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 void set_reg_live ();
73 static void clear_reg_live ();
74 static void restore_referenced_regs ();
75 static int insert_save_restore ();
77 /* Return a machine mode that is legitimate for hard reg REGNO and large
78 enough to save nregs. If we can't find one, return VOIDmode. */
80 static enum machine_mode
81 choose_hard_reg_mode (regno, nregs)
84 enum machine_mode found_mode = VOIDmode, mode;
86 /* We first look for the largest integer mode that can be validly
87 held in REGNO. If none, we look for the largest floating-point mode.
88 If we still didn't find a valid mode, try CCmode. */
90 for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT); mode != VOIDmode;
91 mode = GET_MODE_WIDER_MODE (mode))
92 if (HARD_REGNO_NREGS (regno, mode) == nregs
93 && HARD_REGNO_MODE_OK (regno, mode))
96 if (found_mode != VOIDmode)
99 for (mode = GET_CLASS_NARROWEST_MODE (MODE_FLOAT); mode != VOIDmode;
100 mode = GET_MODE_WIDER_MODE (mode))
101 if (HARD_REGNO_NREGS (regno, mode) == nregs
102 && HARD_REGNO_MODE_OK (regno, mode))
105 if (found_mode != VOIDmode)
108 if (HARD_REGNO_NREGS (regno, CCmode) == nregs
109 && HARD_REGNO_MODE_OK (regno, CCmode))
112 /* We can't find a mode valid for this register. */
116 /* Initialize for caller-save.
118 Look at all the hard registers that are used by a call and for which
119 regclass.c has not already excluded from being used across a call.
121 Ensure that we can find a mode to save the register and that there is a
122 simple insn to save and restore the register. This latter check avoids
123 problems that would occur if we tried to save the MQ register of some
124 machines directly into memory. */
129 char *first_obj = (char *) oballoc (0);
135 /* First find all the registers that we need to deal with and all
136 the modes that they can have. If we can't find a mode to use,
137 we can't have the register live over calls. */
139 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
141 if (call_used_regs[i] && ! call_fixed_regs[i])
143 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
145 regno_save_mode[i][j] = choose_hard_reg_mode (i, j);
146 if (regno_save_mode[i][j] == VOIDmode && j == 1)
148 call_fixed_regs[i] = 1;
149 SET_HARD_REG_BIT (call_fixed_reg_set, i);
154 regno_save_mode[i][1] = VOIDmode;
157 /* The following code tries to approximate the conditions under which
158 we can easily save and restore a register without scratch registers or
159 other complexities. It will usually work, except under conditions where
160 the validity of an insn operand is dependent on the address offset.
161 No such cases are currently known.
163 We first find a typical offset from some BASE_REG_CLASS register.
164 This address is chosen by finding the first register in the class
165 and by finding the smallest power of two that is a valid offset from
166 that register in every mode we will use to save registers. */
168 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
169 if (TEST_HARD_REG_BIT (reg_class_contents[(int) BASE_REG_CLASS], i))
172 if (i == FIRST_PSEUDO_REGISTER)
175 addr_reg = gen_rtx (REG, Pmode, i);
177 for (offset = 1 << (HOST_BITS_PER_INT / 2); offset; offset >>= 1)
179 address = gen_rtx (PLUS, Pmode, addr_reg, GEN_INT (offset));
181 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
182 if (regno_save_mode[i][1] != VOIDmode
183 && ! strict_memory_address_p (regno_save_mode[i][1], address))
186 if (i == FIRST_PSEUDO_REGISTER)
190 /* If we didn't find a valid address, we must use register indirect. */
194 /* Next we try to form an insn to save and restore the register. We
195 see if such an insn is recognized and meets its constraints. */
199 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
200 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
201 if (regno_save_mode[i][j] != VOIDmode)
203 rtx mem = gen_rtx (MEM, regno_save_mode[i][j], address);
204 rtx reg = gen_rtx (REG, regno_save_mode[i][j], i);
205 rtx savepat = gen_rtx (SET, VOIDmode, mem, reg);
206 rtx restpat = gen_rtx (SET, VOIDmode, reg, mem);
207 rtx saveinsn = emit_insn (savepat);
208 rtx restinsn = emit_insn (restpat);
211 reg_save_code[i][j] = recog_memoized (saveinsn);
212 reg_restore_code[i][j] = recog_memoized (restinsn);
214 /* Now extract both insns and see if we can meet their constraints. */
215 ok = (reg_save_code[i][j] != -1 && reg_restore_code[i][j] != -1);
218 insn_extract (saveinsn);
219 ok = constrain_operands (reg_save_code[i][j], 1);
220 insn_extract (restinsn);
221 ok &= constrain_operands (reg_restore_code[i][j], 1);
226 regno_save_mode[i][j] = VOIDmode;
229 call_fixed_regs[i] = 1;
230 SET_HARD_REG_BIT (call_fixed_reg_set, i);
240 /* Initialize save areas by showing that we haven't allocated any yet. */
247 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
248 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
249 regno_save_mem[i][j] = 0;
252 /* Allocate save areas for any hard registers that might need saving.
