| blob | 79203d7a05097e55d542c9f904a14553dfe37357 |
1 /* Data flow analysis for GNU compiler.
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000 Free Software Foundation, Inc.
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
10 any later version.
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
23 /* This file contains the data flow analysis pass of the compiler. It
24 computes data flow information which tells combine_instructions
25 which insns to consider combining and controls register allocation.
27 Additional data flow information that is too bulky to record is
28 generated during the analysis, and is used at that time to create
29 autoincrement and autodecrement addressing.
31 The first step is dividing the function into basic blocks.
32 find_basic_blocks does this. Then life_analysis determines
33 where each register is live and where it is dead.
35 ** find_basic_blocks **
37 find_basic_blocks divides the current function's rtl into basic
38 blocks and constructs the CFG. The blocks are recorded in the
39 basic_block_info array; the CFG exists in the edge structures
40 referenced by the blocks.
42 find_basic_blocks also finds any unreachable loops and deletes them.
44 ** life_analysis **
46 life_analysis is called immediately after find_basic_blocks.
47 It uses the basic block information to determine where each
48 hard or pseudo register is live.
50 ** live-register info **
52 The information about where each register is live is in two parts:
53 the REG_NOTES of insns, and the vector basic_block->global_live_at_start.
55 basic_block->global_live_at_start has an element for each basic
56 block, and the element is a bit-vector with a bit for each hard or
57 pseudo register. The bit is 1 if the register is live at the
58 beginning of the basic block.
60 Two types of elements can be added to an insn's REG_NOTES.
61 A REG_DEAD note is added to an insn's REG_NOTES for any register
62 that meets both of two conditions: The value in the register is not
63 needed in subsequent insns and the insn does not replace the value in
64 the register (in the case of multi-word hard registers, the value in
65 each register must be replaced by the insn to avoid a REG_DEAD note).
67 In the vast majority of cases, an object in a REG_DEAD note will be
68 used somewhere in the insn. The (rare) exception to this is if an
69 insn uses a multi-word hard register and only some of the registers are
70 needed in subsequent insns. In that case, REG_DEAD notes will be
71 provided for those hard registers that are not subsequently needed.
72 Partial REG_DEAD notes of this type do not occur when an insn sets
73 only some of the hard registers used in such a multi-word operand;
74 omitting REG_DEAD notes for objects stored in an insn is optional and
75 the desire to do so does not justify the complexity of the partial
76 REG_DEAD notes.
78 REG_UNUSED notes are added for each register that is set by the insn
79 but is unused subsequently (if every register set by the insn is unused
80 and the insn does not reference memory or have some other side-effect,
81 the insn is deleted instead). If only part of a multi-word hard
82 register is used in a subsequent insn, REG_UNUSED notes are made for
83 the parts that will not be used.
85 To determine which registers are live after any insn, one can
86 start from the beginning of the basic block and scan insns, noting
87 which registers are set by each insn and which die there.
89 ** Other actions of life_analysis **
91 life_analysis sets up the LOG_LINKS fields of insns because the
92 information needed to do so is readily available.
94 life_analysis deletes insns whose only effect is to store a value
95 that is never used.
97 life_analysis notices cases where a reference to a register as
98 a memory address can be combined with a preceding or following
99 incrementation or decrementation of the register. The separate
100 instruction to increment or decrement is deleted and the address
101 is changed to a POST_INC or similar rtx.
103 Each time an incrementing or decrementing address is created,
104 a REG_INC element is added to the insn's REG_NOTES list.
106 life_analysis fills in certain vectors containing information about
107 register usage: REG_N_REFS, REG_N_DEATHS, REG_N_SETS, REG_LIVE_LENGTH,
108 REG_N_CALLS_CROSSED and REG_BASIC_BLOCK.
110 life_analysis sets current_function_sp_is_unchanging if the function
111 doesn't modify the stack pointer. */
113 /* TODO:
115 Split out from life_analysis:
116 - local property discovery (bb->local_live, bb->local_set)
117 - global property computation
118 - log links creation
119 - pre/post modify transformation
120 */
121 \f
142 #define obstack_chunk_alloc xmalloc
143 #define obstack_chunk_free free
146 /* EXIT_IGNORE_STACK should be nonzero if, when returning from a function,
147 the stack pointer does not matter. The value is tested only in
148 functions that have frame pointers.
149 No definition is equivalent to always zero. */
150 #ifndef EXIT_IGNORE_STACK
151 #define EXIT_IGNORE_STACK 0
152 #endif
154 #ifndef HAVE_epilogue
155 #define HAVE_epilogue 0
156 #endif
157 #ifndef HAVE_prologue
158 #define HAVE_prologue 0
159 #endif
160 #ifndef HAVE_sibcall_epilogue
161 #define HAVE_sibcall_epilogue 0
162 #endif
164 /* The contents of the current function definition are allocated
165 in this obstack, and all are freed at the end of the function.
166 For top-level functions, this is temporary_obstack.
167 Separate obstacks are made for nested functions. */
171 /* Number of basic blocks in the current function. */
175 /* Number of edges in the current function. */
179 /* The basic block array. */
181 varray_type basic_block_info;
183 /* The special entry and exit blocks. */
197 },
198 {
210 }
211 };
213 /* Nonzero if the second flow pass has completed. */
216 /* Maximum register number used in this function, plus one. */
220 /* Indexed by n, giving various register information */
222 varray_type reg_n_info;
224 /* Size of the reg_n_info table. */
228 /* Element N is the next insn that uses (hard or pseudo) register number N
229 within the current basic block; or zero, if there is no such insn.
230 This is valid only during the final backward scan in propagate_block. */
234 /* Size of a regset for the current function,
235 in (1) bytes and (2) elements. */
240 /* Regset of regs live when calls to `setjmp'-like functions happen. */
241 /* ??? Does this exist only for the setjmp-clobbered warning message? */
243 regset regs_live_at_setjmp;
245 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
246 that have to go in the same hard reg.
247 The first two regs in the list are a pair, and the next two
248 are another pair, etc. */
249 rtx regs_may_share;
251 /* Depth within loops of basic block being scanned for lifetime analysis,
252 plus one. This is the weight attached to references to registers. */
256 /* During propagate_block, this is non-zero if the value of CC0 is live. */
260 /* During propagate_block, this contains a list of all the MEMs we are
261 tracking for dead store elimination. */
265 /* Set of registers that may be eliminable. These are handled specially
266 in updating regs_ever_live. */
270 /* The basic block structure for every insn, indexed by uid. */
272 varray_type basic_block_for_insn;
274 /* The labels mentioned in non-jump rtl. Valid during find_basic_blocks. */
275 /* ??? Should probably be using LABEL_NUSES instead. It would take a
276 bit of surgery to be able to use or co-opt the routines in jump. */
280 /* Forward declarations */
302 basic_block));
304 basic_block));
329 #ifdef AUTO_INC_DEC
333 #endif
357 /* This function is always defined so it can be called from the
358 debugger, and it is declared extern so we don't get warnings about
359 it being unused. */
363 \f
364 /* Find basic blocks of the current function.
365 F is the first insn of the function and NREGS the number of register
366 numbers in use. */
368 void
370 rtx f;
373 {
376 /* Flush out existing data. */
378 {
383 /* Clear bb->aux on all extant basic blocks. We'll use this as a
384 tag for reuse during create_basic_block, just in case some pass
385 copies around basic block notes improperly. */
390 }
394 /* Size the basic block table. The actual structures will be allocated
395 by find_basic_blocks_1, since we want to keep the structure pointers
396 stable across calls to find_basic_blocks. */
397 /* ??? This whole issue would be much simpler if we called find_basic_blocks
398 exactly once, and thereafter we don't have a single long chain of
399 instructions at all until close to the end of compilation when we
400 actually lay them out. */
406 /* Record the block to which an insn belongs. */
407 /* ??? This should be done another way, by which (perhaps) a label is
408 tagged directly with the basic block that it starts. It is used for
409 more than that currently, but IMO that is the only valid use. */
412 #ifdef AUTO_INC_DEC
413 /* Leave space for insns life_analysis makes in some cases for auto-inc.
414 These cases are rare, so we don't need too much space. */
416 #endif
420 /* Discover the edges of our cfg. */
424 /* Do very simple cleanup now, for the benefit of code that runs between
425 here and cleanup_cfg, e.g. thread_prologue_and_epilogue_insns. */
430 #ifdef ENABLE_CHECKING
432 #endif
433 }
435 /* Count the basic blocks of the function. */
437 static int
439 rtx f;
440 {
450 {
458 {
459 count++;
460 }
462 /* Record whether this call created an edge. */
464 {
470 /* If there is an EH region or rethrow, we have an edge. */
474 else
475 {
476 /* If there is a nonlocal goto label and the specified
477 region number isn't -1, we have an edge. (0 means
478 no throw, but might have a nonlocal goto). */
481 }
482 }
493 }
495 /* The rest of the compiler works a bit smoother when we don't have to
496 check for the edge case of do-nothing functions with no basic blocks. */
498 {
501 }
504 }
506 /* Find all basic blocks of the function whose first insn is F.
508 Collect and return a list of labels whose addresses are taken. This
509 will be used in make_edges for use with computed gotos. */
511 static rtx
513 rtx f;
514 {
524 /* We process the instructions in a slightly different way than we did
525 previously. This is so that we see a NOTE_BASIC_BLOCK after we have
526 closed out the previous block, so that it gets attached at the proper
527 place. Since this form should be equivalent to the previous,
528 count_basic_blocks continues to use the old form as a check. */
531 {
537 {
538 /* Record whether this call created an edge. */
543 /* If there is an EH region or rethrow, we have an edge. */
547 else
548 {
549 /* If there is a nonlocal goto label and the specified
550 region number isn't -1, we have an edge. (0 means
551 no throw, but might have a nonlocal goto). */
554 }
555 }
558 {
560 {
563 /* Keep a LIFO list of the currently active exception notes. */
567 {
571 }
573 /* Look for basic block notes with which to keep the
574 basic_block_info pointers stable. Unthread the note now;
575 we'll put it back at the right place in create_basic_block.
576 Or not at all if we've already found a note in this block. */
578 {
582 }
585 }
588 /* A basic block starts at a label. If we've closed one off due
589 to a barrier or some such, no need to do it again. */
591 {
592 /* While we now have edge lists with which other portions of
593 the compiler might determine a call ending a basic block
594 does not imply an abnormal edge, it will be a bit before
595 everything can be updated. So continue to emit a noop at
596 the end of such a block. */
599 {
602 }
606 }
611 /* A basic block ends at a jump. */
614 else
615 {
616 /* ??? Make a special check for table jumps. The way this
617 happens is truly and amazingly gross. We are about to
618 create a basic block that contains just a code label and
619 an addr*vec jump insn. Worse, an addr_diff_vec creates
620 its own natural loop.
622 Prevent this bit of brain damage, pasting things together
623 correctly in make_edges.
625 The correct solution involves emitting the table directly
626 on the tablejump instruction as a note, or JUMP_LABEL. */
630 {
632 n_basic_blocks--;
634 }
635 }
640 /* A basic block ends at a barrier. It may be that an unconditional
641 jump already closed the basic block -- no need to do it again. */
645 /* While we now have edge lists with which other portions of the
646 compiler might determine a call ending a basic block does not
647 imply an abnormal edge, it will be a bit before everything can
648 be updated. So continue to emit a noop at the end of such a
649 block. */
652 {
655 }
659 /* A basic block ends at a call that can either throw or
660 do a non-local goto. */
662 {
663 new_bb_inclusive:
668 new_bb_exclusive:
673 }
674 /* FALLTHRU */
678 {
682 }
684 }
687 {
688 rtx note;
690 /* Make a list of all labels referred to other than by jumps
691 (which just don't have the REG_LABEL notes).
693 Make a special exception for labels followed by an ADDR*VEC,
694 as this would be a part of the tablejump setup code.
