fixed -ffinite-math-only A-A missing optimisation

Co-Authored-By: Richard Guenther <rguenther@suse.de>

From-SVN: r127705

gcc/ChangeLog

+2007-02-16  Christian Bruel  <christian.bruel@st.com>	
+            Richard Guenther <rguenther@suse.de>
+	
+	* fold-const.c (fold_binary): Optimize A-A if -ffinite-math-only.
+	* simplify_rtx (simplify_binary_operation_1): Likewise.
+		
 2007-08-22  Rask Ingemann Lambertsen  <rask@sygehus.dk>
 
 	PR rtl-optimization/32557

gcc/fold-const.c

@@ -10149,10 +10149,7 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 	 Also note that operand_equal_p is always false if an operand
 	 is volatile.  */
 
-      if ((! FLOAT_TYPE_P (type)
-	   || (flag_unsafe_math_optimizations
-	       && !HONOR_NANS (TYPE_MODE (type))
-	       && !HONOR_INFINITIES (TYPE_MODE (type))))
+      if ((!FLOAT_TYPE_P (type) || !HONOR_NANS (TYPE_MODE (type)))
 	  && operand_equal_p (arg0, arg1, 0))
 	return fold_convert (type, integer_zero_node);
 

gcc/simplify-rtx.c

@@ -1769,14 +1769,10 @@ simplify_binary_operation_1 (enum rtx_code code, enum machine_mode mode,
     case MINUS:
       /* We can't assume x-x is 0 even with non-IEEE floating point,
 	 but since it is zero except in very strange circumstances, we
-	 will treat it as zero with -funsafe-math-optimizations and
-	 -ffinite-math-only.  */
+	 will treat it as zero with -ffinite-math-only.  */
       if (rtx_equal_p (trueop0, trueop1)
 	  && ! side_effects_p (op0)
-	  && (! FLOAT_MODE_P (mode)
-	      || (flag_unsafe_math_optimizations
-		  && !HONOR_NANS (mode)
-		  && !HONOR_INFINITIES (mode))))
+	  && (!FLOAT_MODE_P (mode) || !HONOR_NANS (mode)))
 	return CONST0_RTX (mode);
 
       /* Change subtraction from zero into negation.  (0 - x) is the

gcc/testsuite/ChangeLog

+2007-08-21  Christian Bruel  <christian.bruel@st.com>
+
+	* gcc.dg/fold-sub.c: New test.
+	
 2007-08-22  Uros Bizjak  <ubizjak@gmail.com>
 
 	* gcc.dg/20000724-1.c, gcc.dg/980312-1.c, gcc.dg/980313-1.c,

gcc/testsuite/gcc.dg/fold-sub.c

+/* { dg-do compile } */
+/* { dg-options "-ffinite-math-only -fdump-tree-gimple" } */
+
+float f(float x)
+{
+  return x - x;
+}
+
+/* Substraction should be turned into 0.  */
+
+/* { dg-final { scan-tree-dump-not " - " "gimple" } } */
+/* { dg-final { cleanup-tree-dump "gimple" } } */