253 We take a conservative approach here and look for call-clobbered hard
254 registers that are assigned to pseudos that cross calls. This may
255 overestimate slightly (especially if some of these registers are later
256 used as spill registers), but it should not be significant.
258 Then perform register elimination in the addresses of the save area
259 locations; return 1 if all eliminated addresses are strictly valid.
260 We assume that our caller has set up the elimination table to the
261 worst (largest) possible offsets.
263 Set *PCHANGED to 1 if we had to allocate some memory for the save area.
267 In the fallback case we should iterate backwards across all possible
268 modes for the save, choosing the largest available one instead of
269 falling back to the smallest mode immediately. (eg TF -> DF -> SF).
271 We do not try to use "move multiple" instructions that exist
272 on some machines (such as the 68k moveml). It could be a win to try
273 and use them when possible. The hard part is doing it in a way that is
274 machine independent since they might be saving non-consecutive
275 registers. (imagine caller-saving d0,d1,a0,a1 on the 68k) */
278 setup_save_areas (pchanged)
282 HARD_REG_SET hard_regs_used;
286 /* Allocate space in the save area for the largest multi-register
287 pseudos first, then work backwards to single register
290 /* Find and record all call-used hard-registers in this function. */
291 CLEAR_HARD_REG_SET (hard_regs_used);
292 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
293 if (reg_renumber[i] >= 0 && reg_n_calls_crossed[i] > 0)
295 int regno = reg_renumber[i];
297 = regno + HARD_REGNO_NREGS (regno, GET_MODE (regno_reg_rtx[i]));
298 int nregs = endregno - regno;
300 for (j = 0; j < nregs; j++)
302 if (call_used_regs[regno+j])
303 SET_HARD_REG_BIT (hard_regs_used, regno+j);
307 /* Now run through all the call-used hard-registers and allocate
308 space for them in the caller-save area. Try to allocate space
309 in a manner which allows multi-register saves/restores to be done. */
311 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
312 for (j = MOVE_MAX / UNITS_PER_WORD; j > 0; j--)
317 /* If no mode exists for this size, try another. Also break out
318 if we have already saved this hard register. */
319 if (regno_save_mode[i][j] == VOIDmode || regno_save_mem[i][1] != 0)
322 /* See if any register in this group has been saved. */
324 for (k = 0; k < j; k++)
325 if (regno_save_mem[i + k][1])
333 for (k = 0; k < j; k++)
336 ok &= (TEST_HARD_REG_BIT (hard_regs_used, regno) != 0);
339 /* We have found an acceptable mode to store in. */
344 = assign_stack_local (regno_save_mode[i][j],
345 GET_MODE_SIZE (regno_save_mode[i][j]), 0);
347 /* Setup single word save area just in case... */
348 for (k = 0; k < j; k++)
350 /* This should not depend on WORDS_BIG_ENDIAN.
