On 08/17/2017 03:29 PM, Michael Clark wrote:
> hand coded x86 asm (no worse because the sar depends on the lea)
>
> sx5(int):
> shl edi, 27
> sar edi, 27
> movsx eax, dl
Typo in the register, but I know what you mean. More interestingly, edi
already has the sign-extended value, so "mov eax, edi" sufficies (saving one
byte or perhaps allowing better register allocation).
That said, if anyone is tweaking x86-64 patterns on this, consider
sx5(int):
rorx eax, edi, 5
sar eax, 27
where the (newish) bmi2 rorx instruction allows the data to be moved into place
while rotating, avoiding the extra move entirely.
r~
