1 /* Save and restore call-clobbered registers which are live across a call.
2 Copyright (C) 1989, 1992, 1994 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"
32 #define MAX_MOVE_MAX MOVE_MAX
35 #ifndef MAX_UNITS_PER_WORD
36 #define MAX_UNITS_PER_WORD UNITS_PER_WORD
39 /* Modes for each hard register that we can save. The smallest mode is wide
40 enough to save the entire contents of the register. When saving the
41 register because it is live we first try to save in multi-register modes.
42 If that is not possible the save is done one register at a time. */
44 static enum machine_mode
45 regno_save_mode[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MAX_UNITS_PER_WORD + 1];
47 /* For each hard register, a place on the stack where it can be saved,
51 regno_save_mem[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MAX_UNITS_PER_WORD + 1];
53 /* We will only make a register eligible for caller-save if it can be
54 saved in its widest mode with a simple SET insn as long as the memory
55 address is valid. We record the INSN_CODE is those insns here since
56 when we emit them, the addresses might not be valid, so they might not
60 reg_save_code[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MAX_UNITS_PER_WORD + 1];
62 reg_restore_code[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MAX_UNITS_PER_WORD + 1];
64 /* Set of hard regs currently live (during scan of all insns). */
66 static HARD_REG_SET hard_regs_live;
68 /* Set of hard regs currently residing in save area (during insn scan). */
70 static HARD_REG_SET hard_regs_saved;
72 /* Set of hard regs which need to be restored before referenced. */
74 static HARD_REG_SET hard_regs_need_restore;
76 /* Number of registers currently in hard_regs_saved. */
80 static enum machine_mode choose_hard_reg_mode PROTO((int, int));
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 /* Return a machine mode that is legitimate for hard reg REGNO and large
88 enough to save nregs. If we can't find one, return VOIDmode. */
90 static enum machine_mode
91 choose_hard_reg_mode (regno, nregs)
95 enum machine_mode found_mode = VOIDmode, mode;
97 /* We first look for the largest integer mode that can be validly
98 held in REGNO. If none, we look for the largest floating-point mode.
99 If we still didn't find a valid mode, try CCmode. */
101 for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT); mode != VOIDmode;
102 mode = GET_MODE_WIDER_MODE (mode))
103 if (HARD_REGNO_NREGS (regno, mode) == nregs
104 && HARD_REGNO_MODE_OK (regno, mode))
107 if (found_mode != VOIDmode)
110 for (mode = GET_CLASS_NARROWEST_MODE (MODE_FLOAT); mode != VOIDmode;
111 mode = GET_MODE_WIDER_MODE (mode))
112 if (HARD_REGNO_NREGS (regno, mode) == nregs
113 && HARD_REGNO_MODE_OK (regno, mode))
116 if (found_mode != VOIDmode)
119 if (HARD_REGNO_NREGS (regno, CCmode) == nregs
120 && HARD_REGNO_MODE_OK (regno, CCmode))
123 /* We can't find a mode valid for this register. */
127 /* Initialize for caller-save.
129 Look at all the hard registers that are used by a call and for which
130 regclass.c has not already excluded from being used across a call.
132 Ensure that we can find a mode to save the register and that there is a
133 simple insn to save and restore the register. This latter check avoids
134 problems that would occur if we tried to save the MQ register of some
135 machines directly into memory. */
140 char *first_obj = (char *) oballoc (0);
146 /* First find all the registers that we need to deal with and all
147 the modes that they can have. If we can't find a mode to use,
148 we can't have the register live over calls. */
150 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
152 if (call_used_regs[i] && ! call_fixed_regs[i])
154 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
156 regno_save_mode[i][j] = choose_hard_reg_mode (i, j);
157 if (regno_save_mode[i][j] == VOIDmode && j == 1)
159 call_fixed_regs[i] = 1;
160 SET_HARD_REG_BIT (call_fixed_reg_set, i);
165 regno_save_mode[i][1] = VOIDmode;
168 /* The following code tries to approximate the conditions under which
169 we can easily save and restore a register without scratch registers or
170 other complexities. It will usually work, except under conditions where
171 the validity of an insn operand is dependent on the address offset.