696 Make a special exception for the eh_return_stub_label, which
697 we know isn't part of any otherwise visible control flow. */
701 {
705 ;
710 ;
711 else
712 label_value_list
714 }
715 }
716 }
725 }
727 /* Tidy the CFG by deleting unreachable code and whatnot. */
729 void
731 rtx f;
732 {
739 /* Kill the data we won't maintain. */
741 }
743 /* Create a new basic block consisting of the instructions between
744 HEAD and END inclusive. Reuses the note and basic block struct
745 in BB_NOTE, if any. */
747 void
751 {
752 basic_block bb;
758 {
759 /* If we found an existing note, thread it back onto the chain. */
763 else
764 {
767 }
768 }
769 else
770 {
771 /* Otherwise we must create a note and a basic block structure.
772 Since we allow basic block structs in rtl, give the struct
773 the same lifetime by allocating it off the function obstack
774 rather than using malloc. */
781 else
782 {
785 }
787 }
789 /* Always include the bb note in the block. */
798 /* Tag the block so that we know it has been used when considering
799 other basic block notes. */
801 }
802 \f
803 /* Records the basic block struct in BB_FOR_INSN, for every instruction
804 indexed by INSN_UID. MAX is the size of the array. */
806 void
809 {
817 {
824 {
831 }
832 }
833 }
835 /* Free the memory associated with the edge structures. */
837 static void
839 {
844 {
848 {
851 }
855 }
858 {
861 }
867 }
869 /* Identify the edges between basic blocks.
871 NONLOCAL_LABEL_LIST is a list of non-local labels in the function. Blocks
872 that are otherwise unreachable may be reachable with a non-local goto.
874 BB_EH_END is an array indexed by basic block number in which we record
875 the list of exception regions active at the end of the basic block. */
877 static void
879 rtx label_value_list;
880 {
885 /* Assume no computed jump; revise as we create edges. */
888 /* Heavy use of computed goto in machine-generated code can lead to
889 nearly fully-connected CFGs. In that case we spend a significant
890 amount of time searching the edge lists for duplicates. */
892 {
895 }
897 /* By nature of the way these get numbered, block 0 is always the entry. */
901 {
907 /* Examine the last instruction of the block, and discover the
908 ways we can leave the block. */
913 /* A branch. */
915 {
916 rtx tmp;
918 /* ??? Recognize a tablejump and do the right thing. */
924 {
925 rtvec vec;
930 else
937 /* Some targets (eg, ARM) emit a conditional jump that also
938 contains the out-of-range target. Scan for these and
939 add an edge if necessary. */
947 #ifdef CASE_DROPS_THROUGH
948 /* Silly VAXen. The ADDR_VEC is going to be in the way of
949 us naturally detecting fallthru into the next block. */
951 #endif
952 }
954 /* If this is a computed jump, then mark it as reaching
955 everything on the label_value_list and forced_labels list. */
957 {
965 }
967 /* Returns create an exit out. */
971 /* Otherwise, we have a plain conditional or unconditional jump. */
972 else
973 {
977 }
978 }
980 /* If this is a sibling call insn, then this is in effect a
981 combined call and return, and so we need an edge to the
982 exit block. No need to worry about EH edges, since we
983 wouldn't have created the sibling call in the first place. */
987 else
989 /* If this is a CALL_INSN, then mark it as reaching the active EH
990 handler for this CALL_INSN. If we're handling asynchronous
991 exceptions then any insn can reach any of the active handlers.
993 Also mark the CALL_INSN as reaching any nonlocal goto handler. */
996 {
997 /* Add any appropriate EH edges. We do this unconditionally
998 since there may be a REG_EH_REGION or REG_EH_RETHROW note
999 on the call, and this needn't be within an EH region. */
1002 /* If we have asynchronous exceptions, do the same for *all*
1003 exception regions active in the block. */
1006 {
1015 {
1019 }
1020 }
1023 {
1024 /* ??? This could be made smarter: in some cases it's possible
1025 to tell that certain calls will not do a nonlocal goto.
1027 For example, if the nested functions that do the nonlocal
1028 gotos do not have their addresses taken, then only calls to
1029 those functions or to other nested functions that use them
1030 could possibly do nonlocal gotos. */
1031 /* We do know that a REG_EH_REGION note with a value less
1032 than 0 is guaranteed not to perform a non-local goto. */
1038 }
1039 }
1041 /* We know something about the structure of the function __throw in
1042 libgcc2.c. It is the only function that ever contains eh_stub
1043 labels. It modifies its return address so that the last block
1044 returns to one of the eh_stub labels within it. So we have to
1045 make additional edges in the flow graph. */
1049 /* Find out if we can drop through to the next block. */
1054 {
1060 }
1061 }
1066 }
1068 /* Create an edge between two basic blocks. FLAGS are auxiliary information
1069 about the edge that is accumulated between calls. */
1071 void
1076 {
1078 edge e;
1080 /* Don't bother with edge cache for ENTRY or EXIT; there aren't that
1081 many edges to them, and we didn't allocate memory for it. */
1082 use_edge_cache = (edge_cache
1086 /* Make sure we don't add duplicate edges. */
1090 {
1093 }
1096 n_edges++;
1109 }
1111 /* Create an edge from a basic block to a label. */
1113 static void
1116 basic_block src;
1117 rtx label;
1119 {
1123 /* If the label was never emitted, this insn is junk, but avoid a
1124 crash trying to refer to BLOCK_FOR_INSN (label). This can happen
1125 as a result of a syntax error and a diagnostic has already been
1126 printed. */
1132 }
1134 /* Create the edges generated by INSN in REGION. */
1136 static void
1140 basic_block src;
1141 rtx insn;
1143 {
1150 {
1153 }
1154 }
1156 /* EH_REGION notes appearing between basic blocks is ambiguous, and even
1157 dangerous if we intend to move basic blocks around. Move such notes
1158 into the following block. */
1160 static void
1162 {
1171 {
1176 {
1181 {
1182 /* Unlink from the insn chain. */
1186 /* Queue it. */
1189 }
1190 }
1195 /* Find where to insert these things. */
1201 {
1205 }
1206 }
1207 }
1209 /* Recompute eh_beg/eh_end for each basic block. */
1211 static void
1213 rtx f;
1214 {
1220 {
1225 {
1230 {
1234 }
1235 }
1238 {
1244 }
1245 }
1246 }
1248 /* Identify critical edges and set the bits appropriately. */
1250 static void
1252 {
1254 basic_block bb;
1256 /* We begin with the entry block. This is not terribly important now,
1257 but could be if a front end (Fortran) implemented alternate entry
1258 points. */
1263 {
1264 edge e;
1266 /* (1) Critical edges must have a source with multiple successors. */
1268 {
1270 {
1271 /* (2) Critical edges must have a destination with multiple
1272 predecessors. Note that we know there is at least one
1273 predecessor -- the edge we followed to get here. */
1276 else
1278 }
1279 }
1280 else
1281 {
1284 }
1289 }
1290 }
1291 \f
1292 /* Split a (typically critical) edge. Return the new block.
1293 Abort on abnormal edges.
1295 ??? The code generally expects to be called on critical edges.
1296 The case of a block ending in an unconditional jump to a
1297 block with multiple predecessors is not handled optimally. */
1299 basic_block
1301 edge edge_in;
1302 {
1304 edge edge_out;
1305 rtx bb_note;
1308 /* Abnormal edges cannot be split. */
1315 /* Remove the existing edge from the destination's pred list. */
1316 {
1322 }
1324 /* Create the new structures. */
1327 n_edges++;
1333 /* ??? This info is likely going to be out of date very soon. */
1335 {
1338 }
1339 else
1340 {
1343 }
1345 /* Wire them up. */
1361 /* Tricky case -- if there existed a fallthru into the successor
1362 (and we're not it) we must add a new unconditional jump around
1363 the new block we're actually interested in.
1365 Further, if that edge is critical, this means a second new basic
1366 block must be created to hold it. In order to simplify correct
1367 insn placement, do this before we touch the existing basic block
1368 ordering for the block we were really wanting. */
1370 {
1371 edge e;
1377 {
1378 basic_block jump_block;
1379 rtx pos;
1383 {
1384 /* Non critical -- we can simply add a jump to the end
1385 of the existing predecessor. */
1387 }
1388 else
1389 {
1390 /* We need a new block to hold the jump. The simplest
1391 way to do the bulk of the work here is to recursively
1392 call ourselves. */
1395 }
1397 /* Now add the jump insn ... */
1405 /* ... let jump know that label is in use, ... */
1409 /* ... and clear fallthru on the outgoing edge. */
1412 /* Continue splitting the interesting edge. */
1413 }
1414 }
1416 /* Place the new block just in front of the successor. */
1420 else
1423 {
1427 }
1431 /* Create the basic block note.
1433 Where we place the note can have a noticable impact on the generated
1434 code. Consider this cfg:
1437 E
1438 |
1439 0
1440 / \
1441 +->1-->2--->E
1442 | |
1443 +--+
1445 If we need to insert an insn on the edge from block 0 to block 1,
1446 we want to ensure the instructions we insert are outside of any
1447 loop notes that physically sit between block 0 and block 1. Otherwise
1448 we confuse the loop optimizer into thinking the loop is a phony. */
1457 else
1462 /* Not quite simple -- for non-fallthru edges, we must adjust the
1463 predecessor's jump instruction to target our new block. */
1465 {
1473 /* ??? Recognize a tablejump and adjust all matching cases. */
1479 {
1480 rtvec vec;
1485 else
1490 {
1494 }
1496 /* Handle casesi dispatch insns */
1502 {
1504 new_label);
1507 }
1508 }
1509 else
1510 {
1511 /* This would have indicated an abnormal edge. */
1515 /* A return instruction can't be redirected. */
1519 /* If the insn doesn't go where we think, we're confused. */
1524 }
1528 }
1531 }
1533 /* Queue instructions for insertion on an edge between two basic blocks.
1534 The new instructions and basic blocks (if any) will not appear in the
1535 CFG until commit_edge_insertions is called. */
1537 void
1539 rtx pattern;
1540 edge e;
1541 {
1542 /* We cannot insert instructions on an abnormal critical edge.
1543 It will be easier to find the culprit if we die now. */
1550 else
1557 }
1559 /* Update the CFG for the instructions queued on edge E. */
1561 static void
1563 edge e;
1564 {
1566 basic_block bb;
1568 /* Pull the insns off the edge now since the edge might go away. */
1572 /* Figure out where to put these things. If the destination has
1573 one predecessor, insert there. Except for the exit block. */
1576 {
1579 /* Get the location correct wrt a code label, and "nice" wrt
1580 a basic block note, and before everything else. */
1589 else
1591 }
1593 /* If the source has one successor and the edge is not abnormal,
1594 insert there. Except for the entry block. */
1598 {
1600 /* It is possible to have a non-simple jump here. Consider a target
1601 where some forms of unconditional jumps clobber a register. This
1602 happens on the fr30 for example.
