middle-end/108995 - avoid folding when sanitizing overflow

The following plugs one place in extract_muldiv where it should avoid
folding when sanitizing overflow.

	PR middle-end/108995
	* fold-const.cc (extract_muldiv_1): Avoid folding
	(CST * b) / CST2 when sanitizing overflow and we rely on
	overflow being undefined.

	* gcc.dg/ubsan/pr108995.c: New testcase.

diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 99882ef820a1fe2be2f6153937b700a43f532a53..02a24c5fe65116f2bc6ba2cb0cd56a9fbbe96e5b 100644 (file)
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -7093,6 +7093,7 @@ extract_muldiv_1 (tree t, tree c, enum tree_code code, tree wide_type,
         If we have an unsigned type, we cannot do this since it will change
         the result if the original computation overflowed.  */
       if (TYPE_OVERFLOW_UNDEFINED (ctype)
+         && !TYPE_OVERFLOW_SANITIZED (ctype)
          && ((code == MULT_EXPR && tcode == EXACT_DIV_EXPR)
              || (tcode == MULT_EXPR
                  && code != TRUNC_MOD_EXPR && code != CEIL_MOD_EXPR
@@ -7102,8 +7103,7 @@ extract_muldiv_1 (tree t, tree c, enum tree_code code, tree wide_type,
          if (wi::multiple_of_p (wi::to_wide (op1), wi::to_wide (c),
                                 TYPE_SIGN (type)))
            {
-             if (TYPE_OVERFLOW_UNDEFINED (ctype))
-               *strict_overflow_p = true;
+             *strict_overflow_p = true;
              return fold_build2 (tcode, ctype, fold_convert (ctype, op0),
                                  fold_convert (ctype,
                                                const_binop (TRUNC_DIV_EXPR,
@@ -7112,8 +7112,7 @@ extract_muldiv_1 (tree t, tree c, enum tree_code code, tree wide_type,
          else if (wi::multiple_of_p (wi::to_wide (c), wi::to_wide (op1),
                                      TYPE_SIGN (type)))
            {
-             if (TYPE_OVERFLOW_UNDEFINED (ctype))
-               *strict_overflow_p = true;
+             *strict_overflow_p = true;
              return fold_build2 (code, ctype, fold_convert (ctype, op0),
                                  fold_convert (ctype,
                                                const_binop (TRUNC_DIV_EXPR,

diff --git a/gcc/testsuite/gcc.dg/ubsan/pr108995.c b/gcc/testsuite/gcc.dg/ubsan/pr108995.c
new file mode 100644 (file)
index 0000000..166825b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ubsan/pr108995.c
@@ -0,0 +1,18 @@
+/* { dg-do run { target int32 } } */
+/* { dg-shouldfail "ubsan" } */
+/* With optimization we constant fold and diagnose the overflow and do
+   not sanitize anything.  */
+/* { dg-skip-if "" { *-*-* } { "*" } { ! "-O0" } } */
+/* { dg-options "-fsanitize=undefined -fno-sanitize-recover=undefined" } */
+
+int a;
+const int b = 44514;
+int *c = &a;
+
+int main ()
+{
+  *c = 65526 * b / 6;
+  return 0;
+}
+
+/* { dg-output "signed integer overflow: 44514 \\* 65526 cannot be represented in type 'int'" } */