172 No such cases are currently known.
174 We first find a typical offset from some BASE_REG_CLASS register.
175 This address is chosen by finding the first register in the class
176 and by finding the smallest power of two that is a valid offset from
177 that register in every mode we will use to save registers. */
179 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
180 if (TEST_HARD_REG_BIT (reg_class_contents[(int) BASE_REG_CLASS], i))
183 if (i == FIRST_PSEUDO_REGISTER)
186 addr_reg = gen_rtx (REG, Pmode, i);
188 for (offset = 1 << (HOST_BITS_PER_INT / 2); offset; offset >>= 1)
190 address = gen_rtx (PLUS, Pmode, addr_reg, GEN_INT (offset));
192 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
193 if (regno_save_mode[i][1] != VOIDmode
194 && ! strict_memory_address_p (regno_save_mode[i][1], address))
197 if (i == FIRST_PSEUDO_REGISTER)
201 /* If we didn't find a valid address, we must use register indirect. */
205 /* Next we try to form an insn to save and restore the register. We
206 see if such an insn is recognized and meets its constraints. */
210 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
211 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
212 if (regno_save_mode[i][j] != VOIDmode)
214 rtx mem = gen_rtx (MEM, regno_save_mode[i][j], address);
215 rtx reg = gen_rtx (REG, regno_save_mode[i][j], i);
216 rtx savepat = gen_rtx (SET, VOIDmode, mem, reg);
217 rtx restpat = gen_rtx (SET, VOIDmode, reg, mem);
218 rtx saveinsn = emit_insn (savepat);
219 rtx restinsn = emit_insn (restpat);
222 reg_save_code[i][j] = recog_memoized (saveinsn);
223 reg_restore_code[i][j] = recog_memoized (restinsn);
225 /* Now extract both insns and see if we can meet their constraints. */
226 ok = (reg_save_code[i][j] != -1 && reg_restore_code[i][j] != -1);
229 insn_extract (saveinsn);
230 ok = constrain_operands (reg_save_code[i][j], 1);
231 insn_extract (restinsn);
232 ok &= constrain_operands (reg_restore_code[i][j], 1);
237 regno_save_mode[i][j] = VOIDmode;
240 call_fixed_regs[i] = 1;
241 SET_HARD_REG_BIT (call_fixed_reg_set, i);
251 /* Initialize save areas by showing that we haven't allocated any yet. */
258 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
259 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
260 regno_save_mem[i][j] = 0;
263 /* Allocate save areas for any hard registers that might need saving.
264 We take a conservative approach here and look for call-clobbered hard
265 registers that are assigned to pseudos that cross calls. This may
266 overestimate slightly (especially if some of these registers are later
267 used as spill registers), but it should not be significant.
269 Then perform register elimination in the addresses of the save area
270 locations; return 1 if all eliminated addresses are strictly valid.
271 We assume that our caller has set up the elimination table to the
272 worst (largest) possible offsets.
274 Set *PCHANGED to 1 if we had to allocate some memory for the save area.
278 In the fallback case we should iterate backwards across all possible
279 modes for the save, choosing the largest available one instead of
280 falling back to the smallest mode immediately. (eg TF -> DF -> SF).
282 We do not try to use "move multiple" instructions that exist
283 on some machines (such as the 68k moveml). It could be a win to try
284 and use them when possible. The hard part is doing it in a way that is
285 machine independent since they might be saving non-consecutive
286 registers. (imagine caller-saving d0,d1,a0,a1 on the 68k) */
289 setup_save_areas (pchanged)
293 HARD_REG_SET hard_regs_used;
297 /* Allocate space in the save area for the largest multi-register
298 pseudos first, then work backwards to single register
301 /* Find and record all call-used hard-registers in this function. */
302 CLEAR_HARD_REG_SET (hard_regs_used);
303 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
304 if (reg_renumber[i] >= 0 && reg_n_calls_crossed[i] > 0)
306 int regno = reg_renumber[i];
308 = regno + HARD_REGNO_NREGS (regno, GET_MODE (regno_reg_rtx[i]));
309 int nregs = endregno - regno;
311 for (j = 0; j < nregs; j++)
313 if (call_used_regs[regno+j])
314 SET_HARD_REG_BIT (hard_regs_used, regno+j);
318 /* Now run through all the call-used hard-registers and allocate
319 space for them in the caller-save area. Try to allocate space
320 in a manner which allows multi-register saves/restores to be done. */
322 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
323 for (j = MOVE_MAX / UNITS_PER_WORD; j > 0; j--)
328 /* If no mode exists for this size, try another. Also break out
329 if we have already saved this hard register. */
330 if (regno_save_mode[i][j] == VOIDmode || regno_save_mem[i][1] != 0)
333 /* See if any register in this group has been saved. */
335 for (k = 0; k < j; k++)
336 if (regno_save_mem[i + k][1])
344 for (k = 0; k < j; k++)
347 ok &= (TEST_HARD_REG_BIT (hard_regs_used, regno) != 0);
350 /* We have found an acceptable mode to store in. */
355 = assign_stack_local (regno_save_mode[i][j],
356 GET_MODE_SIZE (regno_save_mode[i][j]), 0);
358 /* Setup single word save area just in case... */
359 for (k = 0; k < j; k++)
361 /* This should not depend on WORDS_BIG_ENDIAN.
