES contains the reg notes
3183 pertaining to the insn. */
3185 static int
3187 rtx x;
3188 regset needed;
3190 rtx notes ATTRIBUTE_UNUSED;
3191 {
3194 #ifdef AUTO_INC_DEC
3195 /* If flow is invoked after reload, we must take existing AUTO_INC
3196 expresions into account. */
3198 {
3200 {
3202 {
3205 /* Don't delete insns to set global regs. */
3209 }
3210 }
3211 }
3212 #endif
3214 /* If setting something that's a reg or part of one,
3215 see if that register's altered value will be live. */
3218 {
3221 /* A SET that is a subroutine call cannot be dead. */
3225 #ifdef HAVE_cc0
3228 #endif
3231 {
3232 rtx temp;
3233 /* Walk the set of memory locations we are currently tracking
3234 and see if one is an identical match to this memory location.
3235 If so, this memory write is dead (remember, we're walking
3236 backwards from the end of the block to the start. */
3239 {
3243 }
3244 }
3251 {
3254 /* Don't delete insns to set global regs. */
3256 /* Make sure insns to set frame pointer aren't deleted. */
3259 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
3262 #endif
3263 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
3264 /* Make sure insns to set arg pointer are never deleted
3265 (if the arg pointer isn't fixed, there will be a USE for
3266 it, so we can treat it normally). */
3268 #endif
3272 /* If this is a hard register, verify that subsequent words are
3273 not needed. */
3275 {
3281 }
3284 }
3285 }
3287 /* If performing several activities,
3288 insn is dead if each activity is individually dead.
3289 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
3290 that's inside a PARALLEL doesn't make the insn worth keeping. */
3292 {
3302 }
3304 /* A CLOBBER of a pseudo-register that is dead serves no purpose. That
3305 is not necessarily true for hard registers. */
3311 /* We do not check other CLOBBER or USE here. An insn consisting of just
3312 a CLOBBER or just a USE should not be deleted. */
3314 }
3316 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
3317 return 1 if the entire library call is dead.
3318 This is true if X copies a register (hard or pseudo)
3319 and if the hard return reg of the call insn is dead.
3320 (The caller should have tested the destination of X already for death.)
3322 If this insn doesn't just copy a register, then we don't
3323 have an ordinary libcall. In that case, cse could not have
3324 managed to substitute the source for the dest later on,
3325 so we can assume the libcall is dead.
3327 NEEDED is the bit vector of pseudoregs live before this insn.
3328 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
3330 static int
3332 rtx x;
3333 regset needed;
3334 rtx note;
3335 rtx insn;
3336 {
3340 {
3343 {
3345 rtx call_pat;
3348 /* Find the call insn. */
3352 /* If there is none, do nothing special,
3353 since ordinary death handling can understand these insns. */
3357 /* See if the hard reg holding the value is dead.
3358 If this is a PARALLEL, find the call within it. */
3361 {
3367 /* This may be a library call that is returning a value
3368 via invisible pointer. Do nothing special, since
3369 ordinary death handling can understand these insns. */
3374 }
3377 }
3378 }
3380 }
3382 /* Return 1 if register REGNO was used before it was set, i.e. if it is
3383 live at function entry. Don't count global register variables, variables
3384 in registers that can be used for function arg passing, or variables in
3385 fixed hard registers. */
3387 int
3390 {
3399 }
3401 /* 1 if register REGNO was alive at a place where `setjmp' was called
3402 and was set more than once or is an argument.
3403 Such regs may be clobbered by `longjmp'. */
3405 int
3408 {
3415 }
3416 \f
3417 /* INSN references memory, possibly using autoincrement addressing modes.
3418 Find any entries on the mem_set_list that need to be invalidated due
3419 to an address change. */
3420 static void
3422 rtx insn;
3423 {
3426 {
3428 {
3433 {
3435 {
3436 /* Splice temp out of list. */
3439 else
3441 }
3442 else
3445 }
3446 }
3447 }
3448 }
3450 /* Process the registers that are set within X.
3451 Their bits are set to 1 in the regset DEAD,
3452 because they are dead prior to this insn.
3454 If INSN is nonzero, it is the insn being processed
3455 and the fact that it is nonzero implies this is the FINAL pass
3456 in propagate_block. In this case, various info about register
3457 usage is stored, LOG_LINKS fields of insns are set up. */
3459 static void
3461 regset needed;
3462 regset dead;
3463 rtx x;
3464 rtx insn;
3465 regset significant;
3466 {
3472 {
3475 {
3479 }
3480 }
3481 }
3483 /* Process a single SET rtx, X. */
3485 static void
3487 regset needed;
3488 regset dead;
3489 rtx x;
3490 rtx insn;
3491 regset significant;
3492 {
3496 /* Some targets place small structures in registers for
3497 return values of functions. We have to detect this
3498 case specially here to get correct flow information. */
3501 {
3507 }
3509 /* Modifying just one hardware register of a multi-reg value
3510 or just a byte field of a register
3511 does not mean the value from before this insn is now dead.
3512 But it does mean liveness of that register at the end of the block
3513 is significant.
3515 Within mark_set_1, however, we treat it as if the register is
3516 indeed modified. mark_used_regs will, however, also treat this
3517 register as being used. Thus, we treat these insns as setting a
3518 new value for the register as a function of its old value. This
3519 cases LOG_LINKS to be made appropriately and this will help combine. */
3526 /* If this set is a MEM, then it kills any aliased writes.
