Initial revision

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@92 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 1574 insertions, 0 deletions

diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c
new file mode 100644
index 00000000000..95271f04651
--- /dev/null
+++ b/gcc/rtlanal.c
@@ -0,0 +1,1574 @@
+/* Analyze RTL for C-Compiler
+   Copyright (C) 1987-1991 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"
+
+void note_stores ();
+int reg_set_p ();
+
+/* Bit flags that specify the machine subtype we are compiling for.
+   Bits are tested using macros TARGET_... defined in the tm.h file
+   and set by `-m...' switches.  Must be defined in rtlanal.c.  */
+
+int target_flags;
+
+/* Return 1 if the value of X is unstable
+   (would be different at a different point in the program).
+   The frame pointer, arg pointer, etc. are considered stable
+   (within one function) and so is anything marked `unchanging'.  */
+
+int
+rtx_unstable_p (x)
+     rtx x;
+{
+  register RTX_CODE code = GET_CODE (x);
+  register int i;
+  register char *fmt;
+
+  if (code == MEM)
+    return ! RTX_UNCHANGING_P (x);
+
+  if (code == QUEUED)
+    return 1;
+
+  if (code == CONST || code == CONST_INT)
+    return 0;
+
+  if (code == REG)
+    return ! (REGNO (x) == FRAME_POINTER_REGNUM
+	      || REGNO (x) == ARG_POINTER_REGNUM
+	      || RTX_UNCHANGING_P (x));
+
+  fmt = GET_RTX_FORMAT (code);
+  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
+    if (fmt[i] == 'e')
+      if (rtx_unstable_p (XEXP (x, i)))
+	return 1;
+  return 0;
+}
+
+/* Return 1 if X has a value that can vary even between two
+   executions of the program.  0 means X can be compared reliably
+   against certain constants or near-constants.
+   The frame pointer and the arg pointer are considered constant.  */
+
+int
+rtx_varies_p (x)
+     rtx x;
+{
+  register RTX_CODE code = GET_CODE (x);
+  register int i;
+  register char *fmt;
+
+  switch (code)
+    {
+    case MEM:
+    case QUEUED:
+      return 1;
+
+    case CONST:
+    case CONST_INT:
+    case CONST_DOUBLE:
+    case SYMBOL_REF:
+    case LABEL_REF:
+      return 0;
+
+    case REG:
+      /* Note that we have to test for the actual rtx used for the frame
+	 and arg pointers and not just the register number in case we have
+	 eliminated the frame and/or arg pointer and are using it
+	 for pseudos.  */
+      return ! (x == frame_pointer_rtx || x == arg_pointer_rtx);
+
+    case LO_SUM:
+      /* The operand 0 of a LO_SUM is considered constant
+	 (in fact is it related specifically to operand 1).  */
+      return rtx_varies_p (XEXP (x, 1));
+    }
+
+  fmt = GET_RTX_FORMAT (code);
+  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
+    if (fmt[i] == 'e')
+      if (rtx_varies_p (XEXP (x, i)))
+	return 1;
+  return 0;
+}
+
+/* Return 0 if the use of X as an address in a MEM can cause a trap.  */
+
+int
+rtx_addr_can_trap_p (x)
+     register rtx x;
+{
+  register enum rtx_code code = GET_CODE (x);
+
+  switch (code)
+    {
+    case SYMBOL_REF:
+    case LABEL_REF:
+      /* SYMBOL_REF is problematic due to the possible presence of
+	 a #pragma weak, but to say that loads from symbols can trap is
+	 *very* costly.  It's not at all clear what's best here.  For
+	 now, we ignore the impact of #pragma weak.  */
+      return 0;
+
+    case REG:
+      /* As in rtx_varies_p, we have to use the actual rtx, not reg number.  */
+      return ! (x == frame_pointer_rtx || x == stack_pointer_rtx
+		|| x == arg_pointer_rtx);
+
+    case CONST:
+      return rtx_addr_can_trap_p (XEXP (x, 0));
+
+    case PLUS:
+      /* An address is assumed not to trap if it is an address that can't
+	 trap plus a constant integer.  */
+      return (rtx_addr_can_trap_p (XEXP (x, 0))
+	      || GET_CODE (XEXP (x, 1)) != CONST_INT);
+
+    case LO_SUM:
+      return rtx_addr_can_trap_p (XEXP (x, 1));
+    }
+
+  /* If it isn't one of the case above, it can cause a trap.  */
+  return 1;
+}
+
+/* Return 1 if X refers to a memory location whose address 
+   cannot be compared reliably with constant addresses,
+   or if X refers to a BLKmode memory object.  */
+
+int
+rtx_addr_varies_p (x)
+     rtx x;
+{
+  register enum rtx_code code;
+  register int i;
+  register char *fmt;
+
+  if (x == 0)
+    return 0;
+
+  code = GET_CODE (x);
+  if (code == MEM)
+    return GET_MODE (x) == BLKmode || rtx_varies_p (XEXP (x, 0));
+
+  fmt = GET_RTX_FORMAT (code);
+  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
+    if (fmt[i] == 'e')
+      if (rtx_addr_varies_p (XEXP (x, i)))
+	return 1;
+  return 0;
+}
+
+/* Return the value of the integer term in X, if one is apparent;
+   otherwise return 0.
+   Only obvious integer terms are detected.
+   This is used in cse.c with the `related_value' field.*/
+
+int
+get_integer_term (x)
+     rtx x;
+{
+  if (GET_CODE (x) == CONST)
+    x = XEXP (x, 0);
+
+  if (GET_CODE (x) == MINUS
+      && GET_CODE (XEXP (x, 1)) == CONST_INT)
+    return - INTVAL (XEXP (x, 1));
+  if (GET_CODE (x) == PLUS
+      && GET_CODE (XEXP (x, 1)) == CONST_INT)
+    return INTVAL (XEXP (x, 1));
+  return 0;
+}
+
+/* If X is a constant, return the value sans apparent integer term;
+   otherwise return 0.
