combine.c (nonzero_bits, case PLUS): If pointers extend unsigned and this is the sum of a pointer and a constant...

	* combine.c (nonzero_bits, case PLUS): If pointers extend unsigned
	and this is the sum of a pointer and a constant, we know the result
	did not overflow.
	(num_sign_bit_copies, case PLUS): Likewise.
	* explow.c (convert_memory_address): Remove opposite SUBREG.
	* function.c (instantiate_new_reg): New function (from common code).
	(instantiate_virtual_regs_1): Call it.
	For PLUS, handle if (plus (subreg (virt-reg) (const_int))
	if pointers sign- or zero-extend.
	* simplify-rtx.c (simplify_unary_operation, case ZERO_EXTEND):
	If pointers extend unsigned, use inside of SUBREG.
	(simplify_unary_operation, case SIGN_EXTEND): Likewise, if sign extend.

From-SVN: r39489

5 files changed, 114 insertions, 54 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 547f50f..f0c7159 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,18 @@
+Mon Feb  5 21:56:16 2001  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
+
+	* combine.c (nonzero_bits, case PLUS): If pointers extend unsigned
+	and this is the sum of a pointer and a constant, we know the result
+	did not overflow.
+	(num_sign_bit_copies, case PLUS): Likewise.
+	* explow.c (convert_memory_address): Remove opposite SUBREG.
+	* function.c (instantiate_new_reg): New function (from common code).
+	(instantiate_virtual_regs_1): Call it.
+	For PLUS, handle if (plus (subreg (virt-reg) (const_int))
+	if pointers sign- or zero-extend.
+	* simplify-rtx.c (simplify_unary_operation, case ZERO_EXTEND):
+	If pointers extend unsigned, use inside of SUBREG.
+	(simplify_unary_operation, case SIGN_EXTEND): Likewise, if sign extend.
+
 2001-02-05  Benjamin Kosnik  <bkoz@redhat.com>
 
 	* Makefile.in (-DGPLUSPLUS_TOOL_INCLUDE_DIR): Change to target
diff --git a/gcc/combine.c b/gcc/combine.c
index 74b02b5..662f05f 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -8308,6 +8308,16 @@ nonzero_bits (x, mode)
 
 	if (result_low > 0)
 	  nonzero &= ~(((HOST_WIDE_INT) 1 << result_low) - 1);
+
+#ifdef POINTERS_EXTEND_UNSIGNED
+	/* If pointers extend unsigned and this is an addition or subtraction
+	   to a pointer in Pmode, all the bits above ptr_mode are known to be
+	   zero.  */
+	if (POINTERS_EXTEND_UNSIGNED && GET_MODE (x) == Pmode
+	    && (code == PLUS || code == MINUS)
+	    && GET_CODE (XEXP (x, 0)) == REG && REG_POINTER (XEXP (x, 0)))
+	  nonzero &= GET_MODE_MASK (ptr_mode);
+#endif
       }
       break;
 
@@ -8646,7 +8656,20 @@ num_sign_bit_copies (x, mode)
 
       num0 = num_sign_bit_copies (XEXP (x, 0), mode);
       num1 = num_sign_bit_copies (XEXP (x, 1), mode);
-      return MAX (1, MIN (num0, num1) - 1);
+      result = MAX (1, MIN (num0, num1) - 1);
+
+#ifdef POINTERS_EXTEND_UNSIGNED
+      /* If pointers extend signed and this is an addition or subtraction
+	 to a pointer in Pmode, all the bits above ptr_mode are known to be
+	 sign bit copies.  */
+      if (! POINTERS_EXTEND_UNSIGNED && GET_MODE (x) == Pmode
+	  && (code == PLUS || code == MINUS)
+	  && GET_CODE (XEXP (x, 0)) == REG && REG_POINTER (XEXP (x, 0)))
+	result = MAX ((GET_MODE_BITSIZE (Pmode)
+		       - GET_MODE_BITSIZE (ptr_mode) + 1),
+		      result);
+#endif
+      return result;
 
     case MULT:
       /* The number of bits of the product is the sum of the number of
diff --git a/gcc/explow.c b/gcc/explow.c
index d36ceff..b7c0bb9 100644
--- a/gcc/explow.c
+++ b/gcc/explow.c
@@ -386,6 +386,11 @@ convert_memory_address (to_mode, x)
     case CONST_DOUBLE:
       return x;
 
