[fpc-devel] x86-64: MOVZX peephole optimisations

[J. Gareth Moreton]

 In that case, I would argue that it should optimise for more modern
processors - that is, favour MOVZX, especially as the first few Pentium
processors were released in the 90s.  If backwards-compatibility is more
of a concern, well, if compiling for x86-64, when it's certain that the
processor was released no earlier than the early 2000s (because, for
x86_64-win64, SSE2 has to be present) and hence MOVZX is efficient, while
i386 and i8086 can favour MOV/AND.

 Nevertheless, there is code in parts of the compiler that check for things
like "if current_settings.cputype
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