https://gcc.gnu.org/g:d6cf49eaf5ac237c57785dce42c89deac911affa
commit r13-8783-gd6cf49eaf5ac237c57785dce42c89deac911affa
Author: Andrew Pinski <quic_apin...@quicinc.com>
Date: Mon May 20 00:16:40 2024 -0700
match: Disable `(type)zero_one_valuep*CST` for 1bit signed types [PR115154]
The problem here is the pattern added in r13-1162-g9991d84d2a8435
assumes that it is well defined to multiply zero_one_valuep by the truncated
converted integer constant. It is well defined for all types except for
signed 1bit types.
Where `a * -1` is produced which is undefined/
So disable this pattern for 1bit signed types.
Note the pattern added in r14-3432-gddd64a6ec3b38e is able to workaround
the undefinedness except when
`-fsanitize=undefined` is turned on, this is why I added a testcase for
that.
Bootstrapped and tested on x86_64-linux-gnu with no regressions.
PR tree-optimization/115154
gcc/ChangeLog:
* match.pd (convert (mult zero_one_valued_p@1 INTEGER_CST@2)):
Disable
for 1bit signed types.
gcc/testsuite/ChangeLog:
* c-c++-common/ubsan/signed1bitfield-1.c: New test.
* gcc.c-torture/execute/signed1bitfield-1.c: New test.
Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
(cherry picked from commit 49c87d22535ac4f8aacf088b3f462861c26cacb4)
Diff:
---
gcc/match.pd | 6 ++++--
.../c-c++-common/ubsan/signed1bitfield-1.c | 25 ++++++++++++++++++++++
.../gcc.c-torture/execute/signed1bitfield-1.c | 23 ++++++++++++++++++++
3 files changed, 52 insertions(+), 2 deletions(-)
diff --git a/gcc/match.pd b/gcc/match.pd
index dc34e7ead9f..fda4a211efc 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2023,12 +2023,14 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(mult (convert @0) @1)))
/* Narrow integer multiplication by a zero_one_valued_p operand.
- Multiplication by [0,1] is guaranteed not to overflow. */
+ Multiplication by [0,1] is guaranteed not to overflow except for
+ 1bit signed types. */
(simplify
(convert (mult@0 zero_one_valued_p@1 INTEGER_CST@2))
(if (INTEGRAL_TYPE_P (type)
&& INTEGRAL_TYPE_P (TREE_TYPE (@0))
- && TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (@0)))
+ && TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (@0))
+ && (TYPE_UNSIGNED (type) || TYPE_PRECISION (type) > 1))
(mult (convert @1) (convert @2))))
/* (X << C) != 0 can be simplified to X, when C is zero_one_valued_p.
diff --git a/gcc/testsuite/c-c++-common/ubsan/signed1bitfield-1.c
b/gcc/testsuite/c-c++-common/ubsan/signed1bitfield-1.c
new file mode 100644
index 00000000000..2ba8cf4dab0
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/ubsan/signed1bitfield-1.c
@@ -0,0 +1,25 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fsanitize=undefined" } */
+
+/* PR tree-optimization/115154 */
+/* This was being miscompiled with -fsanitize=undefined due to
+ `(signed:1)(t*5)` being transformed into `-((signed:1)t)` which
+ is undefined. */
+
+struct s {
+ signed b : 1;
+} f;
+int i = 55;
+__attribute__((noinline))
+void check(int a)
+{
+ if (!a)
+ __builtin_abort();
+}
+int main() {
+ int t = i != 5;
+ t = t*5;
+ f.b = t;
+ int tt = f.b;
+ check(f.b);
+}
diff --git a/gcc/testsuite/gcc.c-torture/execute/signed1bitfield-1.c
b/gcc/testsuite/gcc.c-torture/execute/signed1bitfield-1.c
new file mode 100644
index 00000000000..ab888ca3a04
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/signed1bitfield-1.c
@@ -0,0 +1,23 @@
+/* PR tree-optimization/115154 */
+/* This was being miscompiled to `(signed:1)(t*5)`
+ being transformed into `-((signed:1)t)` which is undefined.
+ Note there is a pattern which removes the negative in some cases
+ which works around the issue. */
+
+struct {
+ signed b : 1;
+} f;
+int i = 55;
+__attribute__((noinline))
+void check(int a)
+{
+ if (!a)
+ __builtin_abort();
+}
+int main() {
+ int t = i != 5;
+ t = t*5;
+ f.b = t;
+ int tt = f.b;
+ check(f.b);
+}
