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| author | Robin Murphy <robin.murphy@arm.com> | 2017-05-12 13:48:41 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-03-07 11:25:56 +0100 |
| commit | e32210d1f0fcdf27a60ddf1211b7a5ab2df44fc0 (patch) | |
| tree | 545b37bb55216f6a3fb262ef42cd3ac2db64ed36 | |
| parent | beb25678ff55ced63626582afc39ef358c4bed64 (diff) | |
| download | linux-stable-e32210d1f0fcdf27a60ddf1211b7a5ab2df44fc0.tar.gz linux-stable-e32210d1f0fcdf27a60ddf1211b7a5ab2df44fc0.tar.bz2 linux-stable-e32210d1f0fcdf27a60ddf1211b7a5ab2df44fc0.zip | |
arm64: Remove redundant mov from LL/SC cmpxchg
commit 8df728e1ae614f592961e51f65d3e3212ede5a75 upstream.
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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -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) \ |