3527 If this set is a REG, then it kills any MEMs which use the reg. */
3530 {
3535 {
3540 {
3541 /* Splice this entry out of the list. */
3544 else
3546 }
3547 else
3550 }
3551 }
3553 /* If the memory reference had embedded side effects (autoincrement
3554 address modes. Then we may need to kill some entries on the
3555 memory set list. */
3560 /* We do not know the size of a BLKmode store, so we do not track
3561 them for redundant store elimination. */
3563 /* There are no REG_INC notes for SP, so we can't assume we'll see
3564 everything that invalidates it. To be safe, don't eliminate any
3565 stores though SP; none of them should be redundant anyway. */
3572 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
3575 #endif
3576 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
3578 #endif
3580 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
3581 {
3585 /* Mark it as a significant register for this basic block. */
3589 /* Mark it as dead before this insn. */
3592 /* A hard reg in a wide mode may really be multiple registers.
3593 If so, mark all of them just like the first. */
3595 {
3598 /* Nothing below is needed for the stack pointer; get out asap.
3599 Eg, log links aren't needed, since combine won't use them. */
3605 {
3614 }
3615 }
3616 /* Additional data to record if this is the final pass. */
3618 {
3622 /* If this is a hard reg, record this function uses the reg. */
3625 {
3630 {
3631 /* The next use is no longer "next", since a store
3632 intervenes. */
3637 }
3638 }
3639 else
3640 {
3641 /* The next use is no longer "next", since a store
3642 intervenes. */
3645 /* Keep track of which basic blocks each reg appears in. */
3652 /* Count (weighted) references, stores, etc. This counts a
3653 register twice if it is modified, but that is correct. */
3658 /* The insns where a reg is live are normally counted
3659 elsewhere, but we want the count to include the insn
3660 where the reg is set, and the normal counting mechanism
3661 would not count it. */
3663 }
3666 {
3667 /* Make a logical link from the next following insn
3668 that uses this register, back to this insn.
3669 The following insns have already been processed.
3671 We don't build a LOG_LINK for hard registers containing
3672 in ASM_OPERANDs. If these registers get replaced,
3673 we might wind up changing the semantics of the insn,
3674 even if reload can make what appear to be valid assignments
3675 later. */
3681 }
3683 {
3684 /* Note that dead stores have already been deleted when possible
3685 If we get here, we have found a dead store that cannot
3686 be eliminated (because the same insn does something useful).
3687 Indicate this by marking the reg being set as dying here. */
3691 }
3692 else
3693 {
3694 /* This is a case where we have a multi-word hard register
3695 and some, but not all, of the words of the register are
3696 needed in subsequent insns. Write REG_UNUSED notes
3697 for those parts that were not needed. This case should
3698 be rare. */
3710 }
3711 }
3712 }
3716 /* If this is the last pass and this is a SCRATCH, show it will be dying
3717 here and count it. */
3719 {
3722 }
3723 }
3724 \f
3725 #ifdef AUTO_INC_DEC
3727 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
3728 reference. */
3730 static void
3732 regset needed;
3733 rtx x;
3734 rtx insn;
3735 {
3738 rtx set;
3740 /* Here we detect use of an index register which might be good for
3741 postincrement, postdecrement, preincrement, or predecrement. */
3747 {
3750 rtx use;
3751 rtx incr;
3754 /* Is the next use an increment that might make auto-increment? */
3759 /* Can't add side effects to jumps; if reg is spilled and
3760 reloaded, there's no way to store back the altered value. */
3765 && ((HAVE_POST_INCREMENT
3767 || (HAVE_POST_DECREMENT
3769 || (HAVE_PRE_INCREMENT
3771 || (HAVE_PRE_DECREMENT
3773 /* Make sure this reg appears only once in this insn. */
3776 {
3783 {
3784 /* This is the simple case. Try to make the auto-inc. If
3785 we can't, we are done. Otherwise, we will do any
3786 needed updates below. */
3791 }
3793 /* PREV_INSN used here to check the semi-open interval
3794 [insn,incr). */
3796 /* We must also check for sets of q as q may be
3797 a call clobbered hard register and there may
3798 be a call between PREV_INSN (insn) and incr. */
3800 {
3801 /* We have *p followed sometime later by q = p+size.
3802 Both p and q must be live afterward,
3803 and q is not used between INSN and its assignment.
3804 Change it to q = p, ...*q..., q = q+size.
3805 Then fall into the usual case. */
3807 basic_block bb;
3818 /* If we can't make the auto-inc, or can't make the
3819 replacement into Y, exit. There's no point in making
3820 the change below if we can't do the auto-inc and doing
3821 so is not correct in the pre-inc case. */
3830 /* We now know we'll be doing this change, so emit the
3831 new insn(s) and do the updates. */
3837 /* INCR will become a NOTE and INSN won't contain a
3838 use of ADDR. If a use of ADDR was just placed in
3839 the insn before INSN, make that the next use.
3840 Otherwise, invalidate it. */
3845 else
3851 /* REGNO is now used in INCR which is below INSN, but
3852 it previously wasn't live here. If we don't mark
3853 it as needed, we'll put a REG_DEAD note for it
3854 on this insn, which is incorrect. */
3857 /* If there are any calls between INSN and INCR, show
3858 that REGNO now crosses them. */
3862 }
3863 else
3866 /* If we haven't returned, it means we were able to make the
3867 auto-inc, so update the status. First, record that this insn
3868 has an implicit side effect. */
3873 /* Modify the old increment-insn to simply copy
3874 the already-incremented value of our register. */
3878 /* If that makes it a no-op (copying the register into itself) delete
3879 it so it won't appear to be a "use" and a "set" of this
3880 register. */
3882 {
3886 }
3889 {
3890 /* Count an extra reference to the reg. When a reg is
3891 incremented, spilling it is worse, so we want to make
3892 that less likely. */
3895 /* Count the increment as a setting of the register,
3896 even though it isn't a SET in rtl. */
3898 }
3899 }
3900 }
3901 }
3903 \f
3904 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
3905 This is done assuming the registers needed from X
3906 are those that have 1-bits in NEEDED.
3908 On the final pass, FINAL is 1. This means try for autoincrement
3909 and count the uses and deaths of each pseudo-reg.