+   Only obvious integer terms are detected.  */
+
+rtx
+get_related_value (x)
+     rtx x;
+{
+  if (GET_CODE (x) != CONST)
+    return 0;
+  x = XEXP (x, 0);
+  if (GET_CODE (x) == PLUS
+      && GET_CODE (XEXP (x, 1)) == CONST_INT)
+    return XEXP (x, 0);
+  else if (GET_CODE (x) == MINUS
+	   && GET_CODE (XEXP (x, 1)) == CONST_INT)
+    return XEXP (x, 0);
+  return 0;
+}
+
+/* Nonzero if register REG appears somewhere within IN.
+   Also works if REG is not a register; in this case it checks
+   for a subexpression of IN that is Lisp "equal" to REG.  */
+
+int
+reg_mentioned_p (reg, in)
+     register rtx reg, in;
+{
+  register char *fmt;
+  register int i;
+  register enum rtx_code code;
+
+  if (in == 0)
+    return 0;
+
+  if (reg == in)
+    return 1;
+
+  if (GET_CODE (in) == LABEL_REF)
+    return reg == XEXP (in, 0);
+
+  code = GET_CODE (in);
+
+  switch (code)
+    {
+      /* Compare registers by number.  */
+    case REG:
+      return GET_CODE (reg) == REG && REGNO (in) == REGNO (reg);
+
+      /* These codes have no constituent expressions
+	 and are unique.  */
+    case SCRATCH:
+    case CC0:
+    case PC:
+      return 0;
+
+    case CONST_INT:
+      return GET_CODE (reg) == CONST_INT && INTVAL (in) == INTVAL (reg);
+      
+    case CONST_DOUBLE:
+      /* These are kept unique for a given value.  */
+      return 0;
+    }
+
+  if (GET_CODE (reg) == code && rtx_equal_p (reg, in))
+    return 1;
+
+  fmt = GET_RTX_FORMAT (code);
+
+  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
+    {
+      if (fmt[i] == 'E')
+	{
+	  register int j;
+	  for (j = XVECLEN (in, i) - 1; j >= 0; j--)
+	    if (reg_mentioned_p (reg, XVECEXP (in, i, j)))
+	      return 1;
+	}
+      else if (fmt[i] == 'e'
+	       && reg_mentioned_p (reg, XEXP (in, i)))
+	return 1;
+    }
+  return 0;
+}
+
+/* Return 1 if in between BEG and END, exclusive of BEG and END, there is
+   no CODE_LABEL insn.  */
+
+int
+no_labels_between_p (beg, end)
+     rtx beg, end;
+{
+  register rtx p;
+  for (p = NEXT_INSN (beg); p != end; p = NEXT_INSN (p))
+    if (GET_CODE (p) == CODE_LABEL)
+      return 0;
+  return 1;
+}
+
+/* Nonzero if register REG is used in an insn between
+   FROM_INSN and TO_INSN (exclusive of those two).  */
+
+int
+reg_used_between_p (reg, from_insn, to_insn)
+     rtx reg, from_insn, to_insn;
+{
+  register rtx insn;
+
+  if (from_insn == to_insn)
+    return 0;
+
+  for (insn = NEXT_INSN (from_insn); insn != to_insn; insn = NEXT_INSN (insn))
+    if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
+	&& reg_overlap_mentioned_p (reg, PATTERN (insn)))
+      return 1;
+  return 0;
+}
+
+/* Nonzero if the old value of X, a register, is referenced in BODY.  If X
+   is entirely replaced by a new value and the only use is as a SET_DEST,
+   we do not consider it a reference.  */
+
+int
+reg_referenced_p (x, body)
+     rtx x;
+     rtx body;
+{
+  int i;
+
+  switch (GET_CODE (body))
+    {
+    case SET:
+      if (reg_overlap_mentioned_p (x, SET_SRC (body)))
+	return 1;
+
+      /* If the destination is anything other than CC0, PC, a REG or a SUBREG
+	 of a REG that occupies all of the REG, the insn references X if
+	 it is mentioned in the destination.  */
+      if (GET_CODE (SET_DEST (body)) != CC0
+	  && GET_CODE (SET_DEST (body)) != PC
+	  && GET_CODE (SET_DEST (body)) != REG
+	  && ! (GET_CODE (SET_DEST (body)) == SUBREG
+		&& GET_CODE (SUBREG_REG (SET_DEST (body))) == REG
+		&& (((GET_MODE_SIZE (GET_MODE (SUBREG_REG (SET_DEST (body))))
+		      + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD)
+		    == ((GET_MODE_SIZE (GET_MODE (SET_DEST (body)))
+			 + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD)))
+	  && reg_overlap_mentioned_p (x, SET_DEST (body)))
+	return 1;
+      break;
+
+    case ASM_OPERANDS:
+      for (i = ASM_OPERANDS_INPUT_LENGTH (body) - 1; i >= 0; i--)
+	if (reg_overlap_mentioned_p (x, ASM_OPERANDS_INPUT (body, i)))
+	  return 1;
+      break;
+
+    case CALL:
+    case USE:
+      return reg_overlap_mentioned_p (x, body);
+
+    case TRAP_IF:
+      return reg_overlap_mentioned_p (x, TRAP_CONDITION (body));
+
+    case PARALLEL:
+      for (i = XVECLEN (body, 0) - 1; i >= 0; i--)
+	if (reg_referenced_p (x, XVECEXP (body, 0, i)))
+	  return 1;
+      break;
+    }
+
+  return 0;
+}
+
+/* Nonzero if register REG is referenced in an insn between
+   FROM_INSN and TO_INSN (exclusive of those two).  Sets of REG do
+   not count. */
+
+int
+reg_referenced_between_p (reg, from_insn, to_insn)
+     rtx reg, from_insn, to_insn;
+{
+  register rtx insn;
+
+  if (from_insn == to_insn)
+    return 0;
+
+  for (insn = NEXT_INSN (from_insn); insn != to_insn; insn = NEXT_INSN (insn))
+    if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
+	&& reg_referenced_p (reg, PATTERN (insn)))
+      return 1;
+  return 0;
+}
+
+/* Nonzero if register REG is set or clobbered in an insn between
