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 #define CEIL(x,y) (((x) + (y) - 1) / (y))
33 /* Modes for each hard register that we can save. The smallest mode is wide
34 enough to save the entire contents of the register. When saving the
35 register because it is live we first try to save in multi-register modes.
36 If that is not possible the save is done one register at a time. */
38 static enum machine_mode
39 regno_save_mode[FIRST_PSEUDO_REGISTER][MOVE_MAX / UNITS_PER_WORD + 1];
41 /* For each hard register, a place on the stack where it can be saved,
45 regno_save_mem[FIRST_PSEUDO_REGISTER][MOVE_MAX / UNITS_PER_WORD + 1];
47 /* We will only make a register eligible for caller-save if it can be
48 saved in its widest mode with a simple SET insn as long as the memory
49 address is valid. We record the INSN_CODE is those insns here since
50 when we emit them, the addresses might not be valid, so they might not
54 reg_save_code[FIRST_PSEUDO_REGISTER][MOVE_MAX / UNITS_PER_WORD + 1];
56 reg_restore_code[FIRST_PSEUDO_REGISTER][MOVE_MAX / UNITS_PER_WORD + 1];
58 /* Set of hard regs currently live (during scan of all insns). */
60 static HARD_REG_SET hard_regs_live;
62 /* Set of hard regs currently residing in save area (during insn scan). */
64 static HARD_REG_SET hard_regs_saved;
66 /* Set of hard regs which need to be restored before referenced. */
68 static HARD_REG_SET hard_regs_need_restore;
70 /* Number of registers currently in hard_regs_saved. */
74 static void set_reg_live ();
75 static void clear_reg_live ();
76 static void restore_referenced_regs ();
77 static int insert_save_restore ();
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)
86 enum machine_mode found_mode = VOIDmode, mode;
88 /* We first look for the largest integer mode that can be validly
89 held in REGNO. If none, we look for the largest floating-point mode.
90 If we still didn't find a valid mode, try CCmode. */
92 for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT); mode != VOIDmode;
93 mode = GET_MODE_WIDER_MODE (mode))
94 if (HARD_REGNO_NREGS (regno, mode) == nregs
95 && HARD_REGNO_MODE_OK (regno, mode))
98 if (found_mode != VOIDmode)
101 for (mode = GET_CLASS_NARROWEST_MODE (MODE_FLOAT); 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 if (HARD_REGNO_NREGS (regno, CCmode) == nregs
111 && HARD_REGNO_MODE_OK (regno, CCmode))
114 /* We can't find a mode valid for this register. */
118 /* Initialize for caller-save.
120 Look at all the hard registers that are used by a call and for which
121 regclass.c has not already excluded from being used across a call.
123 Ensure that we can find a mode to save the register and that there is a
124 simple insn to save and restore the register. This latter check avoids
125 problems that would occur if we tried to save the MQ register of some
126 machines directly into memory. */
131 char *first_obj = (char *) oballoc (0);
137 /* First find all the registers that we need to deal with and all
138 the modes that they can have. If we can't find a mode to use,
139 we can't have the register live over calls. */
141 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
143 if (call_used_regs[i] && ! call_fixed_regs[i])
145 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
147 regno_save_mode[i][j] = choose_hard_reg_mode (i, j);
148 if (regno_save_mode[i][j] == VOIDmode && j == 1)
150 call_fixed_regs[i] = 1;
151 SET_HARD_REG_BIT (call_fixed_reg_set, i);
156 regno_save_mode[i][1] = VOIDmode;
159 /* The following code tries to approximate the conditions under which
160 we can easily save and restore a register without scratch registers or
161 other complexities. It will usually work, except under conditions where
162 the validity of an insn operand is dependent on the address offset.