3911 INSN is the containing instruction. If INSN is dead, this function is not
3912 called. */
3914 static void
3916 regset needed;
3917 regset live;
3918 rtx x;
3920 rtx insn;
3921 {
3926 retry:
3929 {
3940 #ifdef HAVE_cc0
3944 #endif
3947 /* If we are clobbering a MEM, mark any registers inside the address
3948 as being used. */
3954 /* Invalidate the data for the last MEM stored, but only if MEM is
3955 something that can be stored into. */
3959 else
3960 {
3965 {
3967 {
3968 /* Splice temp out of the list. */
3971 else
3973 }
3974 else
3977 }
3978 }
3980 /* If the memory reference had embedded side effects (autoincrement
3981 address modes. Then we may need to kill some entries on the
3982 memory set list. */
3986 #ifdef AUTO_INC_DEC
3989 #endif
3999 /* While we're here, optimize this case. */
4002 /* In case the SUBREG is not of a register, don't optimize */
4004 {
4007 }
4009 /* ... fall through ... */
4012 /* See a register other than being set
4013 => mark it as needed. */
4016 {
4022 /* A hard reg in a wide mode may really be multiple registers.
4023 If so, mark all of them just like the first. */
4025 {
4028 /* For stack ptr or fixed arg pointer,
4029 nothing below can be necessary, so waste no more time. */
4031 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
4034 #endif
4035 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
4037 #endif
4040 {
4041 /* If this is a register we are going to try to eliminate,
4042 don't mark it live here. If we are successful in
4043 eliminating it, it need not be live unless it is used for
4044 pseudos, in which case it will have been set live when
4045 it was allocated to the pseudos. If the register will not
4046 be eliminated, reload will set it live at that point. */
4051 }
4052 /* No death notes for global register variables;
4053 their values are live after this function exits. */
4055 {
4059 }
4063 {
4070 }
4071 }
4073 {
4074 /* Record where each reg is used, so when the reg
4075 is set we know the next insn that uses it. */
4080 {
4081 /* If a hard reg is being used,
4082 record that this function does use it. */
4087 do
4090 }
4091 else
4092 {
4093 /* Keep track of which basic block each reg appears in. */
4102 /* Count (weighted) number of uses of each reg. */
4105 }
4107 /* Record and count the insns in which a reg dies.
4108 If it is used in this insn and was dead below the insn
4109 then it dies in this insn. If it was set in this insn,
4110 we do not make a REG_DEAD note; likewise if we already
4111 made such a note. */
4115 #if 0
4117 #endif
4118 )
4119 {
4120 /* Check for the case where the register dying partially
4121 overlaps the register set by this insn. */
4124 {
4128 }
4130 /* If none of the words in X is needed, make a REG_DEAD
4131 note. Otherwise, we must make partial REG_DEAD notes. */
4133 {
4137 }
4138 else
4139 {
4142 /* Don't make a REG_DEAD note for a part of a register
4143 that is set in the insn. */
4154 }
4155 }
4156 }
4157 }
4161 {
4165 /* If storing into MEM, don't show it as being used. But do
4166 show the address as being used. */
4168 {
4169 #ifdef AUTO_INC_DEC
4172 #endif
4176 }
4178 /* Storing in STRICT_LOW_PART is like storing in a reg
4179 in that this SET might be dead, so ignore it in TESTREG.
4180 but in some other ways it is like using the reg.
4182 Storing in a SUBREG or a bit field is like storing the entire
4183 register in that if the register's value is not used
4184 then this SET is not needed. */
4189 {
4197 /* Modifying a single register in an alternate mode
4198 does not use any of the old value. But these other
4199 ways of storing in a register do use the old value. */
4202 ;
4203 else
4207 }
4209 /* If this is a store into a register,
4210 recursively scan the value being stored. */
4217 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
4220 #endif
4221 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
4223 #endif
4224 ))
4225 /* We used to exclude global_regs here, but that seems wrong.
4226 Storing in them is like storing in mem. */
4227 {
4232 }
4233 }
4237 /* If exiting needs the right stack value, consider this insn as
4238 using the stack pointer. In any event, consider it as using
4239 all global registers and all registers used by return. */
4241 || (! FRAME_POINTER_REQUIRED
4242 && ! current_function_calls_alloca
4249 #ifdef EPILOGUE_USES
4251 #endif
4252 )
4260 {
4261 /* Traditional and volatile asm instructions must be considered to use
4262 and clobber all hard registers, all pseudo-registers and all of
4263 memory. So must TRAP_IF and UNSPEC_VOLATILE operations.
4265 Consider for instance a volatile asm that changes the fpu rounding
4266 mode. An insn should not be moved across this even if it only uses
4267 pseudo-regs because it might give an incorrectly rounded result.
4269 ?!? Unfortunately, marking all hard registers as live causes massive
4270 problems for the register allocator and marking all pseudos as live
4271 creates mountains of uninitialized variable warnings.
4273 So for now, just clear the memory set list and mark any regs
4274 we can find in ASM_OPERANDS as used. */
4278 /* For all ASM_OPERANDS, we must traverse the vector of input operands.
4279 We can not just fall through here since then we would be confused
4280 by the ASM_INPUT rtx inside ASM_OPERANDS, which do not indicate
4281 traditional asms unlike their normal usage. */
4283 {
4289 }
4291 }
4296 }
4298 /* Recursively scan the operands of this expression. */
4300 {
4305 {
4307 {
4308 /* Tail recursive case: save a function call level. */
4310 {
4313 }
4315 }
4317 {
4321 }
4322 }
4323 }
4324 }
4325 \f
4326 #ifdef AUTO_INC_DEC
4328 static int
4330 rtx insn;
4331 {
4332 /* Find the next use of this reg. If in same basic block,
4333 make it do pre-increment or pre-decrement if appropriate. */
4341 /* Don't do this if the reg dies, or gets set in y; a standard addressing
4342 mode would be better. */
4345 {
4346 /* We have found a suitable auto-increment
4347 and already changed insn Y to do it.
