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 <[email protected]>
Signed-off-by: Robin Murphy <[email protected]>
Signed-off-by: Catalin Marinas <[email protected]>

0 files changed, 0 insertions, 0 deletions