+    case SUBREG:
+      if (GET_MODE (SUBREG_REG (x)) == to_mode)
+	return SUBREG_REG (x);
+      break;
+
     case LABEL_REF:
       temp = gen_rtx_LABEL_REF (to_mode, XEXP (x, 0));
       LABEL_REF_NONLOCAL_P (temp) = LABEL_REF_NONLOCAL_P (x);
diff --git a/gcc/function.c b/gcc/function.c
index 5421450..259ccca 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -269,6 +269,7 @@ static void optimize_bit_field	PARAMS ((rtx, rtx, rtx *));
 static void instantiate_decls	PARAMS ((tree, int));
 static void instantiate_decls_1	PARAMS ((tree, int));
 static void instantiate_decl	PARAMS ((rtx, HOST_WIDE_INT, int));
+static rtx instantiate_new_reg	PARAMS ((rtx, HOST_WIDE_INT *));
 static int instantiate_virtual_regs_1 PARAMS ((rtx *, rtx, int));
 static void delete_handlers	PARAMS ((void));
 static void pad_to_arg_alignment PARAMS ((struct args_size *, int,
@@ -3680,6 +3681,35 @@ instantiate_decl (x, size, valid_only)
   XEXP (x, 0) = addr;
 }
 
+/* Given a piece of RTX and a pointer to a HOST_WIDE_INT, if the RTX
+   is a virtual register, return the requivalent hard register and set the
+   offset indirectly through the pointer.  Otherwise, return 0.  */
+
+static rtx
+instantiate_new_reg (x, poffset)
+     rtx x;
+     HOST_WIDE_INT *poffset;
+{
+  rtx new;
+  HOST_WIDE_INT offset;
+
+  if (x == virtual_incoming_args_rtx)
+    new = arg_pointer_rtx, offset = in_arg_offset;
+  else if (x == virtual_stack_vars_rtx)
+    new = frame_pointer_rtx, offset = var_offset;
+  else if (x == virtual_stack_dynamic_rtx)
+    new = stack_pointer_rtx, offset = dynamic_offset;
+  else if (x == virtual_outgoing_args_rtx)
+    new = stack_pointer_rtx, offset = out_arg_offset;
+  else if (x == virtual_cfa_rtx)
+    new = arg_pointer_rtx, offset = cfa_offset;
+  else
+    return 0;
+
+  *poffset = offset;
+  return new;
+}
+
 /* Given a pointer to a piece of rtx and an optional pointer to the
    containing object, instantiate any virtual registers present in it.
 
@@ -3739,21 +3769,14 @@ instantiate_virtual_regs_1 (loc, object, extra_insns)
 	 the actual register should receive the source minus the
 	 appropriate offset.  This is used, for example, in the handling
 	 of non-local gotos.  */
-      if (SET_DEST (x) == virtual_incoming_args_rtx)
-	new = arg_pointer_rtx, offset = -in_arg_offset;
-      else if (SET_DEST (x) == virtual_stack_vars_rtx)
-	new = frame_pointer_rtx, offset = -var_offset;
-      else if (SET_DEST (x) == virtual_stack_dynamic_rtx)
-	new = stack_pointer_rtx, offset = -dynamic_offset;
-      else if (SET_DEST (x) == virtual_outgoing_args_rtx)
-	new = stack_pointer_rtx, offset = -out_arg_offset;
-      else if (SET_DEST (x) == virtual_cfa_rtx)
-	new = arg_pointer_rtx, offset = -cfa_offset;
-
-      if (new)
+      if ((new = instantiate_new_reg (SET_DEST (x), &offset)) != 0)
 	{
 	  rtx src = SET_SRC (x);
 
+	  /* We are setting the register, not using it, so the relevant
+	     offset is the negative of the offset to use were we using
+	     the register.  */
+	  offset = - offset;
 	  instantiate_virtual_regs_1 (&src, NULL_RTX, 0);
 
 	  /* The only valid sources here are PLUS or REG.  Just do
@@ -3793,40 +3816,37 @@ instantiate_virtual_regs_1 (loc, object, extra_insns)
 	  /* Check for (plus (plus VIRT foo) (const_int)) first.  */
 	  if (GET_CODE (XEXP (x, 0)) == PLUS)
 	    {
-	      rtx inner = XEXP (XEXP (x, 0), 0);
-
-	      if (inner == virtual_incoming_args_rtx)
-		new = arg_pointer_rtx, offset = in_arg_offset;
-	      else if (inner == virtual_stack_vars_rtx)
-		new = frame_pointer_rtx, offset = var_offset;
-	      else if (inner == virtual_stack_dynamic_rtx)
-		new = stack_pointer_rtx, offset = dynamic_offset;
-	      else if (inner == virtual_outgoing_args_rtx)
-		new = stack_pointer_rtx, offset = out_arg_offset;
-	      else if (inner == virtual_cfa_rtx)
-		new = arg_pointer_rtx, offset = cfa_offset;
+	      if ((new = instantiate_new_reg (XEXP (XEXP (x, 0), 0), &offset)))
+		{
+		  instantiate_virtual_regs_1 (&XEXP (XEXP (x, 0), 1), object,
+					      extra_insns);
+		  new = gen_rtx_PLUS (Pmode, new, XEXP (XEXP (x, 0), 1));
+		}
 	      else
 		{
 		  loc = &XEXP (x, 0);
 		  goto restart;
 		}
-
-	      instantiate_virtual_regs_1 (&XEXP (XEXP (x, 0), 1), object,
-					  extra_insns);
-	      new = gen_rtx_PLUS (Pmode, new, XEXP (XEXP (x, 0), 1));
 	    }
 
