1 /* Save and restore call-clobbered registers which are live across a call.
2 Copyright (C) 1989, 1992 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, 675 Mass Ave, Cambridge, MA 02139, USA. */
22 #include "insn-config.h"
25 #include "hard-reg-set.h"
27 #include "basic-block.h"
31 /* Modes for each hard register that we can save. The smallest mode is wide
32 enough to save the entire contents of the register. When saving the
33 register because it is live we first try to save in multi-register modes.
34 If that is not possible the save is done one register at a time. */
36 static enum machine_mode
37 regno_save_mode[FIRST_PSEUDO_REGISTER][MOVE_MAX / UNITS_PER_WORD + 1];
39 /* For each hard register, a place on the stack where it can be saved,
43 regno_save_mem[FIRST_PSEUDO_REGISTER][MOVE_MAX / UNITS_PER_WORD + 1];
45 /* We will only make a register eligible for caller-save if it can be
46 saved in its widest mode with a simple SET insn as long as the memory
47 address is valid. We record the INSN_CODE is those insns here since
48 when we emit them, the addresses might not be valid, so they might not
52 reg_save_code[FIRST_PSEUDO_REGISTER][MOVE_MAX / UNITS_PER_WORD + 1];
54 reg_restore_code[FIRST_PSEUDO_REGISTER][MOVE_MAX / UNITS_PER_WORD + 1];
56 /* Set of hard regs currently live (during scan of all insns). */
58 static HARD_REG_SET hard_regs_live;
60 /* Set of hard regs currently residing in save area (during insn scan). */
62 static HARD_REG_SET hard_regs_saved;
64 /* Set of hard regs which need to be restored before referenced. */
66 static HARD_REG_SET hard_regs_need_restore;
68 /* Number of registers currently in hard_regs_saved. */
72 static enum machine_mode choose_hard_reg_mode PROTO((int, int));
73 static void set_reg_live PROTO((rtx, rtx));
74 static void clear_reg_live PROTO((rtx));
75 static void restore_referenced_regs PROTO((rtx, rtx, enum machine_mode));
76 static int insert_save_restore PROTO((rtx, int, int,
77 enum machine_mode, int));
79 /* Return a machine mode that is legitimate for hard reg REGNO and large
80 enough to save nregs. If we can't find one, return VOIDmode. */
82 static enum machine_mode
83 choose_hard_reg_mode (regno, nregs)
87 enum machine_mode found_mode = VOIDmode, mode;
89 /* We first look for the largest integer mode that can be validly
90 held in REGNO. If none, we look for the largest floating-point mode.
91 If we still didn't find a valid mode, try CCmode. */
93 for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT); mode != VOIDmode;
94 mode = GET_MODE_WIDER_MODE (mode))
95 if (HARD_REGNO_NREGS (regno, mode) == nregs
96 && HARD_REGNO_MODE_OK (regno, mode))
99 if (found_mode != VOIDmode)
102 for (mode = GET_CLASS_NARROWEST_MODE (MODE_FLOAT); mode != VOIDmode;
103 mode = GET_MODE_WIDER_MODE (mode))
104 if (HARD_REGNO_NREGS (regno, mode) == nregs
105 && HARD_REGNO_MODE_OK (regno, mode))
108 if (found_mode != VOIDmode)
111 if (HARD_REGNO_NREGS (regno, CCmode) == nregs
112 && HARD_REGNO_MODE_OK (regno, CCmode))
115 /* We can't find a mode valid for this register. */
119 /* Initialize for caller-save.
121 Look at all the hard registers that are used by a call and for which
122 regclass.c has not already excluded from being used across a call.
124 Ensure that we can find a mode to save the register and that there is a
125 simple insn to save and restore the register. This latter check avoids
126 problems that would occur if we tried to save the MQ register of some
127 machines directly into memory. */
132 char *first_obj = (char *) oballoc (0);
138 /* First find all the registers that we need to deal with and all
139 the modes that they can have. If we can't find a mode to use,
140 we can't have the register live over calls. */
142 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
144 if (call_used_regs[i] && ! call_fixed_regs[i])
146 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
148 regno_save_mode[i][j] = choose_hard_reg_mode (i, j);
149 if (regno_save_mode[i][j] == VOIDmode && j == 1)
151 call_fixed_regs[i] = 1;
152 SET_HARD_REG_BIT (call_fixed_reg_set, i);
157 regno_save_mode[i][1] = VOIDmode;
160 /* The following code tries to approximate the conditions under which
161 we can easily save and restore a register without scratch registers or
162 other complexities. It will usually work, except under conditions where
163 the validity of an insn operand is dependent on the address offset.