+   FROM_INSN and TO_INSN (exclusive of those two).  */
+
+int
+reg_set_between_p (reg, from_insn, to_insn)
+     rtx reg, from_insn, to_insn;
+{
+  register rtx insn;
+
+  if (from_insn == to_insn)
+    return 0;
+
+  for (insn = NEXT_INSN (from_insn); insn != to_insn; insn = NEXT_INSN (insn))
+    if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
+	&& reg_set_p (reg, PATTERN (insn)))
+      return 1;
+  return 0;
+}
+
+/* Internals of reg_set_between_p.  */
+
+static rtx reg_set_reg;
+static int reg_set_flag;
+
+void
+reg_set_p_1 (x)
+     rtx x;
+{
+  /* We don't want to return 1 if X is a MEM that contains a register
+     within REG_SET_REG.  */
+
+  if ((GET_CODE (x) != MEM)
+      && reg_overlap_mentioned_p (reg_set_reg, x))
+    reg_set_flag = 1;
+}
+
+int
+reg_set_p (reg, insn)
+     rtx reg, insn;
+{
+  rtx body = insn;
+
+  /* We can be passed an insn or part of one.  If we are passed an insn,
+     check if a side-effect of the insn clobbers REG.  */
+  if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
+    {
+      if (FIND_REG_INC_NOTE (insn, reg)
+	  || (GET_CODE (insn) == CALL_INSN
+	      /* We'd like to test call_used_regs here, but rtlanal.c can't
+		 reference that variable due to its use in genattrtab.  So
+		 we'll just be more conservative.  */
+	      && ((GET_CODE (reg) == REG
+		   && REGNO (reg) < FIRST_PSEUDO_REGISTER)
+		  || GET_CODE (reg) == MEM)))
+	return 1;
+
+      body = PATTERN (insn);
+    }
+
+  reg_set_reg = reg;
+  reg_set_flag = 0;
+  note_stores (body, reg_set_p_1);
+  return reg_set_flag;
+}
+
+/* Similar to reg_set_between_p, but check all registers in X.  Return 0
+   only if none of them are modified between START and END.  Return 1 if
+   X contains a MEM; this routine does not perform any memory aliasing.  */
+
+int
+modified_between_p (x, start, end)
+     rtx x;
+     rtx start, end;
+{
+  enum rtx_code code = GET_CODE (x);
+  char *fmt;
+  int i;
+
+  switch (code)
+    {
+    case CONST_INT:
+    case CONST_DOUBLE:
+    case CONST:
+    case SYMBOL_REF:
+    case LABEL_REF:
+      return 0;
+
+    case PC:
+    case CC0:
+      return 1;
+
+    case MEM:
+      /* If the memory is not constant, assume it is modified.  If it is
+	 constant, we still have to check the address.  */
+      if (! RTX_UNCHANGING_P (x))
+	return 1;
+      break;
+
+    case REG:
+      return reg_set_between_p (x, start, end);
+    }
+
+  fmt = GET_RTX_FORMAT (code);
+  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
+    if (fmt[i] == 'e'
+	&& modified_between_p (XEXP (x, i), start, end))
+      return 1;
+
+  return 0;
+}
+
+/* Given an INSN, return a SET expression if this insn has only a single SET.
+   It may also have CLOBBERs, USEs, or SET whose output
+   will not be used, which we ignore.  */
+
+rtx
+single_set (insn)
+     rtx insn;
+{
+  rtx set;
+  int i;
+  
+  if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
+    return 0;
+
+  if (GET_CODE (PATTERN (insn)) == SET)
+    return PATTERN (insn);
+  
+  else if (GET_CODE (PATTERN (insn)) == PARALLEL)
+    {
+      for (i = 0, set = 0; i < XVECLEN (PATTERN (insn), 0); i++)
+	if (GET_CODE (XVECEXP (PATTERN (insn), 0, i)) == SET
+	    && ! (find_reg_note (insn, REG_UNUSED,
+				SET_DEST (XVECEXP (PATTERN (insn), 0, i)))
+		  || side_effects_p (XVECEXP (PATTERN (insn), 0, i))))
+	  {
+	    if (set)
+	      return 0;
+	    else
+	      set = XVECEXP (PATTERN (insn), 0, i);
+	  }
+      return set;
+    }
+  
+  return 0;
+}
+
+/* Return the last thing that X was assigned from before *PINSN.  Verify that
+   the object is not modified up to VALID_TO.  If it was, if we hit
+   a partial assignment to X, or hit a CODE_LABEL first, return X.  If we
+   found an assignment, update *PINSN to point to it.  */
+
+rtx
+find_last_value (x, pinsn, valid_to)
+     rtx x;
+     rtx *pinsn;
+     rtx valid_to;
+{
+  rtx p;
+
+  for (p = PREV_INSN (*pinsn); p && GET_CODE (p) != CODE_LABEL;
+       p = PREV_INSN (p))
+    if (GET_RTX_CLASS (GET_CODE (p)) == 'i')
+      {
+	rtx set = single_set (p);
+	rtx note = find_reg_note (p, REG_EQUAL, 0);
+
+	if (set && rtx_equal_p (x, SET_DEST (set)))
+	  {
+	    rtx src = SET_SRC (set);
+
+	    if (note && GET_CODE (XEXP (note, 0)) != EXPR_LIST)
+	      src = XEXP (note, 0);
+
+	    if (! modified_between_p (src, PREV_INSN (p), valid_to)
+		/* Reject hard registers because we don't usually want
+		   to use them; we'd rather use a pseudo.  */
+		&& ! (GET_CODE (src) == REG
+		      && REGNO (src) < FIRST_PSEUDO_REGISTER))
+	      {
+		*pinsn = p;
+		return src;
+	      }
+	  }
+	  
+	/* If set in non-simple way, we don't have a value.  */
+	if (reg_set_p (x, p))
+	  break;
+      }
+
+  return x;
+}     
+
+/* Return nonzero if register in range [REGNO, ENDREGNO)
+   appears either explicitly or implicitly in X
+   other than being stored into.
+
+   References contained within the substructure at LOC do not count.
