re PR tree-optimization/83517 (Missed optimization in math expression: (x+x)/x == 2)

2018-01-08  Richard Biener  <rguenther@suse.de>

	PR middle-end/83517
	* match.pd ((t * 2) / 2) -> t): Add missing :c.

	* gcc.dg/pr83517.c: New testcase.

From-SVN: r256328

gcc/ChangeLog

+2018-01-08  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/83517
+	* match.pd ((t * 2) / 2) -> t): Add missing :c.
+
 2018-01-06  Aldy Hernandez  <aldyh@redhat.com>
 
 	PR middle-end/81897

gcc/match.pd

@@ -510,7 +510,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 /* Simplify (t * 2) / 2) -> t.  */
 (for div (trunc_div ceil_div floor_div round_div exact_div)
  (simplify
-  (div (mult @0 @1) @1)
+  (div (mult:c @0 @1) @1)
   (if (ANY_INTEGRAL_TYPE_P (type)
        && TYPE_OVERFLOW_UNDEFINED (type))
    @0)))

gcc/testsuite/ChangeLog

+2018-01-08  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/83517
+	* gcc.dg/pr83517.c: New testcase.
+
 2018-01-06  Aldy Hernandez  <aldyh@redhat.com>
 
 	PR middle-end/81897

gcc/testsuite/gcc.dg/pr83517.c

+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-original" } */
+
+int test(int x)
+{
+  return (x+x)/x;
+}
+
+/* { dg-final { scan-tree-dump "return 2;" "original" } } */