164 No such cases are currently known.
166 We first find a typical offset from some BASE_REG_CLASS register.
167 This address is chosen by finding the first register in the class
168 and by finding the smallest power of two that is a valid offset from
169 that register in every mode we will use to save registers. */
171 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
172 if (TEST_HARD_REG_BIT (reg_class_contents[(int) BASE_REG_CLASS], i))
175 if (i == FIRST_PSEUDO_REGISTER)
178 addr_reg = gen_rtx (REG, Pmode, i);
180 for (offset = 1 << (HOST_BITS_PER_INT / 2); offset; offset >>= 1)
182 address = gen_rtx (PLUS, Pmode, addr_reg, GEN_INT (offset));
184 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
185 if (regno_save_mode[i][1] != VOIDmode
186 && ! strict_memory_address_p (regno_save_mode[i][1], address))
189 if (i == FIRST_PSEUDO_REGISTER)
193 /* If we didn't find a valid address, we must use register indirect. */
197 /* Next we try to form an insn to save and restore the register. We
198 see if such an insn is recognized and meets its constraints. */
202 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
203 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
204 if (regno_save_mode[i][j] != VOIDmode)
206 rtx mem = gen_rtx (MEM, regno_save_mode[i][j], address);
207 rtx reg = gen_rtx (REG, regno_save_mode[i][j], i);
208 rtx savepat = gen_rtx (SET, VOIDmode, mem, reg);
209 rtx restpat = gen_rtx (SET, VOIDmode, reg, mem);
210 rtx saveinsn = emit_insn (savepat);
211 rtx restinsn = emit_insn (restpat);
214 reg_save_code[i][j] = recog_memoized (saveinsn);
215 reg_restore_code[i][j] = recog_memoized (restinsn);
217 /* Now extract both insns and see if we can meet their constraints. */
218 ok = (reg_save_code[i][j] != -1 && reg_restore_code[i][j] != -1);
221 insn_extract (saveinsn);
222 ok = constrain_operands (reg_save_code[i][j], 1);
223 insn_extract (restinsn);
224 ok &= constrain_operands (reg_restore_code[i][j], 1);
229 regno_save_mode[i][j] = VOIDmode;
232 call_fixed_regs[i] = 1;
233 SET_HARD_REG_BIT (call_fixed_reg_set, i);
243 /* Initialize save areas by showing that we haven't allocated any yet. */
250 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
251 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
252 regno_save_mem[i][j] = 0;
255 /* Allocate save areas for any hard registers that might need saving.
256 We take a conservative approach here and look for call-clobbered hard
257 registers that are assigned to pseudos that cross calls. This may
258 overestimate slightly (especially if some of these registers are later
259 used as spill registers), but it should not be significant.
261 Then perform register elimination in the addresses of the save area
262 locations; return 1 if all eliminated addresses are strictly valid.
263 We assume that our caller has set up the elimination table to the
264 worst (largest) possible offsets.
266 Set *PCHANGED to 1 if we had to allocate some memory for the save area.
270 In the fallback case we should iterate backwards across all possible
271 modes for the save, choosing the largest available one instead of
272 falling back to the smallest mode immediately. (eg TF -> DF -> SF).
274 We do not try to use "move multiple" instructions that exist
275 on some machines (such as the 68k moveml). It could be a win to try
276 and use them when possible. The hard part is doing it in a way that is
277 machine independent since they might be saving non-consecutive
278 registers. (imagine caller-saving d0,d1,a0,a1 on the 68k) */
281 setup_save_areas (pchanged)
285 HARD_REG_SET hard_regs_used;
289 /* Allocate space in the save area for the largest multi-register
290 pseudos first, then work backwards to single register
293 /* Find and record all call-used hard-registers in this function. */
294 CLEAR_HARD_REG_SET (hard_regs_used);
295 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
296 if (reg_renumber[i] >= 0 && reg_n_calls_crossed[i] > 0)
298 int regno = reg_renumber[i];
300 = regno + HARD_REGNO_NREGS (regno, GET_MODE (regno_reg_rtx[i]));
301 int nregs = endregno - regno;
303 for (j = 0; j < nregs; j++)
305 if (call_used_regs[regno+j])
306 SET_HARD_REG_BIT (hard_regs_used, regno+j);
310 /* Now run through all the call-used hard-registers and allocate
311 space for them in the caller-save area. Try to allocate space
312 in a manner which allows multi-register saves/restores to be done. */
314 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
315 for (j = MOVE_MAX / UNITS_PER_WORD; j > 0; j--)
320 /* If no mode exists for this size, try another. Also break out
321 if we have already saved this hard register. */
322 if (regno_save_mode[i][j] == VOIDmode || regno_save_mem[i][1] != 0)
325 /* See if any register in this group has been saved. */
327 for (k = 0; k < j; k++)
328 if (regno_save_mem[i + k][1])
336 for (k = 0; k < j; k++)
339 ok &= (TEST_HARD_REG_BIT (hard_regs_used, regno) != 0);
342 /* We have found an acceptable mode to store in. */
347 = assign_stack_local (regno_save_mode[i][j],
348 GET_MODE_SIZE (regno_save_mode[i][j]), 0);
350 /* Setup single word save area just in case... */
351 for (k = 0; k < j; k++)
353 /* This should not depend on WORDS_BIG_ENDIAN.
