1 /* Save and restore call-clobbered registers which are live across a call.
2 Copyright (C) 1989, 1992, 1994, 1995, 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)
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. */
25 #include "insn-config.h"
28 #include "hard-reg-set.h"
30 #include "basic-block.h"
38 #define MAX_MOVE_MAX MOVE_MAX
41 #ifndef MIN_UNITS_PER_WORD
42 #define MIN_UNITS_PER_WORD UNITS_PER_WORD
45 #define MOVE_MAX_WORDS (MOVE_MAX / UNITS_PER_WORD)
47 /* Modes for each hard register that we can save. The smallest mode is wide
48 enough to save the entire contents of the register. When saving the
49 register because it is live we first try to save in multi-register modes.
50 If that is not possible the save is done one register at a time. */
52 static enum machine_mode
53 regno_save_mode[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MIN_UNITS_PER_WORD + 1];
55 /* For each hard register, a place on the stack where it can be saved,
59 regno_save_mem[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MIN_UNITS_PER_WORD + 1];
61 /* We will only make a register eligible for caller-save if it can be
62 saved in its widest mode with a simple SET insn as long as the memory
63 address is valid. We record the INSN_CODE is those insns here since
64 when we emit them, the addresses might not be valid, so they might not
68 reg_save_code[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MIN_UNITS_PER_WORD + 1];
70 reg_restore_code[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MIN_UNITS_PER_WORD + 1];
72 /* Set of hard regs currently residing in save area (during insn scan). */
74 static HARD_REG_SET hard_regs_saved;
76 /* Number of registers currently in hard_regs_saved. */
78 static int n_regs_saved;
80 /* Computed by mark_referenced_regs, all regs referenced in a given
82 static HARD_REG_SET referenced_regs;
84 /* Computed in mark_set_regs, holds all registers set by the current
86 static HARD_REG_SET this_insn_sets;
89 static void mark_set_regs PARAMS ((rtx, rtx, void *));
90 static void mark_referenced_regs PARAMS ((rtx));
91 static int insert_save PARAMS ((struct insn_chain *, int, int,
93 static int insert_restore PARAMS ((struct insn_chain *, int, int,
95 static struct insn_chain *insert_one_insn PARAMS ((struct insn_chain *, int,
96 enum insn_code, rtx));
97 static void add_stored_regs PARAMS ((rtx, rtx, void *));
99 /* Initialize for caller-save.
101 Look at all the hard registers that are used by a call and for which
102 regclass.c has not already excluded from being used across a call.
104 Ensure that we can find a mode to save the register and that there is a
105 simple insn to save and restore the register. This latter check avoids
106 problems that would occur if we tried to save the MQ register of some
107 machines directly into memory. */
112 char *first_obj = (char *) oballoc (0);
118 /* First find all the registers that we need to deal with and all
119 the modes that they can have. If we can't find a mode to use,
120 we can't have the register live over calls. */
122 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
124 if (call_used_regs[i] && ! call_fixed_regs[i])
126 for (j = 1; j <= MOVE_MAX_WORDS; j++)
128 regno_save_mode[i][j] = HARD_REGNO_CALLER_SAVE_MODE (i, j);
129 if (regno_save_mode[i][j] == VOIDmode && j == 1)
131 call_fixed_regs[i] = 1;
132 SET_HARD_REG_BIT (call_fixed_reg_set, i);
137 regno_save_mode[i][1] = VOIDmode;
140 /* The following code tries to approximate the conditions under which
141 we can easily save and restore a register without scratch registers or
142 other complexities. It will usually work, except under conditions where
143 the validity of an insn operand is dependent on the address offset.
