[gcc r13-6550] middle-end/108995 - avoid folding when sanitizing overflow

[Richard Biener <rguenth@gcc.gnu.org>]

https://gcc.gnu.org/g:ace65db9215882b95e2ead1bb0dc8c54c2ea69be

commit r13-6550-gace65db9215882b95e2ead1bb0dc8c54c2ea69be
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Mar 8 09:06:44 2023 +0100

    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:
---
 gcc/fold-const.cc                     |  7 +++----
 gcc/testsuite/gcc.dg/ubsan/pr108995.c | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 99882ef820a..02a24c5fe65 100644
--- 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
index 00000000000..166825b2ef8
--- /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'" } */