simplify-rtx.c (simplify_unary_operation_1): Extend the handling of…

simplify-rtx.c (simplify_unary_operation_1): Extend the handling of SUBREG_PROMOTED_VAR_P to cope with cases where the...

gcc/
	* simplify-rtx.c (simplify_unary_operation_1): Extend the handling
	of SUBREG_PROMOTED_VAR_P to cope with cases where the extended value
	is smaller than the original promoted value.
	(simplify_subreg): If OP is a SUBREG, try to preserve its
	SUBREG_PROMOTED_VAR_P information.

From-SVN: r132755

gcc/ChangeLog

+2008-02-28  Richard Sandiford  <rsandifo@nildram.co.uk>
+
+	* simplify-rtx.c (simplify_unary_operation_1): Extend the handling
+	of SUBREG_PROMOTED_VAR_P to cope with cases where the extended value
+	is smaller than the original promoted value.
+	(simplify_subreg): If OP is a SUBREG, try to preserve its
+	SUBREG_PROMOTED_VAR_P information.
+
 2008-02-28  Steven Bosscher  <stevenb.gcc@gmail.com>
 
 	* tree-ssa-sccvn (vn_ssa_aux_obstack): New obstack.

gcc/simplify-rtx.c

@@ -859,8 +859,8 @@ simplify_unary_operation_1 (enum rtx_code code, enum machine_mode mode, rtx op)
       if (GET_CODE (op) == SUBREG
 	  && SUBREG_PROMOTED_VAR_P (op)
 	  && ! SUBREG_PROMOTED_UNSIGNED_P (op)
-	  && GET_MODE (XEXP (op, 0)) == mode)
-	return XEXP (op, 0);
+	  && GET_MODE_SIZE (mode) <= GET_MODE_SIZE (GET_MODE (XEXP (op, 0))))
+	return rtl_hooks.gen_lowpart_no_emit (mode, op);
 
 #if defined(POINTERS_EXTEND_UNSIGNED) && !defined(HAVE_ptr_extend)
       if (! POINTERS_EXTEND_UNSIGNED
@@ -881,8 +881,8 @@ simplify_unary_operation_1 (enum rtx_code code, enum machine_mode mode, rtx op)
       if (GET_CODE (op) == SUBREG
 	  && SUBREG_PROMOTED_VAR_P (op)
 	  && SUBREG_PROMOTED_UNSIGNED_P (op) > 0
-	  && GET_MODE (XEXP (op, 0)) == mode)
-	return XEXP (op, 0);
+	  && GET_MODE_SIZE (mode) <= GET_MODE_SIZE (GET_MODE (XEXP (op, 0))))
+	return rtl_hooks.gen_lowpart_no_emit (mode, op);
 
 #if defined(POINTERS_EXTEND_UNSIGNED) && !defined(HAVE_ptr_extend)
       if (POINTERS_EXTEND_UNSIGNED > 0
@@ -5021,7 +5021,22 @@ simplify_subreg (enum machine_mode outermode, rtx op,
 	return newx;
       if (validate_subreg (outermode, innermostmode,
 			   SUBREG_REG (op), final_offset))
-        return gen_rtx_SUBREG (outermode, SUBREG_REG (op), final_offset);
+	{
+	  newx = gen_rtx_SUBREG (outermode, SUBREG_REG (op), final_offset);
+	  if (SUBREG_PROMOTED_VAR_P (op)
+	      && SUBREG_PROMOTED_UNSIGNED_P (op) >= 0
+	      && GET_MODE_CLASS (outermode) == MODE_INT
+	      && IN_RANGE (GET_MODE_SIZE (outermode),
+			   GET_MODE_SIZE (innermode),
+			   GET_MODE_SIZE (innermostmode))
+	      && subreg_lowpart_p (newx))
+	    {
+	      SUBREG_PROMOTED_VAR_P (newx) = 1;
+	      SUBREG_PROMOTED_UNSIGNED_SET
+		(newx, SUBREG_PROMOTED_UNSIGNED_P (op));
+	    }
+	  return newx;
+	}
       return NULL_RTX;
     }