Initial revision

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@308 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 568 insertions, 0 deletions

diff --git a/gcc/caller-save.c b/gcc/caller-save.c
new file mode 100644
index 00000000000..3d1c58486f7
--- /dev/null
+++ b/gcc/caller-save.c
@@ -0,0 +1,568 @@
+/* Save and restore call-clobbered registers which are live across a call.
+   Copyright (C) 1989, 1992 Free Software Foundation, Inc.
+
+This file is part of GNU CC.
+
+GNU CC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU CC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU CC; see the file COPYING.  If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+#include "config.h"
+#include "rtl.h"
+#include "insn-config.h"
+#include "flags.h"
+#include "regs.h"
+#include "hard-reg-set.h"
+#include "recog.h"
+#include "basic-block.h"
+#include "reload.h"
+#include "expr.h"
+
+/* A mode for each hard register that we can save.  This mode is wide enough
+   to save the entire contents of the register and will be used whenever the
+   register must be saved because it is live.  */
+
+static enum machine_mode regno_save_mode[FIRST_PSEUDO_REGISTER];
+
+/* For each hard register, a place on the stack where it can be saved,
+   if needed.  */
+
+static rtx regno_save_mem[FIRST_PSEUDO_REGISTER];
+
+/* We will only make a register eligible for caller-save if it can be
+   saved in its widest mode with a simple SET insn as long as the memory
+   address is valid.  We record the INSN_CODE is those insns here since
+   when we emit them, the addresses might not be valid, so they might not
+   be recognized.  */
+
+static enum insn_code reg_save_code[FIRST_PSEUDO_REGISTER];
+static enum insn_code reg_restore_code[FIRST_PSEUDO_REGISTER];
+
+/* Set of hard regs currently live (during scan of all insns).  */
+
+static HARD_REG_SET hard_regs_live;
+
+/* Set of hard regs currently residing in save area (during insn scan).  */
+
+static HARD_REG_SET hard_regs_saved;
+
+/* Number of registers currently in hard_regs_saved.  */
+
+int n_regs_saved;
+
+static void set_reg_live ();
+static void clear_reg_live ();
+static void restore_referenced_regs ();
+static void insert_save_restore ();
+
+/* Return a machine mode that is legitimate for hard reg REGNO and large
+   enough to save the whole register.  If we can't find one, 
+   return VOIDmode.  */
+
+static enum machine_mode
+choose_hard_reg_mode (regno)
+     int regno;
+{
+  enum machine_mode found_mode = VOIDmode, mode;
+
+  /* We first look for the largest integer mode that can be validly
+     held in REGNO.  If none, we look for the largest floating-point mode.
+     If we still didn't find a valid mode, try CCmode.  */
+
+  for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT); mode != VOIDmode;
+       mode = GET_MODE_WIDER_MODE (mode))
+    if (HARD_REGNO_NREGS (regno, mode) == 1
+	&& HARD_REGNO_MODE_OK (regno, mode))
+      found_mode = mode;
+
+  if (found_mode != VOIDmode)
+    return found_mode;
+
+  for (mode = GET_CLASS_NARROWEST_MODE (MODE_FLOAT); mode != VOIDmode;
+       mode = GET_MODE_WIDER_MODE (mode))
+    if (HARD_REGNO_NREGS (regno, mode) == 1
+	&& HARD_REGNO_MODE_OK (regno, mode))
+      found_mode = mode;
+
+  if (found_mode != VOIDmode)
+    return found_mode;
+
+  if (HARD_REGNO_NREGS (regno, CCmode) == 1
+      && HARD_REGNO_MODE_OK (regno, CCmode))
+    return CCmode;
+
+  /* We can't find a mode valid for this register.  */
+  return VOIDmode;
+}
+
+/* Initialize for caller-save.
+
+   Look at all the hard registers that are used by a call and for which
+   regclass.c has not already excluded from being used across a call.