+   LOC may be zero, meaning don't ignore anything.  */
+
+int
+refers_to_regno_p (regno, endregno, x, loc)
+     int regno, endregno;
+     rtx x;
+     rtx *loc;
+{
+  register int i;
+  register RTX_CODE code;
+  register char *fmt;
+
+ repeat:
+  /* The contents of a REG_NONNEG note is always zero, so we must come here
+     upon repeat in case the last REG_NOTE is a REG_NONNEG note.  */
+  if (x == 0)
+    return 0;
+
+  code = GET_CODE (x);
+
+  switch (code)
+    {
+    case REG:
+      i = REGNO (x);
+      return (endregno > i
+	      && regno < i + (i < FIRST_PSEUDO_REGISTER 
+			      ? HARD_REGNO_NREGS (i, GET_MODE (x))
+			      : 1));
+
+    case SUBREG:
+      /* If this is a SUBREG of a hard reg, we can see exactly which
+	 registers are being modified.  Otherwise, handle normally.  */
+      if (GET_CODE (SUBREG_REG (x)) == REG
+	  && REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER)
+	{
+	  int inner_regno = REGNO (SUBREG_REG (x)) + SUBREG_WORD (x);
+	  int inner_endregno
+	    = inner_regno + (inner_regno < FIRST_PSEUDO_REGISTER
+			     ? HARD_REGNO_NREGS (regno, GET_MODE (x)) : 1);
+
+	  return endregno > inner_regno && regno < inner_endregno;
+	}
+      break;
+
+    case CLOBBER:
+    case SET:
+      if (&SET_DEST (x) != loc
+	  /* Note setting a SUBREG counts as referring to the REG it is in for
+	     a pseudo but not for hard registers since we can
+	     treat each word individually.  */
+	  && ((GET_CODE (SET_DEST (x)) == SUBREG
+	       && loc != &SUBREG_REG (SET_DEST (x))
+	       && GET_CODE (SUBREG_REG (SET_DEST (x))) == REG
+	       && REGNO (SUBREG_REG (SET_DEST (x))) >= FIRST_PSEUDO_REGISTER
+	       && refers_to_regno_p (regno, endregno,
+				     SUBREG_REG (SET_DEST (x)), loc))
+	      || (GET_CODE (SET_DEST (x)) != REG
+		  && refers_to_regno_p (regno, endregno, SET_DEST (x), loc))))
+	return 1;
+
+      if (code == CLOBBER || loc == &SET_SRC (x))
+	return 0;
+      x = SET_SRC (x);
+      goto repeat;
+    }
+
+  /* X does not match, so try its subexpressions.  */
+
+  fmt = GET_RTX_FORMAT (code);
+  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
+    {
+      if (fmt[i] == 'e' && loc != &XEXP (x, i))
+	{
+	  if (i == 0)
+	    {
+	      x = XEXP (x, 0);
+	      goto repeat;
+	    }
+	  else
+	    if (refers_to_regno_p (regno, endregno, XEXP (x, i), loc))
+	      return 1;
+	}
+      else if (fmt[i] == 'E')
+	{
+	  register int j;
+	  for (j = XVECLEN (x, i) - 1; j >=0; j--)
+	    if (loc != &XVECEXP (x, i, j)
+		&& refers_to_regno_p (regno, endregno, XVECEXP (x, i, j), loc))
+	      return 1;
+	}
+    }
+  return 0;
+}
+
+/* Nonzero if modifying X will affect IN.  If X is a register or a SUBREG,
+   we check if any register number in X conflicts with the relevant register
+   numbers.  If X is a constant, return 0.  If X is a MEM, return 1 iff IN
+   contains a MEM (we don't bother checking for memory addresses that can't
+   conflict because we expect this to be a rare case.  */
+
+int
+reg_overlap_mentioned_p (x, in)
+     rtx x, in;
+{
+  int regno, endregno;
+
+  if (GET_CODE (x) == SUBREG)
+    {
+      regno = REGNO (SUBREG_REG (x));
+      if (regno < FIRST_PSEUDO_REGISTER)
+	regno += SUBREG_WORD (x);
+    }
+  else if (GET_CODE (x) == REG)
+    regno = REGNO (x);
+  else if (CONSTANT_P (x))
+    return 0;
+  else if (GET_CODE (x) == MEM)
+    {
+      char *fmt;
+      int i;
+
+      if (GET_CODE (in) == MEM)
+	return 1;
+
+      fmt = GET_RTX_FORMAT (GET_CODE (in));
+
+      for (i = GET_RTX_LENGTH (GET_CODE (in)) - 1; i >= 0; i--)
+	if (fmt[i] == 'e' && reg_overlap_mentioned_p (x, XEXP (in, i)))
+	  return 1;
+
+      return 0;
+    }
+  else if (GET_CODE (x) == SCRATCH || GET_CODE (x) == PC
+	   || GET_CODE (x) == CC0)
+    return reg_mentioned_p (x, in);
+  else
+    abort ();
+
+  endregno = regno + (regno < FIRST_PSEUDO_REGISTER
+		      ? HARD_REGNO_NREGS (regno, GET_MODE (x)) : 1);
+
+  return refers_to_regno_p (regno, endregno, in, 0);
+}
+
+/* Used for communications between the next few functions.  */
+
+static int reg_set_last_unknown;
+static rtx reg_set_last_value;
+static int reg_set_last_first_regno, reg_set_last_last_regno;
+
+/* Called via note_stores from reg_set_last.  */
+
+static void
+reg_set_last_1 (x, pat)
+     rtx x;
+     rtx pat;
+{
+  int first, last;
+
+  /* If X is not a register, or is not one in the range we care
+     about, ignore.  */
+  if (GET_CODE (x) != REG)
+    return;
+
+  first = REGNO (x);
+  last = first + (first < FIRST_PSEUDO_REGISTER
+		  ? HARD_REGNO_NREGS (first, GET_MODE (x)) : 1);
+
+  if (first >= reg_set_last_last_regno
+      || last <= reg_set_last_first_regno)
+    return;
+
+  /* If this is a CLOBBER or is some complex LHS, or doesn't modify
+     exactly the registers we care about, show we don't know the value.  */
+  if (GET_CODE (pat) == CLOBBER || SET_DEST (pat) != x
+      || first != reg_set_last_first_regno
+      || last != reg_set_last_last_regno)
+    reg_set_last_unknown = 1;
+  else
+    reg_set_last_value = SET_SRC (pat);
+}
+
+/* Return the last value to which REG was set prior to INSN.  If we can't
+   find it easily, return 0.
