1 /* Save and restore call-clobbered registers which are live across a call.
2 Copyright (C) 1989, 1992, 1994, 1995, 1997 Free Software Foundation, Inc.
4 This file is part of GNU CC.
6 GNU CC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 GNU CC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU CC; see the file COPYING. If not, write to
18 the Free Software Foundation, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
23 #include "insn-config.h"
26 #include "hard-reg-set.h"
28 #include "basic-block.h"
33 #define MAX_MOVE_MAX MOVE_MAX
36 #ifndef MIN_UNITS_PER_WORD
37 #define MIN_UNITS_PER_WORD UNITS_PER_WORD
40 /* Modes for each hard register that we can save. The smallest mode is wide
41 enough to save the entire contents of the register. When saving the
42 register because it is live we first try to save in multi-register modes.
43 If that is not possible the save is done one register at a time. */
45 static enum machine_mode
46 regno_save_mode[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MIN_UNITS_PER_WORD + 1];
48 /* For each hard register, a place on the stack where it can be saved,
52 regno_save_mem[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MIN_UNITS_PER_WORD + 1];
54 /* We will only make a register eligible for caller-save if it can be
55 saved in its widest mode with a simple SET insn as long as the memory
56 address is valid. We record the INSN_CODE is those insns here since
57 when we emit them, the addresses might not be valid, so they might not
61 reg_save_code[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MIN_UNITS_PER_WORD + 1];
63 reg_restore_code[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MIN_UNITS_PER_WORD + 1];
65 /* Set of hard regs currently live (during scan of all insns). */
67 static HARD_REG_SET hard_regs_live;
69 /* Set of hard regs currently residing in save area (during insn scan). */
71 static HARD_REG_SET hard_regs_saved;
73 /* Set of hard regs which need to be restored before referenced. */
75 static HARD_REG_SET hard_regs_need_restore;
77 /* Number of registers currently in hard_regs_saved. */
81 static void set_reg_live PROTO((rtx, rtx));
82 static void clear_reg_live PROTO((rtx));
83 static void restore_referenced_regs PROTO((rtx, rtx, enum machine_mode));
84 static int insert_save_restore PROTO((rtx, int, int,
85 enum machine_mode, int));
87 /* Initialize for caller-save.
89 Look at all the hard registers that are used by a call and for which
90 regclass.c has not already excluded from being used across a call.
92 Ensure that we can find a mode to save the register and that there is a
93 simple insn to save and restore the register. This latter check avoids
94 problems that would occur if we tried to save the MQ register of some
95 machines directly into memory. */
100 char *first_obj = (char *) oballoc (0);
106 /* First find all the registers that we need to deal with and all
107 the modes that they can have. If we can't find a mode to use,
108 we can't have the register live over calls. */
110 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
112 if (call_used_regs[i] && ! call_fixed_regs[i])
114 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
116 regno_save_mode[i][j] = choose_hard_reg_mode (i, j);
117 if (regno_save_mode[i][j] == VOIDmode && j == 1)
119 call_fixed_regs[i] = 1;
120 SET_HARD_REG_BIT (call_fixed_reg_set, i);
125 regno_save_mode[i][1] = VOIDmode;
128 /* The following code tries to approximate the conditions under which
129 we can easily save and restore a register without scratch registers or
130 other complexities. It will usually work, except under conditions where
131 the validity of an insn operand is dependent on the address offset.