354 The order of words in regs is the same as in memory. */
355 rtx temp = gen_rtx (MEM, regno_save_mode[i+k][1],
356 XEXP (regno_save_mem[i][j], 0));
358 regno_save_mem[i+k][1]
359 = adj_offsettable_operand (temp, k * UNITS_PER_WORD);
365 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
366 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
367 if (regno_save_mem[i][j] != 0)
368 ok &= strict_memory_address_p (GET_MODE (regno_save_mem[i][j]),
369 XEXP (eliminate_regs (regno_save_mem[i][j], 0, NULL_RTX), 0));
374 /* Find the places where hard regs are live across calls and save them.
376 INSN_MODE is the mode to assign to any insns that we add. This is used
377 by reload to determine whether or not reloads or register eliminations
378 need be done on these insns. */
381 save_call_clobbered_regs (insn_mode)
382 enum machine_mode insn_mode;
387 for (b = 0; b < n_basic_blocks; b++)
389 regset regs_live = basic_block_live_at_start[b];
390 rtx prev_block_last = PREV_INSN (basic_block_head[b]);
395 /* Compute hard regs live at start of block -- this is the
396 real hard regs marked live, plus live pseudo regs that
397 have been renumbered to hard regs. No registers have yet been
398 saved because we restore all of them before the end of the basic
402 hard_regs_live = *regs_live;
404 COPY_HARD_REG_SET (hard_regs_live, regs_live);
407 CLEAR_HARD_REG_SET (hard_regs_saved);
408 CLEAR_HARD_REG_SET (hard_regs_need_restore);
411 for (offset = 0, i = 0; offset < regset_size; offset++)
413 if (regs_live[offset] == 0)
414 i += REGSET_ELT_BITS;
416 for (bit = 1; bit && i < max_regno; bit <<= 1, i++)
417 if ((regs_live[offset] & bit)
418 && (regno = reg_renumber[i]) >= 0)
420 j < regno + HARD_REGNO_NREGS (regno,
421 PSEUDO_REGNO_MODE (i));
423 SET_HARD_REG_BIT (hard_regs_live, j);
427 /* Now scan the insns in the block, keeping track of what hard
428 regs are live as we go. When we see a call, save the live
429 call-clobbered hard regs. */
431 for (insn = basic_block_head[b]; ; insn = NEXT_INSN (insn))
433 RTX_CODE code = GET_CODE (insn);
435 if (GET_RTX_CLASS (code) == 'i')
439 /* If some registers have been saved, see if INSN references
440 any of them. We must restore them before the insn if so. */
443 restore_referenced_regs (PATTERN (insn), insn, insn_mode);
445 /* NB: the normal procedure is to first enliven any
446 registers set by insn, then deaden any registers that
447 had their last use at insn. This is incorrect now,
448 since multiple pseudos may have been mapped to the
449 same hard reg, and the death notes are ambiguous. So
450 it must be done in the other, safe, order. */
452 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
453 if (REG_NOTE_KIND (link) == REG_DEAD)
454 clear_reg_live (XEXP (link, 0));
456 /* When we reach a call, we need to save all registers that are
457 live, call-used, not fixed, and not already saved. We must
458 test at this point because registers that die in a CALL_INSN
459 are not live across the call and likewise for registers that
460 are born in the CALL_INSN. */
462 if (code == CALL_INSN)
464 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
465 if (call_used_regs[regno] && ! call_fixed_regs[regno]
466 && TEST_HARD_REG_BIT (hard_regs_live, regno)
467 && ! TEST_HARD_REG_BIT (hard_regs_saved, regno))
468 regno += insert_save_restore (insn, 1, regno,
471 hard_regs_need_restore = hard_regs_saved;
473 COPY_HARD_REG_SET (hard_regs_need_restore,
477 /* Must recompute n_regs_saved. */
479 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
480 if (TEST_HARD_REG_BIT (hard_regs_saved, regno))
485 note_stores (PATTERN (insn), set_reg_live);
487 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
488 if (REG_NOTE_KIND (link) == REG_UNUSED)
489 clear_reg_live (XEXP (link, 0));
492 if (insn == basic_block_end[b])
496 /* At the end of the basic block, we must restore any registers that