4348 So flush this increment-instruction. */
4352 /* Count a reference to this reg for the increment
4353 insn we are deleting. When a reg is incremented.
4354 spilling it is worse, so we want to make that
4355 less likely. */
4357 {
4360 }
4362 }
4364 }
4366 /* Try to change INSN so that it does pre-increment or pre-decrement
4367 addressing on register REG in order to add AMOUNT to REG.
4368 AMOUNT is negative for pre-decrement.
4369 Returns 1 if the change could be made.
4370 This checks all about the validity of the result of modifying INSN. */
4372 static int
4375 HOST_WIDE_INT amount;
4376 {
4379 /* Nonzero if we can try to make a pre-increment or pre-decrement.
4380 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
4382 /* Nonzero if we can try to make a post-increment or post-decrement.
4383 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
4384 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
4385 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
4388 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
4391 /* From the sign of increment, see which possibilities are conceivable
4392 on this target machine. */
4406 /* It is not safe to add a side effect to a jump insn
4407 because if the incremented register is spilled and must be reloaded
4408 there would be no way to store the incremented value back in memory. */
4417 {
4420 }
4428 /* See if this combination of instruction and addressing mode exists. */
4436 /* Record that this insn now has an implicit side effect on X. */
4439 }
4442 \f
4443 /* Find the place in the rtx X where REG is used as a memory address.
4444 Return the MEM rtx that so uses it.
4445 If PLUSCONST is nonzero, search instead for a memory address equivalent to
4446 (plus REG (const_int PLUSCONST)).
4448 If such an address does not appear, return 0.
4449 If REG appears more than once, or is used other than in such an address,
4450 return (rtx)1. */
4452 rtx
4455 rtx reg;
4456 HOST_WIDE_INT plusconst;
4457 {
4474 {
4475 /* If REG occurs inside a MEM used in a bit-field reference,
4476 that is unacceptable. */
4479 }
4485 {
4487 {
4493 }
4495 {
4498 {
4504 }
4505 }
4506 }
4509 }
4510 \f
4511 /* Write information about registers and basic blocks into FILE.
4512 This is part of making a debugging dump. */
4514 void
4517 {
4524 {
4546 {
4551 else
4555 }
4559 }
4563 {
4581 {
4585 }
4586 else
4591 {
4595 }
4596 else
4600 }
4603 }
4605 static void
4608 edge e;
4610 {
4617 else
4621 {
4624 };
4632 {
4639 else
4642 }
4644 }
4645 }
4647 \f
4648 /* Like print_rtl, but also print out live information for the start of each
4649 basic block. */
4651 void
4654 rtx rtx_first;
4655 {
4660 else
4661 {
4677 {
4679 rtx x;
4684 {
4692 }
4693 }
4696 {
4698 basic_block bb;
4701 {
4706 {
4711 });
4713 }
4730 }
4731 }
4734 {
4739 }
4740 }
4742 \f
4743 /* Integer list support. */
4745 /* Allocate a node from list *HEAD_PTR. */
4747 static int_list_ptr
4750 {
4754 {
4759 }
4763 }
4765 /* Pointer to head of predecessor/successor block list. */
4768 /* Add a new node to integer list LIST with value VAL.
4769 LIST is a pointer to a list object to allow for different implementations.
4770 If *LIST is initially NULL, the list is empty.
4771 The caller must not care whether the element is added to the front or
4772 to the end of the list (to allow for different implementations). */
4774 static int_list_ptr
4779 {
4786 }
4788 /* Free the blocks of lists at BLK_LIST. */
4790 void
4793 {
4797 {
4800 }
4802 /* Mark list as empty for the next function we compile. */
4804 }
4805 \f
4806 /* Predecessor/successor computation. */
4808 /* Mark PRED_BB a precessor of SUCC_BB,
4809 and conversely SUCC_BB a successor of PRED_BB. */
4811 static void
4819 {
4821 {
4824 }
4826 {
4829 }
4830 }
4832 /* Convert edge lists into pred/succ lists for backward compatibility. */
4834 void
4840 {
4842 edge e;
4850 {
4856 }
4861 }
4863 void
4869 {
4871 int_list_ptr p;
4875 {
4880 {
4884 else
4886 }
4890 {
4894 else
4896 }
4898 {
4905 }
4907 }
4909 }
4911 /* Free basic block data storage. */
4913 void
4915 {
4917 }
4919 /* Compute dominator relationships. */
4920 void
4926 {
4944 {
4947 {
4960 }
4961 passes++;
4962 }
4965 }
4967 /* Compute dominator relationships using new flow graph structures. */
4968 void
4972 {
4990 {
4993 {
5004 }
5005 passes++;
5006 }
5009 }
5011 /* Given DOMINATORS, compute the immediate dominators into IDOM. */
5013 void
5017 {
5023 /* Begin with tmp(n) = dom(n) - { n }. */
5025 {
5028 }
5030 /* Subtract out all of our dominator's dominators. */
5032 {
5039 }
5041 /* Find the one bit set in the bitmap and put it in the output array. */
5043 {
5046 }
5049 }
5051 /* Count for a single SET rtx, X. */
5053 static void
5055 rtx x;
5056 {
5060 /* Find the register that's set/clobbered. */
5068 {
5073 }
5076 {
5079 {
5080 /* Count (weighted) references, stores, etc. This counts a
5081 register twice if it is modified, but that is correct. */
5085 }
5086 }
5087 }
5089 /* Increment REG_N_SETS for each SET or CLOBBER found in X; also increment
5090 REG_N_REFS by the current loop depth for each SET or CLOBBER found. */
5092 static void
5094 rtx x;
5095 {
5101 {
5104 {
5108 }
5109 }
5110 }
5112 /* Increment REG_N_REFS by the current loop depth each register reference
5113 found in X. */
5115 static void
5117 rtx x;
5118 {
5121 retry:
5124 {
5136 #ifdef HAVE_cc0
5139 #endif
5142 /* If we are clobbering a MEM, mark any registers inside the address
5143 as being used. */
5149 /* While we're here, optimize this case. */
5152 /* In case the SUBREG is not of a register, don't optimize */
5154 {
5157 }
5159 /* ... fall through ... */
5167 {
5171 /* If storing into MEM, don't show it as being used. But do
5172 show the address as being used. */
5174 {
5178 }
5180 /* Storing in STRICT_LOW_PART is like storing in a reg
5181 in that this SET might be dead, so ignore it in TESTREG.
