* simplify-rtx.c (simplify_relational_operation_1): Simplify

	(X^Y) == 0 as X == Y and (X^Y) != 0 as X != Y.  Simplify (X^Y) == Y
	as X == 0, and some symmetry related transformations.
	Simplify (X^C1) == C2 as X == (C1^C2).  Split long comment line.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@111443 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b2abdce..526af5d 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,12 @@
 2006-02-25  Roger Sayle  <roger@eyesopen.com>
 
+       * simplify-rtx.c (simplify_relational_operation_1):  Simplify
+       (X^Y) == 0 as X == Y and (X^Y) != 0 as X != Y.  Simplify (X^Y) == Y
+       as X == 0, and some symmetry related transformations.
+       Simplify (X^C1) == C2 as X == (C1^C2).  Split long comment line.
+
+2006-02-25  Roger Sayle  <roger@eyesopen.com>
+
        PR middle-end/23673
        * fold-const.c (fold_binary) <EQ_EXPR>:  Fold (X^Y) == 0 as X == Y
        and (X^Y) != 0 as X != Y.  Fold (X^Y) == Y as X == 0, and some

diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index 8b1f6fd..e84beda 100644 (file)
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -3512,7 +3512,8 @@ simplify_relational_operation_1 (enum rtx_code code, enum machine_mode mode,
     {
       if (INTVAL (op1) == 0 && COMPARISON_P (op0))
        {
-         /* If op0 is a comparison, extract the comparison arguments form it.  */
+         /* If op0 is a comparison, extract the comparison arguments
+            from it.  */
          if (code == NE)
            {
              if (GET_MODE (op0) == mode)
@@ -3561,6 +3562,37 @@ simplify_relational_operation_1 (enum rtx_code code, enum machine_mode mode,
           ? simplify_gen_unary (ZERO_EXTEND, mode, op0, cmp_mode)
           : lowpart_subreg (mode, op0, cmp_mode);
 
+  /* (eq/ne (xor x y) 0) simplifies to (eq/ne x y).  */
+  if ((code == EQ || code == NE)
+      && op1 == const0_rtx
+      && op0code == XOR)
+    return simplify_gen_relational (code, mode, cmp_mode,
+                                   XEXP (op0, 0), XEXP (op0, 1));
+
+  /* (eq/ne (xor x y) x) simplifies to (eq/ne x 0).  */
+  if ((code == EQ || code == NE)
+      && op0code == XOR
+      && rtx_equal_p (XEXP (op0, 0), op1)
+      && !side_effects_p (XEXP (op0, 1)))
+    return simplify_gen_relational (code, mode, cmp_mode, op1, const0_rtx);
+  /* Likewise (eq/ne (xor x y) y) simplifies to (eq/ne y 0).  */
+  if ((code == EQ || code == NE)
+      && op0code == XOR
+      && rtx_equal_p (XEXP (op0, 1), op1)
+      && !side_effects_p (XEXP (op0, 0)))
+    return simplify_gen_relational (code, mode, cmp_mode, op1, const0_rtx);
+
+  /* (eq/ne (xor x C1) C2) simplifies to (eq/ne x (C1^C2)).  */
+  if ((code == EQ || code == NE)
+      && op0code == XOR
+      && (GET_CODE (op1) == CONST_INT
+         || GET_CODE (op1) == CONST_DOUBLE)
+      && (GET_CODE (XEXP (op0, 1)) == CONST_INT
+         || GET_CODE (XEXP (op0, 1)) == CONST_DOUBLE))
+    return simplify_gen_relational (code, mode, cmp_mode, XEXP (op0, 0),
+                                   simplify_gen_binary (XOR, cmp_mode,
+                                                        XEXP (op0, 1), op1));
+
   return NULL_RTX;
 }