351 The order of words in regs is the same as in memory. */
352 rtx temp = gen_rtx (MEM, regno_save_mode[i+k][1],
353 XEXP (regno_save_mem[i][j], 0));
355 regno_save_mem[i+k][1]
356 = adj_offsettable_operand (temp, k * UNITS_PER_WORD);
362 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
363 for (j = 1; j <= MOVE_MAX / UNITS_PER_WORD; j++)
364 if (regno_save_mem[i][j] != 0)
365 ok &= strict_memory_address_p (GET_MODE (regno_save_mem[i][j]),
366 XEXP (eliminate_regs (regno_save_mem[i][j], 0, NULL_RTX), 0));
371 /* Find the places where hard regs are live across calls and save them.
373 INSN_MODE is the mode to assign to any insns that we add. This is used
374 by reload to determine whether or not reloads or register eliminations
375 need be done on these insns. */
378 save_call_clobbered_regs (insn_mode)
379 enum machine_mode insn_mode;
384 for (b = 0; b < n_basic_blocks; b++)
386 regset regs_live = basic_block_live_at_start[b];
387 rtx prev_block_last = PREV_INSN (basic_block_head[b]);
392 /* Compute hard regs live at start of block -- this is the
393 real hard regs marked live, plus live pseudo regs that
394 have been renumbered to hard regs. No registers have yet been
395 saved because we restore all of them before the end of the basic
399 hard_regs_live = *regs_live;
401 COPY_HARD_REG_SET (hard_regs_live, regs_live);
404 CLEAR_HARD_REG_SET (hard_regs_saved);
405 CLEAR_HARD_REG_SET (hard_regs_need_restore);
408 for (offset = 0, i = 0; offset < regset_size; offset++)
410 if (regs_live[offset] == 0)
411 i += REGSET_ELT_BITS;
413 for (bit = 1; bit && i < max_regno; bit <<= 1, i++)
414 if ((regs_live[offset] & bit)
415 && (regno = reg_renumber[i]) >= 0)
417 j < regno + HARD_REGNO_NREGS (regno,
418 PSEUDO_REGNO_MODE (i));
420 SET_HARD_REG_BIT (hard_regs_live, j);
424 /* Now scan the insns in the block, keeping track of what hard
425 regs are live as we go. When we see a call, save the live
426 call-clobbered hard regs. */
428 for (insn = basic_block_head[b]; ; insn = NEXT_INSN (insn))
430 RTX_CODE code = GET_CODE (insn);
432 if (GET_RTX_CLASS (code) == 'i')
436 /* If some registers have been saved, see if INSN references
437 any of them. We must restore them before the insn if so. */
440 restore_referenced_regs (PATTERN (insn), insn, insn_mode);
442 /* NB: the normal procedure is to first enliven any
443 registers set by insn, then deaden any registers that
444 had their last use at insn. This is incorrect now,
445 since multiple pseudos may have been mapped to the
446 same hard reg, and the death notes are ambiguous. So
447 it must be done in the other, safe, order. */
449 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
450 if (REG_NOTE_KIND (link) == REG_DEAD)
451 clear_reg_live (XEXP (link, 0));
453 /* When we reach a call, we need to save all registers that are
454 live, call-used, not fixed, and not already saved. We must
455 test at this point because registers that die in a CALL_INSN
456 are not live across the call and likewise for registers that
457 are born in the CALL_INSN. */
459 if (code == CALL_INSN)
461 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
462 if (call_used_regs[regno] && ! call_fixed_regs[regno]
463 && TEST_HARD_REG_BIT (hard_regs_live, regno)
464 && ! TEST_HARD_REG_BIT (hard_regs_saved, regno))
465 regno += insert_save_restore (insn, 1, regno,
468 hard_regs_need_restore = hard_regs_saved;
470 COPY_HARD_REG_SET (hard_regs_need_restore,
474 /* Must recompute n_regs_saved. */
476 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
477 if (TEST_HARD_REG_BIT (hard_regs_saved, regno))
482 note_stores (PATTERN (insn), set_reg_live);
484 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
485 if (REG_NOTE_KIND (link) == REG_UNUSED)
486 clear_reg_live (XEXP (link, 0));
489 if (insn == basic_block_end[b])
493 /* At the end of the basic block, we must restore any registers that
494 remain saved. If the last insn in the block is a JUMP_INSN, put
495 the restore before the insn, otherwise, put it after the insn. */
498 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
499 if (TEST_HARD_REG_BIT (hard_regs_need_restore, regno))
500 regno += insert_save_restore ((GET_CODE (insn) == JUMP_INSN
501 ? insn : NEXT_INSN (insn)), 0,
502 regno, insn_mode, MOVE_MAX / UNITS_PER_WORD);
504 /* If we added any insns at the start of the block, update the start
505 of the block to point at those insns. */
506 basic_block_head[b] = NEXT_INSN (prev_block_last);
510 /* Here from note_stores when an insn stores a value in a register.
