re PR sanitizer/80800 (UBSAN: yet another false positive)

	PR sanitizer/80800
	* fold-const.c (extract_muldiv_1) <case TRUNC_DIV_EXPR>: Add
	TYPE_OVERFLOW_WRAPS checks.

	* c-c++-common/ubsan/pr80800.c: New test.
	* c-c++-common/Wduplicated-branches-1.c: Adjust an expression.

From-SVN: r248291

gcc/ChangeLog

+2017-05-19  Marek Polacek  <polacek@redhat.com>
+
+	PR sanitizer/80800
+	* fold-const.c (extract_muldiv_1) <case TRUNC_DIV_EXPR>: Add
+	TYPE_OVERFLOW_WRAPS checks.
+
 2017-05-19  Thomas Schwinge  <thomas@codesourcery.com>
 
 	* tree-core.h (enum omp_clause_default_kind): Add

gcc/fold-const.c

@@ -6281,11 +6281,13 @@ extract_muldiv_1 (tree t, tree c, enum tree_code code, tree wide_type,
 	 new operation.  Likewise for the RHS from a MULT_EXPR.  Otherwise,
 	 do something only if the second operand is a constant.  */
       if (same_p
+	  && TYPE_OVERFLOW_WRAPS (ctype)
 	  && (t1 = extract_muldiv (op0, c, code, wide_type,
 				   strict_overflow_p)) != 0)
 	return fold_build2 (tcode, ctype, fold_convert (ctype, t1),
 			    fold_convert (ctype, op1));
       else if (tcode == MULT_EXPR && code == MULT_EXPR
+	       && TYPE_OVERFLOW_WRAPS (ctype)
 	       && (t1 = extract_muldiv (op1, c, code, wide_type,
 					strict_overflow_p)) != 0)
 	return fold_build2 (tcode, ctype, fold_convert (ctype, op0),

gcc/testsuite/ChangeLog

+2017-05-19  Marek Polacek  <polacek@redhat.com>
+
+	PR sanitizer/80800
+	* c-c++-common/ubsan/pr80800.c: New test.
+	* c-c++-common/Wduplicated-branches-1.c: Adjust an expression.
+
 2017-05-19  Thomas Schwinge  <thomas@codesourcery.com>
 
 	* c-c++-common/goacc/default-1.c: Update.

gcc/testsuite/c-c++-common/Wduplicated-branches-1.c

@@ -89,7 +89,7 @@ f (int i, int *p)
   if (i == 8) /* { dg-warning "this condition has identical branches" } */
     return i * 8 * i * 8;
   else
-    return 8 * i * 8 * i;
+    return i * 8 * i * 8;
 
 
   if (i == 9) /* { dg-warning "this condition has identical branches" } */

gcc/testsuite/c-c++-common/ubsan/pr80800.c

+/* PR sanitizer/80800 */
+/* { dg-do run } */
+/* { dg-options "-fsanitize=undefined -fsanitize-undefined-trap-on-error" } */
+
+int n = 20000;
+int z = 0;
+
+int
+fn1 (void)
+{
+  return (n * 10000 * z) * 50;
+}
+
+int
+fn2 (void)
+{
+  return (10000 * n * z) * 50;
+}
+
+int
+main ()
+{
+  fn1 ();
+  fn2 ();
+}