144 No such cases are currently known.
146 We first find a typical offset from some BASE_REG_CLASS register.
147 This address is chosen by finding the first register in the class
148 and by finding the smallest power of two that is a valid offset from
149 that register in every mode we will use to save registers. */
151 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
152 if (TEST_HARD_REG_BIT (reg_class_contents[(int) BASE_REG_CLASS], i))
155 if (i == FIRST_PSEUDO_REGISTER)
158 addr_reg = gen_rtx_REG (Pmode, i);
160 for (offset = 1 << (HOST_BITS_PER_INT / 2); offset; offset >>= 1)
162 address = gen_rtx_PLUS (Pmode, addr_reg, GEN_INT (offset));
164 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
165 if (regno_save_mode[i][1] != VOIDmode
166 && ! strict_memory_address_p (regno_save_mode[i][1], address))
169 if (i == FIRST_PSEUDO_REGISTER)
173 /* If we didn't find a valid address, we must use register indirect. */
177 /* Next we try to form an insn to save and restore the register. We
178 see if such an insn is recognized and meets its constraints. */
182 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
183 for (j = 1; j <= MOVE_MAX_WORDS; j++)
184 if (regno_save_mode[i][j] != VOIDmode)
186 rtx mem = gen_rtx_MEM (regno_save_mode[i][j], address);
187 rtx reg = gen_rtx_REG (regno_save_mode[i][j], i);
188 rtx savepat = gen_rtx_SET (VOIDmode, mem, reg);
189 rtx restpat = gen_rtx_SET (VOIDmode, reg, mem);
190 rtx saveinsn = emit_insn (savepat);
191 rtx restinsn = emit_insn (restpat);
194 reg_save_code[i][j] = recog_memoized (saveinsn);
195 reg_restore_code[i][j] = recog_memoized (restinsn);
197 /* Now extract both insns and see if we can meet their
199 ok = (reg_save_code[i][j] != (enum insn_code)-1
200 && reg_restore_code[i][j] != (enum insn_code)-1);
203 extract_insn (saveinsn);
204 ok = constrain_operands (1);
205 extract_insn (restinsn);
206 ok &= constrain_operands (1);
211 regno_save_mode[i][j] = VOIDmode;
214 call_fixed_regs[i] = 1;
215 SET_HARD_REG_BIT (call_fixed_reg_set, i);
225 /* Initialize save areas by showing that we haven't allocated any yet. */
232 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
233 for (j = 1; j <= MOVE_MAX_WORDS; j++)
234 regno_save_mem[i][j] = 0;
237 /* Allocate save areas for any hard registers that might need saving.
238 We take a conservative approach here and look for call-clobbered hard
239 registers that are assigned to pseudos that cross calls. This may
240 overestimate slightly (especially if some of these registers are later
241 used as spill registers), but it should not be significant.
245 In the fallback case we should iterate backwards across all possible
246 modes for the save, choosing the largest available one instead of
247 falling back to the smallest mode immediately. (eg TF -> DF -> SF).
249 We do not try to use "move multiple" instructions that exist
250 on some machines (such as the 68k moveml). It could be a win to try
251 and use them when possible. The hard part is doing it in a way that is
252 machine independent since they might be saving non-consecutive
253 registers. (imagine caller-saving d0,d1,a0,a1 on the 68k) */
260 HARD_REG_SET hard_regs_used;
262 /* Allocate space in the save area for the largest multi-register
263 pseudos first, then work backwards to single register
266 /* Find and record all call-used hard-registers in this function. */
267 CLEAR_HARD_REG_SET (hard_regs_used);
268 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
269 if (reg_renumber[i] >= 0 && REG_N_CALLS_CROSSED (i) > 0)
271 unsigned int regno = reg_renumber[i];
272 unsigned int endregno
273 = regno + HARD_REGNO_NREGS (regno, GET_MODE (regno_reg_rtx[i]));
275 for (r = regno; r < endregno; r++)
276 if (call_used_regs[r])
277 SET_HARD_REG_BIT (hard_regs_used, r);
280 /* Now run through all the call-used hard-registers and allocate
281 space for them in the caller-save area. Try to allocate space
282 in a manner which allows multi-register saves/restores to be done. */
284 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
285 for (j = MOVE_MAX_WORDS; j > 0; j--)
289 /* If no mode exists for this size, try another. Also break out
290 if we have already saved this hard register. */
291 if (regno_save_mode[i][j] == VOIDmode || regno_save_mem[i][1] != 0)
294 /* See if any register in this group has been saved. */
295 for (k = 0; k < j; k++)
296 if (regno_save_mem[i + k][1])
304 for (k = 0; k < j; k++)
305 if (! TEST_HARD_REG_BIT (hard_regs_used, i + k))
313 /* We have found an acceptable mode to store in. */
315 = assign_stack_local (regno_save_mode[i][j],
316 GET_MODE_SIZE (regno_save_mode[i][j]), 0);
318 /* Setup single word save area just in case... */
319 for (k = 0; k < j; k++)
321 /* This should not depend on WORDS_BIG_ENDIAN.