163 No such cases are currently known.
165 We first find a typical offset from some BASE_REG_CLASS register.
166 This address is chosen by finding the first register in the class
167 and by finding the smallest power of two that is a valid offset from
168 that register in every mode we will use to save registers. */
170 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
171 if (TEST_HARD_REG_BIT (reg_class_contents[(int) BASE_REG_CLASS], i))
174 if (i == FIRST_PSEUDO_REGISTER)
177 addr_reg = gen_rtx (REG, Pmode, i);
179 for (offset = 1 << (HOST_BITS_PER_INT / 2); offset; offset >>= 1)
181 address = gen_rtx (PLUS, Pmode, addr_reg, GEN_INT (offset));
183 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
184 if (regno_save_mode[i][1] != VOIDmode
185 && ! strict_memory_address_p (regno_save_mode[i][1], address))
188 if (i == FIRST_PSEUDO_REGISTER)
192 /* If we didn't find a valid address, we must use register indirect. */
196 /* Next we try to form an insn to save and restore the register. We
197 see if such an insn is recognized and meets its constraints. */
201 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
202 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
203 if (regno_save_mode[i][j] != VOIDmode)
205 rtx mem = gen_rtx (MEM, regno_save_mode[i][j], address);
206 rtx reg = gen_rtx (REG, regno_save_mode[i][j], i);
207 rtx savepat = gen_rtx (SET, VOIDmode, mem, reg);
208 rtx restpat = gen_rtx (SET, VOIDmode, reg, mem);
209 rtx saveinsn = emit_insn (savepat);
210 rtx restinsn = emit_insn (restpat);
213 reg_save_code[i][j] = recog_memoized (saveinsn);
214 reg_restore_code[i][j] = recog_memoized (restinsn);
216 /* Now extract both insns and see if we can meet their constraints. */
217 ok = (reg_save_code[i][j] != -1 && reg_restore_code[i][j] != -1);
220 insn_extract (saveinsn);
221 ok = constrain_operands (reg_save_code[i][j], 1);
222 insn_extract (restinsn);
223 ok &= constrain_operands (reg_restore_code[i][j], 1);
228 call_fixed_regs[i] = 1;
229 SET_HARD_REG_BIT (call_fixed_reg_set, i);
238 /* Initialize save areas by showing that we haven't allocated any yet. */
245 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
246 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
247 regno_save_mem[i][j] = 0;
250 /* Allocate save areas for any hard registers that might need saving.
251 We take a conservative approach here and look for call-clobbered hard
252 registers that are assigned to pseudos that cross calls. This may
253 overestimate slightly (especially if some of these registers are later
254 used as spill registers), but it should not be significant.
256 Then perform register elimination in the addresses of the save area
257 locations; return 1 if all eliminated addresses are strictly valid.
258 We assume that our caller has set up the elimination table to the
259 worst (largest) possible offsets.
261 Set *PCHANGED to 1 if we had to allocate some memory for the save area.
265 In the fallback case we should iterate backwards across all possible
266 modes for the save, choosing the largest available one instead of
267 falling back to the smallest mode immediately. (eg TF -> DF -> SF).
269 We do not try to use "move multiple" instructions that exist
270 on some machines (such as the 68k moveml). It could be a win to try
271 and use them when possible. The hard part is doing it in a way that is
272 machine independent since they might be saving non-consecutive
273 registers. (imagine caller-saving d0,d1,a0,a1 on the 68k) */
276 setup_save_areas (pchanged)
280 HARD_REG_SET hard_regs_used;
284 /* Allocate space in the save area for the largest multi-register
285 pseudos first, then work backwards to single register
288 /* Find and record all call-used hard-registers in this function. */
289 CLEAR_HARD_REG_SET (hard_regs_used);
290 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
291 if (reg_renumber[i] >= 0 && reg_n_calls_crossed[i] > 0)
293 int regno = reg_renumber[i];
295 = regno + HARD_REGNO_NREGS (regno, GET_MODE (regno_reg_rtx[i]));
296 int nregs = endregno - regno;
298 for (j = 0; j < nregs; j++)
300 if (call_used_regs[regno+j])
301 SET_HARD_REG_BIT (hard_regs_used, regno+j);
305 /* Now run through all the call-used hard-registers and allocate
306 space for them in the caller-save area. Try to allocate space
307 in a manner which allows multi-register saves/restores to be done. */
309 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
310 for (j = MOVE_MAX / UNITS_PER_WORD; j > 0; j--)
314 /* If no mode exists for this size, try another. Also break out
315 if we have already saved this hard register. */
316 if (regno_save_mode[i][j] == VOIDmode || regno_save_mem[i][1] != 0)