+
+   We only return a REG or constant because it is too hard to check if a
+   MEM remains unchanged.  */
+
+rtx
+reg_set_last (x, insn)
+     rtx x;
+     rtx insn;
+{
+  rtx orig_insn = insn;
+
+  reg_set_last_first_regno = REGNO (x);
+
+  reg_set_last_last_regno
+    = reg_set_last_first_regno
+      + (reg_set_last_first_regno < FIRST_PSEUDO_REGISTER
+	 ? HARD_REGNO_NREGS (reg_set_last_first_regno, GET_MODE (x)) : 1);
+
+  reg_set_last_unknown = 0;
+  reg_set_last_value = 0;
+
+  /* Scan backwards until reg_set_last_1 changed one of the above flags.
+     Stop when we reach a label or X is a hard reg and we reach a
+     CALL_INSN (if reg_set_last_last_regno is a hard reg).
+
+     If we find a set of X, ensure that its SET_SRC remains unchanged.  */
+
+  for (;
+       insn && GET_CODE (insn) != CODE_LABEL
+       && ! (GET_CODE (insn) == CALL_INSN
+	     && reg_set_last_last_regno <= FIRST_PSEUDO_REGISTER);
+       insn = PREV_INSN (insn))
+    if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
+      {
+	note_stores (PATTERN (insn), reg_set_last_1);
+	if (reg_set_last_unknown)
+	  return 0;
+	else if (reg_set_last_value)
+	  {
+	    if (CONSTANT_P (reg_set_last_value)
+		|| (GET_CODE (reg_set_last_value) == REG
+		    && ! reg_set_between_p (reg_set_last_value,
+					    NEXT_INSN (insn), orig_insn)))
+	      return reg_set_last_value;
+	    else
+	      return 0;
+	  }
+      }
+
+  return 0;
+}
+
+/* This is 1 until after reload pass.  */
+int rtx_equal_function_value_matters;
+
+/* Return 1 if X and Y are identical-looking rtx's.
+   This is the Lisp function EQUAL for rtx arguments.  */
+
+int
+rtx_equal_p (x, y)
+     rtx x, y;
+{
+  register int i;
+  register int j;
+  register enum rtx_code code;
+  register char *fmt;
+
+  if (x == y)
+    return 1;
+  if (x == 0 || y == 0)
+    return 0;
+
+  code = GET_CODE (x);
+  /* Rtx's of different codes cannot be equal.  */
+  if (code != GET_CODE (y))
+    return 0;
+
+  /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
+     (REG:SI x) and (REG:HI x) are NOT equivalent.  */
+
+  if (GET_MODE (x) != GET_MODE (y))
+    return 0;
+
+  /* REG, LABEL_REF, and SYMBOL_REF can be compared nonrecursively.  */
+
+  if (code == REG)
+    /* Until rtl generation is complete, don't consider a reference to the
+       return register of the current function the same as the return from a
+       called function.  This eases the job of function integration.  Once the
+       distinction is no longer needed, they can be considered equivalent.  */
+    return (REGNO (x) == REGNO (y)
+	    && (! rtx_equal_function_value_matters
+		|| REG_FUNCTION_VALUE_P (x) == REG_FUNCTION_VALUE_P (y)));
+  else if (code == LABEL_REF)
+    return XEXP (x, 0) == XEXP (y, 0);
+  else if (code == SYMBOL_REF)
+    return XSTR (x, 0) == XSTR (y, 0);
+  else if (code == SCRATCH || code == CONST_DOUBLE)
+    return 0;
+
+  /* Compare the elements.  If any pair of corresponding elements
+     fail to match, return 0 for the whole things.  */
+
+  fmt = GET_RTX_FORMAT (code);
+  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
+    {
+      switch (fmt[i])
+	{
+	case 'n':
+	case 'i':
+	  if (XINT (x, i) != XINT (y, i))
+	    return 0;
+	  break;
+
+	case 'V':
+	case 'E':
+	  /* Two vectors must have the same length.  */
+	  if (XVECLEN (x, i) != XVECLEN (y, i))
+	    return 0;
+
+	  /* And the corresponding elements must match.  */
+	  for (j = 0; j < XVECLEN (x, i); j++)
+	    if (rtx_equal_p (XVECEXP (x, i, j), XVECEXP (y, i, j)) == 0)
+	      return 0;
+	  break;
+
+	case 'e':
+	  if (rtx_equal_p (XEXP (x, i), XEXP (y, i)) == 0)
+	    return 0;
+	  break;
+
+	case 'S':
+	case 's':
+	  if (strcmp (XSTR (x, i), XSTR (y, i)))
+	    return 0;
+	  break;
+
+	case 'u':
+	  /* These are just backpointers, so they don't matter.  */
+	  break;
+
+	case '0':
+	  break;
+
+	  /* It is believed that rtx's at this level will never
+	     contain anything but integers and other rtx's,
+	     except for within LABEL_REFs and SYMBOL_REFs.  */
+	default:
+	  abort ();
+	}
+    }
+  return 1;
+}
+
+/* Call FUN on each register or MEM that is stored into or clobbered by X.
+   (X would be the pattern of an insn).
+   FUN receives two arguments:
+     the REG, MEM, CC0 or PC being stored in or clobbered,
+     the SET or CLOBBER rtx that does the store.
+
+  If the item being stored in or clobbered is a SUBREG of a hard register,
+  the SUBREG will be passed.  */
+     
+void
+note_stores (x, fun)
+     register rtx x;
+     void (*fun) ();
+{
+  if ((GET_CODE (x) == SET || GET_CODE (x) == CLOBBER))
+    {
+      register rtx dest = SET_DEST (x);
+      while ((GET_CODE (dest) == SUBREG
+	      && (GET_CODE (SUBREG_REG (dest)) != REG
+		  || REGNO (SUBREG_REG (dest)) >= FIRST_PSEUDO_REGISTER))
+	     || GET_CODE (dest) == ZERO_EXTRACT
+	     || GET_CODE (dest) == SIGN_EXTRACT
+	     || GET_CODE (dest) == STRICT_LOW_PART)
+	dest = XEXP (dest, 0);
+      (*fun) (dest, x);
+    }
+  else if (GET_CODE (x) == PARALLEL)
+    {
+      register int i;
+      for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
+	{
+	  register rtx y = XVECEXP (x, 0, i);
+	  if (GET_CODE (y) == SET || GET_CODE (y) == CLOBBER)
+	    {
+	      register rtx dest = SET_DEST (y);
+	      while ((GET_CODE (dest) == SUBREG
+		      && (GET_CODE (SUBREG_REG (dest)) != REG
+			  || (REGNO (SUBREG_REG (dest))
+			      >= FIRST_PSEUDO_REGISTER)))
+		     || GET_CODE (dest) == ZERO_EXTRACT
+		     || GET_CODE (dest) == SIGN_EXTRACT
+		     || GET_CODE (dest) == STRICT_LOW_PART)
+		dest = XEXP (dest, 0);
+	      (*fun) (dest, y);
+	    }
+	}
+    }
+}
+
+/* Return nonzero if X's old contents don't survive after INSN.
