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* [Bug target/98303] New: [x86] Bad register allocation when reproducing assembly code
@ 2020-12-15 21:23 gabravier at gmail dot com
2021-09-18 22:29 ` [Bug target/98303] cmov seems not to swap condition during RA pinskia at gcc dot gnu.org
2021-09-19 23:16 ` pinskia at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: gabravier at gmail dot com @ 2020-12-15 21:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98303
Bug ID: 98303
Summary: [x86] Bad register allocation when reproducing
assembly code
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: gabravier at gmail dot com
Target Milestone: ---
int f1(int n)
{
while (n >= 64)
n -= 64;
return n;
}
On x86, with -O3, this generates :
f1(int):
mov eax, edi
and eax, 63
cmp edi, 63
cmovle eax, edi
ret
This code :
int f2(int n)
{
return (n <= 63) ? n : (n & 63);
}
which behaves equivalently, seems to result in poorer generated code :
f2(int):
mov edx, edi
mov eax, edi
and edx, 63
cmp edi, 63
cmovg eax, edx
ret
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug target/98303] cmov seems not to swap condition during RA
2020-12-15 21:23 [Bug target/98303] New: [x86] Bad register allocation when reproducing assembly code gabravier at gmail dot com
@ 2021-09-18 22:29 ` pinskia at gcc dot gnu.org
2021-09-19 23:16 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-09-18 22:29 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98303
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
Severity|normal |enhancement
Summary|[x86] Bad register |cmov seems not to swap
|allocation when reproducing |condition during RA
|assembly code |
Last reconfirmed| |2021-09-18
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This is the case where register allocator and cmov's (and 2 operands) don't get
along.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug target/98303] cmov seems not to swap condition during RA
2020-12-15 21:23 [Bug target/98303] New: [x86] Bad register allocation when reproducing assembly code gabravier at gmail dot com
2021-09-18 22:29 ` [Bug target/98303] cmov seems not to swap condition during RA pinskia at gcc dot gnu.org
@ 2021-09-19 23:16 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-09-19 23:16 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98303
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |DUPLICATE
Status|NEW |RESOLVED
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 97968.
*** This bug has been marked as a duplicate of bug 97968 ***
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-09-19 23:16 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2020-12-15 21:23 [Bug target/98303] New: [x86] Bad register allocation when reproducing assembly code gabravier at gmail dot com
2021-09-18 22:29 ` [Bug target/98303] cmov seems not to swap condition during RA pinskia at gcc dot gnu.org
2021-09-19 23:16 ` pinskia at gcc dot gnu.org
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