319 for (k = 0; k < j; k++)
322 ok &= (TEST_HARD_REG_BIT (hard_regs_used, regno) != 0);
325 /* We have found an acceptable mode to store in. */
330 = assign_stack_local (regno_save_mode[i][j],
331 GET_MODE_SIZE (regno_save_mode[i][j]), 0);
333 /* Setup singe word save area just in case... */
334 for (k = 0; k < j; k++)
339 if (WORDS_BIG_ENDIAN)
340 offset = k * UNITS_PER_WORD;
342 offset = - k * UNITS_PER_WORD;
345 = gen_rtx(MEM, regno_save_mode[i+k][1],
346 XEXP (regno_save_mem[i][j], 0));
347 regno_save_mem[i+k][1]
348 = adj_offsettable_operand(temp, offset);
354 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
355 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
356 if (regno_save_mem[i][j] != 0)
357 ok &= strict_memory_address_p (GET_MODE (regno_save_mem[i][j]),
358 XEXP (eliminate_regs (regno_save_mem[i][j], 0, NULL_RTX), 0));
363 /* Find the places where hard regs are live across calls and save them.
365 INSN_MODE is the mode to assign to any insns that we add. This is used
366 by reload to determine whether or not reloads or register eliminations
367 need be done on these insns. */
370 save_call_clobbered_regs (insn_mode)
371 enum machine_mode insn_mode;
376 for (b = 0; b < n_basic_blocks; b++)
378 regset regs_live = basic_block_live_at_start[b];
383 /* Compute hard regs live at start of block -- this is the
384 real hard regs marked live, plus live pseudo regs that
385 have been renumbered to hard regs. No registers have yet been
386 saved because we restore all of them before the end of the basic
390 hard_regs_live = *regs_live;
392 COPY_HARD_REG_SET (hard_regs_live, regs_live);
395 CLEAR_HARD_REG_SET (hard_regs_saved);
396 CLEAR_HARD_REG_SET (hard_regs_need_restore);
399 for (offset = 0, i = 0; offset < regset_size; offset++)
401 if (regs_live[offset] == 0)
402 i += REGSET_ELT_BITS;
404 for (bit = 1; bit && i < max_regno; bit <<= 1, i++)
405 if ((regs_live[offset] & bit)
406 && (regno = reg_renumber[i]) >= 0)
408 j < regno + HARD_REGNO_NREGS (regno,
409 PSEUDO_REGNO_MODE (i));
411 SET_HARD_REG_BIT (hard_regs_live, j);
415 /* Now scan the insns in the block, keeping track of what hard
416 regs are live as we go. When we see a call, save the live
417 call-clobbered hard regs. */
419 for (insn = basic_block_head[b]; ; insn = NEXT_INSN (insn))
421 RTX_CODE code = GET_CODE (insn);
423 if (GET_RTX_CLASS (code) == 'i')
427 /* If some registers have been saved, see if INSN references
428 any of them. We must restore them before the insn if so. */
431 restore_referenced_regs (PATTERN (insn), insn, insn_mode);
433 /* NB: the normal procedure is to first enliven any
434 registers set by insn, then deaden any registers that
435 had their last use at insn. This is incorrect now,
436 since multiple pseudos may have been mapped to the
437 same hard reg, and the death notes are ambiguous. So
438 it must be done in the other, safe, order. */
440 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
441 if (REG_NOTE_KIND (link) == REG_DEAD)
442 clear_reg_live (XEXP (link, 0));
444 /* When we reach a call, we need to save all registers that are
445 live, call-used, not fixed, and not already saved. We must
446 test at this point because registers that die in a CALL_INSN
447 are not live across the call and likewise for registers that
448 are born in the CALL_INSN. */
450 if (code == CALL_INSN)
452 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
453 if (call_used_regs[regno] && ! call_fixed_regs[regno]
454 && TEST_HARD_REG_BIT (hard_regs_live, regno)
455 && ! TEST_HARD_REG_BIT (hard_regs_saved, regno))
456 regno += insert_save_restore (insn, 1, regno,
459 hard_regs_need_restore = hard_regs_saved;
461 COPY_HARD_REG_SET (hard_regs_need_restore,
465 /* Must recompute n_regs_saved. */
467 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
468 if (TEST_HARD_REG_BIT (hard_regs_saved, regno))
473 note_stores (PATTERN (insn), set_reg_live);
475 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
476 if (REG_NOTE_KIND (link) == REG_UNUSED)
477 clear_reg_live (XEXP (link, 0));
480 if (insn == basic_block_end[b])
484 /* At the end of the basic block, we must restore any registers that
485 remain saved. If the last insn in the block is a JUMP_INSN, put
486 the restore before the insn, otherwise, put it after the insn. */
489 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
490 if (TEST_HARD_REG_BIT (hard_regs_need_restore, regno))
491 regno += insert_save_restore ((GET_CODE (insn) == JUMP_INSN
492 ? insn : NEXT_INSN (insn)), 0,
493 regno, insn_mode, MOVE_MAX / UNITS_PER_WORD);
498 /* Here from note_stores when an insn stores a value in a register.
