re PR tree-optimization/56355 (abs and multiplication)

2013-03-20  Marc Glisse  <marc.glisse@inria.fr>

	PR tree-optimization/56355
gcc/
	* fold-const.c (tree_binary_nonnegative_warnv_p) <MULT_EXPR>:
	Also handle integers with undefined overflow.

gcc/testsuite/
	* gcc.dg/pr56355-1.c: New file.

From-SVN: r196829

gcc/ChangeLog

+2013-03-20  Marc Glisse  <marc.glisse@inria.fr>
+
+	PR tree-optimization/56355
+	* fold-const.c (tree_binary_nonnegative_warnv_p) <MULT_EXPR>:
+	Also handle integers with undefined overflow.
+
 2013-03-20  Catherine Moore  <clm@codesourcery.com>
 	    Maciej W. Rozycki  <macro@codesourcery.com>
 	    Tom de Vries  <tom@codesourcery.com>

gcc/fold-const.c

@@ -15294,15 +15294,18 @@ tree_binary_nonnegative_warnv_p (enum tree_code code, tree type, tree op0,
       break;
 
     case MULT_EXPR:
-      if (FLOAT_TYPE_P (type))
+      if (FLOAT_TYPE_P (type) || TYPE_OVERFLOW_UNDEFINED (type))
 	{
-	  /* x * x for floating point x is always non-negative.  */
-	  if (operand_equal_p (op0, op1, 0))
-	    return true;
-	  return (tree_expr_nonnegative_warnv_p (op0,
-						 strict_overflow_p)
-		  && tree_expr_nonnegative_warnv_p (op1,
-						    strict_overflow_p));
+	  /* x * x is always non-negative for floating point x
+	     or without overflow.  */
+	  if (operand_equal_p (op0, op1, 0)
+	      || (tree_expr_nonnegative_warnv_p (op0, strict_overflow_p)
+		  && tree_expr_nonnegative_warnv_p (op1, strict_overflow_p)))
+	    {
+	      if (TYPE_OVERFLOW_UNDEFINED (type))
+		*strict_overflow_p = true;
+	      return true;
+	    }
 	}
 
       /* zero_extend(x) * zero_extend(y) is non-negative if x and y are

gcc/testsuite/ChangeLog

+2013-03-20  Marc Glisse  <marc.glisse@inria.fr>
+
+	PR tree-optimization/56355
+	* gcc.dg/pr56355-1.c: New file.
+
 2013-03-20  Catherine Moore  <clm@codesourcery.com>
 	    Richard Sandiford <rdsandiford@googlemail.com>
 

gcc/testsuite/gcc.dg/pr56355-1.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -Wstrict-overflow=4" } */
+
+int
+f (int i)
+{
+  return __builtin_abs (i * i); /* { dg-warning "assuming signed overflow" } */
+}