5182 but in some other ways it is like using the reg.
5184 Storing in a SUBREG or a bit field is like storing the entire
5185 register in that if the register's value is not used
5186 then this SET is not needed. */
5191 {
5192 /* Modifying a single register in an alternate mode
5193 does not use any of the old value. But these other
5194 ways of storing in a register do use the old value. */
5197 ;
5198 else
5202 }
5204 /* If this is a store into a register,
5205 recursively scan the value being stored. */
5210 {
5215 }
5216 }
5221 }
5223 /* Recursively scan the operands of this expression. */
5225 {
5230 {
5232 {
5233 /* Tail recursive case: save a function call level. */
5235 {
5238 }
5240 }
5242 {
5246 }
5247 }
5248 }
5249 }
5251 /* Recompute register set/reference counts immediately prior to register
5252 allocation.
5254 This avoids problems with set/reference counts changing to/from values
5255 which have special meanings to the register allocators.
5257 Additionally, the reference counts are the primary component used by the
5258 register allocators to prioritize pseudos for allocation to hard regs.
5259 More accurate reference counts generally lead to better register allocation.
5261 F is the first insn to be scanned.
5262 LOOP_STEP denotes how much loop_depth should be incremented per
5263 loop nesting level in order to increase the ref count more for references
5264 in a loop.
5266 It might be worthwhile to update REG_LIVE_LENGTH, REG_BASIC_BLOCK and
5267 possibly other information which is used by the register allocators. */
5269 void
5271 rtx f;
5273 {
5274 rtx insn;
5277 /* Clear out the old data. */
5280 {
5283 }
5285 /* Scan each insn in the chain and count how many times each register is
5286 set/used. */
5289 {
5290 /* Keep track of loop depth. */
5292 {
5293 /* Look for loop boundaries. */
5299 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
5300 Abort now rather than setting register status incorrectly. */
5303 }
5305 {
5306 rtx links;
5308 /* This call will increment REG_N_SETS for each SET or CLOBBER
5309 of a register in INSN. It will also increment REG_N_REFS
5310 by the loop depth for each set of a register in INSN. */
5313 /* count_reg_sets does not detect autoincrement address modes, so
5314 detect them here by looking at the notes attached to INSN. */
5316 {
5318 /* Count (weighted) references, stores, etc. This counts a
5319 register twice if it is modified, but that is correct. */
5321 }
5323 /* This call will increment REG_N_REFS by the current loop depth for
5324 each reference to a register in INSN. */
5327 /* count_reg_references will not include counts for arguments to
5328 function calls, so detect them here by examining the
5329 CALL_INSN_FUNCTION_USAGE data. */
5331 {
5332 rtx note;
5335 note;
5339 }
5340 }
5341 }
5342 }
5344 /* Record INSN's block as BB. */
5346 void
5348 rtx insn;
5349 basic_block bb;
5350 {
5353 {
5356 /* Add one-eighth the size so we don't keep calling xrealloc. */
5360 }
5362 }
5364 /* Record INSN's block number as BB. */
5365 /* ??? This has got to go. */
5367 void
5369 rtx insn;
5371 {
5373 }
5374 \f
5375 /* Unlink a chain of insns between START and FINISH inclusive, leaving notes
5376 that must be paired, and return the new chain. */
5378 rtx
5381 {
5385 /* Unchain the insns one by one. It would be quicker to delete all
5386 of these with a single unchaining, rather than one at a time, but
5387 we need to keep the NOTE's. */
5390 {
5395 /* ??? Despite the fact that we're patching out the insn, it's
5396 still referenced in LOG_LINKS. Rather than try and track
5397 them all down and remove them, just mark the insn deleted. */
5401 {
5404 }
5405 else
5406 {
5408 {
5412 }
5413 else
5414 {
5418 }
5419 }
5424 }
5430 }
5432 /* Subroutine of update_life_info. Determines whether multiple
5433 REG_NOTEs need to be distributed for the hard register mentioned in
5434 NOTE. This can happen if a reference to a hard register in the
5435 original insns was split into several smaller hard register
5436 references in the new insns. */
5438 static void
5441 {
5443 rtx insn;
