x86/ACPI/boot: Improve __acpi_acquire_global_lock
Improve __acpi_acquire_global_lock by using a temporary variable.
This enables compiler to perform if-conversion and improves generated
code from:
...
72a: d1 ea shr %edx
72c: 83 e1 fc and $0xfffffffc,%ecx
72f: 83 e2 01 and $0x1,%edx
732: 09 ca or %ecx,%edx
734: 83 c2 02 add $0x2,%edx
737: f0 0f b1 17 lock cmpxchg %edx,(%rdi)
73b: 75 e9 jne 726 <__acpi_acquire_global_lock+0x6>
73d: 83 e2 03 and $0x3,%edx
740: 31 c0 xor %eax,%eax
742: 83 fa 03 cmp $0x3,%edx
745: 0f 95 c0 setne %al
748: f7 d8 neg %eax
to:
...
72a: d1 e9 shr %ecx
72c: 83 e2 fc and $0xfffffffc,%edx
72f: 83 e1 01 and $0x1,%ecx
732: 09 ca or %ecx,%edx
734: 83 c2 02 add $0x2,%edx
737: f0 0f b1 17 lock cmpxchg %edx,(%rdi)
73b: 75 e9 jne 726 <__acpi_acquire_global_lock+0x6>
73d: 8d 41 ff lea -0x1(%rcx),%eax
BTW: the compiler could generate:
lea 0x2(%rcx,%rdx,1),%edx
instead of:
or %ecx,%edx
add $0x2,%edx
but unwated conversion from add to or when bits are known to be zero
prevents this improvement. This is GCC PR108477.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/all/20230320212012.12704-1-ubizjak%40gmail.com
1 file changed