322 The order of words in regs is the same as in memory. */
323 rtx temp = gen_rtx_MEM (regno_save_mode[i + k][1],
324 XEXP (regno_save_mem[i][j], 0));
326 regno_save_mem[i + k][1]
327 = adj_offsettable_operand (temp, k * UNITS_PER_WORD);
331 /* Now loop again and set the alias set of any save areas we made to
332 the alias set used to represent frame objects. */
333 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
334 for (j = MOVE_MAX_WORDS; j > 0; j--)
335 if (regno_save_mem[i][j] != 0)
336 MEM_ALIAS_SET (regno_save_mem[i][j]) = get_frame_alias_set ();
339 /* Find the places where hard regs are live across calls and save them. */
342 save_call_clobbered_regs ()
344 struct insn_chain *chain, *next;
346 CLEAR_HARD_REG_SET (hard_regs_saved);
349 for (chain = reload_insn_chain; chain != 0; chain = next)
351 rtx insn = chain->insn;
352 enum rtx_code code = GET_CODE (insn);
356 if (chain->is_caller_save_insn)
359 if (GET_RTX_CLASS (code) == 'i')
361 /* If some registers have been saved, see if INSN references
362 any of them. We must restore them before the insn if so. */
368 if (code == JUMP_INSN)
369 /* Restore all registers if this is a JUMP_INSN. */
370 COPY_HARD_REG_SET (referenced_regs, hard_regs_saved);
373 CLEAR_HARD_REG_SET (referenced_regs);
374 mark_referenced_regs (PATTERN (insn));
375 AND_HARD_REG_SET (referenced_regs, hard_regs_saved);
378 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
379 if (TEST_HARD_REG_BIT (referenced_regs, regno))
380 regno += insert_restore (chain, 1, regno, MOVE_MAX_WORDS);
383 if (code == CALL_INSN)
386 HARD_REG_SET hard_regs_to_save;
388 /* Use the register life information in CHAIN to compute which
389 regs are live during the call. */
390 REG_SET_TO_HARD_REG_SET (hard_regs_to_save,
391 &chain->live_throughout);
392 compute_use_by_pseudos (&hard_regs_to_save,
393 &chain->live_throughout);
395 /* Record all registers set in this call insn. These don't need
396 to be saved. N.B. the call insn might set a subreg of a
397 multi-hard-reg pseudo; then the pseudo is considered live
398 during the call, but the subreg that is set isn't. */
399 CLEAR_HARD_REG_SET (this_insn_sets);
400 note_stores (PATTERN (insn), mark_set_regs, NULL);
402 /* Compute which hard regs must be saved before this call. */
403 AND_COMPL_HARD_REG_SET (hard_regs_to_save, call_fixed_reg_set);
404 AND_COMPL_HARD_REG_SET (hard_regs_to_save, this_insn_sets);
405 AND_COMPL_HARD_REG_SET (hard_regs_to_save, hard_regs_saved);
406 AND_HARD_REG_SET (hard_regs_to_save, call_used_reg_set);
408 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
409 if (TEST_HARD_REG_BIT (hard_regs_to_save, regno))
410 regno += insert_save (chain, 1, regno, &hard_regs_to_save);
412 /* Must recompute n_regs_saved. */
414 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
415 if (TEST_HARD_REG_BIT (hard_regs_saved, regno))
420 if (chain->next == 0 || chain->next->block > chain->block)
423 /* At the end of the basic block, we must restore any registers that
424 remain saved. If the last insn in the block is a JUMP_INSN, put
425 the restore before the insn, otherwise, put it after the insn. */
428 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
429 if (TEST_HARD_REG_BIT (hard_regs_saved, regno))
430 regno += insert_restore (chain, GET_CODE (insn) == JUMP_INSN,
431 regno, MOVE_MAX_WORDS);
436 /* Here from note_stores when an insn stores a value in a register.
437 Set the proper bit or bits in this_insn_sets. All pseudos that have
438 been assigned hard regs have had their register number changed already,
439 so we can ignore pseudos. */
441 mark_set_regs (reg, setter, data)
443 rtx setter ATTRIBUTE_UNUSED;
444 void *data ATTRIBUTE_UNUSED;
446 register int regno, endregno, i;
447 enum machine_mode mode = GET_MODE (reg);
450 if (GET_CODE (reg) == SUBREG)
452 word = SUBREG_WORD (reg);
453 reg = SUBREG_REG (reg);
456 if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
459 regno = REGNO (reg) + word;
460 endregno = regno + HARD_REGNO_NREGS (regno, mode);
462 for (i = regno; i < endregno; i++)
463 SET_HARD_REG_BIT (this_insn_sets, i);
466 /* Here from note_stores when an insn stores a value in a register.