+
+   Ensure that we can find a mode to save the register and that there is a 
+   simple insn to save and restore the register.  This latter check avoids
+   problems that would occur if we tried to save the MQ register of some
+   machines directly into memory.  */
+
+void
+init_caller_save ()
+{
+  char *first_obj = (char *) oballoc (0);
+  rtx addr_reg;
+  int offset;
+  rtx address;
+  int i;
+
+  /* First find all the registers that we need to deal with and all
+     the modes that they can have.  If we can't find a mode to use,
+     we can't have the register live over calls.  */
+
+  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+    {
+      if (call_used_regs[i] && ! call_fixed_regs[i])
+	{
+	  regno_save_mode[i] = choose_hard_reg_mode (i);
+	  if (regno_save_mode[i] == VOIDmode)
+	    {
+	      call_fixed_regs[i] = 1;
+	      SET_HARD_REG_BIT (call_fixed_reg_set, i);
+	    }
+	}
+      else
+	regno_save_mode[i] = VOIDmode;
+    }
+
+  /* The following code tries to approximate the conditions under which
+     we can easily save and restore a register without scratch registers or
+     other complexities.  It will usually work, except under conditions where
+     the validity of an insn operand is dependent on the address offset.
+     No such cases are currently known.
+
+     We first find a typical offset from some BASE_REG_CLASS register.
+     This address is chosen by finding the first register in the class
+     and by finding the smallest power of two that is a valid offset from
+     that register in every mode we will use to save registers.  */
+
+  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+    if (TEST_HARD_REG_BIT (reg_class_contents[(int) BASE_REG_CLASS], i))
+      break;
+
+  if (i == FIRST_PSEUDO_REGISTER)
+    abort ();
+
+  addr_reg = gen_rtx (REG, Pmode, i);
+
+  for (offset = 1 << (HOST_BITS_PER_INT / 2); offset; offset >>= 1)
+    {
+      address = gen_rtx (PLUS, Pmode, addr_reg,
+			 gen_rtx (CONST_INT, VOIDmode, offset));
+
+      for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+	if (regno_save_mode[i] != VOIDmode
+	    && ! strict_memory_address_p (regno_save_mode[i], address))
+	  break;
+
+      if (i == FIRST_PSEUDO_REGISTER)
+	break;
+    }
+
+  /* If we didn't find a valid address, we must use register indirect.  */
+  if (offset == 0)
+    address = addr_reg;
+
+  /* Next we try to form an insn to save and restore the register.  We
+     see if such an insn is recognized and meets its constraints.  */
+
+  start_sequence ();
+
+  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+    if (regno_save_mode[i] != VOIDmode)
+      {
+	rtx mem = gen_rtx (MEM, regno_save_mode[i], address);
+	rtx reg = gen_rtx (REG, regno_save_mode[i], i);
+	rtx savepat = gen_rtx (SET, VOIDmode, mem, reg);
+	rtx restpat = gen_rtx (SET, VOIDmode, reg, mem);
+	rtx saveinsn = emit_insn (savepat);
+	rtx restinsn = emit_insn (restpat);
+	int ok;
+
+	reg_save_code[i] = recog_memoized (saveinsn);
+	reg_restore_code[i] = recog_memoized (restinsn);
+
+	/* Now extract both insns and see if we can meet their constraints.  */
+	ok = (reg_save_code[i] != -1 && reg_restore_code[i] != -1);
+	if (ok)
+	  {
+	    insn_extract (saveinsn);
+	    ok = constrain_operands (reg_save_code[i], 1);
+	    insn_extract (restinsn);
+	    ok &= constrain_operands (reg_restore_code[i], 1);
+	  }
+
+	if (! ok)
+	  {
+	    call_fixed_regs[i] = 1;
+	    SET_HARD_REG_BIT (call_fixed_reg_set, i);
+	  }
+      }
+
+  end_sequence ();
+
+  obfree (first_obj);
+}
+
+/* Initialize save areas by showing that we haven't allocated any yet.  */
+
+void
+init_save_areas ()
+{
+  int i;
+
+  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+    regno_save_mem[i] = 0;
+}
+
+/* Allocate save areas for any hard registers that might need saving.