362 The order of words in regs is the same as in memory. */
363 rtx temp = gen_rtx (MEM, regno_save_mode[i+k][1],
364 XEXP (regno_save_mem[i][j], 0));
366 regno_save_mem[i+k][1]
367 = adj_offsettable_operand (temp, k * UNITS_PER_WORD);
373 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
374 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
375 if (regno_save_mem[i][j] != 0)
376 ok &= strict_memory_address_p (GET_MODE (regno_save_mem[i][j]),
377 XEXP (eliminate_regs (regno_save_mem[i][j], 0, NULL_RTX), 0));
382 /* Find the places where hard regs are live across calls and save them.
384 INSN_MODE is the mode to assign to any insns that we add. This is used
385 by reload to determine whether or not reloads or register eliminations
386 need be done on these insns. */
389 save_call_clobbered_regs (insn_mode)
390 enum machine_mode insn_mode;
395 for (b = 0; b < n_basic_blocks; b++)
397 regset regs_live = basic_block_live_at_start[b];
398 rtx prev_block_last = PREV_INSN (basic_block_head[b]);
403 /* Compute hard regs live at start of block -- this is the
404 real hard regs marked live, plus live pseudo regs that
405 have been renumbered to hard regs. No registers have yet been
406 saved because we restore all of them before the end of the basic
409 COPY_HARD_REG_SET (hard_regs_live, *regs_live);
411 CLEAR_HARD_REG_SET (hard_regs_saved);
412 CLEAR_HARD_REG_SET (hard_regs_need_restore);
415 for (offset = 0, i = 0; offset < regset_size; offset++)
417 if (regs_live[offset] == 0)
418 i += REGSET_ELT_BITS;
420 for (bit = 1; bit && i < max_regno; bit <<= 1, i++)
421 if ((regs_live[offset] & bit)
422 && (regno = reg_renumber[i]) >= 0)
424 j < regno + HARD_REGNO_NREGS (regno,
425 PSEUDO_REGNO_MODE (i));
427 SET_HARD_REG_BIT (hard_regs_live, j);
431 /* Now scan the insns in the block, keeping track of what hard
432 regs are live as we go. When we see a call, save the live
433 call-clobbered hard regs. */
435 for (insn = basic_block_head[b]; ; insn = NEXT_INSN (insn))
437 RTX_CODE code = GET_CODE (insn);
439 if (GET_RTX_CLASS (code) == 'i')
443 /* If some registers have been saved, see if INSN references
444 any of them. We must restore them before the insn if so. */
447 restore_referenced_regs (PATTERN (insn), insn, insn_mode);
449 /* NB: the normal procedure is to first enliven any
450 registers set by insn, then deaden any registers that
451 had their last use at insn. This is incorrect now,
452 since multiple pseudos may have been mapped to the
453 same hard reg, and the death notes are ambiguous. So
454 it must be done in the other, safe, order. */
456 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
457 if (REG_NOTE_KIND (link) == REG_DEAD)
458 clear_reg_live (XEXP (link, 0));
460 /* When we reach a call, we need to save all registers that are
461 live, call-used, not fixed, and not already saved. We must
462 test at this point because registers that die in a CALL_INSN
463 are not live across the call and likewise for registers that
464 are born in the CALL_INSN. */
466 if (code == CALL_INSN)
468 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
469 if (call_used_regs[regno] && ! call_fixed_regs[regno]
470 && TEST_HARD_REG_BIT (hard_regs_live, regno)
471 && ! TEST_HARD_REG_BIT (hard_regs_saved, regno))
472 regno += insert_save_restore (insn, 1, regno,
475 hard_regs_need_restore = hard_regs_saved;
477 COPY_HARD_REG_SET (hard_regs_need_restore,
481 /* Must recompute n_regs_saved. */
483 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
484 if (TEST_HARD_REG_BIT (hard_regs_saved, regno))
489 note_stores (PATTERN (insn), set_reg_live);
491 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
492 if (REG_NOTE_KIND (link) == REG_UNUSED)
493 clear_reg_live (XEXP (link, 0));
496 if (insn == basic_block_end[b])
500 /* At the end of the basic block, we must restore any registers that
501 remain saved. If the last insn in the block is a JUMP_INSN, put
502 the restore before the insn, otherwise, put it after the insn. */
505 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
506 if (TEST_HARD_REG_BIT (hard_regs_need_restore, regno))
507 regno += insert_save_restore ((GET_CODE (insn) == JUMP_INSN
508 ? insn : NEXT_INSN (insn)), 0,
509 regno, insn_mode, MOVE_MAX / UNITS_PER_WORD);
511 /* If we added any insns at the start of the block, update the start
512 of the block to point at those insns. */
513 basic_block_head[b] = NEXT_INSN (prev_block_last);
517 /* Here from note_stores when an insn stores a value in a register.
