diff options
| author | Robin Murphy <robin.murphy@arm.com> | 2017-05-12 13:48:41 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2017-05-15 18:30:10 +0100 |
| commit | 8df728e1ae614f592961e51f65d3e3212ede5a75 (patch) | |
| tree | df8284b2f7d13200752c5afbbbd98474d256af8c | |
| parent | 2ea659a9ef488125eb46da6eb571de5eae5c43f6 (diff) | |
| download | linux-8df728e1ae614f592961e51f65d3e3212ede5a75.tar.bz2 | |
arm64: Remove redundant mov from LL/SC cmpxchg
The cmpxchg implementation introduced by commit c342f78217e8 ("arm64:
cmpxchg: patch in lse instructions when supported by the CPU") performs
an apparently redundant register move of [old] to [oldval] in the
success case - it always uses the same register width as [oldval] was
originally loaded with, and is only executed when [old] and [oldval] are
known to be equal anyway.
The only effect it seemingly does have is to take up a surprising amount
of space in the kernel text, as removing it reveals:
text data bss dec hex filename
12426658 1348614 4499749 18275021 116dacd vmlinux.o.new
12429238 1348614 4499749 18277601 116e4e1 vmlinux.o.old
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
| -rw-r--r-- | arch/arm64/include/asm/atomic_ll_sc.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/atomic_ll_sc.h b/arch/arm64/include/asm/atomic_ll_sc.h index f819fdcff1ac..f5a2d09afb38 100644 --- a/arch/arm64/include/asm/atomic_ll_sc.h +++ b/arch/arm64/include/asm/atomic_ll_sc.h @@ -264,7 +264,6 @@ __LL_SC_PREFIX(__cmpxchg_case_##name(volatile void *ptr, \ " st" #rel "xr" #sz "\t%w[tmp], %" #w "[new], %[v]\n" \ " cbnz %w[tmp], 1b\n" \ " " #mb "\n" \ - " mov %" #w "[oldval], %" #w "[old]\n" \ "2:" \ : [tmp] "=&r" (tmp), [oldval] "=&r" (oldval), \ [v] "+Q" (*(unsigned long *)ptr) \ |