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* [Bug c/111501] New: RISC-V: non-optimal casting when shifting
@ 2023-09-20 16:24 charlie at rivosinc dot com
2023-09-20 16:31 ` [Bug target/111501] " palmer at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: charlie at rivosinc dot com @ 2023-09-20 16:24 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111501
Bug ID: 111501
Summary: RISC-V: non-optimal casting when shifting
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: charlie at rivosinc dot com
Target Milestone: ---
Created attachment 55949
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55949&action=edit
tar file of -save-temps output
I would expect the first to be able to compile into the second:
unsigned int do_shift(unsigned long csum)
{
return (unsigned short)(csum >> 32);
}
unsigned int do_shift2(unsigned long csum)
{
return (csum << 16) >> 48;
}
However, the asm output is instead:
do_shift:
srli a0,a0,32
slli a0,a0,48
srli a0,a0,48
ret
do_shift2:
slli a0,a0,16
srli a0,a0,48
ret
These are the same so the first should be able to be compiled into the second.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug target/111501] RISC-V: non-optimal casting when shifting
2023-09-20 16:24 [Bug c/111501] New: RISC-V: non-optimal casting when shifting charlie at rivosinc dot com
@ 2023-09-20 16:31 ` palmer at gcc dot gnu.org
2023-09-20 16:34 ` pinskia at gcc dot gnu.org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: palmer at gcc dot gnu.org @ 2023-09-20 16:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111501
palmer at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2023-09-20
Keywords| |missed-optimization
Status|UNCONFIRMED |NEW
Component|c |target
Ever confirmed|0 |1
CC| |palmer at gcc dot gnu.org,
| |vineetg at gcc dot gnu.org
--- Comment #1 from palmer at gcc dot gnu.org ---
Adding Vineet.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug target/111501] RISC-V: non-optimal casting when shifting
2023-09-20 16:24 [Bug c/111501] New: RISC-V: non-optimal casting when shifting charlie at rivosinc dot com
2023-09-20 16:31 ` [Bug target/111501] " palmer at gcc dot gnu.org
@ 2023-09-20 16:34 ` pinskia at gcc dot gnu.org
2024-05-06 19:58 ` cmuellner at gcc dot gnu.org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-09-20 16:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111501
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |pinskia at gcc dot gnu.org
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I think there might be a dup of this bug already.
Also with zbb, GCC gets:
srli a0,a0,32
zext.h a0,a0
ret
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug target/111501] RISC-V: non-optimal casting when shifting
2023-09-20 16:24 [Bug c/111501] New: RISC-V: non-optimal casting when shifting charlie at rivosinc dot com
2023-09-20 16:31 ` [Bug target/111501] " palmer at gcc dot gnu.org
2023-09-20 16:34 ` pinskia at gcc dot gnu.org
@ 2024-05-06 19:58 ` cmuellner at gcc dot gnu.org
2024-05-06 20:15 ` vineetg at gcc dot gnu.org
2024-05-16 9:15 ` cmuellner at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: cmuellner at gcc dot gnu.org @ 2024-05-06 19:58 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111501
Christoph Müllner <cmuellner at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |cmuellner at gcc dot gnu.org
CC| |cmuellner at gcc dot gnu.org
--- Comment #3 from Christoph Müllner <cmuellner at gcc dot gnu.org> ---
I noticed this a while ago as well (when working on the XTheadB* stuff).
This can be addressed with an insn_and_split for zero_extract.
I even wrote a patch for that back then, but forgot to send it out.
I've rebased/retested it now and will send it once the release is out.
Btw, LLVM is catching all of these cases.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug target/111501] RISC-V: non-optimal casting when shifting
2023-09-20 16:24 [Bug c/111501] New: RISC-V: non-optimal casting when shifting charlie at rivosinc dot com
` (2 preceding siblings ...)
2024-05-06 19:58 ` cmuellner at gcc dot gnu.org
@ 2024-05-06 20:15 ` vineetg at gcc dot gnu.org
2024-05-16 9:15 ` cmuellner at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: vineetg at gcc dot gnu.org @ 2024-05-06 20:15 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111501
--- Comment #4 from Vineet Gupta <vineetg at gcc dot gnu.org> ---
Awesome !
The trunk is open and new stuff, RISC-V certainly, is already landing, so no
harm in sending it now ;-)
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug target/111501] RISC-V: non-optimal casting when shifting
2023-09-20 16:24 [Bug c/111501] New: RISC-V: non-optimal casting when shifting charlie at rivosinc dot com
` (3 preceding siblings ...)
2024-05-06 20:15 ` vineetg at gcc dot gnu.org
@ 2024-05-16 9:15 ` cmuellner at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: cmuellner at gcc dot gnu.org @ 2024-05-16 9:15 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111501
Christoph Müllner <cmuellner at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #5 from Christoph Müllner <cmuellner at gcc dot gnu.org> ---
Closing this, as it has been fixed on master.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2024-05-16 9:15 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2023-09-20 16:24 [Bug c/111501] New: RISC-V: non-optimal casting when shifting charlie at rivosinc dot com
2023-09-20 16:31 ` [Bug target/111501] " palmer at gcc dot gnu.org
2023-09-20 16:34 ` pinskia at gcc dot gnu.org
2024-05-06 19:58 ` cmuellner at gcc dot gnu.org
2024-05-06 20:15 ` vineetg at gcc dot gnu.org
2024-05-16 9:15 ` cmuellner at gcc dot gnu.org
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