518 Set the proper bit or bits in hard_regs_live. All pseudos that have
519 been assigned hard regs have had their register number changed already,
520 so we can ignore pseudos. */
523 set_reg_live (reg, setter)
526 register int regno, endregno, i;
527 enum machine_mode mode = GET_MODE (reg);
530 if (GET_CODE (reg) == SUBREG)
532 word = SUBREG_WORD (reg);
533 reg = SUBREG_REG (reg);
536 if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
539 regno = REGNO (reg) + word;
540 endregno = regno + HARD_REGNO_NREGS (regno, mode);
542 for (i = regno; i < endregno; i++)
544 SET_HARD_REG_BIT (hard_regs_live, i);
545 CLEAR_HARD_REG_BIT (hard_regs_saved, i);
546 CLEAR_HARD_REG_BIT (hard_regs_need_restore, i);
550 /* Here when a REG_DEAD note records the last use of a reg. Clear
551 the appropriate bit or bits in hard_regs_live. Again we can ignore
558 register int regno, endregno, i;
560 if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
564 endregno= regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
566 for (i = regno; i < endregno; i++)
568 CLEAR_HARD_REG_BIT (hard_regs_live, i);
569 CLEAR_HARD_REG_BIT (hard_regs_need_restore, i);
570 CLEAR_HARD_REG_BIT (hard_regs_saved, i);
574 /* If any register currently residing in the save area is referenced in X,
575 which is part of INSN, emit code to restore the register in front of INSN.
576 INSN_MODE is the mode to assign to any insns that we add. */
579 restore_referenced_regs (x, insn, insn_mode)
582 enum machine_mode insn_mode;
584 enum rtx_code code = GET_CODE (x);
593 int regno = REGNO (x);
595 /* If this is a pseudo, scan its memory location, since it might
596 involve the use of another register, which might be saved. */
598 if (regno >= FIRST_PSEUDO_REGISTER
599 && reg_equiv_mem[regno] != 0)
600 restore_referenced_regs (XEXP (reg_equiv_mem[regno], 0),
602 else if (regno >= FIRST_PSEUDO_REGISTER
603 && reg_equiv_address[regno] != 0)
604 restore_referenced_regs (reg_equiv_address[regno],
607 /* Otherwise if this is a hard register, restore any piece of it that
608 is currently saved. */
610 else if (regno < FIRST_PSEUDO_REGISTER)
612 int numregs = HARD_REGNO_NREGS (regno, GET_MODE (x));
613 /* Save at most SAVEREGS at a time. This can not be larger than
614 MOVE_MAX, because that causes insert_save_restore to fail. */
615 int saveregs = MIN (numregs, MOVE_MAX / UNITS_PER_WORD);
616 int endregno = regno + numregs;
618 for (i = regno; i < endregno; i++)
619 if (TEST_HARD_REG_BIT (hard_regs_need_restore, i))
620 i += insert_save_restore (insn, 0, i, insn_mode, saveregs);
626 fmt = GET_RTX_FORMAT (code);
627 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
630 restore_referenced_regs (XEXP (x, i), insn, insn_mode);
631 else if (fmt[i] == 'E')
632 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
633 restore_referenced_regs (XVECEXP (x, i, j), insn, insn_mode);
637 /* Insert a sequence of insns to save or restore, SAVE_P says which,
638 REGNO. Place these insns in front of INSN. INSN_MODE is the mode
639 to assign to these insns. MAXRESTORE is the maximum number of registers
640 which should be restored during this call (when SAVE_P == 0). It should
641 never be less than 1 since we only work with entire registers.