511 Set the proper bit or bits in hard_regs_live. All pseudos that have
512 been assigned hard regs have had their register number changed already,
513 so we can ignore pseudos. */
516 set_reg_live (reg, setter)
519 register int regno, endregno, i;
520 enum machine_mode mode = GET_MODE (reg);
523 if (GET_CODE (reg) == SUBREG)
525 word = SUBREG_WORD (reg);
526 reg = SUBREG_REG (reg);
529 if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
532 regno = REGNO (reg) + word;
533 endregno = regno + HARD_REGNO_NREGS (regno, mode);
535 for (i = regno; i < endregno; i++)
537 SET_HARD_REG_BIT (hard_regs_live, i);
538 CLEAR_HARD_REG_BIT (hard_regs_saved, i);
539 CLEAR_HARD_REG_BIT (hard_regs_need_restore, i);
543 /* Here when a REG_DEAD note records the last use of a reg. Clear
544 the appropriate bit or bits in hard_regs_live. Again we can ignore
551 register int regno, endregno, i;
553 if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
557 endregno= regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
559 for (i = regno; i < endregno; i++)
561 CLEAR_HARD_REG_BIT (hard_regs_live, i);
562 CLEAR_HARD_REG_BIT (hard_regs_need_restore, i);
563 CLEAR_HARD_REG_BIT (hard_regs_saved, i);
567 /* If any register currently residing in the save area is referenced in X,
568 which is part of INSN, emit code to restore the register in front of INSN.
569 INSN_MODE is the mode to assign to any insns that we add. */
572 restore_referenced_regs (x, insn, insn_mode)
575 enum machine_mode insn_mode;
577 enum rtx_code code = GET_CODE (x);
586 int regno = REGNO (x);
588 /* If this is a pseudo, scan its memory location, since it might
589 involve the use of another register, which might be saved. */
591 if (regno >= FIRST_PSEUDO_REGISTER
592 && reg_equiv_mem[regno] != 0)
593 restore_referenced_regs (XEXP (reg_equiv_mem[regno], 0),
595 else if (regno >= FIRST_PSEUDO_REGISTER
596 && reg_equiv_address[regno] != 0)
597 restore_referenced_regs (reg_equiv_address[regno],
600 /* Otherwise if this is a hard register, restore any piece of it that
601 is currently saved. */
603 else if (regno < FIRST_PSEUDO_REGISTER)
605 int numregs = MIN (HARD_REGNO_NREGS (regno, GET_MODE (x)),
606 MOVE_MAX / UNITS_PER_WORD);
607 int endregno = regno + numregs;
609 for (i = regno; i < endregno; i++)
610 if (TEST_HARD_REG_BIT (hard_regs_need_restore, i))
611 i += insert_save_restore (insn, 0, i, insn_mode, numregs);
617 fmt = GET_RTX_FORMAT (code);
618 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
621 restore_referenced_regs (XEXP (x, i), insn, insn_mode);
622 else if (fmt[i] == 'E')
623 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
624 restore_referenced_regs (XVECEXP (x, i, j), insn, insn_mode);
628 /* Insert a sequence of insns to save or restore, SAVE_P says which,
629 REGNO. Place these insns in front of INSN. INSN_MODE is the mode
630 to assign to these insns. MAXRESTORE is the maximum number of registers
631 which should be restored during this call (when SAVE_P == 0). It should
632 never be less than 1 since we only work with entire registers.
