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| author | Uros Bizjak <ubizjak@gmail.com> | 2026-02-18 12:00:18 +0100 |
|---|---|---|
| committer | Wei Liu <wei.liu@kernel.org> | 2026-02-18 23:27:20 +0000 |
| commit | 0597696017fe6c172bce7827be32f4bbd02542ab (patch) | |
| tree | 01bc8e012c078d8dc2f072f639fff9ac615788c9 /include/hyperv | |
| parent | 705d01c8d78121ee1634bfc602ac4b0ad1438fab (diff) | |
mshv: Use try_cmpxchg() instead of cmpxchg()
Use !try_cmpxchg() instead of cmpxchg (*ptr, old, new) != old.
x86 CMPXCHG instruction returns success in ZF flag, so this
change saves a compare after CMPXCHG.
The generated assembly code improves from e.g.:
415: 48 8b 44 24 30 mov 0x30(%rsp),%rax
41a: 48 8b 54 24 38 mov 0x38(%rsp),%rdx
41f: f0 49 0f b1 91 a8 02 lock cmpxchg %rdx,0x2a8(%r9)
426: 00 00
428: 48 3b 44 24 30 cmp 0x30(%rsp),%rax
42d: 0f 84 09 ff ff ff je 33c <...>
to:
415: 48 8b 44 24 30 mov 0x30(%rsp),%rax
41a: 48 8b 54 24 38 mov 0x38(%rsp),%rdx
41f: f0 49 0f b1 91 a8 02 lock cmpxchg %rdx,0x2a8(%r9)
426: 00 00
428: 0f 84 0e ff ff ff je 33c <...>
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: Long Li <longli@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Diffstat (limited to 'include/hyperv')
0 files changed, 0 insertions, 0 deletions