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Annotation of gcc/caller-save.c, revision 1.1

1.1     ! root        1: /* Save and restore call-clobbered registers which are live across a call.
        !             2:    Copyright (C) 1989 Free Software Foundation, Inc.
        !             3: 
        !             4: This file is part of GNU CC.
        !             5: 
        !             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 1, or (at your option)
        !             9: any later version.
        !            10: 
        !            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.
        !            15: 
        !            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.  */
        !            19: 
        !            20: #include "config.h"
        !            21: #include "rtl.h"
        !            22: #include "insn-config.h"
        !            23: #include "flags.h"
        !            24: #include "regs.h"
        !            25: #include "hard-reg-set.h"
        !            26: #include "reload.h"
        !            27: #include "recog.h"
        !            28: #include "basic-block.h"
        !            29: 
        !            30: /* Set of hard regs currently live (during scan of all insns).  */
        !            31: 
        !            32: static HARD_REG_SET hard_regs_live;
        !            33: 
        !            34: /* The block of storage on the stack where regs are saved */
        !            35: 
        !            36: static rtx save_block_addr;
        !            37: static int save_block_size;
        !            38: 
        !            39: /* A REG rtx for each hard register that has been saved.  */
        !            40: 
        !            41: static rtx save_reg_rtx[FIRST_PSEUDO_REGISTER];
        !            42: 
        !            43: static void set_reg_live ();
        !            44: static void clear_reg_live ();
        !            45: static void insert_call_saves ();
        !            46: static void emit_mult_save ();
        !            47: static void emit_mult_restore ();
        !            48: static rtx grow_save_block ();
        !            49: static enum machine_mode choose_hard_reg_mode ();
        !            50: 
        !            51: /* Find the places where hard regs are live across calls and save them.  */
        !            52: 
        !            53: save_call_clobbered_regs ()
        !            54: {
        !            55:   rtx insn;
        !            56:   int b;
        !            57: 
        !            58:   if (obey_regdecls)
        !            59:     return;
        !            60:   
        !            61:   save_block_size = 0;
        !            62:   save_block_addr = 0;
        !            63:   bzero (save_reg_rtx, sizeof save_reg_rtx);
        !            64: 
        !            65:   for (b = 0; b < n_basic_blocks; b++)
        !            66:     {
        !            67:       regset regs_live = basic_block_live_at_start[b];
        !            68:       int offset, bit, i;
        !            69: 
        !            70:       /* Compute hard regs live at start of block -- this is the
        !            71:         real hard regs marked live, plus live pseudo regs that
        !            72:         have been renumbered to hard regs.  */
        !            73: 
        !            74: #ifdef HARD_REG_SET
        !            75:       hard_regs_live = *regs_live;
        !            76: #else
        !            77:       COPY_HARD_REG_SET (hard_regs_live, regs_live);
        !            78: #endif
        !            79: 
        !            80:       for (offset = 0, i = 0; offset < regset_size; offset++)
        !            81:        {
        !            82:          if (regs_live[offset] == 0)
        !            83:            i += HOST_BITS_PER_INT;
        !            84:          else
        !            85:            for (bit = 1; bit && i < max_regno; bit <<= 1, i++)
        !            86:              if ((regs_live[offset] & bit) && reg_renumber[i] >= 0)
        !            87:                SET_HARD_REG_BIT (hard_regs_live, reg_renumber[i]);
        !            88:        }
        !            89: 
        !            90:       /* Now scan the insns in the block, keeping track of what hard
        !            91:         regs are live as we go.  When we see a call, save the live
        !            92:         call-clobbered hard regs.  */
        !            93: 
        !            94:       for (insn = basic_block_head[b]; TRUE; insn = NEXT_INSN (insn))
        !            95:        {
        !            96:          RTX_CODE code = GET_CODE (insn);
        !            97: 
        !            98:          if (code == CALL_INSN)
        !            99:            insert_call_saves (insn);
        !           100: 
        !           101:          if (code == INSN || code == CALL_INSN || code == JUMP_INSN)
        !           102:            {
        !           103:              rtx link;
        !           104: 
        !           105:              /* NB: the normal procedure is to first enliven any
        !           106:                 registers set by insn, then deaden any registers that
        !           107:                 had their last use at insn.  This is incorrect now,
        !           108:                 since multiple pseudos may have been mapped to the
        !           109:                 same hard reg, and the death notes are ambiguous.  So
        !           110:                 it must be done in the other, safe, order.  */
        !           111: 
        !           112:              for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
        !           113:                if (REG_NOTE_KIND (link) == REG_DEAD)
        !           114:                  clear_reg_live (XEXP (link, 0));
        !           115: 
        !           116:              note_stores (PATTERN (insn), set_reg_live);
        !           117:            }
        !           118: 
        !           119:          if (insn == basic_block_end[b])
        !           120:            break;
        !           121:        }
        !           122:     }
        !           123: }
        !           124: 
        !           125: /* Here from note_stores when an insn stores a value in a register.