497 remain saved. If the last insn in the block is a JUMP_INSN, put
498 the restore before the insn, otherwise, put it after the insn. */
501 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
502 if (TEST_HARD_REG_BIT (hard_regs_need_restore, regno))
503 regno += insert_save_restore ((GET_CODE (insn) == JUMP_INSN
504 ? insn : NEXT_INSN (insn)), 0,
505 regno, insn_mode, MOVE_MAX / UNITS_PER_WORD);
507 /* If we added any insns at the start of the block, update the start
508 of the block to point at those insns. */
509 basic_block_head[b] = NEXT_INSN (prev_block_last);
513 /* Here from note_stores when an insn stores a value in a register.
514 Set the proper bit or bits in hard_regs_live. All pseudos that have
515 been assigned hard regs have had their register number changed already,
516 so we can ignore pseudos. */
519 set_reg_live (reg, setter)
522 register int regno, endregno, i;
523 enum machine_mode mode = GET_MODE (reg);
526 if (GET_CODE (reg) == SUBREG)
528 word = SUBREG_WORD (reg);
529 reg = SUBREG_REG (reg);
532 if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
535 regno = REGNO (reg) + word;
536 endregno = regno + HARD_REGNO_NREGS (regno, mode);
538 for (i = regno; i < endregno; i++)
540 SET_HARD_REG_BIT (hard_regs_live, i);
541 CLEAR_HARD_REG_BIT (hard_regs_saved, i);
542 CLEAR_HARD_REG_BIT (hard_regs_need_restore, i);
546 /* Here when a REG_DEAD note records the last use of a reg. Clear
547 the appropriate bit or bits in hard_regs_live. Again we can ignore
554 register int regno, endregno, i;
556 if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
560 endregno= regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
562 for (i = regno; i < endregno; i++)
564 CLEAR_HARD_REG_BIT (hard_regs_live, i);
565 CLEAR_HARD_REG_BIT (hard_regs_need_restore, i);
566 CLEAR_HARD_REG_BIT (hard_regs_saved, i);
570 /* If any register currently residing in the save area is referenced in X,
571 which is part of INSN, emit code to restore the register in front of INSN.
572 INSN_MODE is the mode to assign to any insns that we add. */
575 restore_referenced_regs (x, insn, insn_mode)
578 enum machine_mode insn_mode;
580 enum rtx_code code = GET_CODE (x);
589 int regno = REGNO (x);
591 /* If this is a pseudo, scan its memory location, since it might
592 involve the use of another register, which might be saved. */
594 if (regno >= FIRST_PSEUDO_REGISTER
595 && reg_equiv_mem[regno] != 0)
596 restore_referenced_regs (XEXP (reg_equiv_mem[regno], 0),
598 else if (regno >= FIRST_PSEUDO_REGISTER
599 && reg_equiv_address[regno] != 0)
600 restore_referenced_regs (reg_equiv_address[regno],
603 /* Otherwise if this is a hard register, restore any piece of it that
604 is currently saved. */
606 else if (regno < FIRST_PSEUDO_REGISTER)
608 int numregs = HARD_REGNO_NREGS (regno, GET_MODE (x));
609 /* Save at most SAVEREGS at a time. This can not be larger than
610 MOVE_MAX, because that causes insert_save_restore to fail. */
611 int saveregs = MIN (numregs, MOVE_MAX / UNITS_PER_WORD);
612 int endregno = regno + numregs;
614 for (i = regno; i < endregno; i++)
615 if (TEST_HARD_REG_BIT (hard_regs_need_restore, i))
616 i += insert_save_restore (insn, 0, i, insn_mode, saveregs);
622 fmt = GET_RTX_FORMAT (code);
623 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
626 restore_referenced_regs (XEXP (x, i), insn, insn_mode);
627 else if (fmt[i] == 'E')
628 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
629 restore_referenced_regs (XVECEXP (x, i, j), insn, insn_mode);
633 /* Insert a sequence of insns to save or restore, SAVE_P says which,
634 REGNO. Place these insns in front of INSN. INSN_MODE is the mode
635 to assign to these insns. MAXRESTORE is the maximum number of registers
636 which should be restored during this call (when SAVE_P == 0). It should
637 never be less than 1 since we only work with entire registers.
