| commit | e75bef2a4fe259b779765a85589e92657d26fdc9 | |
| author | Robin Murphy <robin.murphy@arm.com> | |
| Tue, 24 Apr 2018 15:25:47 +0000 (24 16:25 +0100) | ||
| committer | Catalin Marinas <catalin.marinas@arm.com> | |
| Wed, 16 May 2018 10:50:52 +0000 (16 11:50 +0100) | ||
| tree | dce158ed5840192161def2c998dd80f77307bb85 | treesnapshot (tar.gz zip) |
| parent | 92faa7bea3e7592673109e32c75d50f8ce6d5ec6 | commitdiff |
arm64: Select ARCH_HAS_FAST_MULTIPLIER
It is probably safe to assume that all Armv8-A implementations have a
multiplier whose efficiency is comparable or better than a sequence of
three or so register-dependent arithmetic instructions. Select
ARCH_HAS_FAST_MULTIPLIER to get ever-so-slightly nicer codegen in the
few dusty old corners which care.
In a contrived benchmark calling hweight64() in a loop, this does indeed
turn out to be a small win overall, with no measurable impact on
Cortex-A57 but about 5% performance improvement on Cortex-A53.
Acked-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>
It is probably safe to assume that all Armv8-A implementations have a
multiplier whose efficiency is comparable or better than a sequence of
three or so register-dependent arithmetic instructions. Select
ARCH_HAS_FAST_MULTIPLIER to get ever-so-slightly nicer codegen in the
few dusty old corners which care.
In a contrived benchmark calling hweight64() in a loop, this does indeed
turn out to be a small win overall, with no measurable impact on
Cortex-A57 but about 5% performance improvement on Cortex-A53.
Acked-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>
| arch/arm64/Kconfig | diffblobblamehistory |