+   We take a conservative approach here and look for call-clobbered hard
+   registers that are assigned to pseudos that cross calls.  This may
+   overestimate slightly (especially if some of these registers are later
+   used as spill registers), but it should not be significant.
+
+   Then perform register elimination in the addresses of the save area
+   locations; return 1 if all eliminated addresses are strictly valid.
+   We assume that our caller has set up the elimination table to the
+   worst (largest) possible offsets.
+
+   Set *PCHANGED to 1 if we had to allocate some memory for the save area.  */
+
+int
+setup_save_areas (pchanged)
+     int *pchanged;
+{
+  int ok = 1;
+  int i;
+
+  for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
+    if (reg_renumber[i] >= 0 && reg_n_calls_crossed[i] > 0)
+      {
+	int regno = reg_renumber[i];
+	int endregno
+	  = regno + HARD_REGNO_NREGS (regno, GET_MODE (regno_reg_rtx[i]));
+	int j;
+
+	for (j = regno; j < endregno; j++)
+	  if (call_used_regs[j] && regno_save_mem[j] == 0)
+	    {
+	      regno_save_mem[j]
+		= assign_stack_local (regno_save_mode[j],
+				      GET_MODE_SIZE (regno_save_mode[j]), 0);
+	      *pchanged = 1;
+	    }
+      }
+
+  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+    if (regno_save_mem[i] != 0)
+      ok &= strict_memory_address_p (regno_save_mode[i],
+				     XEXP (eliminate_regs (regno_save_mem[i],
+							   0, 0),
+					   0));
+
+  return ok;
+}
+
+/* Find the places where hard regs are live across calls and save them.
+
+   INSN_MODE is the mode to assign to any insns that we add.  This is used
+   by reload to determine whether or not reloads or register eliminations
+   need be done on these insns.  */
+
+void
+save_call_clobbered_regs (insn_mode)
+     enum machine_mode insn_mode;
+{
+  rtx insn;
+  int b;
+
+  for (b = 0; b < n_basic_blocks; b++)
+    {
+      regset regs_live = basic_block_live_at_start[b];
+      int offset, bit, i, j;
+      int regno;
+
+      /* Compute hard regs live at start of block -- this is the
+	 real hard regs marked live, plus live pseudo regs that
+	 have been renumbered to hard regs.  No registers have yet been
+	 saved because we restore all of them before the end of the basic
+	 block.  */
+
+#ifdef HARD_REG_SET
+      hard_regs_live = *regs_live;
+#else
+      COPY_HARD_REG_SET (hard_regs_live, regs_live);
+#endif
+
+      CLEAR_HARD_REG_SET (hard_regs_saved);
+      n_regs_saved = 0;
+
+      for (offset = 0, i = 0; offset < regset_size; offset++)
+	{
+	  if (regs_live[offset] == 0)
+	    i += HOST_BITS_PER_INT;
+	  else
+	    for (bit = 1; bit && i < max_regno; bit <<= 1, i++)
+	      if ((regs_live[offset] & bit)
+		  && (regno = reg_renumber[i]) >= 0)
+		for (j = regno;
+		     j < regno + HARD_REGNO_NREGS (regno,
+						   PSEUDO_REGNO_MODE (i));
+		     j++)
+		  SET_HARD_REG_BIT (hard_regs_live, j);
+	}
+
+      /* Now scan the insns in the block, keeping track of what hard
+	 regs are live as we go.  When we see a call, save the live
+	 call-clobbered hard regs.  */
+
+      for (insn = basic_block_head[b]; ; insn = NEXT_INSN (insn))
+	{
+	  RTX_CODE code = GET_CODE (insn);
+
+	  if (GET_RTX_CLASS (code) == 'i')
+	    {
+	      rtx link;
+
+	      /* If some registers have been saved, see if INSN references
+		 any of them.  We must restore them before the insn if so.  */
+
