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* [Bug target/55947] New: non constant memory models lose HLE qualifiers
@ 2013-01-11 20:20 andi-gcc at firstfloor dot org
2013-01-11 21:23 ` [Bug target/55947] " jakub at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: andi-gcc at firstfloor dot org @ 2013-01-11 20:20 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55947
Bug #: 55947
Summary: non constant memory models lose HLE qualifiers
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: andi-gcc@firstfloor.org
get_memmodel does this
/* If the parameter is not a constant, it's a run time value so we'll just
convert it to MEMMODEL_SEQ_CST to avoid annoying runtime checking. */
if (TREE_CODE (exp) != INTEGER_CST)
return MEMMODEL_SEQ_CST;
This implies that if __ATOMIC_HLE_ACQUIRE, __ATOMIC_HLE_RELEASE are passed in
as non constant they will get lost.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug target/55947] non constant memory models lose HLE qualifiers
2013-01-11 20:20 [Bug target/55947] New: non constant memory models lose HLE qualifiers andi-gcc at firstfloor dot org
@ 2013-01-11 21:23 ` jakub at gcc dot gnu.org
2013-01-11 22:02 ` andi-gcc at firstfloor dot org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: jakub at gcc dot gnu.org @ 2013-01-11 21:23 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55947
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-01-11 21:23:11 UTC ---
Yeah, that is intentional. If you want HLE acquire/release, you really should
pass it as constant. What do you think we should emit instead? Runtime switch
based on the memory model?
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug target/55947] non constant memory models lose HLE qualifiers
2013-01-11 20:20 [Bug target/55947] New: non constant memory models lose HLE qualifiers andi-gcc at firstfloor dot org
2013-01-11 21:23 ` [Bug target/55947] " jakub at gcc dot gnu.org
@ 2013-01-11 22:02 ` andi-gcc at firstfloor dot org
2013-03-13 13:50 ` andi-gcc at firstfloor dot org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: andi-gcc at firstfloor dot org @ 2013-01-11 22:02 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55947
--- Comment #2 from Andi Kleen <andi-gcc at firstfloor dot org> 2013-01-11 22:01:49 UTC ---
I would probably add at least a warning. The whole concept of a runtime
switched memory barrier is imho ill-defined.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug target/55947] non constant memory models lose HLE qualifiers
2013-01-11 20:20 [Bug target/55947] New: non constant memory models lose HLE qualifiers andi-gcc at firstfloor dot org
2013-01-11 21:23 ` [Bug target/55947] " jakub at gcc dot gnu.org
2013-01-11 22:02 ` andi-gcc at firstfloor dot org
@ 2013-03-13 13:50 ` andi-gcc at firstfloor dot org
2013-03-13 14:16 ` jakub at gcc dot gnu.org
2024-04-09 2:44 ` pinskia at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: andi-gcc at firstfloor dot org @ 2013-03-13 13:50 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55947
--- Comment #3 from Andi Kleen <andi-gcc at firstfloor dot org> 2013-03-13 13:49:10 UTC ---
It was pointed out to me that atomic triggers this with, when compiled with no
optimization. For HLE wrong hints would be generated.
bool test_and_set(memory_order __m = memory_order_seq_cst) noexcept
{
return __atomic_test_and_set (&_M_i, __m);
}
bool foo(std::atomic_flag fl) {
return fl.test_and_set(std::memory_order_relaxed);
}
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug target/55947] non constant memory models lose HLE qualifiers
2013-01-11 20:20 [Bug target/55947] New: non constant memory models lose HLE qualifiers andi-gcc at firstfloor dot org
` (2 preceding siblings ...)
2013-03-13 13:50 ` andi-gcc at firstfloor dot org
@ 2013-03-13 14:16 ` jakub at gcc dot gnu.org
2024-04-09 2:44 ` pinskia at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: jakub at gcc dot gnu.org @ 2013-03-13 14:16 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55947
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-03-13 14:15:51 UTC ---
Not wrong, if the code isn't inlined and thus the model is variable, HLE hints
will be ignored and seq_cst model will be used.
If you want something else, even for -O0, just use inline with
__attribute__((always_inline)) to ensure it is inlined.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug target/55947] non constant memory models lose HLE qualifiers
2013-01-11 20:20 [Bug target/55947] New: non constant memory models lose HLE qualifiers andi-gcc at firstfloor dot org
` (3 preceding siblings ...)
2013-03-13 14:16 ` jakub at gcc dot gnu.org
@ 2024-04-09 2:44 ` pinskia at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-04-09 2:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55947
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Invalid as explained.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2024-04-09 2:44 UTC | newest]
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2013-01-11 20:20 [Bug target/55947] New: non constant memory models lose HLE qualifiers andi-gcc at firstfloor dot org
2013-01-11 21:23 ` [Bug target/55947] " jakub at gcc dot gnu.org
2013-01-11 22:02 ` andi-gcc at firstfloor dot org
2013-03-13 13:50 ` andi-gcc at firstfloor dot org
2013-03-13 14:16 ` jakub at gcc dot gnu.org
2024-04-09 2:44 ` pinskia at gcc dot gnu.org
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