1604 We know this block has a single successor, so we can just emit
1605 the queued insns before the jump. */
1607 {
1609 }
1610 else
1611 {
1612 /* We'd better be fallthru, or we've lost track of what's what. */
1617 }
1618 }
1620 /* Otherwise we must split the edge. */
1621 else
1622 {
1625 }
1627 /* Now that we've found the spot, do the insertion. */
1629 /* Set the new block number for these insns, if structure is allocated. */
1631 {
1632 rtx i;
1635 }
1638 {
1642 }
1643 else
1644 {
1647 {
1651 {
1653 {
1654 /* ??? Remove all outgoing edges from BB and add one
1655 for EXIT. This is not currently a problem because
1656 this only happens for the (single) epilogue, which
1657 already has a fallthru edge to EXIT. */
1667 }
1668 else
1670 }
1671 }
1672 }
1673 }
1675 /* Update the CFG for all queued instructions. */
1677 void
1679 {
1681 basic_block bb;
1683 #ifdef ENABLE_CHECKING
1685 #endif
1690 {
1694 {
1698 }
1703 }
1704 }
1705 \f
1706 /* Delete all unreachable basic blocks. */
1708 static void
1710 {
1713 edge e;
1719 /* Use basic_block->aux as a marker. Clear them all. */
1724 /* Add our starting points to the worklist. Almost always there will
1725 be only one. It isn't inconcievable that we might one day directly
1726 support Fortran alternate entry points. */
1729 {
1732 /* Mark the block with a handy non-null value. */
1734 }
1736 /* Iterate: find everything reachable from what we've already seen. */
1739 {
1744 {
1747 }
1748 }
1750 /* Delete all unreachable basic blocks. Count down so that we don't
1751 interfere with the block renumbering that happens in delete_block. */
1756 {
1760 /* This block was found. Tidy up the mark. */
1762 else
1764 }
1768 /* If we deleted an exception handler, we may have EH region begin/end
1769 blocks to remove as well. */
1774 }
1776 /* Find EH regions for which there is no longer a handler, and delete them. */
1778 static void
1780 {
1781 rtx insn;
1787 {
1790 {
1792 /* A NULL handler indicates a region is no longer needed,
1793 as long as its rethrow label isn't used. */
1795 {
1798 }
1799 }
1800 }
1801 }
1803 /* Return true if NOTE is not one of the ones that must be kept paired,
1804 so that we may simply delete them. */
1806 static int
1808 rtx note;
1809 {
1812 }
1814 /* Unlink a chain of insns between START and FINISH, leaving notes
1815 that must be paired. */
1817 void
1820 {
1821 /* Unchain the insns one by one. It would be quicker to delete all
1822 of these with a single unchaining, rather than one at a time, but
1823 we need to keep the NOTE's. */
1825 rtx next;
1828 {
1831 ;
1833 ;
1834 else
1840 }
1841 }
1843 /* Delete the insns in a (non-live) block. We physically delete every
1844 non-deleted-note insn, and update the flow graph appropriately.
1846 Return nonzero if we deleted an exception handler. */
1848 /* ??? Preserving all such notes strikes me as wrong. It would be nice
1849 to post-process the stream to remove empty blocks, loops, ranges, etc. */
1851 static int
1853 basic_block b;
1854 {
1858 /* If the head of this block is a CODE_LABEL, then it might be the
1859 label for an exception handler which can't be reached.
1861 We need to remove the label from the exception_handler_label list
1862 and remove the associated NOTE_INSN_EH_REGION_BEG and
1863 NOTE_INSN_EH_REGION_END notes. */
1870 {
1874 {
1876 {
1877 /* Found a match, splice this label out of the EH label list. */
1882 /* Remove the handler from all regions */
1886 }
1888 }
1890 /* This label may be referenced by code solely for its value, or
1891 referenced by static data, or something. We have determined
1892 that it is not reachable, but cannot delete the label itself.
1893 Save code space and continue to delete the balance of the block,
1894 along with properly updating the cfg. */
1896 {
1897 /* If we've only got one of these, skip the whole deleting
1898 insns thing. */
1902 }
1903 }
1905 /* Include any jump table following the basic block. */
1915 /* Include any barrier that may follow the basic block. */
1920 /* Selectively delete the entire chain. */
1923 no_delete_insns:
1925 /* Remove the edges into and out of this block. Note that there may
1926 indeed be edges in, if we are removing an unreachable loop. */
1927 {
1931 {
1936 n_edges--;
1938 }
1940 {
1945 n_edges--;
1947 }
1951 }
1953 /* Remove the basic block from the array, and compact behind it. */
1957 }
1959 /* Remove block B from the basic block array and compact behind it. */
1961 static void
1963 basic_block b;
1964 {
1968 {
1972 }
1975 n_basic_blocks--;
1976 }
1978 /* Delete INSN by patching it out. Return the next insn. */
1980 rtx
1982 rtx insn;
1983 {
1986 rtx note;
1995 else
2001 /* If deleting a jump, decrement the use count of the label. Deleting
2002 the label itself should happen in the normal course of block merging. */
2006 /* Also if deleting an insn that references a label. */
2011 }
2013 /* True if a given label can be deleted. */
2015 static int
2017 rtx label;
2018 {
2019 rtx x;
2034 /* User declared labels must be preserved. */
2039 }
2041 /* Blocks A and B are to be merged into a single block. A has no incoming
2042 fallthru edge, so it can be moved before B without adding or modifying
2043 any jumps (aside from the jump from A to B). */
2045 static int
2048 {
2055 /* We want to delete the BARRIER after the end of the insns we are
2056 going to move. If we don't find a BARRIER, then do nothing. This
2057 can happen in some cases if we have labels we can not delete.
2059 Similarly, do nothing if we can not delete the label at the start
2060 of the target block. */
2066 else
2069 /* Move block and loop notes out of the chain so that we do not
2070 disturb their order.
2072 ??? A better solution would be to squeeze out all the non-nested notes
2073 and adjust the block trees appropriately. Even better would be to have
2074 a tighter connection between block trees and rtl so that this is not
2075 necessary. */
2078 /* Scramble the insn chain. */
2083 {
2086 }
2088 /* Swap the records for the two blocks around. Although we are deleting B,
2089 A is now where B was and we want to compact the BB array from where
2090 A used to be. */
2097 /* Now blocks A and B are contiguous. Merge them. */
2101 }
2103 /* Blocks A and B are to be merged into a single block. B has no outgoing
2104 fallthru edge, so it can be moved after A without adding or modifying
2105 any jumps (aside from the jump from A to B). */
2107 static int
2110 {
2116 /* We want to delete the BARRIER after the end of the insns we are
2117 going to move. If we don't find a BARRIER, then do nothing. This
2118 can happen in some cases if we have labels we can not delete.
2120 Similarly, do nothing if we can not delete the label at the start
2121 of the target block. */
2127 else
2130 /* Move block and loop notes out of the chain so that we do not
2131 disturb their order.
2133 ??? A better solution would be to squeeze out all the non-nested notes
2134 and adjust the block trees appropriately. Even better would be to have
2135 a tighter connection between block trees and rtl so that this is not
2136 necessary. */
2139 /* Scramble the insn chain. */
2142 /* Now blocks A and B are contiguous. Merge them. */
2146 {
2149 }
2152 }
2154 /* Blocks A and B are to be merged into a single block. The insns
2155 are already contiguous, hence `nomove'. */
2157 static void
2160 {
2161 edge e;
2165 /* If there was a CODE_LABEL beginning B, delete it. */
2169 {
2170 /* Detect basic blocks with nothing but a label. This can happen
2171 in particular at the end of a function. */
2175 }
2177 /* Delete the basic block note. */
2180 {
2184 }
2186 /* If there was a jump out of A, delete it. */
2189 {
2190 rtx prev;
2196 #ifdef HAVE_cc0
2197 /* If this was a conditional jump, we need to also delete
2198 the insn that set cc0. */
2201 {
2207 }
2208 #endif
2210 /* Note that a->head != a->end, since we should have at least a
2211 bb note plus the jump, so prev != insn. */
2214 }
2216 /* By definition, there should only be one successor of A, and that is
2217 B. Free that edge struct. */
2218 n_edges--;
2221 /* Adjust the edges out of B for the new owner. */
2226 /* Reassociate the insns of B with A. */
2228 {
2231 {
2234 }
2236 }
2239 /* Compact the basic block array. */
2241 }
2243 /* Attempt to merge basic blocks that are potentially non-adjacent.
2244 Return true iff the attempt succeeded. */
2246 static int
2248 edge e;
2250 {
2251 /* If B has a fallthru edge to C, no need to move anything. */
2253 {
2254 /* If a label still appears somewhere and we cannot delete the label,
2255 then we cannot merge the blocks. The edge was tidied already. */
2265 {
2268 }
2271 }
2272 else
2273 {
2274 edge tmp_edge;
2275 basic_block d;
2279 /* We must make sure to not munge nesting of exception regions,
2280 lexical blocks, and loop notes.
2282 The first is taken care of by requiring that the active eh
2283 region at the end of one block always matches the active eh
2284 region at the beginning of the next block.
2286 The later two are taken care of by squeezing out all the notes. */
2288 /* ??? A throw/catch edge (or any abnormal edge) should be rarely
2289 executed and we may want to treat blocks which have two out
2290 edges, one normal, one abnormal as only having one edge for
2291 block merging purposes. */
2303 /* If B does not have an incoming fallthru, and the exception regions
2304 match, then it can be moved immediately before C without introducing
2305 or modifying jumps.
2307 C can not be the first block, so we do not have to worry about
2308 accessing a non-existent block. */
2315 /* Otherwise, we're going to try to move C after B. Make sure the
2316 exception regions match.
2318 If B is the last basic block, then we must not try to access the
2319 block structure for block B + 1. Luckily in that case we do not
2320 need to worry about matching exception regions. */
2324 {
2325 /* If C does not have an outgoing fallthru, then it can be moved
2326 immediately after B without introducing or modifying jumps. */
2330 /* Otherwise, we'll need to insert an extra jump, and possibly
2331 a new block to contain it. */
2332 /* ??? Not implemented yet. */
2333 }
2336 }
2337 }
2339 /* Top level driver for merge_blocks. */
2341 static void
2343 {
2346 /* Attempt to merge blocks as made possible by edge removal. If a block
2347 has only one successor, and the successor has only one predecessor,
2348 they may be combined. */
2351 {
2353 edge s;
2355 /* A loop because chains of blocks might be combineable. */
2361 /* If the jump insn has side effects, we can't kill the edge. */
2367 /* Don't get confused by the index shift caused by deleting blocks. */
2369 }
2370 }
2372 /* The given edge should potentially be a fallthru edge. If that is in
2373 fact true, delete the jump and barriers that are in the way. */
2375 static void
2377 edge e;
2379 {
2380 rtx q;
2382 /* ??? In a late-running flow pass, other folks may have deleted basic
2383 blocks by nopping out blocks, leaving multiple BARRIERs between here
2384 and the target label. They ought to be chastized and fixed.
2386 We can also wind up with a sequence of undeletable labels between
2387 one block and the next.
2389 So search through a sequence of barriers, labels, and notes for
2390 the head of block C and assert that we really do fall through. */
2395 /* Remove what will soon cease being the jump insn from the source block.
2396 If block B consisted only of this single jump, turn it into a deleted
2397 note. */
2400 {
2401 #ifdef HAVE_cc0
2402 /* If this was a conditional jump, we need to also delete
2403 the insn that set cc0. */
2406 #endif
2409 {
2413 }
2414 else
2416 }
2418 /* Selectively unlink the sequence. */
2423 }
2425 /* Fix up edges that now fall through, or rather should now fall through
2426 but previously required a jump around now deleted blocks. Simplify
2427 the search by only examining blocks numerically adjacent, since this
2428 is how find_basic_blocks created them. */
2430 static void
2432 {
2436 {
2439 edge s;
2441 /* We care about simple conditional or unconditional jumps with
2442 a single successor.
2444 If we had a conditional branch to the next instruction when
2445 find_basic_blocks was called, then there will only be one
2446 out edge for the block which ended with the conditional
2447 branch (since we do not create duplicate edges).
2449 Furthermore, the edge will be marked as a fallthru because we
2450 merge the flags for the duplicate edges. So we do not want to
2451 check that the edge is not a FALLTHRU edge. */
2455 /* If the jump insn has side effects, we can't tidy the edge. */
2459 }
2460 }
2462 /* Discover and record the loop depth at the head of each basic block. */
2464 void
2467 {
2470 /* The loop infrastructure does the real job for us. */
2477 }
2478 \f
2479 /* Perform data flow analysis.