+	      if (n_regs_saved)
+		restore_referenced_regs (PATTERN (insn), insn, insn_mode);
+
+	      /* NB: the normal procedure is to first enliven any
+		 registers set by insn, then deaden any registers that
+		 had their last use at insn.  This is incorrect now,
+		 since multiple pseudos may have been mapped to the
+		 same hard reg, and the death notes are ambiguous.  So
+		 it must be done in the other, safe, order.  */
+
+	      for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
+		if (REG_NOTE_KIND (link) == REG_DEAD)
+		  clear_reg_live (XEXP (link, 0));
+
+	      /* When we reach a call, we need to save all registers that are
+		 live, call-used, not fixed, and not already saved.  We must
+		 test at this point because registers that die in a CALL_INSN
+		 are not live across the call and likewise for registers that
+		 are born in the CALL_INSN.  */
+
+	      if (code == CALL_INSN)
+		for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
+		  if (call_used_regs[regno] && ! call_fixed_regs[regno]
+		      && TEST_HARD_REG_BIT (hard_regs_live, regno)
+		      && ! TEST_HARD_REG_BIT (hard_regs_saved, regno))
+		    insert_save_restore (insn, 1, regno, insn_mode);
+	      
+	      note_stores (PATTERN (insn), set_reg_live);
+
+	      for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
+		if (REG_NOTE_KIND (link) == REG_UNUSED)
+		  clear_reg_live (XEXP (link, 0));
+	    }
+
+	  if (insn == basic_block_end[b])
+	    break;
+	}
+
+      /* At the end of the basic block, we must restore any registers that
+	 remain saved.  If the last insn in the block is a JUMP_INSN, put
+	 the restore before the insn, otherwise, put it after the insn.  */
+
+      if (n_regs_saved)
+	for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
+	  if (TEST_HARD_REG_BIT (hard_regs_saved, regno))
+	    insert_save_restore ((GET_CODE (insn) == JUMP_INSN
+				  ? insn : NEXT_INSN (insn)),
+				 0, regno, insn_mode);
+    }
+}
+
+/* Here from note_stores when an insn stores a value in a register.
+   Set the proper bit or bits in hard_regs_live.  All pseudos that have
+   been assigned hard regs have had their register number changed already,
+   so we can ignore pseudos.  */
+
+static void
+set_reg_live (reg, setter)
+     rtx reg, setter;
+{
+  register int regno, endregno, i;
+  int word = 0;
+
+  if (GET_CODE (reg) == SUBREG)
+    {
+      word = SUBREG_WORD (reg);
+      reg = SUBREG_REG (reg);
+    }
+
+  if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
+    return;
+
+  regno = REGNO (reg) + word;
+  endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
+
+  for (i = regno; i < endregno; i++)
+    SET_HARD_REG_BIT (hard_regs_live, i);
+}
+
+/* Here when a REG_DEAD note records the last use of a reg.  Clear
+   the appropriate bit or bits in hard_regs_live.  Again we can ignore
+   pseudos.  */
+
+static void
+clear_reg_live (reg)
+     rtx reg;
+{
+  register int regno, endregno, i;
+
+  if (GET_CODE (reg) != REG || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
+    return;
+
+  regno = REGNO (reg);
+  endregno= regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
+
+  for (i = regno; i < endregno; i++)
+    CLEAR_HARD_REG_BIT (hard_regs_live, i);
+}      
+
+/* If any register currently residing in the save area is referenced in X,
+   which is part of INSN, emit code to restore the register in front of INSN.