5452 {
5456 }
5461 {
5464 /* Check for references to new_reg in the split insns. */
5466 {
5469 {
5470 /* Create a new reg dead note here. */
5477 /* If killed multiple registers here, then add in the excess. */
5481 }
5482 /* It isn't mentioned anywhere, so no new reg note is needed for
5483 this register. */
5486 }
5487 }
5488 }
5490 /* SET_INSN kills REG; add a REG_DEAD note mentioning REG to the last
5491 use of REG in the insns after SET_INSN and before or including
5492 LAST, if necessary.
5494 A non-zero value is returned if we added a REG_DEAD note, or if we
5495 determined that a REG_DEAD note because of this particular SET
5496 wasn't necessary. */
5498 static int
5501 {
5502 rtx insn;
5505 {
5506 rtx set;
5511 {
5521 {
5522 /* Use the same scheme as combine.c, don't put both REG_DEAD
5523 and REG_UNUSED notes on the same insn. */
5526 {
5532 }
5534 }
5536 {
5537 /* We found an instruction that both uses the register and
5538 sets it, so no new REG_NOTE is needed for the previous
5539 set. */
5541 }
5542 }
5543 }
5545 }
5547 static int
5550 {
5551 rtx set;
5553 /* We need to add a REG_DEAD note to the last place DEST is
5554 referenced. */
5559 {
5569 {
5570 /* Use the same scheme as combine.c, don't put both REG_DEAD
5571 and REG_UNUSED notes on the same insn. */
5574 {
5580 }
5582 }
5583 }
5585 }
5587 /* Find the first insn in the set of insns from FIRST to LAST inclusive
5588 that contains the note NOTE. */
5589 rtx
5592 {
5593 rtx insn;
5596 {
5599 {
5601 }
5603 {
5605 }
5606 }
5608 }
5610 /* Subroutine of update_life_info. Determines whether a SET or
5611 CLOBBER in an insn created by splitting needs a REG_DEAD or
5612 REG_UNUSED note added. */
5614 static void
5617 {
5631 {
5632 #if 0
5633 /* If the original insns already used this register, we may not
5634 add new notes for it. One example for a replacement that
5635 needs this test is when a multi-word memory access with
5636 register-indirect addressing is changed into multiple memory
5637 accesses with auto-increment and one adjusting add
5638 instruction for the address register.
5640 However, there is a problem with this code. We're assuming
5641 that any registers that are set in the new insns are either
5642 set/referenced in the old insns (and thus "inherit" the
5643 liveness of the old insns), or are registers that are dead
5644 before we enter this part of the stream (and thus should be
5645 dead when we leave).
5647 To do this absolutely correctly, we must determine the actual
5648 liveness of the registers before we go randomly adding
5649 REG_DEAD notes. This can probably be accurately done by
5650 calling mark_referenced_resources() on the old stream before
5651 replacing the old insns. */
5652 /* ??? The conclusion reached here -- that we can't add DEAD notes
5653 when the register is preexisting -- is false. I can't envision
5654 a sequence postulated above that wouldn't be properly handled
5655 by the code below. In the meantime, consider the 1->2 split
5657 (set (reg:SI 100) (ne:SI (reg:SI 100) (const_int 0)))
5658 to
5659 (set (reg:CC icc) (compare:CC (reg:SI 100) (const_int 0)))
5660 (set (reg:SI 100) (ne:SI (reg:CC icc) (const_int 0)))
5662 We do in fact need a new DEAD note on the first insn for reg 100. */
5665 {
5671 }
5672 #endif
5674 /* So it's a new register, presumably only used within this
5675 group of insns. Find the last insn in the set of new insns
5676 that DEST is referenced in, and add a dead note to it. */
5678 {
5679 /* If this is a set, it must die somewhere, unless it is the
5680 dest of the original insn, and thus is live after the
5681 original insn. Abort if it isn't supposed to be live after
5682 the original insn.
5684 If this is a clobber, then just add a REG_UNUSED note. */
5686 {
5693 }
5694 else
5695 {
5696 rtx curr;
5700 {
5706 }
5708 /* In case reg was not used later, it is dead store.
5709 add REG_UNUSED note. */
5711 {
5718 }
5719 }
5720 }
5723 {
5726 /* If this is a set, scan backwards for a previous
5727 reference, and attach a REG_DEAD note to it. But we don't
5728 want to do it if the insn is both using and setting the
5729 register.
5731 Global registers are always live. */
5735 {
5738 {
5743 }
5744 }
5745 }
5746 }
5747 }
5749 /* Subroutine of update_life_info. Update the value of reg_n_sets for all
5750 registers modified by X. INC is -1 if the containing insn is being deleted,
5751 and is 1 if the containing insn is a newly generated insn. */
5753 static void
5755 rtx x;
5757 {
5765 {
5769 {
5775 }
5776 else
5778 }
5779 }
5781 /* Scan INSN for a SET that sets REG. If it sets REG via a SUBREG,
5782 then return 2. If it sets REG directly, return 1. Otherwise, return
5783 0. */
5788 static void
5791 {
5793 {
5798 }
5799 }
5801 static int
5803 rtx insn;
5804 rtx reg;
5805 {
5813 }
5815 /* If a replaced SET_INSN (which is part of the insns between
5816 OLD_FIRST_INSN and OLD_LAST_INSN inclusive) is modifying a multiple
5817 register target, and the original dest is now set in the new insns
5818 (between FIRST_INSN and LAST_INSN inclusive) by one or more subreg
5819 sets, then the new insns no longer kill the destination of the
5820 original insn.
5822 We may also be directly using the register in the new insns before
5823 setting it.
5825 In either case, if there exists an instruction in the same basic
5826 block before the replaced insns which uses the original dest (and
5827 contains a corresponding REG_DEAD note), then we must remove this
5828 REG_DEAD note.
5830 SET_INSN is the insn that contains the SET; it may be a PARALLEL
5831 containing the SET insn.
5833 SET is the actual SET insn proper. */
5835 static void
5841 {
5842 rtx insn;
5845 rtx set_dest;
5846 rtx set_pattern;
5854 {
5858 {
5862 }
5864 }
5867 {
5869 }
5874 {
5876 }
5878 /* We have a set of a REG. First we need to determine if this set is
5879 both using and setting the register. (FIXME: if this is in a
5880 PARALLEL, we will have to check the other exprs as well.) */
5882 {
5884 }
5886 /* Now determine if we used or set the register in the old insns
5887 previous to this one. */
5890 {
5892 {
5894 }
5895 }
5897 /* Now determine if we're setting it in the new insns, or using
5898 it. */
5900 {
5903 {
5905 }
5907 {
5908 /* Is the reg now used in this new insn? -- This is probably an
5909 error. */
5912 }
5913 }
5915 {
5916 /* The register is being set via a SUBREG or is being used in
5917 some other way, so it's no longer dead.
5919 Search backwards from first_insn, looking for the first insn
5920 that uses the original dest. Stop if we pass a CODE_LABEL or
5921 a JUMP_INSN.
