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* [Bug c++/97848] New: [missed optimization] tls init function check emitted for consinit thread_local variables (C++20)
@ 2020-11-16 7:46 avi@cloudius-systems.com
2020-11-16 10:50 ` [Bug c++/97848] " rguenth at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: avi@cloudius-systems.com @ 2020-11-16 7:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97848
Bug ID: 97848
Summary: [missed optimization] tls init function check emitted
for consinit thread_local variables (C++20)
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: avi@cloudius-systems.com
Target Milestone: ---
The code
=== begin code ===
extern thread_local constinit int x;
int foo_good() {
return x;
}
void set_foo(int y) {
x = y;
}
=== end code ===
knows that x will be statically initialized, but still emits the code to check
for the TLS init function and maybe call it:
=== begin objdump ===
foo_good():
movl $TLS init function for x, %eax
testq %rax, %rax
je .L7
subq $8, %rsp
call TLS init function for x
movq x@gottpoff(%rip), %rax
movl %fs:(%rax), %eax
addq $8, %rsp
ret
.L7:
movq x@gottpoff(%rip), %rax
movl %fs:(%rax), %eax
ret
set_foo(int):
movl $TLS init function for x, %eax
pushq %rbx
movl %edi, %ebx
testq %rax, %rax
je .L12
call TLS init function for x
.L12:
movq x@gottpoff(%rip), %rax
movl %ebx, %fs:(%rax)
popq %rbx
ret
=== end objdump ===
Instead, we should see the same output as for __thread_local.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/97848] [missed optimization] tls init function check emitted for consinit thread_local variables (C++20)
2020-11-16 7:46 [Bug c++/97848] New: [missed optimization] tls init function check emitted for consinit thread_local variables (C++20) avi@cloudius-systems.com
@ 2020-11-16 10:50 ` rguenth at gcc dot gnu.org
2021-03-23 19:59 ` avi@cloudius-systems.com
2021-11-29 15:32 ` avi at scylladb dot com
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2020-11-16 10:50 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97848
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
Last reconfirmed| |2020-11-16
Keywords| |missed-optimization
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/97848] [missed optimization] tls init function check emitted for consinit thread_local variables (C++20)
2020-11-16 7:46 [Bug c++/97848] New: [missed optimization] tls init function check emitted for consinit thread_local variables (C++20) avi@cloudius-systems.com
2020-11-16 10:50 ` [Bug c++/97848] " rguenth at gcc dot gnu.org
@ 2021-03-23 19:59 ` avi@cloudius-systems.com
2021-11-29 15:32 ` avi at scylladb dot com
2 siblings, 0 replies; 4+ messages in thread
From: avi@cloudius-systems.com @ 2021-03-23 19:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97848
--- Comment #1 from Avi Kivity <avi@cloudius-systems.com> ---
Still bad on trunk. Clang gets this right:
foo_good(): # @foo_good()
movq x@GOTTPOFF(%rip), %rax
movl %fs:(%rax), %eax
retq
set_foo(int): # @set_foo(int)
movq x@GOTTPOFF(%rip), %rax
movl %edi, %fs:(%rax)
retq
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/97848] [missed optimization] tls init function check emitted for consinit thread_local variables (C++20)
2020-11-16 7:46 [Bug c++/97848] New: [missed optimization] tls init function check emitted for consinit thread_local variables (C++20) avi@cloudius-systems.com
2020-11-16 10:50 ` [Bug c++/97848] " rguenth at gcc dot gnu.org
2021-03-23 19:59 ` avi@cloudius-systems.com
@ 2021-11-29 15:32 ` avi at scylladb dot com
2 siblings, 0 replies; 4+ messages in thread
From: avi at scylladb dot com @ 2021-11-29 15:32 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97848
Avi Kivity <avi at scylladb dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #2 from Avi Kivity <avi at scylladb dot com> ---
Fixed on trunk (12.0)
foo_good():
movq x@gottpoff(%rip), %rax
movl %fs:(%rax), %eax
ret
set_foo(int):
movq x@gottpoff(%rip), %rax
movl %edi, %fs:(%rax)
ret
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-11-29 15:32 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-11-16 7:46 [Bug c++/97848] New: [missed optimization] tls init function check emitted for consinit thread_local variables (C++20) avi@cloudius-systems.com
2020-11-16 10:50 ` [Bug c++/97848] " rguenth at gcc dot gnu.org
2021-03-23 19:59 ` avi@cloudius-systems.com
2021-11-29 15:32 ` avi at scylladb dot com
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