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* [Bug target/110722] New: FP is Saved/Restored around inline assembly
@ 2023-07-18 15:35 palmer at gcc dot gnu.org
2023-07-18 19:29 ` [Bug target/110722] " pinskia at gcc dot gnu.org
0 siblings, 1 reply; 2+ messages in thread
From: palmer at gcc dot gnu.org @ 2023-07-18 15:35 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110722
Bug ID: 110722
Summary: FP is Saved/Restored around inline assembly
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: palmer at gcc dot gnu.org
Target Milestone: ---
I'm not sure if this is some ABI-related requirement that I've managed to
forget about, but it looks like we're saving/restoring FP around inline
assembly.
long fp_asm(long arg0)
{
asm volatile ("addi a0, a0, 1" : "+r"(arg0));
return arg0;
}
produces
fp_asm(long):
addi sp,sp,-16
sd s0,8(sp)
addi s0,sp,16
addi a0, a0, 1
ld s0,8(sp)
addi sp,sp,16
jr ra
We've got a ton of inline assembly in Linux these days and defconfig has
`-fno-omit-frame-pointer`, so this probably manifests as a performance issue
for someone somewhere -- though Clement just ran into it because he was
curious, so I don't have anything concrete.
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2023-07-18 15:35 [Bug target/110722] New: FP is Saved/Restored around inline assembly palmer at gcc dot gnu.org
2023-07-18 19:29 ` [Bug target/110722] " pinskia at gcc dot gnu.org
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