        !           126:    Set the proper bit or bits in hard_regs_live.  */
        !           127: 
        !           128: static void
        !           129: set_reg_live (reg, setter)
        !           130:      rtx reg, setter;
        !           131: {
        !           132:   register int regno;
        !           133: 
        !           134:   /* WORD is which word of a multi-register group is being stored.
        !           135:      For the case where the store is actually into a SUBREG of REG.
        !           136:      Except we don't use it; I believe the entire REG needs to be
        !           137:      live.  */
        !           138:   int word = 0;
        !           139: 
        !           140:   if (GET_CODE (reg) == SUBREG)
        !           141:     {
        !           142:       word = SUBREG_WORD (reg);
        !           143:       reg = SUBREG_REG (reg);
        !           144:     }
        !           145: 
        !           146:   if (GET_CODE (reg) != REG)
        !           147:     return;
        !           148: 
        !           149:   regno = REGNO (reg);
        !           150: 
        !           151:   /* For pseudo reg, see if it has been assigned a hardware reg.  */
        !           152:   if (reg_renumber[regno] >= 0)
        !           153:     regno = reg_renumber[regno] /* + word */;
        !           154: 
        !           155:   /* Handle hardware regs (and pseudos allocated to hard regs).  */
        !           156:   if (regno < FIRST_PSEUDO_REGISTER && ! call_fixed_regs[regno])
        !           157:     {
        !           158:       register int last = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
        !           159:       while (regno < last)
        !           160:        {
        !           161:          SET_HARD_REG_BIT (hard_regs_live, regno);
        !           162:          regno++;
        !           163:        }
        !           164:     }
        !           165: }
        !           166: 
        !           167: /* Here when a REG_DEAD note records the last use of a reg.  Clear
        !           168:    the appropriate bit or bits in hard_regs_live.  */
        !           169: 
        !           170: static void
        !           171: clear_reg_live (reg)
        !           172:      rtx reg;
        !           173: {
        !           174:   register int regno = REGNO (reg);
        !           175: 
        !           176:   /* For pseudo reg, see if it has been assigned a hardware reg.  */
        !           177:   if (reg_renumber[regno] >= 0)
        !           178:     regno = reg_renumber[regno];
        !           179: 
        !           180:   /* Handle hardware regs (and pseudos allocated to hard regs).  */
        !           181:   if (regno < FIRST_PSEUDO_REGISTER && ! call_fixed_regs[regno])
        !           182:     {
        !           183:       /* Pseudo regs already assigned hardware regs are treated
        !           184:         almost the same as explicit hardware regs.  */
        !           185:       register int last = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
        !           186:       while (regno < last)
        !           187:        {
        !           188:          CLEAR_HARD_REG_BIT (hard_regs_live, regno);
        !           189:          regno++;
        !           190:        }
        !           191:     }
        !           192: }      
        !           193: 
        !           194: /* Insert insns to save and restore live call-clobbered regs around
        !           195:    call insn INSN.  */
        !           196: 
        !           197: static void
        !           198: insert_call_saves (insn)
        !           199:      rtx insn;
        !           200: {
        !           201:   int regno;
        !           202:   int save_block_size_needed;
        !           203:   int save_block_offset[FIRST_PSEUDO_REGISTER];
        !           204: 
        !           205:   save_block_size_needed = 0;
        !           206:   
        !           207:   for (regno = 0; regno < FIRST_PSEUDO_REGISTER; ++regno)
        !           208:     {
        !           209:       save_block_offset[regno] = -1;
