(subst, case SUBREG): Handle paradoxical SUBREG of constant.

(IF_THEN_ELSE): Add missing "else" and check for comparison before
calling reversible_comparison_p.

From-SVN: r6419

diff --git a/gcc/combine.c b/gcc/combine.c
index 1737e6ec465b6b593621b412e35f2ef27bfa82e1..d682939eb28a2f4c6776c4b992cf8903918a9bca 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -3216,6 +3216,12 @@ subst (x, from, to, in_dest, unique_copy)
          )
        return gen_lowpart_for_combine (mode, SUBREG_REG (x));
 
+      /* A paradoxical SUBREG of a VOIDmode constant is the same constant,
+        since we are saying that the high bits don't matter.  */
+      if (CONSTANT_P (SUBREG_REG (x)) && GET_MODE (SUBREG_REG (x)) == VOIDmode
+         && GET_MODE_SIZE (mode) > GET_MODE_SIZE (op0_mode))
+       return SUBREG_REG (x);
+
       /* If we are narrowing an integral object, we need to see if we can
         simplify the expression for the object knowing that we only need the
         low-order bits.  */
@@ -4002,12 +4008,13 @@ subst (x, from, to, in_dest, unique_copy)
              m = GET_MODE (XEXP (t, 0));
            }
 
-         if (reversible_comparison_p (XEXP (x, 0))
-             && (GET_CODE (f) == PLUS || GET_CODE (f) == MINUS
-                 || GET_CODE (f) == IOR || GET_CODE (f) == XOR
-                 || GET_CODE (f) == ASHIFT
-                 || GET_CODE (f) == LSHIFTRT || GET_CODE (f) == ASHIFTRT)
-             && rtx_equal_p (XEXP (f, 0), t))
+         else if (GET_RTX_CLASS (GET_CODE (XEXP (x, 0))) == '<'
+                  && reversible_comparison_p (XEXP (x, 0))
+                  && (GET_CODE (f) == PLUS || GET_CODE (f) == MINUS
+                      || GET_CODE (f) == IOR || GET_CODE (f) == XOR
+                      || GET_CODE (f) == ASHIFT
+                      || GET_CODE (f) == LSHIFTRT || GET_CODE (f) == ASHIFTRT)
+                  && rtx_equal_p (XEXP (f, 0), t))
            {
              c1 = XEXP (f, 1), op = GET_CODE (f), z = t;
              cond_op = reverse_condition (cond_op);