From: Andrew Pinski <apin...@marvell.com>
So it turns out this is kinda of a latent bug but not really latent.
In GCC 9 and 10, phi-opt would transform a?-1:0 (even for signed 1-bit integer)
to -(type)a but the type is an one bit integer which means the negation is
undefined. GCC 11 fixed the problem by checking for a?pow2cst:0 transformation
before a?-1:0 transformation.
When I added the transformations to match.pd, I had swapped the order not paying
attention and I didn't expect anything of it. Because there was no testcase
failing
due to this.
Anyways this fixes the problem on the trunk by swapping the order in match.pd
and
adding a comment of why the order is this way.
I will try to come up with a patch for GCC 9 and 10 series later on which fixes
the problem there too.
Note I didn't include the original testcase which requires the vectorizer and
AVX-512f
as I can't figure out the right dg options to restrict it to avx-512f but I did
come up
with a testcase which shows the problem and even more shows the problem with
the 9/10
series as mentioned.
OK? Bootstrapped and tested on x86_64-linux-gnu.
PR tree-optimization/102622
gcc/ChangeLog:
* match.pd: Swap the order of a?pow2cst:0 and a?-1:0 transformations.
Swap the order of a?0:pow2cst and a?0:-1 transformations.
gcc/testsuite/ChangeLog:
* gcc.c-torture/execute/bitfld-10.c: New test.
---
gcc/match.pd | 26 ++++++++++++-------
.../gcc.c-torture/execute/bitfld-10.c | 24 +++++++++++++++++
2 files changed, 41 insertions(+), 9 deletions(-)
create mode 100644 gcc/testsuite/gcc.c-torture/execute/bitfld-10.c
diff --git a/gcc/match.pd b/gcc/match.pd
index 9d7c1ac637f..c153e9a6e98 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3949,15 +3949,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
/* a ? 1 : 0 -> a if 0 and 1 are integral types. */
(if (integer_onep (@1))
(convert (convert:boolean_type_node @0)))
- /* a ? -1 : 0 -> -a. */
- (if (INTEGRAL_TYPE_P (type) && integer_all_onesp (@1))
- (negate (convert (convert:boolean_type_node @0))))
/* a ? powerof2cst : 0 -> a << (log2(powerof2cst)) */
(if (INTEGRAL_TYPE_P (type) && integer_pow2p (@1))
(with {
tree shift = build_int_cst (integer_type_node, tree_log2 (@1));
}
- (lshift (convert (convert:boolean_type_node @0)) { shift; })))))
+ (lshift (convert (convert:boolean_type_node @0)) { shift; })))
+ /* a ? -1 : 0 -> -a. No need to check the TYPE_PRECISION not being 1
+ here as the powerof2cst case above will handle that case correctly. */
+ (if (INTEGRAL_TYPE_P (type) && integer_all_onesp (@1))
+ (negate (convert (convert:boolean_type_node @0))))))
(if (integer_zerop (@1))
(with {
tree booltrue = constant_boolean_node (true, boolean_type_node);
@@ -3966,16 +3967,23 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
/* a ? 0 : 1 -> !a. */
(if (integer_onep (@2))
(convert (bit_xor (convert:boolean_type_node @0) { booltrue; } )))
- /* a ? -1 : 0 -> -(!a). */
- (if (INTEGRAL_TYPE_P (type) && integer_all_onesp (@2))
- (negate (convert (bit_xor (convert:boolean_type_node @0) { booltrue; }
))))
/* a ? powerof2cst : 0 -> (!a) << (log2(powerof2cst)) */
- (if (INTEGRAL_TYPE_P (type) && integer_pow2p (@2))
+ (if (INTEGRAL_TYPE_P (type) && integer_pow2p (@2)
+ && TYPE_PRECISION (type) != 1)
(with {
tree shift = build_int_cst (integer_type_node, tree_log2 (@2));
}
(lshift (convert (bit_xor (convert:boolean_type_node @0) { booltrue; }
))
- { shift; }))))))))
+ { shift; })))
+ /* a ? -1 : 0 -> -(!a). No need to check the TYPE_PRECISION not being 1
+ here as the powerof2cst case above will handle that case correctly. */
+ (if (INTEGRAL_TYPE_P (type) && integer_all_onesp (@2))
+ (negate (convert (bit_xor (convert:boolean_type_node @0) { booltrue; }
))))
+ )
+ )
+ )
+ )
+)
#endif
/* Simplification moved from fold_cond_expr_with_comparison. It may also
diff --git a/gcc/testsuite/gcc.c-torture/execute/bitfld-10.c
b/gcc/testsuite/gcc.c-torture/execute/bitfld-10.c
new file mode 100644
index 00000000000..bdbf5733ce7
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/bitfld-10.c
@@ -0,0 +1,24 @@
+/* PR tree-optimization/102622 */
+/* Wrong code introduced due to phi-opt
+ introducing undefined signed interger overflow
+ with one bit signed integer negation. */
+
+struct f{signed t:1;};
+int g(struct f *a, int t) __attribute__((noipa));
+int g(struct f *a, int t)
+{
+ if (t)
+ a->t = -1;
+ else
+ a->t = 0;
+ int t1 = a->t;
+ if (t1) return 1;
+ return t1;
+}
+
+int main(void)
+{
+ struct f a;
+ if (!g(&a, 1)) __builtin_abort();
+ return 0;
+}
--
2.17.1