132 No such cases are currently known.
134 We first find a typical offset from some BASE_REG_CLASS register.
135 This address is chosen by finding the first register in the class
136 and by finding the smallest power of two that is a valid offset from
137 that register in every mode we will use to save registers. */
139 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
140 if (TEST_HARD_REG_BIT (reg_class_contents[(int) BASE_REG_CLASS], i))
143 if (i == FIRST_PSEUDO_REGISTER)
146 addr_reg = gen_rtx (REG, Pmode, i);
148 for (offset = 1 << (HOST_BITS_PER_INT / 2); offset; offset >>= 1)
150 address = gen_rtx (PLUS, Pmode, addr_reg, GEN_INT (offset));
152 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
153 if (regno_save_mode[i][1] != VOIDmode
154 && ! strict_memory_address_p (regno_save_mode[i][1], address))
157 if (i == FIRST_PSEUDO_REGISTER)
161 /* If we didn't find a valid address, we must use register indirect. */
165 /* Next we try to form an insn to save and restore the register. We
166 see if such an insn is recognized and meets its constraints. */
170 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
171 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
172 if (regno_save_mode[i][j] != VOIDmode)
174 rtx mem = gen_rtx (MEM, regno_save_mode[i][j], address);
175 rtx reg = gen_rtx (REG, regno_save_mode[i][j], i);
176 rtx savepat = gen_rtx (SET, VOIDmode, mem, reg);
177 rtx restpat = gen_rtx (SET, VOIDmode, reg, mem);
178 rtx saveinsn = emit_insn (savepat);
179 rtx restinsn = emit_insn (restpat);
182 reg_save_code[i][j] = recog_memoized (saveinsn);
183 reg_restore_code[i][j] = recog_memoized (restinsn);
185 /* Now extract both insns and see if we can meet their
187 ok = (reg_save_code[i][j] != -1 && reg_restore_code[i][j] != -1);
190 insn_extract (saveinsn);
191 ok = constrain_operands (reg_save_code[i][j], 1);
192 insn_extract (restinsn);
193 ok &= constrain_operands (reg_restore_code[i][j], 1);
198 regno_save_mode[i][j] = VOIDmode;
201 call_fixed_regs[i] = 1;
202 SET_HARD_REG_BIT (call_fixed_reg_set, i);
212 /* Initialize save areas by showing that we haven't allocated any yet. */
219 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
220 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
221 regno_save_mem[i][j] = 0;
224 /* Allocate save areas for any hard registers that might need saving.
225 We take a conservative approach here and look for call-clobbered hard
226 registers that are assigned to pseudos that cross calls. This may
227 overestimate slightly (especially if some of these registers are later
228 used as spill registers), but it should not be significant.
230 Then perform register elimination in the addresses of the save area
231 locations; return 1 if all eliminated addresses are strictly valid.
232 We assume that our caller has set up the elimination table to the
233 worst (largest) possible offsets.
235 Set *PCHANGED to 1 if we had to allocate some memory for the save area.
239 In the fallback case we should iterate backwards across all possible
240 modes for the save, choosing the largest available one instead of
241 falling back to the smallest mode immediately. (eg TF -> DF -> SF).
243 We do not try to use "move multiple" instructions that exist
244 on some machines (such as the 68k moveml). It could be a win to try
245 and use them when possible. The hard part is doing it in a way that is
246 machine independent since they might be saving non-consecutive
247 registers. (imagine caller-saving d0,d1,a0,a1 on the 68k) */
250 setup_save_areas (pchanged)
254 HARD_REG_SET hard_regs_used;
258 /* Allocate space in the save area for the largest multi-register
259 pseudos first, then work backwards to single register
262 /* Find and record all call-used hard-registers in this function. */
263 CLEAR_HARD_REG_SET (hard_regs_used);
264 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
265 if (reg_renumber[i] >= 0 && reg_n_calls_crossed[i] > 0)
267 int regno = reg_renumber[i];
269 = regno + HARD_REGNO_NREGS (regno, GET_MODE (regno_reg_rtx[i]));
270 int nregs = endregno - regno;
272 for (j = 0; j < nregs; j++)
274 if (call_used_regs[regno+j])
275 SET_HARD_REG_BIT (hard_regs_used, regno+j);
279 /* Now run through all the call-used hard-registers and allocate
280 space for them in the caller-save area. Try to allocate space
281 in a manner which allows multi-register saves/restores to be done. */
283 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
284 for (j = MOVE_MAX / UNITS_PER_WORD; 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. */
296 for (k = 0; k < j; k++)
297 if (regno_save_mem[i + k][1])
305 for (k = 0; k < j; k++)
308 ok &= (TEST_HARD_REG_BIT (hard_regs_used, regno) != 0);
311 /* We have found an acceptable mode to store in. */
316 = assign_stack_local (regno_save_mode[i][j],
317 GET_MODE_SIZE (regno_save_mode[i][j]), 0);
319 /* Setup single word save area just in case... */
320 for (k = 0; k < j; k++)
322 /* This should not depend on WORDS_BIG_ENDIAN.
