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* [gcc r14-10017] [libstdc++] [testsuite] disable SRA for compare_exchange_padding
@ 2024-04-18 11:14 Alexandre Oliva
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From: Alexandre Oliva @ 2024-04-18 11:14 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:dcf0bd14cda706be8d0c18963812beefca51df39
commit r14-10017-gdcf0bd14cda706be8d0c18963812beefca51df39
Author: Alexandre Oliva <oliva@adacore.com>
Date: Thu Apr 18 08:00:59 2024 -0300
[libstdc++] [testsuite] disable SRA for compare_exchange_padding
On arm-vx7r2, the uses of as.load() as initializer get SRAed, so the
padding bits in the tests are not what we might expect from full-word
struct copies.
I tried adding a function to perform bitwise copying, but even taking
the as.load() argument by const&, we'd still construct a temporary
with SRAed field-wise copying. Unable to find another way to ensure
we wouldn't get a temporary, I went for disabling SRA.
for libstdc++-v3/ChangeLog
* testsuite/29_atomics/atomic/compare_exchange_padding.cc:
Disable SRA.
Diff:
---
libstdc++-v3/testsuite/29_atomics/atomic/compare_exchange_padding.cc | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/compare_exchange_padding.cc b/libstdc++-v3/testsuite/29_atomics/atomic/compare_exchange_padding.cc
index 2f18d426e7f..a6081968ca8 100644
--- a/libstdc++-v3/testsuite/29_atomics/atomic/compare_exchange_padding.cc
+++ b/libstdc++-v3/testsuite/29_atomics/atomic/compare_exchange_padding.cc
@@ -1,6 +1,7 @@
// { dg-do run { target c++20 } }
// { dg-require-atomic-cmpxchg-word "" }
// { dg-add-options libatomic }
+// { dg-additional-options "-fno-tree-sra" }
#include <atomic>
#include <cstring>
@@ -26,10 +27,10 @@ main ()
s.s = 42;
std::atomic<S> as{ s };
- auto ts = as.load();
+ auto ts = as.load(); // SRA might prevent copying of padding bits here.
VERIFY( !compare_struct(s, ts) ); // padding cleared on construction
as.exchange(s);
- auto es = as.load();
+ auto es = as.load(); // SRA might prevent copying of padding bits here.
VERIFY( compare_struct(ts, es) ); // padding cleared on exchange
S n;
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