        !           210:       if (call_used_regs[regno] && ! call_fixed_regs[regno]
        !           211:          && TEST_HARD_REG_BIT (hard_regs_live, regno))
        !           212:        {
        !           213:          enum machine_mode mode = choose_hard_reg_mode (regno);
        !           214:          int align = GET_MODE_UNIT_SIZE (mode);
        !           215:          if (align > BIGGEST_ALIGNMENT / BITS_PER_UNIT)
        !           216:            align = BIGGEST_ALIGNMENT / BITS_PER_UNIT;
        !           217:          save_block_size_needed =
        !           218:            ((save_block_size_needed + align - 1) / align) * align;
        !           219:          save_block_offset[regno] = save_block_size_needed;
        !           220:          save_block_size_needed += GET_MODE_SIZE (mode);
        !           221:          if (! save_reg_rtx[regno])
        !           222:            save_reg_rtx[regno] = gen_rtx (REG, mode, regno);
        !           223:        }
        !           224:     }
        !           225: 
        !           226:   if (save_block_size < save_block_size_needed)
        !           227:     save_block_addr = grow_save_block (save_block_addr,
        !           228:                                       save_block_size_needed);
        !           229:   emit_mult_save (insn, save_block_addr, save_block_offset);
        !           230:   emit_mult_restore (insn, save_block_addr, save_block_offset);
        !           231: }
        !           232: 
        !           233: /* Emit a string of stores to save the hard regs listed in
        !           234:    OFFSET[] at address ADDR; insert the loads after INSN.
        !           235:    OFFSET[reg] is -1 if reg should not be saved, or a
        !           236:    suitably-aligned offset from ADDR.  
        !           237:    The offsets actually used do not have to be those listed
        !           238:    in OFFSET, but should fit in a block of the same size.  */
        !           239: 
        !           240: static void
        !           241: emit_mult_save (insn, addr, offset)
        !           242:      rtx insn, addr;
        !           243:      int offset[];
        !           244: {
        !           245:   int regno;
        !           246: 
        !           247:   for (regno = 0; regno < FIRST_PSEUDO_REGISTER; ++regno)
        !           248:     if (offset[regno] >= 0)
        !           249:       {
        !           250:        rtx reg = save_reg_rtx[regno];
        !           251:        rtx temp =
        !           252:          gen_rtx (MEM, GET_MODE (reg), plus_constant (addr, offset[regno]));
        !           253:        emit_insn_before (gen_move_insn (temp, reg), insn);
        !           254:       }
        !           255: }
        !           256: 
        !           257: /* Emit a string of loads to restore the hard regs listed in
        !           258:    OFFSET[] from address ADDR; insert the loads before INSN.
        !           259:    OFFSET[reg] is -1 if reg should not be loaded, or a
        !           260:    suitably-aligned offset from ADDR.  
        !           261:    The offsets actually used do not need to be those provided in
        !           262:    OFFSET, but should agree with whatever emit_mult_save does.  */
        !           263: 
        !           264: static void
        !           265: emit_mult_restore (insn, addr, offset)
        !           266:      rtx insn, addr;
        !           267:      int offset[];     
        !           268: {
        !           269:   int regno;
        !           270: 
        !           271:   for (regno = FIRST_PSEUDO_REGISTER; --regno >= 0; )
        !           272:     if (offset[regno] >= 0)
        !           273:       {
        !           274:        rtx reg = save_reg_rtx[regno];
        !           275:        rtx temp =
        !           276:          gen_rtx (MEM, GET_MODE (reg), plus_constant (addr, offset[regno]));
        !           277:        emit_insn_after (gen_move_insn (reg, temp), insn);
        !           278:       }
        !           279: }
        !           280: 
        !           281: /* Return the address of a new block of size SIZE on the stack.