2480 F is the first insn of the function and NREGS the number of register numbers
2481 in use. */
2483 void
2485 rtx f;
2489 {
2490 #ifdef ELIMINABLE_REGS
2493 #endif
2495 sbitmap all_blocks;
2497 /* Record which registers will be eliminated. We use this in
2498 mark_used_regs. */
2502 #ifdef ELIMINABLE_REGS
2505 #else
2507 #endif
2509 /* We want alias analysis information for local dead store elimination. */
2514 else
2515 {
2519 }
2521 /* The post-reload life analysis have (on a global basis) the same
2522 registers live as was computed by reload itself. elimination
2523 Otherwise offsets and such may be incorrect.
2525 Reload will make some registers as live even though they do not
2526 appear in the rtl. */
2532 /* Always remove no-op moves. Do this before other processing so
2533 that we don't have to keep re-scanning them. */
2536 /* Some targets can emit simpler epilogues if they know that sp was
2537 not ever modified during the function. After reload, of course,
2538 we've already emitted the epilogue so there's no sense searching. */
2542 /* Allocate and zero out data structures that will record the
2543 data from lifetime analysis. */
2550 /* Find the set of registers live on function exit. */
2553 /* "Update" life info from zero. It'd be nice to begin the
2554 relaxation with just the exit and noreturn blocks, but that set
2555 is not immediately handy. */
2561 /* Clean up. */
2571 }
2573 /* A subroutine of verify_wide_reg, called through for_each_rtx.
2574 Search for REGNO. If found, abort if it is not wider than word_mode. */
2576 static int
2580 {
2585 {
2589 }
2591 }
2593 /* A subroutine of verify_local_live_at_start. Search through insns
2594 between HEAD and END looking for register REGNO. */
2596 static void
2600 {
2602 {
2609 }
2611 /* We didn't find the register at all. Something's way screwy. */
2613 }
2615 /* A subroutine of update_life_info. Verify that there are no untoward
2616 changes in live_at_start during a local update. */
2618 static void
2620 regset new_live_at_start;
2621 basic_block bb;
2622 {
2624 {
2625 /* After reload, there are no pseudos, nor subregs of multi-word
2626 registers. The regsets should exactly match. */
2629 }
2630 else
2631 {
2634 /* Find the set of changed registers. */
2638 {
2639 /* No registers should die. */
2642 /* Verify that the now-live register is wider than word_mode. */
2644 });
2645 }
2646 }
2648 /* Updates life information starting with the basic blocks set in BLOCKS.
2650 If LOCAL_ONLY, such as after splitting or peepholeing, we are only
2651 expecting local modifications to basic blocks. If we find extra
2652 registers live at the beginning of a block, then we either killed
2653 useful data, or we have a broken split that wants data not provided.
2654 If we find registers removed from live_at_start, that means we have
2655 a broken peephole that is killing a register it shouldn't.
2657 ??? This is not true in one situation -- when a pre-reload splitter
2658 generates subregs of a multi-word pseudo, current life analysis will
2659 lose the kill. So we _can_ have a pseudo go live. How irritating.
2661 BLOCK_FOR_INSN is assumed to be correct.
2663 PROP_FLAGS should not contain PROP_LOG_LINKS unless the caller sets
2664 up reg_next_use. Including PROP_REG_INFO does not properly refresh
2665 regs_ever_live unless the caller resets it to zero. */
2667 void
2669 sbitmap blocks;
2672 {
2673 regset tmp;
2674 regset_head tmp_head;
2679 /* For a global update, we go through the relaxation process again. */
2681 {
2685 /* If asked, remove notes from the blocks we'll update. */
2688 }
2691 {
2699 });
2704 {
2705 /* The only pseudos that are live at the beginning of the function
2706 are those that were not set anywhere in the function. local-alloc
2707 doesn't know how to handle these correctly, so mark them as not
2708 local to any one basic block. */
2713 /* We have a problem with any pseudoreg that lives across the setjmp.
2714 ANSI says that if a user variable does not change in value between
2715 the setjmp and the longjmp, then the longjmp preserves it. This
2716 includes longjmp from a place where the pseudo appears dead.
2717 (In principle, the value still exists if it is in scope.)
2718 If the pseudo goes in a hard reg, some other value may occupy
2719 that hard reg where this pseudo is dead, thus clobbering the pseudo.
2720 Conclusion: such a pseudo must not go in a hard reg. */
2723 {
2725 {
2728 }
2729 });
2730 }
2731 }
2733 /* Free the variables allocated by find_basic_blocks.
2735 KEEP_HEAD_END_P is non-zero if basic_block_info is not to be freed. */
2737 void
2740 {
2742 {
2745 }
2748 {
2757 }
2758 }
2760 /* Return nonzero if the destination of SET equals the source. */
2761 static int
2763 rtx set;
2764 {
2769 {
2774 }
2778 }
2780 /* Return nonzero if an insn consists only of SETs, each of which only sets a
2781 value to itself. */
2782 static int
2784 rtx insn;
2785 {
2788 /* Insns carrying these notes are useful later on. */
2796 {
2798 /* If nothing but SETs of registers to themselves,
2799 this insn can also be deleted. */
2801 {
2810 }
2813 }
2815 }
2817 /* Delete any insns that copy a register to itself. */
2819 static void
2821 rtx f;
2822 {
2823 rtx insn;
2825 {
2827 {
2831 }
2832 }
2833 }
2835 /* Determine if the stack pointer is constant over the life of the function.
2836 Only useful before prologues have been emitted. */
2838 static void
2840 rtx x;
2841 rtx pat ATTRIBUTE_UNUSED;
2843 {
2845 /* The stack pointer is only modified indirectly as the result
2846 of a push until later in flow. See the comments in rtl.texi
2847 regarding Embedded Side-Effects on Addresses. */
2855 }
2857 static void
2859 rtx f;
2860 {
2861 rtx insn;
2863 /* Assume that the stack pointer is unchanging if alloca hasn't
2864 been used. */
2870 {
2872 {
2873 /* Check if insn modifies the stack pointer. */
2875 NULL);
2878 }
2879 }
2880 }
2882 /* Mark a register in SET. Hard registers in large modes get all
2883 of their component registers set as well. */
2884 static void
2886 rtx reg;
2888 {
2897 {
2901 }
2902 }
2904 /* Mark those regs which are needed at the end of the function as live
2905 at the end of the last basic block. */
2906 static void
2908 regset set;
2909 {
2912 /* If exiting needs the right stack value, consider the stack pointer
2913 live at the end of the function. */
2915 || ! EXIT_IGNORE_STACK
2916 || (! FRAME_POINTER_REQUIRED
2917 && ! current_function_calls_alloca
2920 {
2922 }
2924 /* Mark the frame pointer if needed at the end of the function. If
2925 we end up eliminating it, it will be removed from the live list
2926 of each basic block by reload. */
2929 {
2931 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2932 /* If they are different, also mark the hard frame pointer as live */
2934 #endif
2935 }
2937 #ifdef PIC_OFFSET_TABLE_REGNUM
2938 #ifndef PIC_OFFSET_TABLE_REG_CALL_CLOBBERED
2939 /* Many architectures have a GP register even without flag_pic.
2940 Assume the pic register is not in use, or will be handled by
2941 other means, if it is not fixed. */
2944 #endif
2945 #endif
2947 /* Mark all global registers, and all registers used by the epilogue
2948 as being live at the end of the function since they may be
2949 referenced by our caller. */
2952 #ifdef EPILOGUE_USES
2954 #endif
2955 )
2958 /* Mark all call-saved registers that we actaully used. */
2960 {
2964 }
2966 /* Mark function return value. */
2968 }
2970 /* Propagate global life info around the graph of basic blocks. Begin
2971 considering blocks with their corresponding bit set in BLOCKS_IN.
2972 BLOCKS_OUT is set for every block that was changed. */
2974 static void
2978 {
2981 regset_head tmp_head;
2982 regset_head new_live_at_end_head;
2988 /* Create a worklist. Allocate an extra slot for ENTRY_BLOCK, and one
2989 because the `head == tail' style test for an empty queue doesn't
2990 work with a full queue. */
2995 /* Clear out the garbage that might be hanging out in bb->aux. */
2999 /* Queue the blocks set in the initial mask. Do this in reverse block
3000 number order so that we are more likely for the first round to do
3001 useful work. We use AUX non-null to flag that the block is queued. */
3003 {
3007 });
3012 {
3014 basic_block bb;
3015 edge e;
3022 /* Begin by propogating live_at_start from the successor blocks. */
3025 {
3028 }
3031 {
3034 }
3036 /* On our first pass through this block, we'll go ahead and continue.
3037 Recognize first pass by local_set NULL. On subsequent passes, we
3038 get to skip out early if live_at_end wouldn't have changed. */
3041 {
3044 }
3045 else
3046 {
3047 /* If any bits were removed from live_at_end, we'll have to
3048 rescan the block. This wouldn't be necessary if we had
3049 precalculated local_live, however with PROP_SCAN_DEAD_CODE
3050 local_live is really dependant on live_at_end. */
3056 {
3057 /* Find the set of changed bits. Take this opportunity
3058 to notice that this set is empty and early out. */
3065 /* If any of the changed bits overlap with local_set,
3066 we'll have to rescan the block. Detect overlap by
3067 the AND with ~local_set turning off bits. */
3069 BITMAP_AND_COMPL);
3070 }
3071 }
3073 /* Let our caller know that BB changed enough to require its
3074 death notes updated. */
3078 {
3079 /* Add to live_at_start the set of all registers in
3080 new_live_at_end that aren't in the old live_at_end. */
3083 BITMAP_AND_COMPL);
3091 }
3092 else
3093 {
3096 /* Rescan the block insn by insn to turn (a copy of) live_at_end
3097 into live_at_start. */
3100 /* If live_at start didn't change, no need to go farther. */
3105 }
3107 /* Queue all predecessors of BB so that we may re-examine
3108 their live_at_end. */
3110 {
3113 {
3118 }
3119 }
3120 }
3126 {
3129 });
3132 }
3133 \f
3134 /* Subroutines of life analysis. */
3136 /* Allocate the permanent data structures that represent the results
3137 of life analysis. Not static since used also for stupid life analysis. */
3139 void
3141 {
3145 {
3150 }
3152 ENTRY_BLOCK_PTR->global_live_at_end
3154 EXIT_BLOCK_PTR->global_live_at_start
3158 }
3160 void
3162 {
3165 /* Recalculate the register space, in case it has grown. Old style
3166 vector oriented regsets would set regset_{size,bytes} here also. */
3169 /* Reset all the data we'll collect in propagate_block and its
3170 subroutines. */
3172 {
3179 }
3180 }
3182 /* Compute the registers live at the beginning of a basic block
3183 from those live at the end.
3185 When called, OLD contains those live at the end.
3186 On return, it contains those live at the beginning.
3187 FIRST and LAST are the first and last insns of the basic block.
3189 FINAL is nonzero if we are doing the final pass which is not
3190 for computing the life info (since that has already been done)
3191 but for acting on it. On this pass, we delete dead stores,
3192 set up the logical links and dead-variables lists of instructions,
3193 and merge instructions for autoincrement and autodecrement addresses.
3195 SIGNIFICANT is nonzero only the first time for each basic block.
3196 If it is nonzero, it points to a regset in which we store
3197 a 1 for each register that is set within the block.
3199 BNUM is the number of the basic block. */
3201 static void
3203 basic_block bb;
3204 regset old;
3205 regset significant;
3207 {
3209 rtx prev;
3210 regset live;
3211 regset_head live_head;
3212 regset dead;
3213 regset_head dead_head;
3215 /* Find the loop depth for this block. Ignore loop level changes in the
3216 middle of the basic block -- for register allocation purposes, the
3217 important uses will be in the blocks wholely contained within the loop
3218 not in the loop pre-header or post-trailer. */
3227 {
3230 /* Process the regs live at the end of the block.