+   This will be true if X is (cc0) or if X is a register and
+   X dies in INSN or because INSN entirely sets X.
+
+   "Entirely set" means set directly and not through a SUBREG,
+   ZERO_EXTRACT or SIGN_EXTRACT, so no trace of the old contents remains.
+   Likewise, REG_INC does not count.
+
+   REG may be a hard or pseudo reg.  Renumbering is not taken into account,
+   but for this use that makes no difference, since regs don't overlap
+   during their lifetimes.  Therefore, this function may be used
+   at any time after deaths have been computed (in flow.c).
+
+   If REG is a hard reg that occupies multiple machine registers, this
+   function will only return 1 if each of those registers will be replaced
+   by INSN.  */
+
+int
+dead_or_set_p (insn, x)
+     rtx insn;
+     rtx x;
+{
+  register int regno, last_regno;
+  register int i;
+
+  /* Can't use cc0_rtx below since this file is used by genattrtab.c.  */
+  if (GET_CODE (x) == CC0)
+    return 1;
+
+  if (GET_CODE (x) != REG)
+    abort ();
+
+  regno = REGNO (x);
+  last_regno = (regno >= FIRST_PSEUDO_REGISTER ? regno
+		: regno + HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1);
+
+  for (i = regno; i <= last_regno; i++)
+    if (! dead_or_set_regno_p (insn, i))
+      return 0;
+
+  return 1;
+}
+
+/* Utility function for dead_or_set_p to check an individual register.  Also
+   called from flow.c.  */
+
+int
+dead_or_set_regno_p (insn, test_regno)
+     rtx insn;
+     int test_regno;
+{
+  int regno, endregno;
+  rtx link;
+
+  /* See if there is a death note for something that includes TEST_REGNO.  */
+  for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
+    {
+      if (REG_NOTE_KIND (link) != REG_DEAD || GET_CODE (XEXP (link, 0)) != REG)
+	continue;
+
+      regno = REGNO (XEXP (link, 0));
+      endregno = (regno >= FIRST_PSEUDO_REGISTER ? regno + 1
+		  : regno + HARD_REGNO_NREGS (regno,
+					      GET_MODE (XEXP (link, 0))));
+
+      if (test_regno >= regno && test_regno < endregno)
+	return 1;
+    }
+
+  if (GET_CODE (PATTERN (insn)) == SET)
+    {
+      rtx dest = SET_DEST (PATTERN (insn));
+ 
+      /* A value is totally replaced if it is the destination or the
+	 destination is a SUBREG of REGNO that does not change the number of
+	 words in it.  */
+     if (GET_CODE (dest) == SUBREG
+	  && (((GET_MODE_SIZE (GET_MODE (dest))
+		+ UNITS_PER_WORD - 1) / UNITS_PER_WORD)
+	      == ((GET_MODE_SIZE (GET_MODE (SUBREG_REG (dest)))
+		   + UNITS_PER_WORD - 1) / UNITS_PER_WORD)))
+	dest = SUBREG_REG (dest);
+
+      if (GET_CODE (dest) != REG)
+	return 0;
+
+      regno = REGNO (dest);
+      endregno = (regno >= FIRST_PSEUDO_REGISTER ? regno + 1
+		  : regno + HARD_REGNO_NREGS (regno, GET_MODE (dest)));
+
+      return (test_regno >= regno && test_regno < endregno);
+    }
+  else if (GET_CODE (PATTERN (insn)) == PARALLEL)
+    {
+      register int i;
+
+      for (i = XVECLEN (PATTERN (insn), 0) - 1; i >= 0; i--)
+	{
+	  rtx body = XVECEXP (PATTERN (insn), 0, i);
+
+	  if (GET_CODE (body) == SET || GET_CODE (body) == CLOBBER)
+	    {
+	      rtx dest = SET_DEST (body);
+
+	      if (GET_CODE (dest) == SUBREG
+		  && (((GET_MODE_SIZE (GET_MODE (dest))
+			+ UNITS_PER_WORD - 1) / UNITS_PER_WORD)
+		      == ((GET_MODE_SIZE (GET_MODE (SUBREG_REG (dest)))
+			   + UNITS_PER_WORD - 1) / UNITS_PER_WORD)))
+		dest = SUBREG_REG (dest);
+
+	      if (GET_CODE (dest) != REG)
+		continue;
+
+	      regno = REGNO (dest);
+	      endregno = (regno >= FIRST_PSEUDO_REGISTER ? regno + 1
+			  : regno + HARD_REGNO_NREGS (regno, GET_MODE (dest)));
+
+	      if (test_regno >= regno && test_regno < endregno)
+		return 1;
+	    }
+	}
+    }
+
+  return 0;
+}
+
+/* Return the reg-note of kind KIND in insn INSN, if there is one.