634 Note that we have verified in init_caller_save that we can do this
635 with a simple SET, so use it. Set INSN_CODE to what we save there
636 since the address might not be valid so the insn might not be recognized.
637 These insns will be reloaded and have register elimination done by
638 find_reload, so we need not worry about that here.
640 Return the extra number of registers saved. */
643 insert_save_restore (insn, save_p, regno, insn_mode, maxrestore)
647 enum machine_mode insn_mode;
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 /* If INSN is a CALL_INSN, we must insert our insns before any
665 USE insns in front of the CALL_INSN. */
667 if (GET_CODE (insn) == CALL_INSN)
668 while (GET_CODE (PREV_INSN (insn)) == INSN
669 && GET_CODE (PATTERN (PREV_INSN (insn))) == USE)
670 insn = PREV_INSN (insn);
673 /* If INSN references CC0, put our insns in front of the insn that sets
674 CC0. This is always safe, since the only way we could be passed an
675 insn that references CC0 is for a restore, and doing a restore earlier
676 isn't a problem. We do, however, assume here that CALL_INSNs don't
677 reference CC0. Guard against non-INSN's like CODE_LABEL. */
679 if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
680 && reg_referenced_p (cc0_rtx, PATTERN (insn)))
681 insn = prev_nonnote_insn (insn);
684 /* Get the pattern to emit and update our status. */
690 /* See if we can save several registers with a single instruction.
691 Work backwards to the single register case. */
692 for (i = MOVE_MAX / UNITS_PER_WORD; i > 0; i--)
695 if (regno_save_mem[regno][i] != 0)
696 for (j = 0; j < i; j++)
698 if (! call_used_regs[regno + j] || call_fixed_regs[regno + j]
699 || ! TEST_HARD_REG_BIT (hard_regs_live, regno + j)
700 || TEST_HARD_REG_BIT (hard_regs_saved, regno + j))
706 /* Must do this one save at a time */
710 pat = gen_rtx (SET, VOIDmode, regno_save_mem[regno][i],
711 gen_rtx (REG, GET_MODE (regno_save_mem[regno][i]), regno));
712 code = reg_save_code[regno][i];
714 /* Set hard_regs_saved for all the registers we saved. */
715 for (k = 0; k < i; k++)
717 SET_HARD_REG_BIT (hard_regs_saved, regno + k);
718 SET_HARD_REG_BIT (hard_regs_need_restore, regno + k);
731 /* See if we can restore `maxrestore' registers at once. Work
732 backwards to the single register case. */
733 for (i = maxrestore; i > 0; i--)
736 if (regno_save_mem[regno][i])
737 for (j = 0; j < i; j++)
739 if (! TEST_HARD_REG_BIT (hard_regs_need_restore, regno + j))
745 /* Must do this one restore at a time */
749 pat = gen_rtx (SET, VOIDmode,
750 gen_rtx (REG, GET_MODE (regno_save_mem[regno][i]),
752 regno_save_mem[regno][i]);
753 code = reg_restore_code[regno][i];
756 /* Clear status for all registers we restored. */
757 for (k = 0; k < i; k++)
759 CLEAR_HARD_REG_BIT (hard_regs_need_restore, regno + k);
767 /* Emit the insn and set the code and mode. */
769 insn = emit_insn_before (pat, insn);
770 PUT_MODE (insn, insn_mode);
771 INSN_CODE (insn) = code;
773 /* Tell our callers how many extra registers we saved/restored */