3231 Mark them as not local to any one basic block. */
3233 {
3235 });
3236 }
3238 /* Scan the block an insn at a time from end to beginning. */
3241 {
3245 {
3246 /* If this is a call to `setjmp' et al,
3247 warn if any non-volatile datum is live. */
3252 }
3254 /* Update the life-status of regs for this insn.
3255 First DEAD gets which regs are set in this insn
3256 then LIVE gets which regs are used in this insn.
3257 Then the regs live before the insn
3258 are those live after, with DEAD regs turned off,
3259 and then LIVE regs turned on. */
3262 {
3269 {
3275 }
3277 /* We almost certainly don't want to delete prologue or epilogue
3278 instructions. Warn about probable compiler losage. */
3280 && reload_completed
3283 || (HAVE_sibcall_epilogue
3285 {
3287 {
3291 }
3293 }
3295 /* If an instruction consists of just dead store(s) on final pass,
3296 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
3297 We could really delete it with delete_insn, but that
3298 can cause trouble for first or last insn in a basic block. */
3300 {
3301 rtx inote;
3302 /* If the insn referred to a label, note that the label is
3303 now less used. */
3305 {
3307 {
3309 rtx next;
3312 /* If this label was attached to an ADDR_VEC, it's
3313 safe to delete the ADDR_VEC. In fact, it's pretty
3314 much mandatory to delete it, because the ADDR_VEC may
3315 be referencing labels that no longer exist. */
3321 {
3331 }
3332 }
3333 }
3339 /* CC0 is now known to be dead. Either this insn used it,
3340 in which case it doesn't anymore, or clobbered it,
3341 so the next insn can't use it. */
3344 /* If this insn is copying the return value from a library call,
3345 delete the entire library call. */
3347 {
3353 {
3358 }
3359 }
3361 }
3366 /* See if this is an increment or decrement that can be
3367 merged into a following memory address. */
3368 #ifdef AUTO_INC_DEC
3369 {
3372 /* Does this instruction increment or decrement a register? */
3381 /* Ok, look for a following memory ref we can combine with.
3382 If one is found, change the memory ref to a PRE_INC
3383 or PRE_DEC, cancel this insn, and return 1.
3384 Return 0 if nothing has been done. */
3387 }
3390 /* If this is not the final pass, and this insn is copying the
3391 value of a library call and it's dead, don't scan the
3392 insns that perform the library call, so that the call's
3393 arguments are not marked live. */
3395 {
3396 /* Mark the dest reg as `significant'. */
3402 }
3408 /* We have an insn to pop a constant amount off the stack.
3409 (Such insns use PLUS regardless of the direction of the stack,
3410 and any insn to adjust the stack by a constant is always a pop.)
3411 These insns, if not dead stores, have no effect on life. */
3412 ;
3413 else
3414 {
3415 /* Any regs live at the time of a call instruction
3416 must not go in a register clobbered by calls.
3417 Find all regs now live and record this for them. */
3422 {
3424 });
3426 /* LIVE gets the regs used in INSN;
3427 DEAD gets those set by it. Dead insns don't make anything
3428 live. */
3433 /* If an insn doesn't use CC0, it becomes dead since we
3434 assume that every insn clobbers it. So show it dead here;
3435 mark_used_regs will set it live if it is referenced. */
3441 /* Sometimes we may have inserted something before INSN (such as
3442 a move) when we make an auto-inc. So ensure we will scan
3443 those insns. */
3444 #ifdef AUTO_INC_DEC
3446 #endif
3449 {
3452 rtx note;
3455 note;
3461 /* Each call clobbers all call-clobbered regs that are not
3462 global or fixed. Note that the function-value reg is a
3463 call-clobbered reg, and mark_set_regs has already had
3464 a chance to handle it. */
3469 {
3473 }
3475 /* The stack ptr is used (honorarily) by a CALL insn. */
3478 /* Calls may also reference any of the global registers,
3479 so they are made live. */
3486 /* Calls also clobber memory. */
3488 }
3490 /* Update OLD for the registers used or set. */
3494 }
3496 /* On final pass, update counts of how many insns in which
3497 each reg is live. */
3500 }
3501 flushed:
3504 }
3509 }
3510 \f
3511 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
3512 (SET expressions whose destinations are registers dead after the insn).
3513 NEEDED is the regset that says which regs are alive after the insn.
3515 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL.
3517 If X is the entire body of an insn, NOTES contains the reg notes
3518 pertaining to the insn. */
3520 static int
3522 rtx x;
3523 regset needed;
3525 rtx notes ATTRIBUTE_UNUSED;
3526 {
3529 #ifdef AUTO_INC_DEC
3530 /* If flow is invoked after reload, we must take existing AUTO_INC
3531 expresions into account. */
3533 {
3535 {
3537 {
3540 /* Don't delete insns to set global regs. */
3544 }
3545 }
3546 }
3547 #endif
3549 /* If setting something that's a reg or part of one,
3550 see if that register's altered value will be live. */
3553 {
3556 #ifdef HAVE_cc0
3559 #endif
3561 /* A SET that is a subroutine call cannot be dead. */
3563 {
3566 }
3568 /* Don't eliminate loads from volatile memory or volatile asms. */
3573 {
3574 rtx temp;
3579 /* Walk the set of memory locations we are currently tracking
3580 and see if one is an identical match to this memory location.
3581 If so, this memory write is dead (remember, we're walking
3582 backwards from the end of the block to the start. */
3585 {
3589 }
3590 }
3591 else
3592 {
3599 {
3602 /* Obvious. */
3606 /* If this is a hard register, verify that subsequent
3607 words are not needed. */
3609 {
3615 }
3617 /* Don't delete insns to set global regs. */
3621 /* Make sure insns to set the stack pointer aren't deleted. */
3625 /* Make sure insns to set the frame pointer aren't deleted. */
3629 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
3633 #endif
3635 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
3636 /* Make sure insns to set arg pointer are never deleted
3637 (if the arg pointer isn't fixed, there will be a USE
3638 for it, so we can treat it normally). */
3641 #endif
3643 /* Otherwise, the set is dead. */
3645 }
3646 }
3647 }
3649 /* If performing several activities, insn is dead if each activity
3650 is individually dead. Also, CLOBBERs and USEs can be ignored; a
3651 CLOBBER or USE that's inside a PARALLEL doesn't make the insn
3652 worth keeping. */
3654 {
3664 }
3666 /* A CLOBBER of a pseudo-register that is dead serves no purpose. That
3667 is not necessarily true for hard registers. */
3673 /* We do not check other CLOBBER or USE here. An insn consisting of just
3674 a CLOBBER or just a USE should not be deleted. */
3676 }
3678 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
3679 return 1 if the entire library call is dead.
3680 This is true if X copies a register (hard or pseudo)
3681 and if the hard return reg of the call insn is dead.
3682 (The caller should have tested the destination of X already for death.)
3684 If this insn doesn't just copy a register, then we don't
3685 have an ordinary libcall. In that case, cse could not have
3686 managed to substitute the source for the dest later on,
3687 so we can assume the libcall is dead.
3689 NEEDED is the bit vector of pseudoregs live before this insn.
3690 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
3692 static int
3694 rtx x;
3695 regset needed;
3696 rtx note;
3697 rtx insn;
3698 {
3702 {
3705 {
3707 rtx call_pat;
3710 /* Find the call insn. */
3714 /* If there is none, do nothing special,
3715 since ordinary death handling can understand these insns. */
3719 /* See if the hard reg holding the value is dead.
3720 If this is a PARALLEL, find the call within it. */
3723 {
3729 /* This may be a library call that is returning a value
3730 via invisible pointer. Do nothing special, since
3731 ordinary death handling can understand these insns. */
3736 }
3739 }
3740 }
3742 }
3744 /* Return 1 if register REGNO was used before it was set, i.e. if it is
3745 live at function entry. Don't count global register variables, variables
3746 in registers that can be used for function arg passing, or variables in
3747 fixed hard registers. */
3749 int
3752 {
3761 }
3763 /* 1 if register REGNO was alive at a place where `setjmp' was called
3764 and was set more than once or is an argument.
3765 Such regs may be clobbered by `longjmp'. */
3767 int
3770 {
3777 }
3778 \f
3779 /* INSN references memory, possibly using autoincrement addressing modes.
3780 Find any entries on the mem_set_list that need to be invalidated due
3781 to an address change. */
3782 static void
3784 rtx insn;
3785 {
3788 {
3790 {
3793 rtx next;
3796 {
3799 {
3800 /* Splice temp out of list. */
3803 else
3806 }
3807 else
3810 }
3811 }
3812 }
3813 }
3815 /* Process the registers that are set within X. Their bits are set to
3816 1 in the regset DEAD, because they are dead prior to this insn.
3818 If INSN is nonzero, it is the insn being processed.
3820 FLAGS is the set of operations to perform. */
3822 static void
3824 regset needed;
3825 regset dead;
3826 rtx x;
3827 rtx insn;
3828 regset significant;
3830 {
3836 {
3839 {
3844 }
3845 }
3846 }
3848 /* Process a single SET rtx, X. */
3850 static void
3852 regset needed;
3853 regset dead;
3854 rtx x;
3855 rtx insn;
3856 regset significant;
3858 {
3862 /* Some targets place small structures in registers for
3863 return values of functions. We have to detect this
3864 case specially here to get correct flow information. */
3867 {
3874 }
3876 /* Modifying just one hardware register of a multi-reg value
3877 or just a byte field of a register
3878 does not mean the value from before this insn is now dead.
3879 But it does mean liveness of that register at the end of the block
3880 is significant.
3882 Within mark_set_1, however, we treat it as if the register is
3883 indeed modified. mark_used_regs will, however, also treat this
3884 register as being used. Thus, we treat these insns as setting a
3885 new value for the register as a function of its old value. This
3886 cases LOG_LINKS to be made appropriately and this will help combine. */
3893 /* If this set is a MEM, then it kills any aliased writes.
3894 If this set is a REG, then it kills any MEMs which use the reg. */
3896 {
3899 {
3902 rtx next;
3905 {
3911 {
3912 /* Splice this entry out of the list. */
3915 else
3918 }
3919 else
3922 }
3923 }
3925 /* If the memory reference had embedded side effects (autoincrement
3926 address modes. Then we may need to kill some entries on the
3927 memory set list. */
3932 /* We do not know the size of a BLKmode store, so we do not track
3933 them for redundant store elimination. */
3935 /* There are no REG_INC notes for SP, so we can't assume we'll see
3936 everything that invalidates it. To be safe, don't eliminate any
3937 stores though SP; none of them should be redundant anyway. */
3940 }
3946 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
3949 #endif
3950 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
3952 #endif
3954 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
3955 {
3959 /* Mark it as a significant register for this basic block. */
3963 /* Mark it as dead before this insn. */
3966 /* A hard reg in a wide mode may really be multiple registers.
3967 If so, mark all of them just like the first. */
3969 {
3972 /* Nothing below is needed for the stack pointer; get out asap.
3973 Eg, log links aren't needed, since combine won't use them. */
3979 {
3988 }
3989 }
3991 /* Additional data to record if this is the final pass. */
3994 {
4002 /* If this is a hard reg, record this function uses the reg. */
4005 {
4011 {
4012 /* The next use is no longer "next", since a store
4013 intervenes. */
4015 }
4019 {
4022 }
4023 }
4024 else
4025 {
4026 /* The next use is no longer "next", since a store
4027 intervenes. */
4031 /* Keep track of which basic blocks each reg appears in. */
4034 {
4040 /* Count (weighted) references, stores, etc. This counts a
4041 register twice if it is modified, but that is correct. */
4045 /* The insns where a reg is live are normally counted
4046 elsewhere, but we want the count to include the insn
4047 where the reg is set, and the normal counting mechanism
4048 would not count it. */
4050 }
4051 }
4054 {
4056 {
4057 /* Make a logical link from the next following insn
4058 that uses this register, back to this insn.