5923 If we find such an insn and it has a REG_DEAD note referring
5924 to the original dest, then delete the note. */
5927 {
5933 {
5936 {
5938 }
5939 /* ??? -- Is this right? */
5941 }
5942 }
5943 }
5945 {
5946 /* The reg is not being set or used in the new insns at all. */
5949 /* Should never reach here for a pseudo reg. */
5953 /* This can happen for a hard register, if the new insns do not
5954 contain instructions which would be no-ops referring to the
5955 old registers.
5957 We try to verify that this is the case by checking to see if
5958 the original instruction uses all of the registers that it
5959 set. This case is OK, because deleting a no-op can not affect
5960 REG_DEAD notes on other insns. If this is not the case, then
5961 abort. */
5966 {
5968 NULL_PTR))
5970 }
5973 }
5974 }
5976 /* Updates all flow-analysis related quantities (including REG_NOTES) for
5977 the insns from FIRST to LAST inclusive that were created by replacing
5978 the insns from ORIG_INSN_FIRST to ORIG_INSN_LAST inclusive. NOTES
5979 are the original REG_NOTES. */
5981 void
5983 rtx notes;
5986 {
5988 rtx next;
5990 rtx orig_insn;
5991 rtx tem;
5993 /* Get and save the destination set by the original insn, if there
5994 was only one insn replaced. */
5997 {
6002 }
6003 else
6004 {
6007 }
6009 /* Move REG_NOTES from the original insns to where they now belong. */
6012 {
6015 {
6018 /* Move these notes from the original insn to the last new
6019 insn where the register is mentioned. */
6022 {
6025 {
6026 /* Sometimes need to convert REG_UNUSED notes to
6027 REG_DEAD notes. */
6031 {
6033 }
6035 /* The reg only dies in one insn, the last one that uses
6036 it. */
6038 }
6039 /* It must die somewhere, fail if we couldn't find where it died.
6041 We abort because otherwise the register will be live
6042 longer than it should, and we'll probably take an
6043 abort later. What we should do instead is search back
6044 and find the appropriate places to insert the note. */
6046 {
6048 {
6050 }
6052 }
6053 }
6057 {
6058 rtx note_dest;
6060 /* If the insn that set the register to 0 was deleted, this
6061 note cannot be relied on any longer. The destination might
6062 even have been moved to memory.
6063 This was observed for SH4 with execute/920501-6.c compilation,
6064 -O2 -fomit-frame-pointer -finline-functions . */
6070 {
6072 }
6073 else
6074 {
6076 orig_last_insn);
6078 {
6082 }
6083 }
6084 /* This note applies to the dest of the original insn. Find the
6085 first new insn that now has the same dest, and move the note
6086 there. */
6092 {
6096 {
6099 /* The reg is only zero before one insn, the first that
6100 uses it. */
6102 }
6103 /* If this note refers to a multiple word hard
6104 register, it may have been split into several smaller
6105 hard register references. We could split the notes,
6106 but simply dropping them is good enough. */
6113 /* It must be set somewhere; bail if we couldn't find
6114 where it was set. */
6115 }
6116 }
6121 /* A REG_EQUIV or REG_EQUAL note on an insn with more than one
6122 set is meaningless. Just drop the note. */
6128 /* These notes apply to the dest of the original insn. Find the last
6129 new insn that now has the same dest, and move the note there.
6131 If we are replacing multiple insns, just drop the note. */
6140 {
6144 {
6147 /* Only put this note on one of the new insns. */
6149 }
6151 /* The original dest must still be set someplace. Abort if we
6152 couldn't find it. */
6154 {
6155 /* However, if this note refers to a multiple word hard
6156 register, it may have been split into several smaller
6157 hard register references. We could split the notes,
6158 but simply dropping them is good enough. */
6164 /* Likewise for multi-word memory references. */
6169 }
6170 }
6174 /* Move a REG_LIBCALL note to the first insn created, and update
6175 the corresponding REG_RETVAL note. */
6186 /* Move a REG_EXEC_COUNT note to the first insn created. */
6192 /* Move a REG_RETVAL note to the last insn created, and update
6193 the corresponding REG_LIBCALL note. */
6205 /* This should be moved to whichever instruction is a JUMP_INSN. */
6208 {
6210 {
6213 /* Only put this note on one of the new insns. */
6215 }
6216 /* Fail if we couldn't find a JUMP_INSN. */
6219 }
6223 /* reload sometimes leaves obsolete REG_INC notes around. */
6226 /* This should be moved to whichever instruction now has the
6227 increment operation. */
6231 /* Should be moved to the new insn(s) which use the label. */
6242 /* These two notes will never appear until after reorg, so we don't
6243 have to handle them here. */
6246 }
6247 }
6249 /* Each new insn created has a new set. If the destination is a
6250 register, then this reg is now live across several insns, whereas
6251 previously the dest reg was born and died within the same insn.
6252 To reflect this, we now need a REG_DEAD note on the insn where
6253 this dest reg dies.
6255 Similarly, the new insns may have clobbers that need REG_UNUSED
6256 notes. */
6259 {
6260 rtx pat;
6268 {
6270 {
6273 {
6278 }
6279 }
6280 }
6282 {
6284 }
6285 }
6287 /* Check to see if we have any REG_DEAD notes on insns previous to
6288 the new ones that are now incorrect and need to be removed. */
6291 {
6297 }
6299 /* Update reg_n_sets. This is necessary to prevent local alloc from
6300 converting REG_EQUAL notes to REG_EQUIV when the new insns are setting
6301 a reg multiple times instead of once. */
6304 {
6305 rtx x;
6306 RTX_CODE code;
6316 {
6319 {
6323 }
6324 }
6327 }
6330 {
6337 {
6340 {
6344 }
6345 }
6349 }
6350 }
6351 \f
6352 /* Prepends the set of REG_NOTES in NEW to NOTES, and returns NEW. */
6353 static rtx
6356 {
6357 rtx end;
6360 {
6362 }
6364 {
6366 }
6369 {
6371 }
6374 }
6375 \f
6376 /* Replace the insns from FIRST to LAST inclusive with the set of insns in
6377 NEW, and update the life analysis info accordingly. */
6378 void
6381 {
6388 {
6392 }
6398 {
6403 }
6404 /* This is probably bogus. */
6406 {
6408 {
6411 }
6412 }
6415 }
6416 \f
6417 /* Verify the CFG consistency. This function check some CFG invariants and
6418 aborts when something is wrong. Hope that this function will help to
6419 convert many optimization passes to preserve CFG consistent.
