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* [Bug c++/94184] New: Global variable inline constructor elision.
@ 2020-03-15 19:36 maxim.yegorushkin at gmail dot com
2020-03-15 19:52 ` [Bug c++/94184] " pinskia at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: maxim.yegorushkin at gmail dot com @ 2020-03-15 19:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94184
Bug ID: 94184
Summary: Global variable inline constructor elision.
Product: gcc
Version: 9.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: maxim.yegorushkin at gmail dot com
Target Milestone: ---
The following code:
struct A {
int a_;
A(int a) : a_(a) {}
};
struct B {
int a_;
constexpr B(int a) : a_(a) {}
};
A a{1};
B b{1};
When compiled with `gcc-9.2 -O3 -march=skylake -mtune=skylake -std=gnu++17`
generates a call to `A` constructor for variable `a`:
_GLOBAL__sub_I_a:
mov DWORD PTR [rip+0x200bd6],0x1 # 601030 <__TMC_END__>
ret
And no call for `B` constructor for variable `b`, as expected of `constexpr`.
`clang-9.0 -O3 -march=skylake -mtune=skylake -std=gnu++17`, however, elides the
constructor calls for both `a` and `b` global variables, regardless of
`constexpr`.
Why can't `gcc` elide the call to `A` constructor for `a`, since `A` constuctor
is an inline function with a clear side-effect?
https://gcc.godbolt.org/z/5y3cD5
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/94184] Global variable inline constructor elision.
2020-03-15 19:36 [Bug c++/94184] New: Global variable inline constructor elision maxim.yegorushkin at gmail dot com
@ 2020-03-15 19:52 ` pinskia at gcc dot gnu.org
2022-10-17 13:40 ` trass3r at gmail dot com
2022-10-17 14:11 ` ppalka at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2020-03-15 19:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94184
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
Keywords| |missed-optimization
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
There is another bug about this already.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/94184] Global variable inline constructor elision.
2020-03-15 19:36 [Bug c++/94184] New: Global variable inline constructor elision maxim.yegorushkin at gmail dot com
2020-03-15 19:52 ` [Bug c++/94184] " pinskia at gcc dot gnu.org
@ 2022-10-17 13:40 ` trass3r at gmail dot com
2022-10-17 14:11 ` ppalka at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: trass3r at gmail dot com @ 2022-10-17 13:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94184
Trass3r <trass3r at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |trass3r at gmail dot com
--- Comment #2 from Trass3r <trass3r at gmail dot com> ---
Even simpler example:
const struct A
{
A() {}
int a = 0;
} a;
The global ctor doesn't get eliminated while clang removes it:
https://godbolt.org/z/9bjzMbx85
.section .text.startup,"ax",@progbits
.type _GLOBAL__sub_I_example.cpp, @function
_GLOBAL__sub_I_example.cpp:
ret
It works if you remove the member a.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/94184] Global variable inline constructor elision.
2020-03-15 19:36 [Bug c++/94184] New: Global variable inline constructor elision maxim.yegorushkin at gmail dot com
2020-03-15 19:52 ` [Bug c++/94184] " pinskia at gcc dot gnu.org
2022-10-17 13:40 ` trass3r at gmail dot com
@ 2022-10-17 14:11 ` ppalka at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: ppalka at gcc dot gnu.org @ 2022-10-17 14:11 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94184
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |DUPLICATE
Status|UNCONFIRMED |RESOLVED
CC| |ppalka at gcc dot gnu.org
--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
dup of PR102876 I think
*** This bug has been marked as a duplicate of bug 102876 ***
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-10-17 14:11 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2020-03-15 19:36 [Bug c++/94184] New: Global variable inline constructor elision maxim.yegorushkin at gmail dot com
2020-03-15 19:52 ` [Bug c++/94184] " pinskia at gcc dot gnu.org
2022-10-17 13:40 ` trass3r at gmail dot com
2022-10-17 14:11 ` ppalka at gcc dot gnu.org
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