4059 The following insns have already been processed.
4061 We don't build a LOG_LINK for hard registers containing
4062 in ASM_OPERANDs. If these registers get replaced,
4063 we might wind up changing the semantics of the insn,
4064 even if reload can make what appear to be valid
4065 assignments later. */
4070 }
4071 }
4073 {
4078 {
4079 /* Note that dead stores have already been deleted
4080 when possible. If we get here, we have found a
4081 dead store that cannot be eliminated (because the
4082 same insn does something useful). Indicate this
4083 by marking the reg being set as dying here. */
4086 }
4087 }
4088 else
4089 {
4091 {
4092 /* This is a case where we have a multi-word hard register
4093 and some, but not all, of the words of the register are
4094 needed in subsequent insns. Write REG_UNUSED notes
4095 for those parts that were not needed. This case should
4096 be rare. */
4104 = (alloc_EXPR_LIST
4108 }
4109 }
4110 }
4111 }
4113 {
4116 }
4118 /* If this is the last pass and this is a SCRATCH, show it will be dying
4119 here and count it. */
4121 {
4125 }
4126 }
4127 \f
4128 #ifdef AUTO_INC_DEC
4130 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
4131 reference. */
4133 static void
4135 regset needed;
4136 rtx x;
4137 rtx insn;
4138 {
4141 rtx set;
4143 /* Here we detect use of an index register which might be good for
4144 postincrement, postdecrement, preincrement, or predecrement. */
4150 {
4153 rtx use;
4154 rtx incr;
4157 /* Is the next use an increment that might make auto-increment? */
4162 /* Can't add side effects to jumps; if reg is spilled and
4163 reloaded, there's no way to store back the altered value. */
4168 && ((HAVE_POST_INCREMENT
4170 || (HAVE_POST_DECREMENT
4172 || (HAVE_PRE_INCREMENT
4174 || (HAVE_PRE_DECREMENT
4176 /* Make sure this reg appears only once in this insn. */
4179 {
4186 {
4187 /* This is the simple case. Try to make the auto-inc. If
4188 we can't, we are done. Otherwise, we will do any
4189 needed updates below. */
4194 }
4196 /* PREV_INSN used here to check the semi-open interval
4197 [insn,incr). */
4199 /* We must also check for sets of q as q may be
4200 a call clobbered hard register and there may
4201 be a call between PREV_INSN (insn) and incr. */
4203 {
4204 /* We have *p followed sometime later by q = p+size.
4205 Both p and q must be live afterward,
4206 and q is not used between INSN and its assignment.
4207 Change it to q = p, ...*q..., q = q+size.
4208 Then fall into the usual case. */
4210 basic_block bb;
4221 /* If we can't make the auto-inc, or can't make the
4222 replacement into Y, exit. There's no point in making
4223 the change below if we can't do the auto-inc and doing
4224 so is not correct in the pre-inc case. */
4233 /* We now know we'll be doing this change, so emit the
4234 new insn(s) and do the updates. */
4240 /* INCR will become a NOTE and INSN won't contain a
4241 use of ADDR. If a use of ADDR was just placed in
4242 the insn before INSN, make that the next use.
4243 Otherwise, invalidate it. */
4248 else
4254 /* REGNO is now used in INCR which is below INSN, but
4255 it previously wasn't live here. If we don't mark
4256 it as needed, we'll put a REG_DEAD note for it
4257 on this insn, which is incorrect. */
4260 /* If there are any calls between INSN and INCR, show
4261 that REGNO now crosses them. */
4265 }
4266 else
4269 /* If we haven't returned, it means we were able to make the
4270 auto-inc, so update the status. First, record that this insn
4271 has an implicit side effect. */
4276 /* Modify the old increment-insn to simply copy
4277 the already-incremented value of our register. */
4281 /* If that makes it a no-op (copying the register into itself) delete
4282 it so it won't appear to be a "use" and a "set" of this
4283 register. */
4285 {
4289 }
4292 {
4293 /* Count an extra reference to the reg. When a reg is
4294 incremented, spilling it is worse, so we want to make
4295 that less likely. */
4298 /* Count the increment as a setting of the register,
4299 even though it isn't a SET in rtl. */
4301 }
4302 }
4303 }
4304 }
4306 \f
4307 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
4308 This is done assuming the registers needed from X
4309 are those that have 1-bits in NEEDED.
4311 FLAGS is the set of enabled operations.
4313 INSN is the containing instruction. If INSN is dead, this function is not
4314 called. */
4316 static void
4318 regset needed;
4319 regset live;
4320 rtx x;
4322 rtx insn;
4323 {
4328 retry:
4331 {
4342 #ifdef HAVE_cc0
4346 #endif
4349 /* If we are clobbering a MEM, mark any registers inside the address
4350 as being used. */
4356 /* Don't bother watching stores to mems if this is not the
4357 final pass. We'll not be deleting dead stores this round. */
4359 {
4360 /* Invalidate the data for the last MEM stored, but only if MEM is
4361 something that can be stored into. */
4365 else
4366 {
4369 rtx next;
4372 {
4375 {
4376 /* Splice temp out of the list. */
4379 else
4382 }
4383 else
4386 }
4387 }
4389 /* If the memory reference had embedded side effects (autoincrement
4390 address modes. Then we may need to kill some entries on the
4391 memory set list. */
4394 }
4396 #ifdef AUTO_INC_DEC
4399 #endif
4409 /* While we're here, optimize this case. */
4412 /* In case the SUBREG is not of a register, don't optimize */
4414 {
4417 }
4419 /* ... fall through ... */
4422 /* See a register other than being set
4423 => mark it as needed. */
4426 {
4432 /* A hard reg in a wide mode may really be multiple registers.
4433 If so, mark all of them just like the first. */
4435 {
4438 /* For stack ptr or fixed arg pointer,
4439 nothing below can be necessary, so waste no more time. */
4441 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
4444 #endif
4445 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
4447 #endif
4450 {
4451 /* If this is a register we are going to try to eliminate,
4452 don't mark it live here. If we are successful in
4453 eliminating it, it need not be live unless it is used for
4454 pseudos, in which case it will have been set live when
4455 it was allocated to the pseudos. If the register will not
4456 be eliminated, reload will set it live at that point. */
4462 }
4463 /* No death notes for global register variables;
4464 their values are live after this function exits. */
4466 {
4470 }
4474 {
4481 }
4482 }
4485 {
4486 /* Record where each reg is used, so when the reg
4487 is set we know the next insn that uses it. */
4490 }
4492 {
4494 {
4495 /* If a hard reg is being used,
4496 record that this function does use it. */
4501 do
4504 }
4505 else
4506 {
4507 /* Keep track of which basic block each reg appears in. */
4516 /* Count (weighted) number of uses of each reg. */
4519 }
4520 }
4522 /* Record and count the insns in which a reg dies.
4523 If it is used in this insn and was dead below the insn
4524 then it dies in this insn. If it was set in this insn,
4525 we do not make a REG_DEAD note; likewise if we already
4526 made such a note. */
4529 {
4532 #if 0
4534 #endif
4535 )
4536 {
4537 /* Check for the case where the register dying partially
4538 overlaps the register set by this insn. */
4541 {
4545 }
4547 /* If none of the words in X is needed, make a REG_DEAD
4548 note. Otherwise, we must make partial REG_DEAD notes. */
4550 {
4554 }
4555 else
4556 {
4559 /* Don't make a REG_DEAD note for a part of a register
4560 that is set in the insn. */
4567 = (alloc_EXPR_LIST
4571 }
4572 }
4573 }
4574 }
4578 {
4582 /* If storing into MEM, don't show it as being used. But do
4583 show the address as being used. */
4585 {
4586 #ifdef AUTO_INC_DEC
4589 #endif
4593 }
4595 /* Storing in STRICT_LOW_PART is like storing in a reg
4596 in that this SET might be dead, so ignore it in TESTREG.
4597 but in some other ways it is like using the reg.
4599 Storing in a SUBREG or a bit field is like storing the entire
4600 register in that if the register's value is not used
4601 then this SET is not needed. */
4606 {
4614 /* Modifying a single register in an alternate mode
4615 does not use any of the old value. But these other
4616 ways of storing in a register do use the old value. */
4619 ;
4620 else
4624 }
4626 /* If this is a store into a register,
4627 recursively scan the value being stored. */
4634 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
4637 #endif
4638 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
4640 #endif
4641 ))
4642 /* We used to exclude global_regs here, but that seems wrong.
4643 Storing in them is like storing in mem. */
4644 {
4649 }
4650 }
4657 {
4658 /* Traditional and volatile asm instructions must be considered to use
4659 and clobber all hard registers, all pseudo-registers and all of
4660 memory. So must TRAP_IF and UNSPEC_VOLATILE operations.
4662 Consider for instance a volatile asm that changes the fpu rounding
4663 mode. An insn should not be moved across this even if it only uses
4664 pseudo-regs because it might give an incorrectly rounded result.
4666 ?!? Unfortunately, marking all hard registers as live causes massive
4667 problems for the register allocator and marking all pseudos as live
4668 creates mountains of uninitialized variable warnings.
4670 So for now, just clear the memory set list and mark any regs
4671 we can find in ASM_OPERANDS as used. */
4675 /* For all ASM_OPERANDS, we must traverse the vector of input operands.
4676 We can not just fall through here since then we would be confused
4677 by the ASM_INPUT rtx inside ASM_OPERANDS, which do not indicate
4678 traditional asms unlike their normal usage. */
4680 {
4686 }
4688 }
4693 }
4695 /* Recursively scan the operands of this expression. */
4697 {
4702 {
4704 {
4705 /* Tail recursive case: save a function call level. */
4707 {
4710 }
4712 }
4714 {
4718 }
4719 }
4720 }
4721 }
4722 \f
4723 #ifdef AUTO_INC_DEC
4725 static int
4727 rtx insn;
4728 {
4729 /* Find the next use of this reg. If in same basic block,
4730 make it do pre-increment or pre-decrement if appropriate. */
4738 /* Don't do this if the reg dies, or gets set in y; a standard addressing
4739 mode would be better. */
4742 {
4743 /* We have found a suitable auto-increment
4744 and already changed insn Y to do it.
4745 So flush this increment-instruction. */
4749 /* Count a reference to this reg for the increment
4750 insn we are deleting. When a reg is incremented.
4751 spilling it is worse, so we want to make that
4752 less likely. */
4754 {
4757 }
4759 }
4761 }
4763 /* Try to change INSN so that it does pre-increment or pre-decrement
4764 addressing on register REG in order to add AMOUNT to REG.
4765 AMOUNT is negative for pre-decrement.
4766 Returns 1 if the change could be made.
4767 This checks all about the validity of the result of modifying INSN. */
4769 static int
4772 HOST_WIDE_INT amount;
4773 {
4776 /* Nonzero if we can try to make a pre-increment or pre-decrement.
4777 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
4779 /* Nonzero if we can try to make a post-increment or post-decrement.
4780 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
4781 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
4782 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
4785 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
4788 /* From the sign of increment, see which possibilities are conceivable
4789 on this target machine. */
4803 /* It is not safe to add a side effect to a jump insn
4804 because if the incremented register is spilled and must be reloaded
4805 there would be no way to store the incremented value back in memory. */
4814 {
4817 }
4825 /* See if this combination of instruction and addressing mode exists. */
4833 /* Record that this insn now has an implicit side effect on X. */
4836 }
4839 \f
4840 /* Find the place in the rtx X where REG is used as a memory address.
4841 Return the MEM rtx that so uses it.
4842 If PLUSCONST is nonzero, search instead for a memory address equivalent to
4843 (plus REG (const_int PLUSCONST)).