643 Note that we have verified in init_caller_save that we can do this
644 with a simple SET, so use it. Set INSN_CODE to what we save there
645 since the address might not be valid so the insn might not be recognized.
646 These insns will be reloaded and have register elimination done by
647 find_reload, so we need not worry about that here.
649 Return the extra number of registers saved. */
652 insert_save_restore (insn, save_p, regno, insn_mode, maxrestore)
656 enum machine_mode insn_mode;
663 /* A common failure mode if register status is not correct in the RTL
664 is for this routine to be called with a REGNO we didn't expect to
665 save. That will cause us to write an insn with a (nil) SET_DEST
666 or SET_SRC. Instead of doing so and causing a crash later, check
667 for this common case and abort here instead. This will remove one
668 step in debugging such problems. */
670 if (regno_save_mem[regno][1] == 0)
673 /* If INSN is a CALL_INSN, we must insert our insns before any
674 USE insns in front of the CALL_INSN. */
676 if (GET_CODE (insn) == CALL_INSN)
677 while (GET_CODE (PREV_INSN (insn)) == INSN
678 && GET_CODE (PATTERN (PREV_INSN (insn))) == USE)
679 insn = PREV_INSN (insn);
682 /* If INSN references CC0, put our insns in front of the insn that sets
683 CC0. This is always safe, since the only way we could be passed an
684 insn that references CC0 is for a restore, and doing a restore earlier
685 isn't a problem. We do, however, assume here that CALL_INSNs don't
686 reference CC0. Guard against non-INSN's like CODE_LABEL. */
688 if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
689 && reg_referenced_p (cc0_rtx, PATTERN (insn)))
690 insn = prev_nonnote_insn (insn);
693 /* Get the pattern to emit and update our status. */
699 /* See if we can save several registers with a single instruction.
700 Work backwards to the single register case. */
701 for (i = MOVE_MAX / UNITS_PER_WORD; i > 0; i--)
704 if (regno_save_mem[regno][i] != 0)
705 for (j = 0; j < i; j++)
707 if (! call_used_regs[regno + j] || call_fixed_regs[regno + j]
708 || ! TEST_HARD_REG_BIT (hard_regs_live, regno + j)
709 || TEST_HARD_REG_BIT (hard_regs_saved, regno + j))
715 /* Must do this one save at a time */
719 pat = gen_rtx (SET, VOIDmode, regno_save_mem[regno][i],
720 gen_rtx (REG, GET_MODE (regno_save_mem[regno][i]), regno));
721 code = reg_save_code[regno][i];
723 /* Set hard_regs_saved for all the registers we saved. */
724 for (k = 0; k < i; k++)
726 SET_HARD_REG_BIT (hard_regs_saved, regno + k);
727 SET_HARD_REG_BIT (hard_regs_need_restore, regno + k);
740 /* See if we can restore `maxrestore' registers at once. Work
741 backwards to the single register case. */
742 for (i = maxrestore; i > 0; i--)
745 if (regno_save_mem[regno][i])
746 for (j = 0; j < i; j++)
748 if (! TEST_HARD_REG_BIT (hard_regs_need_restore, regno + j))
754 /* Must do this one restore at a time */
758 pat = gen_rtx (SET, VOIDmode,
759 gen_rtx (REG, GET_MODE (regno_save_mem[regno][i]),
761 regno_save_mem[regno][i]);
762 code = reg_restore_code[regno][i];
765 /* Clear status for all registers we restored. */
766 for (k = 0; k < i; k++)
768 CLEAR_HARD_REG_BIT (hard_regs_need_restore, regno + k);
776 /* Emit the insn and set the code and mode. */
778 insn = emit_insn_before (pat, insn);
779 PUT_MODE (insn, insn_mode);
780 INSN_CODE (insn) = code;
782 /* Tell our callers how many extra registers we saved/restored */