+   If DATUM is nonzero, look for one whose datum is DATUM.  */
+
+rtx
+find_reg_note (insn, kind, datum)
+     rtx insn;
+     enum reg_note kind;
+     rtx datum;
+{
+  register rtx link;
+
+  for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
+    if (REG_NOTE_KIND (link) == kind
+	&& (datum == 0 || datum == XEXP (link, 0)))
+      return link;
+  return 0;
+}
+
+/* Return the reg-note of kind KIND in insn INSN which applies to register
+   number REGNO, if any.  Return 0 if there is no such reg-note.  */
+
+rtx
+find_regno_note (insn, kind, regno)
+     rtx insn;
+     enum reg_note kind;
+     int regno;
+{
+  register rtx link;
+
+  for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
+    if (REG_NOTE_KIND (link) == kind
+	/* Verify that it is a register, so that scratch and MEM won't cause a
+	   problem here.  */
+	&& GET_CODE (XEXP (link, 0)) == REG
+	&& REGNO (XEXP (link, 0)) == regno)
+      return link;
+  return 0;
+}
+
+/* Remove register note NOTE from the REG_NOTES of INSN.  */
+
+void
+remove_note (insn, note)
+     register rtx note;
+     register rtx insn;
+{
+  register rtx link;
+
+  if (REG_NOTES (insn) == note)
+    {
+      REG_NOTES (insn) = XEXP (note, 1);
+      return;
+    }
+
+  for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
+    if (XEXP (link, 1) == note)
+      {
+	XEXP (link, 1) = XEXP (note, 1);
+	return;
+      }
+
+  abort ();
+}
+
+/* Nonzero if X contains any volatile memory references
+   or volatile ASM_OPERANDS expressions.  */
+
+int
+volatile_refs_p (x)
+     rtx x;
+{
+  register RTX_CODE code;
+
+  code = GET_CODE (x);
+  switch (code)
+    {
+    case LABEL_REF:
+    case SYMBOL_REF:
+    case CONST_INT:
+    case CONST:
+    case CONST_DOUBLE:
+    case CC0:
+    case PC:
+    case REG:
+    case SCRATCH:
+    case CLOBBER:
+    case ASM_INPUT:
+    case ADDR_VEC:
+    case ADDR_DIFF_VEC:
+      return 0;
+
+    case CALL:
+ /* case TRAP_IF: This isn't clear yet.  */
+      return 1;
+
+    case MEM:
+    case ASM_OPERANDS:
+      if (MEM_VOLATILE_P (x))
+	return 1;
+    }
+
+  /* Recursively scan the operands of this expression.  */
+
+  {
+    register char *fmt = GET_RTX_FORMAT (code);
+    register int i;
+    
+    for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
+      {
+	if (fmt[i] == 'e')
+	  {
+	    if (volatile_refs_p (XEXP (x, i)))
+	      return 1;
+	  }
+	if (fmt[i] == 'E')
+	  {
+	    register int j;
+	    for (j = 0; j < XVECLEN (x, i); j++)
+	      if (volatile_refs_p (XVECEXP (x, i, j)))
+		return 1;
+	  }
+      }
+  }
+  return 0;
+}
+
+/* Similar to above, except that it also rejects register pre- and post-
+   incrementing.  */
+
+int
+side_effects_p (x)
+     rtx x;
+{
+  register RTX_CODE code;
+
+  code = GET_CODE (x);
+  switch (code)
+    {
+    case LABEL_REF:
+    case SYMBOL_REF:
+    case CONST_INT:
+    case CONST:
+    case CONST_DOUBLE:
+    case CC0:
+    case PC:
+    case REG:
+    case SCRATCH:
+    case ASM_INPUT:
+    case ADDR_VEC:
+    case ADDR_DIFF_VEC:
+      return 0;
+
+    case CLOBBER:
+      /* Reject CLOBBER with a non-VOID mode.  These are made by combine.c
+	 when some combination can't be done.  If we see one, don't think
+	 that we can simplify the expression.  */
+      return (GET_MODE (x) != VOIDmode);
+
+    case PRE_INC:
+    case PRE_DEC:
+    case POST_INC:
+    case POST_DEC:
+    case CALL:
+ /* case TRAP_IF: This isn't clear yet.  */
+      return 1;
+
+    case MEM:
+    case ASM_OPERANDS:
+      if (MEM_VOLATILE_P (x))
+	return 1;
+    }
+
+  /* Recursively scan the operands of this expression.  */
+
+  {
+    register char *fmt = GET_RTX_FORMAT (code);
+    register int i;
+    
+    for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
+      {
+	if (fmt[i] == 'e')
+	  {
+	    if (side_effects_p (XEXP (x, i)))
+	      return 1;
+	  }
+	if (fmt[i] == 'E')
+	  {
+	    register int j;
+	    for (j = 0; j < XVECLEN (x, i); j++)
+	      if (side_effects_p (XVECEXP (x, i, j)))
+		return 1;
+	  }
+      }
+  }
+  return 0;
+}
+
+/* Return nonzero if evaluating rtx X might cause a trap.  */
+
+int
+may_trap_p (x)
+     rtx x;
+{
+  int i;
+  enum rtx_code code;
+  char *fmt;
+
+  if (x == 0)
+    return 0;
+  code = GET_CODE (x);
+  switch (code)
+    {
+      /* Handle these cases quickly.  */
+    case CONST_INT:
+    case CONST_DOUBLE:
+    case SYMBOL_REF:
+    case LABEL_REF:
+    case CONST:
+    case PC:
+    case CC0:
+    case REG:
+    case SCRATCH:
+      return 0;
+
+      /* Conditional trap can trap!  */
+    case TRAP_IF:
+      return 1;
+
+      /* Memory ref can trap unless it's a static var or a stack slot.  */
+    case MEM:
+      return rtx_addr_can_trap_p (XEXP (x, 0));
+
+      /* Division by a non-constant might trap.  */
+    case DIV:
+    case MOD:
+    case UDIV:
+    case UMOD:
+      if (! CONSTANT_P (XEXP (x, 1)))
+	return 1;
+      /* This was const0_rtx, but by not using that,
+	 we can link this file into other programs.  */
+      if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) == 0)
+	return 1;
+    default:
+      /* Any floating arithmetic may trap.  */
+      if (GET_MODE_CLASS (GET_MODE (x)) == MODE_FLOAT)
+	return 1;
+    }
+
+  fmt = GET_RTX_FORMAT (code);
+  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
+    {
+      if (fmt[i] == 'e')
+	{
+	  if (may_trap_p (XEXP (x, i)))
+	    return 1;
+	}
+      else if (fmt[i] == 'E')
+	{
+	  register int j;
+	  for (j = 0; j < XVECLEN (x, i); j++)
+	    if (may_trap_p (XVECEXP (x, i, j)))
+	      return 1;
+	}
+    }
+  return 0;
+}
+
+/* Return nonzero if X contains a comparison that is not either EQ or NE,
+   i.e., an inequality.  */
+
+int
+inequality_comparisons_p (x)
+     rtx x;
+{
+  register char *fmt;
+  register int len, i;
+  register enum rtx_code code = GET_CODE (x);
+
+  switch (code)
+    {
+    case REG:
+    case SCRATCH:
+    case PC:
+    case CC0:
+    case CONST_INT:
+    case CONST_DOUBLE:
+    case CONST:
+    case LABEL_REF:
+    case SYMBOL_REF:
+      return 0;
+
+    case LT:
+    case LTU:
+    case GT:
+    case GTU:
+    case LE:
+    case LEU:
+    case GE:
+    case GEU:
+      return 1;
+    }
+
+  len = GET_RTX_LENGTH (code);
+  fmt = GET_RTX_FORMAT (code);
+
+  for (i = 0; i < len; i++)
+    {
+      if (fmt[i] == 'e')
+	{
+	  if (inequality_comparisons_p (XEXP (x, i)))
+	    return 1;
+	}
+      else if (fmt[i] == 'E')
+	{
+	  register int j;
+	  for (j = XVECLEN (x, i) - 1; j >= 0; j--)
+	    if (inequality_comparisons_p (XVECEXP (x, i, j)))
+	      return 1;
+	}
+    }
+	    
+  return 0;
+}
+
+/* Replace any occurrence of FROM in X with TO.