4845 If such an address does not appear, return 0.
4846 If REG appears more than once, or is used other than in such an address,
4847 return (rtx)1. */
4849 rtx
4852 rtx reg;
4853 HOST_WIDE_INT plusconst;
4854 {
4871 {
4872 /* If REG occurs inside a MEM used in a bit-field reference,
4873 that is unacceptable. */
4876 }
4882 {
4884 {
4890 }
4892 {
4895 {
4901 }
4902 }
4903 }
4906 }
4907 \f
4908 /* Write information about registers and basic blocks into FILE.
4909 This is part of making a debugging dump. */
4911 void
4913 regset r;
4915 {
4918 {
4921 }
4924 {
4929 });
4930 }
4932 void
4934 regset r;
4935 {
4938 }
4940 void
4943 {
4950 {
4972 {
4977 else
4981 }
4985 }
4989 {
5011 }
5014 }
5016 void
5018 {
5020 }
5022 static void
5025 edge e;
5027 {
5034 else
5038 {
5041 };
5049 {
5056 else
5059 }
5061 }
5062 }
5064 \f
5065 /* Print out one basic block with live information at start and end. */
5066 void
5068 basic_block bb;
5070 {
5071 rtx insn;
5072 rtx last;
5073 edge e;
5103 }
5105 void
5107 basic_block bb;
5108 {
5110 }
5112 void
5115 {
5117 }
5119 /* Like print_rtl, but also print out live information for the start of each
5120 basic block. */
5122 void
5125 rtx rtx_first;
5126 {
5131 else
5132 {
5144 {
5146 rtx x;
5151 {
5159 }
5160 }
5163 {
5165 basic_block bb;
5168 {
5173 }
5189 }
5194 }
5197 {
5202 }
5203 }
5205 /* Compute dominator relationships using new flow graph structures. */
5206 void
5210 {
5213 edge e;
5216 /* Allocate a worklist array/queue. Entries are only added to the
5217 list if they were not already on the list. So the size is
5218 bounded by the number of basic blocks. */
5226 {
5227 /* The optimistic setting of dominators requires us to put every
5228 block on the work list initially. */
5230 {
5233 }
5235 /* We want a maximal solution, so initially assume everything dominates
5236 everything else. */
5239 /* Mark successors of the entry block so we can identify them below. */
5243 /* Iterate until the worklist is empty. */
5245 {
5246 /* Take the first entry off the worklist. */
5250 /* Compute the intersection of the dominators of all the
5251 predecessor blocks.
5253 If one of the predecessor blocks is the ENTRY block, then the
5254 intersection of the dominators of the predecessor blocks is
5255 defined as the null set. We can identify such blocks by the
5256 special value in the AUX field in the block structure. */
5258 {
5259 /* Do not clear the aux field for blocks which are
5260 successors of the ENTRY block. That way we we never
5261 add them to the worklist again.
5263 The intersect of dominators of the preds of this block is
5264 defined as the null set. */
5266 }
5267 else
5268 {
5269 /* Clear the aux field of this block so it can be added to
5270 the worklist again if necessary. */
5273 }
5275 /* Make sure each block always dominates itself. */
5278 /* If the out state of this block changed, then we need to
5279 add the successors of this block to the worklist if they
5280 are not already on the worklist. */
5282 {
5284 {
5286 {
5289 }
5290 }
5291 }
5292 }
5293 }
5296 {
5297 /* The optimistic setting of dominators requires us to put every
5298 block on the work list initially. */
5300 {
5303 }
5305 /* We want a maximal solution, so initially assume everything post
5306 dominates everything else. */
5309 /* Mark predecessors of the exit block so we can identify them below. */
5313 /* Iterate until the worklist is empty. */
5315 {
5316 /* Take the first entry off the worklist. */
5320 /* Compute the intersection of the post dominators of all the
5321 successor blocks.
5323 If one of the successor blocks is the EXIT block, then the
5324 intersection of the dominators of the successor blocks is
5325 defined as the null set. We can identify such blocks by the
5326 special value in the AUX field in the block structure. */
5328 {
5329 /* Do not clear the aux field for blocks which are
5330 predecessors of the EXIT block. That way we we never
5331 add them to the worklist again.
5333 The intersect of dominators of the succs of this block is
5334 defined as the null set. */
5336 }
5337 else
5338 {
5339 /* Clear the aux field of this block so it can be added to
5340 the worklist again if necessary. */
5344 }
5346 /* Make sure each block always post dominates itself. */
5349 /* If the out state of this block changed, then we need to
5350 add the successors of this block to the worklist if they
5351 are not already on the worklist. */
5355 {
5357 {
5359 {
5362 }
5363 }
5364 }
5365 }
5366 }
5368 }
5370 /* Given DOMINATORS, compute the immediate dominators into IDOM. */
5372 void
5376 {
5382 /* Begin with tmp(n) = dom(n) - { n }. */
5384 {
5387 }
5389 /* Subtract out all of our dominator's dominators. */
5391 {
5398 }
5400 /* Find the one bit set in the bitmap and put it in the output array. */
5402 {
5405 }
5408 }
5410 /* Count for a single SET rtx, X. */
5412 static void
5414 rtx x;
5415 {
5419 /* Find the register that's set/clobbered. */
5427 {
5432 }
5435 {
5438 {
5439 /* Count (weighted) references, stores, etc. This counts a
5440 register twice if it is modified, but that is correct. */
5443 }
5444 }
5445 }
5447 /* Increment REG_N_SETS for each SET or CLOBBER found in X; also increment
5448 REG_N_REFS by the current loop depth for each SET or CLOBBER found. */
5450 static void
5452 rtx x;
5453 {
5459 {
5462 {
5466 }
5467 }
5468 }
5470 /* Increment REG_N_REFS by the current loop depth each register reference
5471 found in X. */
5473 static void
5475 rtx x;
5476 {
5479 retry:
5482 {
5494 #ifdef HAVE_cc0
5497 #endif
5500 /* If we are clobbering a MEM, mark any registers inside the address
5501 as being used. */
5507 /* While we're here, optimize this case. */
5510 /* In case the SUBREG is not of a register, don't optimize */
5512 {
5515 }
5517 /* ... fall through ... */
5525 {
5529 /* If storing into MEM, don't show it as being used. But do
5530 show the address as being used. */
5532 {
5536 }
5538 /* Storing in STRICT_LOW_PART is like storing in a reg
5539 in that this SET might be dead, so ignore it in TESTREG.
5540 but in some other ways it is like using the reg.
5542 Storing in a SUBREG or a bit field is like storing the entire
5543 register in that if the register's value is not used
5544 then this SET is not needed. */
5549 {
5550 /* Modifying a single register in an alternate mode
5551 does not use any of the old value. But these other
5552 ways of storing in a register do use the old value. */
5555 ;
5556 else
5560 }
5562 /* If this is a store into a register,
5563 recursively scan the value being stored. */
5568 {
5573 }
5574 }
5579 }
5581 /* Recursively scan the operands of this expression. */
5583 {
5588 {
5590 {
5591 /* Tail recursive case: save a function call level. */
5593 {
5596 }
5598 }
5600 {
5604 }
5605 }
5606 }
5607 }
5609 /* Recompute register set/reference counts immediately prior to register
5610 allocation.
5612 This avoids problems with set/reference counts changing to/from values
5613 which have special meanings to the register allocators.
5615 Additionally, the reference counts are the primary component used by the
5616 register allocators to prioritize pseudos for allocation to hard regs.
5617 More accurate reference counts generally lead to better register allocation.
5619 F is the first insn to be scanned.
5621 LOOP_STEP denotes how much loop_depth should be incremented per
5622 loop nesting level in order to increase the ref count more for
5623 references in a loop.
5625 It might be worthwhile to update REG_LIVE_LENGTH, REG_BASIC_BLOCK and
5626 possibly other information which is used by the register allocators. */
5628 void
5630 rtx f ATTRIBUTE_UNUSED;
5632 {
5633 rtx insn;
5637 /* Clear out the old data. */
5640 {
5643 }
5645 /* Scan each insn in the chain and count how many times each register is
5646 set/used. */
5648 {
5652 {
5654 {
5655 rtx links;
5657 /* This call will increment REG_N_SETS for each SET or CLOBBER
5658 of a register in INSN. It will also increment REG_N_REFS
5659 by the loop depth for each set of a register in INSN. */
5662 /* count_reg_sets does not detect autoincrement address modes, so
5663 detect them here by looking at the notes attached to INSN. */
5665 {
5667 /* Count (weighted) references, stores, etc. This counts a
5668 register twice if it is modified, but that is correct. */
5670 }
5672 /* This call will increment REG_N_REFS by the current loop depth for
5673 each reference to a register in INSN. */
5676 /* count_reg_references will not include counts for arguments to
5677 function calls, so detect them here by examining the
5678 CALL_INSN_FUNCTION_USAGE data. */
5680 {
5681 rtx note;
5684 note;
5688 }
5689 }
5692 }
5693 }
5694 }
5696 /* Optionally removes all the REG_DEAD and REG_UNUSED notes from a set of
5697 blocks. If BLOCKS is NULL, assume the universal set. Returns a count
5698 of the number of registers that died. */
5700 int
5702 sbitmap blocks;
5704 {
5708 {
5709 basic_block bb;
5710 rtx insn;
5718 {
5720 {
5725 {
5727 {
5730 {
5736 else
5739 }
5740 /* FALLTHRU */
5744 {
5749 }
5750 /* FALLTHRU */
5756 }
5757 }
5758 }
5762 }
5763 }
5766 }
5768 /* Record INSN's block as BB. */
5770 void
5772 rtx insn;
5773 basic_block bb;
5774 {
5777 {
5780 /* Add one-eighth the size so we don't keep calling xrealloc. */
5784 }
5786 }
5788 /* Record INSN's block number as BB. */
5789 /* ??? This has got to go. */
5791 void
5793 rtx insn;
5795 {
5797 }
5798 \f
5799 /* Verify the CFG consistency. This function check some CFG invariants and
5800 aborts when something is wrong. Hope that this function will help to
5801 convert many optimization passes to preserve CFG consistent.
5803 Currently it does following checks:
5805 - test head/end pointers
5806 - overlapping of basic blocks
5807 - edge list corectness
5808 - headers of basic blocks (the NOTE_INSN_BASIC_BLOCK note)
5809 - tails of basic blocks (ensure that boundary is necesary)
5810 - scans body of the basic block for JUMP_INSN, CODE_LABEL
5811 and NOTE_INSN_BASIC_BLOCK
5812 - check that all insns are in the basic blocks
5813 (except the switch handling code, barriers and notes)
5814 - check that all returns are followed by barriers
5816 In future it can be extended check a lot of other stuff as well
5817 (reachability of basic blocks, life information, etc. etc.). */
5819 void
5821 {
5825 rtx x;
5830 /* First pass check head/end pointers and set bb_info array used by
5831 later passes. */
5833 {
5836 /* Check the head pointer and make sure that it is pointing into
5837 insn list. */
5842 {
5846 }
5848 /* Check the end pointer and make sure that it is pointing into
5849 insn list. */
5851 {
5853 {
5857 }
5862 }
5864 {
5868 }
5869 }
5871 /* Now check the basic blocks (boundaries etc.) */
5873 {
5875 /* Check corectness of edge lists */
5876 edge e;
5880 {
5882 {
5891 }
5893 {
5898 {
5901 }
5902 }
5904 }
5908 {
5910 {
5918 }
5920 {
5925 {
5928 }
5929 }
5931 }
5933 /* OK pointers are correct. Now check the header of basic
5934 block. It ought to contain optional CODE_LABEL followed
5935 by NOTE_BASIC_BLOCK. */
5938 {
5940 {
5944 }
5946 }
5950 {
5954 }
5957 {
5958 /* Do checks for empty blocks here */
5959 }
5960 else
5961 {
5964 {
5967 {
5971 }
5979 {
5982 }
5985 }
5986 }
5987 }
5991 {
5993 {
5995 {
6001 /* An addr_vec is placed outside any block block. */
6006 {
6008 }
6010 /* But in any case, non-deletable labels can appear anywhere. */
6015 }
6016 }
6025 }
6030 /* Clean up. */
6032 }
6033 \f
6034 /* Functions to access an edge list with a vector representation.
