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* [Bug target/114004] New: GCC emits a superfluous instruction for simple test case on ppc
@ 2024-02-20 0:53 bergner at gcc dot gnu.org
2024-02-20 0:59 ` [Bug target/114004] " pinskia at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: bergner at gcc dot gnu.org @ 2024-02-20 0:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114004
Bug ID: 114004
Summary: GCC emits a superfluous instruction for simple test
case on ppc
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: bergner at gcc dot gnu.org
Target Milestone: ---
We emit a superfluous rldicl insn for the following test case. The rlwinm is
all that is needed/required. This is not a regression.
bergner@ltcden2-lp1:PR112103$ cat bug.c
unsigned int
rot (unsigned int x)
{
return x & 0xbfffffff;
}
bergner@ltcden2-lp1:PR112103$ /opt/gcc-nightly/trunk/bin/gcc -S -O2 bug.c
bergner@ltcden2-lp1:PR112103$ cat bug.s
.file "bug.c"
.machine power10
.abiversion 2
.section ".text"
.align 2
.p2align 4,,15
.globl rot
.type rot, @function
rot:
.LFB0:
.cfi_startproc
.localentry rot,1
rlwinm 3,3,0,2,0
rldicl 3,3,0,32
blr
.long 0
.byte 0,0,0,0,0,0,0,0
.cfi_endproc
.LFE0:
.size rot,.-rot
.ident "GCC: (GNU) 14.0.1 20240219 (experimental) [remotes/origin/HEAD
r14-9074-gd70facd54a]"
.section .note.GNU-stack,"",@progbits
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/114004] GCC emits a superfluous instruction for simple test case on ppc
2024-02-20 0:53 [Bug target/114004] New: GCC emits a superfluous instruction for simple test case on ppc bergner at gcc dot gnu.org
@ 2024-02-20 0:59 ` pinskia at gcc dot gnu.org
2024-02-27 14:26 ` jskumari at gcc dot gnu.org
2024-04-06 21:50 ` segher at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-02-20 0:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114004
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2024-02-20
Status|UNCONFIRMED |NEW
CC| |pinskia at gcc dot gnu.org
Ever confirmed|0 |1
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed. I thought I saw something similar to this years ago.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/114004] GCC emits a superfluous instruction for simple test case on ppc
2024-02-20 0:53 [Bug target/114004] New: GCC emits a superfluous instruction for simple test case on ppc bergner at gcc dot gnu.org
2024-02-20 0:59 ` [Bug target/114004] " pinskia at gcc dot gnu.org
@ 2024-02-27 14:26 ` jskumari at gcc dot gnu.org
2024-04-06 21:50 ` segher at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: jskumari at gcc dot gnu.org @ 2024-02-27 14:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114004
Surya Kumari Jangala <jskumari at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/114004] GCC emits a superfluous instruction for simple test case on ppc
2024-02-20 0:53 [Bug target/114004] New: GCC emits a superfluous instruction for simple test case on ppc bergner at gcc dot gnu.org
2024-02-20 0:59 ` [Bug target/114004] " pinskia at gcc dot gnu.org
2024-02-27 14:26 ` jskumari at gcc dot gnu.org
@ 2024-04-06 21:50 ` segher at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: segher at gcc dot gnu.org @ 2024-04-06 21:50 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114004
--- Comment #2 from Segher Boessenkool <segher at gcc dot gnu.org> ---
So, the rlwinm keeps all the top 32 bits intact, but those are all zero to
begin
with. Somehow we don't see that, or don't take that into account anyway.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2024-04-06 21:50 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2024-02-20 0:53 [Bug target/114004] New: GCC emits a superfluous instruction for simple test case on ppc bergner at gcc dot gnu.org
2024-02-20 0:59 ` [Bug target/114004] " pinskia at gcc dot gnu.org
2024-02-27 14:26 ` jskumari at gcc dot gnu.org
2024-04-06 21:50 ` segher at gcc dot gnu.org
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