re PR middle-end/11771 (Segfault with simple double arithmetics)

	PR middle-end/11771
	* fold-const.c (negate_expr_p <MINUS_EXPR>): Change to match the
	logic in negate_expr, i.e. we don't invert (A-B) for floating
	point types unless flag_unsafe_math_optimizations.

	* gcc.c-torture/compile/20030804-1.c: New test case.

From-SVN: r70159

gcc/ChangeLog

 2003-08-04  Roger Sayle  <roger@eyesopen.com>
 
+	PR middle-end/11771
+	* fold-const.c (negate_expr_p <MINUS_EXPR>): Change to match the
+	logic in negate_expr, i.e. we don't invert (A-B) for floating
+	point types unless flag_unsafe_math_optimizations.
+
+2003-08-04  Roger Sayle  <roger@eyesopen.com>
+
 	* fold-const.c (fold <PLUS_EXPR>): Transform x+x into x*2.0.
 	Optimize x*c+x and x+x*c into x*(c+1) and x*c1+x*c2 into x*(c1+c2)
 	for floating point expressions with -ffast-math.

gcc/fold-const.c

@@ -841,9 +841,12 @@ negate_expr_p (tree t)
 
     case REAL_CST:
     case NEGATE_EXPR:
-    case MINUS_EXPR:
       return true;
 
+    case MINUS_EXPR:
+      /* We can't turn -(A-B) into B-A when we honor signed zeros.  */
+      return ! FLOAT_TYPE_P (type) || flag_unsafe_math_optimizations;
+
     default:
       break;
     }

gcc/testsuite/ChangeLog

 2003-08-04  Roger Sayle  <roger@eyesopen.com>
 
+	PR middle-end/11771
+	* gcc.c-torture/compile/20030804-1.c: New test case.
+
+2003-08-04  Roger Sayle  <roger@eyesopen.com>
+
 	* gcc.dg/20030804-1.c: New test case.
 
 2003-08-04  Alexandre Oliva  <aoliva@redhat.com>

gcc/testsuite/gcc.c-torture/compile/20030804-1.c

+/* Extracted from PR middle-end/11771.  */
+/* The following testcase used to ICE without -ffast-math from unbounded
+   recursion in fold.  This was due to the logic in negate_expr_p not
+   matching that in negate_expr.  */
+
+double f(double x) {
+    return -(1 - x) + (x ? -(1 - x) : 0);
+}
+