-	  else if (XEXP (x, 0) == virtual_incoming_args_rtx)
-	    new = arg_pointer_rtx, offset = in_arg_offset;
-	  else if (XEXP (x, 0) == virtual_stack_vars_rtx)
-	    new = frame_pointer_rtx, offset = var_offset;
-	  else if (XEXP (x, 0) == virtual_stack_dynamic_rtx)
-	    new = stack_pointer_rtx, offset = dynamic_offset;
-	  else if (XEXP (x, 0) == virtual_outgoing_args_rtx)
-	    new = stack_pointer_rtx, offset = out_arg_offset;
-	  else if (XEXP (x, 0) == virtual_cfa_rtx)
-	    new = arg_pointer_rtx, offset = cfa_offset;
-	  else
+#ifdef POINTERS_EXTEND_UNSIGNED
+	  /* If we have (plus (subreg (virtual-reg)) (const_int)), we know
+	     we can commute the PLUS and SUBREG because pointers into the
+	     frame are well-behaved.  */
+	  else if (GET_CODE (XEXP (x, 0)) == SUBREG && GET_MODE (x) == ptr_mode
+		   && GET_CODE (XEXP (x, 1)) == CONST_INT
+		   && 0 != (new
+			    = instantiate_new_reg (SUBREG_REG (XEXP (x, 0)),
+						   &offset))
+		   && validate_change (object, loc,
+				       plus_constant (gen_lowpart (ptr_mode,
+								   new),
+						      offset
+						      + INTVAL (XEXP (x, 1))),
+				       0))
+		return 1;
+#endif
+	  else if ((new = instantiate_new_reg (XEXP (x, 0), &offset)) == 0)
 	    {
 	      /* We know the second operand is a constant.  Unless the
 		 first operand is a REG (which has been already checked),
@@ -4025,18 +4045,7 @@ instantiate_virtual_regs_1 (loc, object, extra_insns)
     case REG:
       /* Try to replace with a PLUS.  If that doesn't work, compute the sum
 	 in front of this insn and substitute the temporary.  */
-      if (x == virtual_incoming_args_rtx)
-	new = arg_pointer_rtx, offset = in_arg_offset;
-      else if (x == virtual_stack_vars_rtx)
-	new = frame_pointer_rtx, offset = var_offset;
-      else if (x == virtual_stack_dynamic_rtx)
-	new = stack_pointer_rtx, offset = dynamic_offset;
-      else if (x == virtual_outgoing_args_rtx)
-	new = stack_pointer_rtx, offset = out_arg_offset;
-      else if (x == virtual_cfa_rtx)
-	new = arg_pointer_rtx, offset = cfa_offset;
-
-      if (new)
+      if ((new = instantiate_new_reg (x, &offset)) != 0)
 	{
 	  temp = plus_constant (new, offset);
 	  if (!validate_change (object, loc, temp, 0))
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index 6ae44b2..afd8d26 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -623,7 +623,11 @@ simplify_unary_operation (code, mode, op, op_mode)
 #ifdef POINTERS_EXTEND_UNSIGNED
 	  if (! POINTERS_EXTEND_UNSIGNED
 	      && mode == Pmode && GET_MODE (op) == ptr_mode
-	      && CONSTANT_P (op))
+	      && (CONSTANT_P (op)
+		  || (GET_CODE (op) == SUBREG
+		      && GET_CODE (SUBREG_REG (op)) == REG
+		      && REG_POINTER (SUBREG_REG (op))
+		      && GET_MODE (SUBREG_REG (op)) == Pmode)))
 	    return convert_memory_address (Pmode, op);
 #endif
 	  break;
@@ -632,7 +636,11 @@ simplify_unary_operation (code, mode, op, op_mode)
 	case ZERO_EXTEND:
 	  if (POINTERS_EXTEND_UNSIGNED
 	      && mode == Pmode && GET_MODE (op) == ptr_mode
-	      && CONSTANT_P (op))
+	      && (CONSTANT_P (op)
+		  || (GET_CODE (op) == SUBREG
+		      && GET_CODE (SUBREG_REG (op)) == REG
+		      && REG_POINTER (SUBREG_REG (op))
+		      && GET_MODE (SUBREG_REG (op)) == Pmode)))
 	    return convert_memory_address (Pmode, op);
 	  break;
 #endif