re PR middle-end/56917 (-ftrapv detects a overflow wrongly.)

	PR middle-end/56917
	* fold-const.c (fold_unary_loc): Perform the negation in A's type
	when transforming ~ (A - 1) or ~ (A + -1) to -A.

	* c-c++-common/ubsan/pr56917.c: New test.

From-SVN: r218395

gcc/ChangeLog

+2014-12-04  Marek Polacek  <polacek@redhat.com>
+
+	PR middle-end/56917
+	* fold-const.c (fold_unary_loc): Perform the negation in A's type
+	when transforming ~ (A - 1) or ~ (A + -1) to -A.
+
 2014-12-04  Tobias Burnus  <burnus@net-b.de>
 
 	* Makefile.in: Remove CLOOGLIB and CLOOGINC.

gcc/fold-const.c

@@ -8141,9 +8141,14 @@ fold_unary_loc (location_t loc, enum tree_code code, tree type, tree op0)
 		    && integer_onep (TREE_OPERAND (arg0, 1)))
 		   || (TREE_CODE (arg0) == PLUS_EXPR
 		       && integer_all_onesp (TREE_OPERAND (arg0, 1)))))
-	return fold_build1_loc (loc, NEGATE_EXPR, type,
-			    fold_convert_loc (loc, type,
-					      TREE_OPERAND (arg0, 0)));
+	{
+	  /* Perform the negation in ARG0's type and only then convert
+	     to TYPE as to avoid introducing undefined behavior.  */
+	  tree t = fold_build1_loc (loc, NEGATE_EXPR,
+				    TREE_TYPE (TREE_OPERAND (arg0, 0)),
+				    TREE_OPERAND (arg0, 0));
+	  return fold_convert_loc (loc, type, t);
+	}
       /* Convert ~(X ^ Y) to ~X ^ Y or X ^ ~Y if ~X or ~Y simplify.  */
       else if (TREE_CODE (arg0) == BIT_XOR_EXPR
 	       && (tem = fold_unary_loc (loc, BIT_NOT_EXPR, type,

gcc/testsuite/ChangeLog

+2014-12-04  Marek Polacek  <polacek@redhat.com>
+
+	PR middle-end/56917
+	* c-c++-common/ubsan/pr56917.c: New test.
+
 2014-12-04  Martin Jambor  <mjambor@suse.cz>
 
 	* gcc.dg/ipa/propalign-1.c: New test.

gcc/testsuite/c-c++-common/ubsan/pr56917.c

+/* PR middle-end/56917 */
+/* { dg-do run } */
+/* { dg-options "-fsanitize=undefined -fno-sanitize-recover=undefined" } */
+
+#define INT_MIN (-__INT_MAX__ - 1)
+#define LONG_MIN (-__LONG_MAX__ - 1L)
+#define LLONG_MIN (-__LONG_LONG_MAX__ - 1LL)
+
+int __attribute__ ((noinline,noclone))
+fn1 (unsigned int u)
+{
+  return (-(int) (u - 1U)) - 1;
+}
+
+long __attribute__ ((noinline,noclone))
+fn2 (unsigned long int ul)
+{
+  return (-(long) (ul - 1UL)) - 1L;
+}
+
+long long __attribute__ ((noinline,noclone))
+fn3 (unsigned long long int ull)
+{
+  return (-(long long) (ull - 1ULL)) - 1LL;
+}
+
+int
+main (void)
+{
+  if (fn1 (__INT_MAX__ + 1U) != INT_MIN
+      || fn2 (__LONG_MAX__ + 1UL) != LONG_MIN
+      || fn3 (__LONG_LONG_MAX__ + 1ULL) != LLONG_MIN)
+    __builtin_abort ();
+}