(subst, comparison cases): Expand any compound operation that is an operand...

(subst, comparison cases): Expand any compound operation that is an
operand; rerun subst on simplified result in one new case.

From-SVN: r2922

diff --git a/gcc/combine.c b/gcc/combine.c
index 360c81e5daf8620d3375769ef728c4df189fe6b3..db80ef293774060d6059162edea5673260bb8fc7 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -3370,17 +3370,27 @@ subst (x, from, to, in_dest, unique_copy)
          /* If STORE_FLAG_VALUE is 1, we can convert (ne x 0) to simply X
             if only the low-order bit is significant in X (such as when
             X is a ZERO_EXTRACT of one bit.  Similarly, we can convert
-            EQ to (xor X 1).  */
+            EQ to (xor X 1).  Remove any ZERO_EXTRACT we made when thinking
+            this was a comparison.  It may now be simpler to use, e.g., an
+            AND.  If a ZERO_EXTRACT is indeed appropriate, it will
+            be placed back by the call to make_compound_operation in the
+            SET case.  */
          if (new_code == NE && GET_MODE_CLASS (mode) == MODE_INT
              && op1 == const0_rtx
              && significant_bits (op0, GET_MODE (op0)) == 1)
-           return gen_lowpart_for_combine (mode, op0);
+           return gen_lowpart_for_combine (mode,
+                                           expand_compound_operation (op0));
          else if (new_code == EQ && GET_MODE_CLASS (mode) == MODE_INT
                   && op1 == const0_rtx
                   && significant_bits (op0, GET_MODE (op0)) == 1)
-           return gen_rtx_combine (XOR, mode,
-                                   gen_lowpart_for_combine (mode, op0),
-                                   const1_rtx);
+           {
+             op0 = expand_compound_operation (op0);
+
+             x = gen_rtx_combine (XOR, mode,
+                                  gen_lowpart_for_combine (mode, op0),
+                                  const1_rtx);
+             goto restart;
+           }
 #endif
 
 #if STORE_FLAG_VALUE == -1
@@ -3392,6 +3402,7 @@ subst (x, from, to, in_dest, unique_copy)
              && op1 == const0_rtx
              && significant_bits (op0, GET_MODE (op0)) == 1)
            {
+             op0 = expand_compound_operation (op0);
              x = gen_rtx_combine (NEG, mode,
                                   gen_lowpart_for_combine (mode, op0));
              goto restart;
@@ -3411,7 +3422,8 @@ subst (x, from, to, in_dest, unique_copy)
              && mode == GET_MODE (op0)
              && (i = exact_log2 (significant_bits (op0, GET_MODE (op0)))) >= 0)
            {
-             x = simplify_shift_const (NULL_RTX, ASHIFT, mode, op0,
+             x = simplify_shift_const (NULL_RTX, ASHIFT, mode,
+                                       expand_compound_operation (op0),
                                        GET_MODE_BITSIZE (mode) - 1 - i);
              if (GET_CODE (x) == AND && XEXP (x, 1) == const_true_rtx)
                return XEXP (x, 0);