+   INSN_MODE is the mode to assign to any insns that we add.  */
+
+static void
+restore_referenced_regs (x, insn, insn_mode)
+     rtx x;
+     rtx insn;
+     enum machine_mode insn_mode;
+{
+  enum rtx_code code = GET_CODE (x);
+  char *fmt;
+  int i, j;
+
+  if (code == REG)
+    {
+      int regno = REGNO (x);
+
+      /* If this is a pseudo, scan its memory location, since it might
+	 involve the use of another register, which might be saved.  */
+
+      if (regno >= FIRST_PSEUDO_REGISTER
+	  && reg_equiv_mem[regno] != 0)
+	restore_referenced_regs (XEXP (reg_equiv_mem[regno], 0),
+				 insn, insn_mode);
+      else if (regno >= FIRST_PSEUDO_REGISTER
+	       && reg_equiv_address[regno] != 0)
+	restore_referenced_regs (XEXP (reg_equiv_address[regno], 0),
+				 insn, insn_mode);
+
+      /* Otherwise if this is a hard register, restore any piece of it that
+	 is currently saved.  */
+
+      else if (regno < FIRST_PSEUDO_REGISTER)
+	{
+	  int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (x));
+
+	  for (i = regno; i < endregno; i ++)
+	    if (TEST_HARD_REG_BIT (hard_regs_saved, i))
+	      insert_save_restore (insn, 0, i, insn_mode);
+	}
+
+      return;
+    }
+	  
+  fmt = GET_RTX_FORMAT (code);
+  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
+    {
+      if (fmt[i] == 'e')
+	restore_referenced_regs (XEXP (x, i), insn, insn_mode);
+      else if (fmt[i] == 'E')
+	for (j = XVECLEN (x, i) - 1; j >= 0; j--)
+	  restore_referenced_regs (XVECEXP (x, i, j), insn, insn_mode);
+    }
+}
+
+/* Insert a sequence of insns to save or restore, SAVE_P says which,
+   REGNO.  Place these insns in front of INSN.  INSN_MODE is the mode
+   to assign to these insns. 
+
+   Note that we have verified in init_caller_save that we can do this
+   with a simple SET, so use it.  Set INSN_CODE to what we save there
+   since the address might not be valid so the insn might not be recognized.
+   These insns will be reloaded and have register elimination done by
+   find_reload, so we need not worry about that here.  */
+
+static void
+insert_save_restore (insn, save_p, regno, insn_mode)
+     rtx insn;
+     int save_p;
+     int regno;
+     enum machine_mode insn_mode;
+{
+  rtx pat;
+  enum insn_code code;
+  int i;
+
+  /* If INSN is a CALL_INSN, we must insert our insns before any
+     USE insns in front of the CALL_INSN.  */
+
+  if (GET_CODE (insn) == CALL_INSN)
+    while (GET_CODE (PREV_INSN (insn)) == INSN
+	   && GET_CODE (PATTERN (PREV_INSN (insn))) == USE)
+      insn = PREV_INSN (insn);
+
+#ifdef HAVE_cc0
+  /* If INSN references CC0, put our insns in front of the insn that sets
+     CC0.  This is always safe, since the only way we could be passed an
+     insn that references CC0 is for a restore, and doing a restore earlier
+     isn't a problem.  We do, however, assume here that CALL_INSNs don't
+     reference CC0.  Guard against non-INSN's like CODE_LABEL.  */
+
+  if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
+      && reg_referenced_p (cc0_rtx, PATTERN (insn)))
+    insn = prev_nonnote_insn (insn);
+#endif
+
+  /* Get the pattern to emit and update our status.  */
+  if (save_p)
+    {
+      pat = gen_rtx (SET, VOIDmode, regno_save_mem[regno],
+		     gen_rtx (REG, regno_save_mode[regno], regno));
+      code = reg_save_code[regno];
+      SET_HARD_REG_BIT (hard_regs_saved, regno);
+      n_regs_saved++;
+    }
+  else
+    {
+      pat = gen_rtx (SET, VOIDmode,
+		     gen_rtx (REG, regno_save_mode[regno], regno),
+		     regno_save_mem[regno]);
+      code = reg_restore_code[regno];
+      CLEAR_HARD_REG_BIT (hard_regs_saved, regno);
+      n_regs_saved--;
+    }
+
+  /* Emit the insn and set the code and mode.  */
+
+  insn = emit_insn_before (pat, insn);
+  PUT_MODE (insn, insn_mode);
+  INSN_CODE (insn) = code;
+}