Hi everyone,
So to get to the point, I've spotted another potential peephole
optimisation specifically on x86_64:
movq (%rdx),%rax
shrq $32,%rax
Is it acceptable to change this to the following?
movl 4(%rdx),%eax
Logically it's equivalent thanks to the guarantee that the upper 32-bits
of the destination register will be zeroed, but I know sometimes there
might be a penalty for reading from memory that isn't aligned to a
16-byte boundary, say.
A "movl; shrl $16" version may be possible with movzx, but I'm not
certain if that will be even more inefficient due to the offset now
being 2 rather than 4.
Gareth aka. Kit
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