499 Set the proper bit or bits in hard_regs_live. All pseudos that have
500 been assigned hard regs have had their register number changed already,
501 so we can ignore pseudos. */
504 set_reg_live (reg, setter)
507 register int regno, endregno, i;
508 enum machine_mode mode = GET_MODE (reg);
511 if (GET_CODE (reg) == SUBREG)
513 word = SUBREG_WORD (reg);
514 reg = SUBREG_REG (reg);
517 if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
520 regno = REGNO (reg) + word;
521 endregno = regno + HARD_REGNO_NREGS (regno, mode);
523 for (i = regno; i < endregno; i++)
525 SET_HARD_REG_BIT (hard_regs_live, i);
526 CLEAR_HARD_REG_BIT (hard_regs_saved, i);
527 CLEAR_HARD_REG_BIT (hard_regs_need_restore, i);
531 /* Here when a REG_DEAD note records the last use of a reg. Clear
532 the appropriate bit or bits in hard_regs_live. Again we can ignore
539 register int regno, endregno, i;
541 if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
545 endregno= regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
547 for (i = regno; i < endregno; i++)
549 CLEAR_HARD_REG_BIT (hard_regs_live, i);
550 CLEAR_HARD_REG_BIT (hard_regs_need_restore, i);
551 CLEAR_HARD_REG_BIT (hard_regs_saved, i);
555 /* If any register currently residing in the save area is referenced in X,
556 which is part of INSN, emit code to restore the register in front of INSN.
557 INSN_MODE is the mode to assign to any insns that we add. */
560 restore_referenced_regs (x, insn, insn_mode)
563 enum machine_mode insn_mode;
565 enum rtx_code code = GET_CODE (x);
574 int regno = REGNO (x);
576 /* If this is a pseudo, scan its memory location, since it might
577 involve the use of another register, which might be saved. */
579 if (regno >= FIRST_PSEUDO_REGISTER
580 && reg_equiv_mem[regno] != 0)
581 restore_referenced_regs (XEXP (reg_equiv_mem[regno], 0),
583 else if (regno >= FIRST_PSEUDO_REGISTER
584 && reg_equiv_address[regno] != 0)
585 restore_referenced_regs (reg_equiv_address[regno],
588 /* Otherwise if this is a hard register, restore any piece of it that
589 is currently saved. */
591 else if (regno < FIRST_PSEUDO_REGISTER)
593 int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (x));
595 for (i = regno; i < endregno; i++)
596 if (TEST_HARD_REG_BIT (hard_regs_need_restore, i))
597 i += insert_save_restore (insn, 0, i, insn_mode,
598 CEIL (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD));
604 fmt = GET_RTX_FORMAT (code);
605 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
608 restore_referenced_regs (XEXP (x, i), insn, insn_mode);
609 else if (fmt[i] == 'E')
610 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
611 restore_referenced_regs (XVECEXP (x, i, j), insn, insn_mode);
615 /* Insert a sequence of insns to save or restore, SAVE_P says which,
616 REGNO. Place these insns in front of INSN. INSN_MODE is the mode
617 to assign to these insns. MAXRESTORE is the maximum number of registers
618 which should be restored during this call (when SAVE_P == 0). It should
619 never be less than 1 since we only work with entire registers.