6421 Currently it does following checks:
6423 - test head/end pointers
6424 - overlapping of basic blocks
6425 - edge list corectness
6426 - headers of basic blocks (the NOTE_INSN_BASIC_BLOCK note)
6427 - tails of basic blocks (ensure that boundary is necesary)
6428 - scans body of the basic block for JUMP_INSN, CODE_LABEL
6429 and NOTE_INSN_BASIC_BLOCK
6430 - check that all insns are in the basic blocks
6431 (except the switch handling code, barriers and notes)
6433 In future it can be extended check a lot of other stuff as well
6434 (reachability of basic blocks, life information, etc. etc.). */
6436 void
6438 {
6442 rtx x;
6448 /* First pass check head/end pointers and set bb_info array used by
6449 later passes. */
6451 {
6454 /* Check the head pointer and make sure that it is pointing into
6455 insn list. */
6460 {
6464 }
6466 /* Check the end pointer and make sure that it is pointing into
6467 insn list. */
6469 {
6471 {
6475 }
6480 }
6482 {
6486 }
6487 }
6489 /* Now check the basic blocks (boundaries etc.) */
6491 {
6493 /* Check corectness of edge lists */
6494 edge e;
6498 {
6500 {
6509 }
6511 {
6516 {
6519 }
6520 }
6522 }
6526 {
6528 {
6536 }
6538 {
6543 {
6546 }
6547 }
6549 }
6551 /* OK pointers are correct. Now check the header of basic
6552 block. It ought to contain optional CODE_LABEL followed
6553 by NOTE_BASIC_BLOCK. */
6556 {
6558 {
6562 }
6564 }
6568 {
6572 }
6575 {
6576 /* Do checks for empty blocks here */
6577 }
6578 else
6579 {
6582 {
6585 {
6589 }
6597 {
6600 }
6603 }
6604 }
6605 }
6609 {
6611 {
6613 {
6619 /* An addr_vec is placed outside any block block. */
6624 {
6626 }
6628 /* But in any case, non-deletable labels can appear anywhere. */
6633 }
6634 }
6637 }
6638 }
6639 \f
6640 /* Functions to access an edge list with a vector representation.
6641 Enough data is kept such that given an index number, the
6642 pred and succ that edge reprsents can be determined, or
6643 given a pred and a succ, it's index number can be returned.
6644 This allows algorithms which comsume a lot of memory to
6645 represent the normally full matrix of edge (pred,succ) with a
6646 single indexed vector, edge (EDGE_INDEX (pred, succ)), with no
6647 wasted space in the client code due to sparse flow graphs. */
6649 /* This functions initializes the edge list. Basically the entire
6650 flowgraph is processed, and all edges are assigned a number,
6651 and the data structure is filed in. */
6654 {
6656 edge e;
6665 /* Determine the number of edges in the flow graph by counting successor
6666 edges on each basic block. */
6668 {
6672 num_edges++;
6673 }
6674 /* Don't forget successors of the entry block. */
6676 num_edges++;
6685 /* Follow successors of the entry block, and register these edges. */
6687 {
6689 num_edges++;
6690 }
6693 {
6696 /* Follow all successors of blocks, and register these edges. */
6698 {
6700 num_edges++;
6701 }
6702 }
6704 }
6706 /* This function free's memory associated with an edge list. */
6707 void
6710 {
6712 {
6715 }
6716 }
6718 /* This function provides debug output showing an edge list. */
6719 void
6723 {
6729 {
6733 else
6738 else
6740 }
6741 }
6743 /* This function provides an internal consistancy check of an edge list,
6744 verifying that all edges are present, and that there are no
6745 extra edges. */
6746 void
6750 {
6752 edge e;
6755 {
6759 {
6764 {
6767 }
6774 }
6775 }
6777 {
6782 {
6785 }
6792 }
6793 /* We've verified that all the edges are in the list, no lets make sure
6794 there are no spurious edges in the list. */
6798 {
6806 {
6809 }
6812 {
6815 }
6825 }
6827 {
6835 {
6838 }
6841 {
6844 }
6848 succ);
6854 }
6856 {
6864 {
6867 }
6870 {
6873 }
6877 pred);
6882 EXIT_BLOCK_PTR));
6883 }
6884 }
6886 /* This routine will determine what, if any, edge there is between
6887 a specified predecessor and successor. */
6889 int
6893 {
6896 {
6900 }
6902 }
6904 /* This function will remove an edge from the flow graph. */
6905 static void
6907 edge e;
6908 {
6911 edge tmp;
6922 else
6932 else
6936 }
6938 /* This routine will remove any fake successor edges for a basic block.
6939 When the edge is removed, it is also removed from whatever predecessor
6940 list it is in. */
6941 static void
6943 basic_block bb;
6944 {
6945 edge e;
6947 {
6952 }
6953 }
6955 /* This routine will remove all fake edges from the flow graph. If
6956 we remove all fake successors, it will automatically remove all
6957 fake predecessors. */
6958 void
6960 {
6962 edge e;
6963 basic_block bb;
6966 {
6970 }
6971 /* We've handled all successors except the entry block's. */
6973 }
6975 /* This functions will add a fake edge between any block which has no
6976 successors, and the exit block. Some data flow equations require these
6977 edges to exist. */
6978 void
6980 {
6986 }