323 The order of words in regs is the same as in memory. */
324 rtx temp = gen_rtx (MEM, regno_save_mode[i+k][1],
325 XEXP (regno_save_mem[i][j], 0));
327 regno_save_mem[i+k][1]
328 = adj_offsettable_operand (temp, k * UNITS_PER_WORD);
334 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
335 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
336 if (regno_save_mem[i][j] != 0)
337 ok &= strict_memory_address_p (GET_MODE (regno_save_mem[i][j]),
338 XEXP (eliminate_regs (regno_save_mem[i][j], 0, NULL_RTX, 1), 0));
343 /* Find the places where hard regs are live across calls and save them.
345 INSN_MODE is the mode to assign to any insns that we add. This is used
346 by reload to determine whether or not reloads or register eliminations
347 need be done on these insns. */
350 save_call_clobbered_regs (insn_mode)
351 enum machine_mode insn_mode;
356 for (b = 0; b < n_basic_blocks; b++)
358 regset regs_live = basic_block_live_at_start[b];
359 rtx prev_block_last = PREV_INSN (basic_block_head[b]);
364 /* Compute hard regs live at start of block -- this is the
365 real hard regs marked live, plus live pseudo regs that
366 have been renumbered to hard regs. No registers have yet been
367 saved because we restore all of them before the end of the basic
371 hard_regs_live = *regs_live;
373 COPY_HARD_REG_SET (hard_regs_live, regs_live);
376 CLEAR_HARD_REG_SET (hard_regs_saved);
377 CLEAR_HARD_REG_SET (hard_regs_need_restore);
380 for (offset = 0, i = 0; offset < regset_size; offset++)
382 if (regs_live[offset] == 0)
383 i += REGSET_ELT_BITS;
385 for (bit = 1; bit && i < max_regno; bit <<= 1, i++)
386 if ((regs_live[offset] & bit)
387 && (regno = reg_renumber[i]) >= 0)
389 j < regno + HARD_REGNO_NREGS (regno,
390 PSEUDO_REGNO_MODE (i));
392 SET_HARD_REG_BIT (hard_regs_live, j);
396 /* Now scan the insns in the block, keeping track of what hard
397 regs are live as we go. When we see a call, save the live
398 call-clobbered hard regs. */
400 for (insn = basic_block_head[b]; ; insn = NEXT_INSN (insn))
402 RTX_CODE code = GET_CODE (insn);
404 if (GET_RTX_CLASS (code) == 'i')
408 /* If some registers have been saved, see if INSN references
409 any of them. We must restore them before the insn if so. */
412 restore_referenced_regs (PATTERN (insn), insn, insn_mode);
414 /* NB: the normal procedure is to first enliven any
415 registers set by insn, then deaden any registers that
416 had their last use at insn. This is incorrect now,
417 since multiple pseudos may have been mapped to the
418 same hard reg, and the death notes are ambiguous. So
419 it must be done in the other, safe, order. */
421 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
422 if (REG_NOTE_KIND (link) == REG_DEAD)
423 clear_reg_live (XEXP (link, 0));
425 /* When we reach a call, we need to save all registers that are
426 live, call-used, not fixed, and not already saved. We must
427 test at this point because registers that die in a CALL_INSN
428 are not live across the call and likewise for registers that
429 are born in the CALL_INSN.
