re PR middle-end/49958 (fold performs invalid association)

2011-08-03  Richard Guenther  <rguenther@suse.de>

	PR middle-end/49958
	* fold-const.c (fold_binary_loc): Only associate
	(+ (+ (* a b) c) (* d e)) as (+ (+ (* a b) (* d e)) c) if
	overflow wraps.

        * gcc.dg/torture/pr49958.c: New testcase.

From-SVN: r177270

gcc/ChangeLog

+2011-08-03  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/49958
+	* fold-const.c (fold_binary_loc): Only associate
+	(+ (+ (* a b) c) (* d e)) as (+ (+ (* a b) (* d e)) c) if
+	overflow wraps.
+
 2011-08-03  Alan Modra  <amodra@gmail.com>
 
 	PR rtl-optimization/49941

gcc/fold-const.c

@@ -9711,12 +9711,13 @@ fold_binary_loc (location_t loc,
 	  /* Reassociate (plus (plus (mult) (foo)) (mult)) as
 	     (plus (plus (mult) (mult)) (foo)) so that we can
 	     take advantage of the factoring cases below.  */
-	  if (((TREE_CODE (arg0) == PLUS_EXPR
-		|| TREE_CODE (arg0) == MINUS_EXPR)
-	       && TREE_CODE (arg1) == MULT_EXPR)
-	      || ((TREE_CODE (arg1) == PLUS_EXPR
-		   || TREE_CODE (arg1) == MINUS_EXPR)
-		  && TREE_CODE (arg0) == MULT_EXPR))
+	  if (TYPE_OVERFLOW_WRAPS (type)
+	      && (((TREE_CODE (arg0) == PLUS_EXPR
+		    || TREE_CODE (arg0) == MINUS_EXPR)
+		   && TREE_CODE (arg1) == MULT_EXPR)
+		  || ((TREE_CODE (arg1) == PLUS_EXPR
+		       || TREE_CODE (arg1) == MINUS_EXPR)
+		      && TREE_CODE (arg0) == MULT_EXPR)))
 	    {
 	      tree parg0, parg1, parg, marg;
 	      enum tree_code pcode;

gcc/testsuite/ChangeLog

 2011-08-03  Richard Guenther  <rguenther@suse.de>
 
+	PR middle-end/49958
+	* gcc.dg/torture/pr49958.c: New testcase.
+
+2011-08-03  Richard Guenther  <rguenther@suse.de>
+
 	PR tree-optimization/49938
 	* g++.dg/torture/pr49938.C: New testcase.
 

gcc/testsuite/gcc.dg/torture/pr49958.c

+/* { dg-do run } */
+/* { dg-options "-fstrict-overflow" } */
+
+extern void abort (void);
+int foo (int i, int j, int o, int m) { return i*o + 1 + j*m > 1; }
+int main()
+{
+  if (foo (- __INT_MAX__ - 1, -1, 1, 1))
+    abort ();
+  return 0;
+}