467 Set the proper bit or bits in the passed regset. All pseudos that have
468 been assigned hard regs have had their register number changed already,
469 so we can ignore pseudos. */
471 add_stored_regs (reg, setter, data)
476 register int regno, endregno, i;
477 enum machine_mode mode = GET_MODE (reg);
480 if (GET_CODE (setter) == CLOBBER)
483 while (GET_CODE (reg) == SUBREG)
485 word += SUBREG_WORD (reg);
486 reg = SUBREG_REG (reg);
489 if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
492 regno = REGNO (reg) + word;
493 endregno = regno + HARD_REGNO_NREGS (regno, mode);
495 for (i = regno; i < endregno; i++)
496 SET_REGNO_REG_SET ((regset) data, i);
499 /* Walk X and record all referenced registers in REFERENCED_REGS. */
501 mark_referenced_regs (x)
504 enum rtx_code code = GET_CODE (x);
509 mark_referenced_regs (SET_SRC (x));
510 if (code == SET || code == CLOBBER)
514 if (code == REG || code == PC || code == CC0
515 || (code == SUBREG && GET_CODE (SUBREG_REG (x)) == REG))
518 if (code == MEM || code == SUBREG)
526 int regno = REGNO (x);
527 int hardregno = (regno < FIRST_PSEUDO_REGISTER ? regno
528 : reg_renumber[regno]);
532 int nregs = HARD_REGNO_NREGS (hardregno, GET_MODE (x));
534 SET_HARD_REG_BIT (referenced_regs, hardregno + nregs);
536 /* If this is a pseudo that did not get a hard register, scan its
537 memory location, since it might involve the use of another
538 register, which might be saved. */
539 else if (reg_equiv_mem[regno] != 0)
540 mark_referenced_regs (XEXP (reg_equiv_mem[regno], 0));
541 else if (reg_equiv_address[regno] != 0)
542 mark_referenced_regs (reg_equiv_address[regno]);
546 fmt = GET_RTX_FORMAT (code);
547 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
550 mark_referenced_regs (XEXP (x, i));
551 else if (fmt[i] == 'E')
552 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
553 mark_referenced_regs (XVECEXP (x, i, j));
557 /* Insert a sequence of insns to restore. Place these insns in front of
558 CHAIN if BEFORE_P is nonzero, behind the insn otherwise. MAXRESTORE is
559 the maximum number of registers which should be restored during this call.
560 It should never be less than 1 since we only work with entire registers.
562 Note that we have verified in init_caller_save that we can do this
563 with a simple SET, so use it. Set INSN_CODE to what we save there
564 since the address might not be valid so the insn might not be recognized.
565 These insns will be reloaded and have register elimination done by
566 find_reload, so we need not worry about that here.
568 Return the extra number of registers saved. */
571 insert_restore (chain, before_p, regno, maxrestore)
572 struct insn_chain *chain;
579 enum insn_code code = CODE_FOR_nothing;
581 struct insn_chain *new;
583 /* A common failure mode if register status is not correct in the RTL
584 is for this routine to be called with a REGNO we didn't expect to
585 save. That will cause us to write an insn with a (nil) SET_DEST
586 or SET_SRC. Instead of doing so and causing a crash later, check
587 for this common case and abort here instead. This will remove one
588 step in debugging such problems. */
590 if (regno_save_mem[regno][1] == 0)
593 /* Get the pattern to emit and update our status.
595 See if we can restore `maxrestore' registers at once. Work
596 backwards to the single register case. */
597 for (i = maxrestore; i > 0; i--)
602 if (regno_save_mem[regno][i] == 0)
605 for (j = 0; j < i; j++)
606 if (! TEST_HARD_REG_BIT (hard_regs_saved, regno + j))
611 /* Must do this one restore at a time */
619 pat = gen_rtx_SET (VOIDmode,
620 gen_rtx_REG (GET_MODE (regno_save_mem[regno][numregs]),
622 regno_save_mem[regno][numregs]);
623 code = reg_restore_code[regno][numregs];
624 new = insert_one_insn (chain, before_p, code, pat);
626 /* Clear status for all registers we restored. */
627 for (k = 0; k < i; k++)
629 CLEAR_HARD_REG_BIT (hard_regs_saved, regno + k);
630 SET_REGNO_REG_SET (&new->dead_or_set, regno + k);
636 /* Tell our callers how many extra registers we saved/restored */
640 /* Like insert_restore above, but save registers instead. */
642 insert_save (chain, before_p, regno, to_save)
643 struct insn_chain *chain;
646 HARD_REG_SET *to_save;
650 enum insn_code code = CODE_FOR_nothing;
652 struct insn_chain *new;
654 /* A common failure mode if register status is not correct in the RTL
655 is for this routine to be called with a REGNO we didn't expect to
656 save. That will cause us to write an insn with a (nil) SET_DEST
657 or SET_SRC. Instead of doing so and causing a crash later, check
658 for this common case and abort here instead. This will remove one
659 step in debugging such problems. */
661 if (regno_save_mem[regno][1] == 0)
664 /* Get the pattern to emit and update our status.