        !           282:    The old save block is at ADDR; ADDR is 0 if no block exists yet.  */
        !           283: 
        !           284: static rtx
        !           285: grow_save_block (addr, size)
        !           286:      rtx addr;
        !           287:      int size;
        !           288: {
        !           289:   rtx newaddr;
        !           290: 
        !           291:   /* Keep the size a multiple of the main allocation unit.  */
        !           292:   size = (((size + (BIGGEST_ALIGNMENT / BITS_PER_UNIT) - 1)
        !           293:           / (BIGGEST_ALIGNMENT / BITS_PER_UNIT))
        !           294:          * (BIGGEST_ALIGNMENT / BITS_PER_UNIT));
        !           295: 
        !           296:   /* If no save block exists yet, create one and return it.  */
        !           297:   if (! addr)
        !           298:     {
        !           299:       save_block_size = size;
        !           300:       return XEXP (assign_stack_local (BLKmode, size), 0);
        !           301:     }
        !           302: 
        !           303:   /* Get a new block and coalesce it with the old one.  */
        !           304:   newaddr = XEXP (assign_stack_local (BLKmode, size - save_block_size), 0);
        !           305:   if (GET_CODE (newaddr) == PLUS
        !           306:       && XEXP (newaddr, 0) == frame_pointer_rtx
        !           307:       && GET_CODE (XEXP (newaddr, 1)) == CONST_INT
        !           308:       && GET_CODE (addr) == PLUS
        !           309:       && XEXP (addr, 0) == frame_pointer_rtx
        !           310:       && GET_CODE (XEXP (addr, 1)) == CONST_INT
        !           311:       && ((INTVAL (XEXP (newaddr, 1)) - INTVAL (XEXP (addr, 1))
        !           312:           == size - save_block_size)
        !           313:          || (INTVAL (XEXP (addr, 1)) - INTVAL (XEXP (newaddr, 1))
        !           314:              == size - save_block_size)))
        !           315:     {
        !           316:       save_block_size = size;
        !           317:       if (INTVAL (XEXP (newaddr, 1)) < INTVAL (XEXP (addr, 1)))
        !           318:        return newaddr;
        !           319:       else
        !           320:        return addr;
        !           321:     }
        !           322: 
        !           323:   /* They didn't coalesce, find out why */
        !           324:   abort ();                    
        !           325: 
        !           326:   save_block_size = size;
        !           327:   return XEXP (assign_stack_local (BLKmode, size), 0);
        !           328: }
        !           329: 
        !           330: /* Return a machine mode that is legitimate for hard reg REGNO
        !           331:    and large enough to save the whole register.  */
        !           332: 
        !           333: static enum machine_mode
        !           334: choose_hard_reg_mode (regno)
        !           335:      int regno;
        !           336: {
        !           337:   enum reg_class class = REGNO_REG_CLASS (regno);
        !           338: 
        !           339:   if (CLASS_MAX_NREGS (class, DImode) == 1
        !           340:       && HARD_REGNO_MODE_OK (regno, DImode))
        !           341:     return DImode;
        !           342:   else if (CLASS_MAX_NREGS (class, DFmode) == 1
        !           343:           && HARD_REGNO_MODE_OK (regno, DFmode))
        !           344:     return DFmode;
        !           345:   else if (CLASS_MAX_NREGS (class, SImode) == 1
        !           346:           && HARD_REGNO_MODE_OK (regno, SImode))
        !           347:     return SImode;
        !           348:   else if (CLASS_MAX_NREGS (class, SFmode) == 1
        !           349:           && HARD_REGNO_MODE_OK (regno, SFmode))
        !           350:     return SFmode;
        !           351:   else if (CLASS_MAX_NREGS (class, HImode) == 1
        !           352:           && HARD_REGNO_MODE_OK (regno, HImode))
        !           353:     return HImode;
        !           354:   else
        !           355:     abort ();
        !           356: }

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