Fix result of folding of xor operation on two identical vectors.

OKed by Roger Sayle.

From-SVN: r98107

gcc/ChangeLog

+2005-04-13 Fariborz Jahanian <fjahanian@apple.com>
+
+	* simplify-rtx.c (simplify_binary_operation_1): Return
+	scalar or vector of constant 0, depending on the xor's 
+	mode.
+
 2005-04-13  Dale Johannesen  <dalej@apple.com>
 
         * objc/Make-lang.in (objc-lang.o):  Depend on tree-gimple.h.

gcc/simplify-rtx.c

@@ -1641,7 +1641,7 @@ simplify_binary_operation_1 (enum rtx_code code, enum machine_mode mode,
       if (trueop0 == trueop1
 	  && ! side_effects_p (op0)
 	  && GET_MODE_CLASS (mode) != MODE_CC)
-	return const0_rtx;
+	 return CONST0_RTX (mode);
 
       /* Canonicalize XOR of the most significant bit to PLUS.  */
       if ((GET_CODE (op1) == CONST_INT

gcc/testsuite/gcc.dg/i386-xorps.c

+/* { dg-do compile { target i?86-*-* } } */
+/* { dg-options "-Os -msse2" } */
+
+typedef float __m128 __attribute__ ((vector_size (16)));
+
+static __inline __m128
+_mm_mul_ps (__m128 __A, __m128 __B)
+{
+  return __builtin_ia32_mulps (__A, __B);
+}
+
+static __inline __m128
+_mm_sub_ps (__m128 __A, __m128 __B)
+{
+  return  __builtin_ia32_subps (__A, __B);
+}
+
+__m128 POW_FUNC (__m128 x, __m128 y)
+{
+    __m128 xmm0 = x, xmm1 = y, xmm2;
+
+    xmm0 = __builtin_ia32_xorps (xmm1, xmm1);
+
+    xmm0 = _mm_mul_ps (xmm0, xmm1);
+
+    xmm0 = _mm_sub_ps (xmm0, xmm1);
+
+    xmm0 = _mm_mul_ps (xmm0, xmm1);
+
+    return xmm0;
+}