6035 Enough data is kept such that given an index number, the
6036 pred and succ that edge reprsents can be determined, or
6037 given a pred and a succ, it's index number can be returned.
6038 This allows algorithms which comsume a lot of memory to
6039 represent the normally full matrix of edge (pred,succ) with a
6040 single indexed vector, edge (EDGE_INDEX (pred, succ)), with no
6041 wasted space in the client code due to sparse flow graphs. */
6043 /* This functions initializes the edge list. Basically the entire
6044 flowgraph is processed, and all edges are assigned a number,
6045 and the data structure is filed in. */
6048 {
6050 edge e;
6059 /* Determine the number of edges in the flow graph by counting successor
6060 edges on each basic block. */
6062 {
6066 num_edges++;
6067 }
6068 /* Don't forget successors of the entry block. */
6070 num_edges++;
6079 /* Follow successors of the entry block, and register these edges. */
6081 {
6083 num_edges++;
6084 }
6087 {
6090 /* Follow all successors of blocks, and register these edges. */
6092 {
6094 num_edges++;
6095 }
6096 }
6098 }
6100 /* This function free's memory associated with an edge list. */
6101 void
6104 {
6106 {
6109 }
6110 }
6112 /* This function provides debug output showing an edge list. */
6113 void
6117 {
6123 {
6127 else
6132 else
6134 }
6135 }
6137 /* This function provides an internal consistancy check of an edge list,
6138 verifying that all edges are present, and that there are no
6139 extra edges. */
6140 void
6144 {
6146 edge e;
6149 {
6153 {
6158 {
6161 }
6168 }
6169 }
6171 {
6176 {
6179 }
6186 }
6187 /* We've verified that all the edges are in the list, no lets make sure
6188 there are no spurious edges in the list. */
6192 {
6200 {
6203 }
6206 {
6209 }
6219 }
6221 {
6229 {
6232 }
6235 {
6238 }
6242 succ);
6248 }
6250 {
6258 {
6261 }
6264 {
6267 }
6271 pred);
6276 EXIT_BLOCK_PTR));
6277 }
6278 }
6280 /* This routine will determine what, if any, edge there is between
6281 a specified predecessor and successor. */
6283 int
6287 {
6290 {
6294 }
6296 }
6298 /* This function will remove an edge from the flow graph. */
6299 void
6301 edge e;
6302 {
6305 edge tmp;
6316 else
6326 else
6329 n_edges--;
6331 }
6333 /* This routine will remove any fake successor edges for a basic block.
6334 When the edge is removed, it is also removed from whatever predecessor
6335 list it is in. */
6336 static void
6338 basic_block bb;
6339 {
6340 edge e;
6342 {
6347 }
6348 }
6350 /* This routine will remove all fake edges from the flow graph. If
6351 we remove all fake successors, it will automatically remove all
6352 fake predecessors. */
6353 void
6355 {
6361 /* We've handled all successors except the entry block's. */
6363 }
6365 /* This functions will add a fake edge between any block which has no
6366 successors, and the exit block. Some data flow equations require these
6367 edges to exist. */
6368 void
6370 {
6376 }
6377 \f
6378 /* Dump the list of basic blocks in the bitmap NODES. */
6379 static void
6384 {
6390 }
6393 /* Dump the list of exiting edges in the array EDGES. */
6394 static void
6400 {
6407 }
6410 /* Dump loop related CFG information. */
6411 static void
6415 {
6422 {
6423 edge succ;
6429 }
6432 /* Dump the DFS node order. */
6434 {
6439 }
6440 }
6443 /* Return non-zero if the nodes of LOOP are a subset of OUTER. */
6444 static int
6448 {
6450 }
6453 /* Dump the loop information specified by LOOPS to the stream FILE. */
6454 void
6459 {
6471 {
6474 fprintf (file, ";; loop %d (%d to %d):\n;; header %d, latch %d, pre-header %d, depth %d, level %d, outer %ld\n",
6486 {
6490 {
6494 {
6500 /* If the union of LOOP and OLOOP is different than
6501 the larger of LOOP and OLOOP then LOOP and OLOOP
6502 must be disjoint. */
6508 }
6509 }
6510 }
6513 {
6514 /* Print diagnostics to compare our concept of a loop with
6515 what the loop notes say. */
6526 }
6527 }
6531 }
6534 /* Free all the memory allocated for LOOPS. */
6535 void
6538 {
6540 {
6546 /* Free the loop descriptors. */
6548 {
6555 }
6565 }
6566 }
6569 /* Find the exits from the loop using the bitmap of loop nodes NODES
6570 and store in EXITS array. Return the number of exits from the
6571 loop. */
6572 static int
6576 {
6577 edge e;
6583 /* Check all nodes within the loop to see if there are any
6584 successors not in the loop. Note that a node may have multiple
6585 exiting edges. */
6589 {
6593 num_exits++;
6594 }
6595 });
6602 /* Store all exiting edges into an array. */
6606 {
6611 }
6612 });
6615 }
6618 /* Find the nodes contained within the loop with header HEADER and
6619 latch LATCH and store in NODES. Return the number of nodes within
6620 the loop. */
6621 static int
6623 basic_block header;
6624 basic_block latch;
6625 sbitmap nodes;
6626 {
6634 /* Start with only the loop header in the set of loop nodes. */
6637 num_nodes++;
6640 /* Push the loop latch on to the stack. */
6642 {
6645 num_nodes++;
6647 }
6650 {
6651 basic_block node;
6652 edge e;
6656 {
6659 /* If each ancestor not marked as part of loop, add to set of
6660 loop nodes and push on to stack. */
6663 {
6666 num_nodes++;
6668 }
6669 }
6670 }
6673 }
6676 /* Compute the depth first search order and store in the array
6677 DFS_ORDER, marking the nodes visited in VISITED. Returns the
6678 number of nodes visited. */
6679 static int
6682 {
6683 edge e;
6687 sbitmap visited;
6689 /* Allocate stack for back-tracking up CFG. */
6693 /* Allocate bitmap to track nodes that have been visited. */
6696 /* None of the nodes in the CFG have been visited yet. */
6699 /* Start with the first successor edge from the entry block. */
6702 {
6706 /* Mark that we have visited this node. */
6710 /* If this node has not been visited before, push the current
6711 edge on to the stack and proceed with the first successor
6712 edge of this node. */
6715 {
6718 }
6719 else
6720 {
6723 {
6724 /* DEST has no successors (for example, a non-returning
6725 function is called) so do not push the current edge
6726 but carry on with its next successor. */
6729 }
6732 {
6735 /* Pop edge off stack. */
6738 }
6740 }
6741 }
6745 /* The number of nodes visited should not be greater than
6746 n_basic_blocks. */
6750 /* There are some nodes left in the CFG that are unreachable. */
6754 }
6757 /* Return the block for the pre-header of the loop with header
6758 HEADER where DOM specifies the dominator information. Return NULL if
6759 there is no pre-header. */
6760 static basic_block
6762 basic_block header;
6764 {
6765 basic_block pre_header;
6766 edge e;
6768 /* If block p is a predecessor of the header and is the only block
6769 that the header does not dominate, then it is the pre-header. */
6772 {
6777 {
6780 else
6781 {
6782 /* There are multiple edges into the header from outside
6783 the loop so there is no pre-header block. */
6786 }
6787 }
6788 }
6790 }
6793 /* Add LOOP to the loop hierarchy tree where PREVLOOP was the loop
6794 previously added. The insertion algorithm assumes that the loops
6795 are added in the order found by a depth first search of the CFG. */
6796 static void
6800 {
6803 {
6807 }
6810 {
6812 {
6816 }
6818 }
6822 }
6825 /* Build the loop hierarchy tree for LOOPS. */
6826 static void
6829 {
6837 /* Root the loop hierarchy tree with the first loop found.
6838 Since we used a depth first search this should be the
6839 outermost loop. */
6843 /* Add the remaining loops to the tree. */
6846 }
6849 /* Helper function to compute loop nesting depth and enclosed loop level
6850 for the natural loop specified by LOOP at the loop depth DEPTH.
6851 Returns the loop level. */
6852 static int
6856 {
6863 /* Traverse loop tree assigning depth and computing level as the
6864 maximum level of all the inner loops of this loop. The loop
6865 level is equivalent to the height of the loop in the loop tree
6866 and corresponds to the number of enclosed loop levels (including
6867 itself). */
6869 {
6876 }
6880 }
6883 /* Compute the loop nesting depth and enclosed loop level for the loop
6884 hierarchy tree specfied by LOOPS. Return the maximum enclosed loop
6885 level. */
6887 static int
6890 {
6895 /* Traverse all the outer level loops. */
6897 {
6901 }
6903 }
6906 /* Find all the natural loops in the function and save in LOOPS structure
6907 and recalculate loop_depth information in basic block structures.
6908 Return the number of natural loops found. */
6910 int
6913 {
6917 edge e;
6918 sbitmap headers;
6927 /* Taking care of this degenerate case makes the rest of
6928 this code simpler. */
6932 /* Compute the dominators. */
6936 /* Count the number of loop edges (back edges). This should be the
6937 same as the number of natural loops. Also clear the loop_depth
6938 and as we work from inner->outer in a loop nest we call
6939 find_loop_nodes_find which will increment loop_depth for nodes
6940 within the current loop, which happens to enclose inner loops. */
6944 {
6947 {
6950 /* Look for back edges where a predecessor is dominated
6951 by this block. A natural loop has a single entry
6952 node (header) that dominates all the nodes in the
6953 loop. It also has single back edge to the header
6954 from a latch node. Note that multiple natural loops
6955 may share the same header. */
6957 num_loops++;
6958 }
6959 }
6962 {
6963 /* Compute depth first search order of the CFG so that outer
6964 natural loops will be found before inner natural loops. */
6968 /* Allocate loop structures. */
6969 loops->array
6978 /* Find and record information about all the natural loops
6979 in the CFG. */
6982 {
6983 basic_block header;
6985 /* Search the nodes of the CFG in DFS order that we can find
6986 outer loops first. */
6989 /* Look for all the possible latch blocks for this header. */
6991 {
6994 /* Look for back edges where a predecessor is dominated
6995 by this block. A natural loop has a single entry
6996 node (header) that dominates all the nodes in the
6997 loop. It also has single back edge to the header
6998 from a latch node. Note that multiple natural loops
6999 may share the same header. */
7002 {
7010 /* Keep track of blocks that are loop headers so
7011 that we can tell which loops should be merged. */
7016 /* Find nodes contained within the loop. */
7018 loop->num_nodes
7021 /* Compute first and last blocks within the loop.
7022 These are often the same as the loop header and
7023 loop latch respectively, but this is not always
7024 the case. */
7025 loop->first
7027 loop->last
7030 /* Find edges which exit the loop. Note that a node
7031 may have several exit edges. */
7032 loop->num_exits
7035 /* Look to see if the loop has a pre-header node. */
7036 loop->pre_header
7039 num_loops++;
7040 }
7041 }
7042 }
7044 /* Natural loops with shared headers may either be disjoint or
7045 nested. Disjoint loops with shared headers cannot be inner
7046 loops and should be merged. For now just mark loops that share
7047 headers. */
7053 }
7057 /* Save CFG derived information to avoid recomputing it. */
7061 /* Build the loop hierarchy tree. */
7064 /* Assign the loop nesting depth and enclosed loop level for each
7065 loop. */
7069 }
7072 /* Return non-zero if edge E enters header of LOOP from outside of LOOP. */
7073 int
7076 edge e;
7077 {
7082 }
7085 /* Clear LOG_LINKS fields of insns in a chain. */
7086 void
7088 rtx insns;
7089 {
7090 rtx i;
7094 }