[fpc-devel] Request to remove "movzwl %ax, %eax" -> "andl $0xffff, %ax" optimisations

Sven Barth pascaldragon at googlemail.com
Wed Nov 27 18:30:46 CET 2019

J. Gareth Moreton <gareth at moreton-family.com> schrieb am Mi., 27. Nov.
2019, 18:08:

> Hi everyone,
> Specifically to Florian, Jonas and Pierre, I would like to remove the
> "movz-> and" family of optimisations from the x86 peephole optimiser
> because the zero-extension commands no longer have the performance
> penalty that they had back in the 90s.  Both instructions have a
> read/write dependency, but movzx uses fewer bytes.

In my opinion that should depend on the selected optimization processor
(-OpX) as one might still want generate code for older processors.


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