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* [gcc(refs/users/aoliva/heads/testbase)] fold-const: Fix A <= 0 ? A : -A folding [PR95810]
@ 2020-07-07 0:59 Alexandre Oliva
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From: Alexandre Oliva @ 2020-07-07 0:59 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:01e10b0ee77e82cb331414c569e02dc7a2c4999e
commit 01e10b0ee77e82cb331414c569e02dc7a2c4999e
Author: Jakub Jelinek <jakub@redhat.com>
Date: Wed Jun 24 10:40:02 2020 +0200
fold-const: Fix A <= 0 ? A : -A folding [PR95810]
We folded A <= 0 ? A : -A into -ABS (A), which is for signed integral types
incorrect - can invoke on INT_MIN UB twice, once on ABS and once on its
negation.
The following patch fixes it by instead folding it to (type)-ABSU (A).
2020-06-24 Jakub Jelinek <jakub@redhat.com>
PR middle-end/95810
* fold-const.c (fold_cond_expr_with_comparison): Optimize
A <= 0 ? A : -A into (type)-absu(A) rather than -abs(A).
* gcc.dg/ubsan/pr95810.c: New test.
Diff:
---
gcc/fold-const.c | 18 ++++++++++++++++--
gcc/testsuite/gcc.dg/ubsan/pr95810.c | 13 +++++++++++++
2 files changed, 29 insertions(+), 2 deletions(-)
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 212d0ba0aab..67a379f4f2b 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -5770,8 +5770,22 @@ fold_cond_expr_with_comparison (location_t loc, tree type,
case LT_EXPR:
if (TYPE_UNSIGNED (TREE_TYPE (arg1)))
break;
- tem = fold_build1_loc (loc, ABS_EXPR, TREE_TYPE (arg1), arg1);
- return negate_expr (fold_convert_loc (loc, type, tem));
+ if (ANY_INTEGRAL_TYPE_P (TREE_TYPE (arg1))
+ && !TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg1)))
+ {
+ /* A <= 0 ? A : -A for A INT_MIN is valid, but -abs(INT_MIN)
+ is not, invokes UB both in abs and in the negation of it.
+ So, use ABSU_EXPR instead. */
+ tree utype = unsigned_type_for (TREE_TYPE (arg1));
+ tem = fold_build1_loc (loc, ABSU_EXPR, utype, arg1);
+ tem = negate_expr (tem);
+ return fold_convert_loc (loc, type, tem);
+ }
+ else
+ {
+ tem = fold_build1_loc (loc, ABS_EXPR, TREE_TYPE (arg1), arg1);
+ return negate_expr (fold_convert_loc (loc, type, tem));
+ }
default:
gcc_assert (TREE_CODE_CLASS (comp_code) == tcc_comparison);
break;
diff --git a/gcc/testsuite/gcc.dg/ubsan/pr95810.c b/gcc/testsuite/gcc.dg/ubsan/pr95810.c
new file mode 100644
index 00000000000..535ace69089
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ubsan/pr95810.c
@@ -0,0 +1,13 @@
+/* PR middle-end/95810 */
+/* { dg-do run } */
+/* { dg-options "-fsanitize=undefined -fno-sanitize-recover=undefined" } */
+
+int
+main ()
+{
+ int x = -__INT_MAX__ - 1;
+ x = (x <= 0 ? x : -x);
+ if (x != -__INT_MAX__ - 1)
+ __builtin_abort ();
+ return 0;
+}
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