+
+   Note that copying is not done so X must not be shared unless all copies
+   are to be modified.  */
+
+rtx
+replace_rtx (x, from, to)
+     rtx x, from, to;
+{
+  register int i, j;
+  register char *fmt;
+
+  if (x == from)
+    return to;
+
+  /* Allow this function to make replacements in EXPR_LISTs.  */
+  if (x == 0)
+    return 0;
+
+  fmt = GET_RTX_FORMAT (GET_CODE (x));
+  for (i = GET_RTX_LENGTH (GET_CODE (x)) - 1; i >= 0; i--)
+    {
+      if (fmt[i] == 'e')
+	XEXP (x, i) = replace_rtx (XEXP (x, i), from, to);
+      else if (fmt[i] == 'E')
+	for (j = XVECLEN (x, i) - 1; j >= 0; j--)
+	  XVECEXP (x, i, j) = replace_rtx (XVECEXP (x, i, j), from, to);
+    }
+
+  return x;
+}  
+
+/* Throughout the rtx X, replace many registers according to REG_MAP.
+   Return the replacement for X (which may be X with altered contents).
+   REG_MAP[R] is the replacement for register R, or 0 for don't replace.
+   NREGS is the length of REG_MAP; regs >= NREGS are not mapped.  
+
+   We only support REG_MAP entries of REG or SUBREG.  Also, hard registers
+   should not be mapped to pseudos or vice versa since validate_change
+   is not called.
+
+   If REPLACE_DEST is 1, replacements are also done in destinations;
+   otherwise, only sources are replaced.  */
+
+rtx
+replace_regs (x, reg_map, nregs, replace_dest)
+     rtx x;
+     rtx *reg_map;
+     int nregs;
+     int replace_dest;
+{
+  register enum rtx_code code;
+  register int i;
+  register char *fmt;
+
+  if (x == 0)
+    return x;
+
+  code = GET_CODE (x);
+  switch (code)
+    {
+    case SCRATCH:
+    case PC:
+    case CC0:
+    case CONST_INT:
+    case CONST_DOUBLE:
+    case CONST:
+    case SYMBOL_REF:
+    case LABEL_REF:
+      return x;
+
+    case REG:
+      /* Verify that the register has an entry before trying to access it.  */
+      if (REGNO (x) < nregs && reg_map[REGNO (x)] != 0)
+	return reg_map[REGNO (x)];
+      return x;
+
+    case SUBREG:
+      /* Prevent making nested SUBREGs.  */
+      if (GET_CODE (SUBREG_REG (x)) == REG && REGNO (SUBREG_REG (x)) < nregs
+	  && reg_map[REGNO (SUBREG_REG (x))] != 0
+	  && GET_CODE (reg_map[REGNO (SUBREG_REG (x))]) == SUBREG)
+	{
+	  rtx map_val = reg_map[REGNO (SUBREG_REG (x))];
+	  rtx map_inner = SUBREG_REG (map_val);
+
+	  if (GET_MODE (x) == GET_MODE (map_inner))
+	    return map_inner;
+	  else
+	    {
+	      /* We cannot call gen_rtx here since we may be linked with
+		 genattrtab.c.  */
+	      /* Let's try clobbering the incoming SUBREG and see
+		 if this is really safe.  */
+	      SUBREG_REG (x) = map_inner;
+	      SUBREG_WORD (x) += SUBREG_WORD (map_val);
+	      return x;
+#if 0
+	      rtx new = rtx_alloc (SUBREG);
+	      PUT_MODE (new, GET_MODE (x));
+	      SUBREG_REG (new) = map_inner;
+	      SUBREG_WORD (new) = SUBREG_WORD (x) + SUBREG_WORD (map_val);
+#endif
+	    }
+	}
+      break;
+
+    case SET:
+      if (replace_dest)
+	SET_DEST (x) = replace_regs (SET_DEST (x), reg_map, nregs, 0);
+
+      else if (GET_CODE (SET_DEST (x)) == MEM
+	       || GET_CODE (SET_DEST (x)) == STRICT_LOW_PART)
+	/* Even if we are not to replace destinations, replace register if it
+	   is CONTAINED in destination (destination is memory or
+	   STRICT_LOW_PART).  */
+	XEXP (SET_DEST (x), 0) = replace_regs (XEXP (SET_DEST (x), 0),
+					       reg_map, nregs, 0);
+      else if (GET_CODE (SET_DEST (x)) == ZERO_EXTRACT)
+	/* Similarly, for ZERO_EXTRACT we replace all operands.  */
+	break;
+
+      SET_SRC (x) = replace_regs (SET_SRC (x), reg_map, nregs, 0);
+      return x;
+    }
+
+  fmt = GET_RTX_FORMAT (code);
+  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
+    {
+      if (fmt[i] == 'e')
+	XEXP (x, i) = replace_regs (XEXP (x, i), reg_map, nregs, replace_dest);
+      if (fmt[i] == 'E')
+	{
+	  register int j;
+	  for (j = 0; j < XVECLEN (x, i); j++)
+	    XVECEXP (x, i, j) = replace_regs (XVECEXP (x, i, j), reg_map,
+					      nregs, replace_dest);
+	}
+    }
+  return x;
+}