666 See if we can save several registers with a single instruction.
667 Work backwards to the single register case. */
668 for (i = MOVE_MAX_WORDS; i > 0; i--)
672 if (regno_save_mem[regno][i] == 0)
675 for (j = 0; j < i; j++)
676 if (! TEST_HARD_REG_BIT (*to_save, regno + j))
681 /* Must do this one save at a time */
689 pat = gen_rtx_SET (VOIDmode, regno_save_mem[regno][numregs],
690 gen_rtx_REG (GET_MODE (regno_save_mem[regno][numregs]),
692 code = reg_save_code[regno][numregs];
693 new = insert_one_insn (chain, before_p, code, pat);
695 /* Set hard_regs_saved and dead_or_set for all the registers we saved. */
696 for (k = 0; k < numregs; k++)
698 SET_HARD_REG_BIT (hard_regs_saved, regno + k);
699 SET_REGNO_REG_SET (&new->dead_or_set, regno + k);
703 /* Tell our callers how many extra registers we saved/restored */
707 /* Emit a new caller-save insn and set the code. */
708 static struct insn_chain *
709 insert_one_insn (chain, before_p, code, pat)
710 struct insn_chain *chain;
715 rtx insn = chain->insn;
716 struct insn_chain *new;
719 /* If INSN references CC0, put our insns in front of the insn that sets
720 CC0. This is always safe, since the only way we could be passed an
721 insn that references CC0 is for a restore, and doing a restore earlier
722 isn't a problem. We do, however, assume here that CALL_INSNs don't
723 reference CC0. Guard against non-INSN's like CODE_LABEL. */
725 if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
727 && reg_referenced_p (cc0_rtx, PATTERN (insn)))
728 chain = chain->prev, insn = chain->insn;
731 new = new_insn_chain ();
736 new->prev = chain->prev;
738 new->prev->next = new;
740 reload_insn_chain = new;
744 new->insn = emit_insn_before (pat, insn);
745 /* ??? It would be nice if we could exclude the already / still saved
746 registers from the live sets. */
747 COPY_REG_SET (&new->live_throughout, &chain->live_throughout);
748 /* Registers that die in CHAIN->INSN still live in the new insn. */
749 for (link = REG_NOTES (chain->insn); link; link = XEXP (link, 1))
751 if (REG_NOTE_KIND (link) == REG_DEAD)
753 rtx reg = XEXP (link, 0);
756 if (GET_CODE (reg) != REG)
760 if (regno >= FIRST_PSEUDO_REGISTER)
761 regno = reg_renumber[regno];
764 for (i = HARD_REGNO_NREGS (regno, GET_MODE (reg)) - 1;
766 SET_REGNO_REG_SET (&new->live_throughout, regno + i);
769 CLEAR_REG_SET (&new->dead_or_set);
770 if (chain->insn == BLOCK_HEAD (chain->block))
771 BLOCK_HEAD (chain->block) = new->insn;
775 new->next = chain->next;
777 new->next->prev = new;
780 new->insn = emit_insn_after (pat, insn);
781 /* ??? It would be nice if we could exclude the already / still saved
782 registers from the live sets, and observe REG_UNUSED notes. */
783 COPY_REG_SET (&new->live_throughout, &chain->live_throughout);
784 /* Registers that are set in CHAIN->INSN live in the new insn.
785 (Unless there is a REG_UNUSED note for them, but we don't
786 look for them here.) */
787 note_stores (PATTERN (chain->insn), add_stored_regs,
788 &new->live_throughout);
789 CLEAR_REG_SET (&new->dead_or_set);
790 if (chain->insn == BLOCK_END (chain->block))
791 BLOCK_END (chain->block) = new->insn;
793 new->block = chain->block;
794 new->is_caller_save_insn = 1;
796 INSN_CODE (new->insn) = code;