431 If registers are filled with parameters for this function,
432 and some of these are also being set by this function, then
433 they will not appear to die (no REG_DEAD note for them),
434 to check if in fact they do, collect the set registers in
435 hard_regs_live first. */
437 if (code == CALL_INSN)
439 HARD_REG_SET this_call_sets;
441 HARD_REG_SET old_hard_regs_live;
443 /* Save the hard_regs_live information. */
444 COPY_HARD_REG_SET (old_hard_regs_live, hard_regs_live);
446 /* Now calculate hard_regs_live for this CALL_INSN
448 CLEAR_HARD_REG_SET (hard_regs_live);
449 note_stores (PATTERN (insn), set_reg_live);
450 COPY_HARD_REG_SET (this_call_sets, hard_regs_live);
452 /* Restore the hard_regs_live information. */
453 COPY_HARD_REG_SET (hard_regs_live, old_hard_regs_live);
456 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
457 if (call_used_regs[regno] && ! call_fixed_regs[regno]
458 && TEST_HARD_REG_BIT (hard_regs_live, regno)
459 /* It must not be set by this instruction. */
460 && ! TEST_HARD_REG_BIT (this_call_sets, regno)
461 && ! TEST_HARD_REG_BIT (hard_regs_saved, regno))
462 regno += insert_save_restore (insn, 1, regno,
465 /* Put the information for this CALL_INSN on top of what
467 IOR_HARD_REG_SET (hard_regs_live, this_call_sets);
468 COPY_HARD_REG_SET (hard_regs_need_restore, hard_regs_saved);
470 /* Must recompute n_regs_saved. */
472 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
473 if (TEST_HARD_REG_BIT (hard_regs_saved, regno))
478 note_stores (PATTERN (insn), set_reg_live);
480 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
481 if (REG_NOTE_KIND (link) == REG_INC)
482 set_reg_live (XEXP (link, 0), NULL_RTX);
486 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
487 if (REG_NOTE_KIND (link) == REG_UNUSED)
488 clear_reg_live (XEXP (link, 0));
491 if (insn == basic_block_end[b])
495 /* At the end of the basic block, we must restore any registers that
496 remain saved. If the last insn in the block is a JUMP_INSN, put
497 the restore before the insn, otherwise, put it after the insn. */
500 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
501 if (TEST_HARD_REG_BIT (hard_regs_need_restore, regno))
502 regno += insert_save_restore ((GET_CODE (insn) == JUMP_INSN
503 ? insn : NEXT_INSN (insn)), 0,
504 regno, insn_mode, MOVE_MAX / UNITS_PER_WORD);
506 /* If we added any insns at the start of the block, update the start
507 of the block to point at those insns. */
508 basic_block_head[b] = NEXT_INSN (prev_block_last);
512 /* Here from note_stores when an insn stores a value in a register.
513 Set the proper bit or bits in hard_regs_live. All pseudos that have
514 been assigned hard regs have had their register number changed already,
515 so we can ignore pseudos. */
518 set_reg_live (reg, setter)
521 register int regno, endregno, i;
522 enum machine_mode mode = GET_MODE (reg);
525 if (GET_CODE (reg) == SUBREG)
527 word = SUBREG_WORD (reg);
528 reg = SUBREG_REG (reg);
531 if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
534 regno = REGNO (reg) + word;
535 endregno = regno + HARD_REGNO_NREGS (regno, mode);
537 for (i = regno; i < endregno; i++)
539 SET_HARD_REG_BIT (hard_regs_live, i);
540 CLEAR_HARD_REG_BIT (hard_regs_saved, i);
541 CLEAR_HARD_REG_BIT (hard_regs_need_restore, i);
545 /* Here when a REG_DEAD note records the last use of a reg. Clear
546 the appropriate bit or bits in hard_regs_live. Again we can ignore
553 register int regno, endregno, i;
555 if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
559 endregno= regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
561 for (i = regno; i < endregno; i++)
563 CLEAR_HARD_REG_BIT (hard_regs_live, i);
564 CLEAR_HARD_REG_BIT (hard_regs_need_restore, i);
565 CLEAR_HARD_REG_BIT (hard_regs_saved, i);
569 /* If any register currently residing in the save area is referenced in X,
570 which is part of INSN, emit code to restore the register in front of INSN.
571 INSN_MODE is the mode to assign to any insns that we add. */
574 restore_referenced_regs (x, insn, insn_mode)
577 enum machine_mode insn_mode;
579 enum rtx_code code = GET_CODE (x);
588 int regno = REGNO (x);
590 /* If this is a pseudo, scan its memory location, since it might
591 involve the use of another register, which might be saved. */
593 if (regno >= FIRST_PSEUDO_REGISTER
594 && reg_equiv_mem[regno] != 0)
595 restore_referenced_regs (XEXP (reg_equiv_mem[regno], 0),
597 else if (regno >= FIRST_PSEUDO_REGISTER
598 && reg_equiv_address[regno] != 0)
599 restore_referenced_regs (reg_equiv_address[regno],
602 /* Otherwise if this is a hard register, restore any piece of it that
603 is currently saved. */
605 else if (regno < FIRST_PSEUDO_REGISTER)
607 int numregs = HARD_REGNO_NREGS (regno, GET_MODE (x));
608 /* Save at most SAVEREGS at a time. This can not be larger than
609 MOVE_MAX, because that causes insert_save_restore to fail. */
610 int saveregs = MIN (numregs, MOVE_MAX / UNITS_PER_WORD);
611 int endregno = regno + numregs;
613 for (i = regno; i < endregno; i++)
614 if (TEST_HARD_REG_BIT (hard_regs_need_restore, i))
615 i += insert_save_restore (insn, 0, i, insn_mode, saveregs);
621 fmt = GET_RTX_FORMAT (code);
622 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
625 restore_referenced_regs (XEXP (x, i), insn, insn_mode);
626 else if (fmt[i] == 'E')
627 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
628 restore_referenced_regs (XVECEXP (x, i, j), insn, insn_mode);
632 /* Insert a sequence of insns to save or restore, SAVE_P says which,
633 REGNO. Place these insns in front of INSN. INSN_MODE is the mode
634 to assign to these insns. MAXRESTORE is the maximum number of registers
635 which should be restored during this call (when SAVE_P == 0). It should
636 never be less than 1 since we only work with entire registers.