639 Note that we have verified in init_caller_save that we can do this
640 with a simple SET, so use it. Set INSN_CODE to what we save there
641 since the address might not be valid so the insn might not be recognized.
642 These insns will be reloaded and have register elimination done by
643 find_reload, so we need not worry about that here.
645 Return the extra number of registers saved. */
648 insert_save_restore (insn, save_p, regno, insn_mode, maxrestore)
652 enum machine_mode insn_mode;
659 /* A common failure mode if register status is not correct in the RTL
660 is for this routine to be called with a REGNO we didn't expect to
661 save. That will cause us to write an insn with a (nil) SET_DEST
662 or SET_SRC. Instead of doing so and causing a crash later, check
663 for this common case and abort here instead. This will remove one
664 step in debugging such problems. */
666 if (regno_save_mem[regno][1] == 0)
669 /* If INSN is a CALL_INSN, we must insert our insns before any
670 USE insns in front of the CALL_INSN. */
672 if (GET_CODE (insn) == CALL_INSN)
673 while (GET_CODE (PREV_INSN (insn)) == INSN
674 && GET_CODE (PATTERN (PREV_INSN (insn))) == USE)
675 insn = PREV_INSN (insn);
678 /* If INSN references CC0, put our insns in front of the insn that sets
679 CC0. This is always safe, since the only way we could be passed an
680 insn that references CC0 is for a restore, and doing a restore earlier
681 isn't a problem. We do, however, assume here that CALL_INSNs don't
682 reference CC0. Guard against non-INSN's like CODE_LABEL. */
684 if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
685 && reg_referenced_p (cc0_rtx, PATTERN (insn)))
686 insn = prev_nonnote_insn (insn);
689 /* Get the pattern to emit and update our status. */
695 /* See if we can save several registers with a single instruction.
696 Work backwards to the single register case. */
697 for (i = MOVE_MAX / UNITS_PER_WORD; i > 0; i--)
700 if (regno_save_mem[regno][i] != 0)
701 for (j = 0; j < i; j++)
703 if (! call_used_regs[regno + j] || call_fixed_regs[regno + j]
704 || ! TEST_HARD_REG_BIT (hard_regs_live, regno + j)
705 || TEST_HARD_REG_BIT (hard_regs_saved, regno + j))
711 /* Must do this one save at a time */
715 pat = gen_rtx (SET, VOIDmode, regno_save_mem[regno][i],
716 gen_rtx (REG, GET_MODE (regno_save_mem[regno][i]), regno));
717 code = reg_save_code[regno][i];
719 /* Set hard_regs_saved for all the registers we saved. */
720 for (k = 0; k < i; k++)
722 SET_HARD_REG_BIT (hard_regs_saved, regno + k);
723 SET_HARD_REG_BIT (hard_regs_need_restore, regno + k);
736 /* See if we can restore `maxrestore' registers at once. Work
737 backwards to the single register case. */
738 for (i = maxrestore; i > 0; i--)
741 if (regno_save_mem[regno][i])
742 for (j = 0; j < i; j++)
744 if (! TEST_HARD_REG_BIT (hard_regs_need_restore, regno + j))
750 /* Must do this one restore at a time */
754 pat = gen_rtx (SET, VOIDmode,
755 gen_rtx (REG, GET_MODE (regno_save_mem[regno][i]),
757 regno_save_mem[regno][i]);
758 code = reg_restore_code[regno][i];
761 /* Clear status for all registers we restored. */
762 for (k = 0; k < i; k++)
764 CLEAR_HARD_REG_BIT (hard_regs_need_restore, regno + k);
772 /* Emit the insn and set the code and mode. */
774 insn = emit_insn_before (pat, insn);
775 PUT_MODE (insn, insn_mode);
776 INSN_CODE (insn) = code;
778 /* Tell our callers how many extra registers we saved/restored */