621 Note that we have verified in init_caller_save that we can do this
622 with a simple SET, so use it. Set INSN_CODE to what we save there
623 since the address might not be valid so the insn might not be recognized.
624 These insns will be reloaded and have register elimination done by
625 find_reload, so we need not worry about that here.
627 Return the extra number of registers saved. */
630 insert_save_restore (insn, save_p, regno, insn_mode, maxrestore)
634 enum machine_mode insn_mode;
641 /* A common failure mode if register status is not correct in the RTL
642 is for this routine to be called with a REGNO we didn't expect to
643 save. That will cause us to write an insn with a (nil) SET_DEST
644 or SET_SRC. Instead of doing so and causing a crash later, check
645 for this common case and abort here instead. This will remove one
646 step in debugging such problems. */
648 if (regno_save_mem[regno][1] == 0)
651 /* If INSN is a CALL_INSN, we must insert our insns before any
652 USE insns in front of the CALL_INSN. */
654 if (GET_CODE (insn) == CALL_INSN)
655 while (GET_CODE (PREV_INSN (insn)) == INSN
656 && GET_CODE (PATTERN (PREV_INSN (insn))) == USE)
657 insn = PREV_INSN (insn);
660 /* If INSN references CC0, put our insns in front of the insn that sets
661 CC0. This is always safe, since the only way we could be passed an
662 insn that references CC0 is for a restore, and doing a restore earlier
663 isn't a problem. We do, however, assume here that CALL_INSNs don't
664 reference CC0. Guard against non-INSN's like CODE_LABEL. */
666 if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
667 && reg_referenced_p (cc0_rtx, PATTERN (insn)))
668 insn = prev_nonnote_insn (insn);
671 /* Get the pattern to emit and update our status. */
677 /* See if we can save several registers with a single instruction.
678 Work backwards to the single register case. */
679 for (i = MOVE_MAX / UNITS_PER_WORD; i > 0; i--)
682 if (regno_save_mem[regno][i] != 0)
683 for (j = 0; j < i; j++)
685 if (! call_used_regs[regno + j] && call_fixed_regs[regno + j]
686 && ! TEST_HARD_REG_BIT (hard_regs_live, regno + j)
687 && TEST_HARD_REG_BIT (hard_regs_saved, regno + j))
693 /* Must do this one save at a time */
697 pat = gen_rtx (SET, VOIDmode, regno_save_mem[regno][i],
698 gen_rtx (REG, GET_MODE (regno_save_mem[regno][i]), regno));
699 code = reg_save_code[regno][i];
701 /* Set hard_regs_saved for all the registers we saved. */
702 for (k = 0; k < i; k++)
704 SET_HARD_REG_BIT (hard_regs_saved, regno + k);
705 SET_HARD_REG_BIT (hard_regs_need_restore, regno + k);
718 /* See if we can restore `maxrestore' registers at once. Work
719 backwards to the single register case. */
720 for (i = maxrestore; i > 0; i--)
723 if (regno_save_mem[regno][i])
724 for (j = 0; j < i; j++)
726 if (! TEST_HARD_REG_BIT (hard_regs_need_restore, regno + j))
732 /* Must do this one restore at a time */
736 pat = gen_rtx (SET, VOIDmode,
737 gen_rtx (REG, GET_MODE (regno_save_mem[regno][i]),
739 regno_save_mem[regno][i]);
740 code = reg_restore_code[regno][i];
743 /* Clear status for all registers we restored. */
744 for (k = 0; k < i; k++)
746 CLEAR_HARD_REG_BIT (hard_regs_need_restore, regno + k);
754 /* Emit the insn and set the code and mode. */
756 insn = emit_insn_before (pat, insn);
757 PUT_MODE (insn, insn_mode);
758 INSN_CODE (insn) = code;
760 /* Tell our callers how many extra registers we saved/restored */