638 Note that we have verified in init_caller_save that we can do this
639 with a simple SET, so use it. Set INSN_CODE to what we save there
640 since the address might not be valid so the insn might not be recognized.
641 These insns will be reloaded and have register elimination done by
642 find_reload, so we need not worry about that here.
644 Return the extra number of registers saved. */
647 insert_save_restore (insn, save_p, regno, insn_mode, maxrestore)
651 enum machine_mode insn_mode;
658 /* A common failure mode if register status is not correct in the RTL
659 is for this routine to be called with a REGNO we didn't expect to
660 save. That will cause us to write an insn with a (nil) SET_DEST
661 or SET_SRC. Instead of doing so and causing a crash later, check
662 for this common case and abort here instead. This will remove one
663 step in debugging such problems. */
665 if (regno_save_mem[regno][1] == 0)
669 /* If INSN references CC0, put our insns in front of the insn that sets
670 CC0. This is always safe, since the only way we could be passed an
671 insn that references CC0 is for a restore, and doing a restore earlier
672 isn't a problem. We do, however, assume here that CALL_INSNs don't
673 reference CC0. Guard against non-INSN's like CODE_LABEL. */
675 if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
676 && reg_referenced_p (cc0_rtx, PATTERN (insn)))
677 insn = prev_nonnote_insn (insn);
680 /* Get the pattern to emit and update our status. */
686 /* See if we can save several registers with a single instruction.
687 Work backwards to the single register case. */
688 for (i = MOVE_MAX / UNITS_PER_WORD; i > 0; i--)
691 if (regno_save_mem[regno][i] != 0)
692 for (j = 0; j < i; j++)
694 if (! call_used_regs[regno + j] || call_fixed_regs[regno + j]
695 || ! TEST_HARD_REG_BIT (hard_regs_live, regno + j)
696 || TEST_HARD_REG_BIT (hard_regs_saved, regno + j))
702 /* Must do this one save at a time */
706 pat = gen_rtx (SET, VOIDmode, regno_save_mem[regno][i],
707 gen_rtx (REG, GET_MODE (regno_save_mem[regno][i]), regno));
708 code = reg_save_code[regno][i];
710 /* Set hard_regs_saved for all the registers we saved. */
711 for (k = 0; k < i; k++)
713 SET_HARD_REG_BIT (hard_regs_saved, regno + k);
714 SET_HARD_REG_BIT (hard_regs_need_restore, regno + k);
727 /* See if we can restore `maxrestore' registers at once. Work
728 backwards to the single register case. */
729 for (i = maxrestore; i > 0; i--)
732 if (regno_save_mem[regno][i])
733 for (j = 0; j < i; j++)
735 if (! TEST_HARD_REG_BIT (hard_regs_need_restore, regno + j))
741 /* Must do this one restore at a time */
745 pat = gen_rtx (SET, VOIDmode,
746 gen_rtx (REG, GET_MODE (regno_save_mem[regno][i]),
748 regno_save_mem[regno][i]);
749 code = reg_restore_code[regno][i];
752 /* Clear status for all registers we restored. */
753 for (k = 0; k < i; k++)
755 CLEAR_HARD_REG_BIT (hard_regs_need_restore, regno + k);
763 /* Emit the insn and set the code and mode. */
765 insn = emit_insn_before (pat, insn);
766 PUT_MODE (insn, insn_mode);
767 INSN_CODE (insn) = code;
769 /* Tell our callers how many extra registers we saved/restored */