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Re: [PATCH] Optimize andl $0xffffffff, %eax


Jakub Jelinek <jakub@redhat.com> writes:
> I fear that's too risky, on most targets zero_extend?i?i2 is implemented
> using and, so if simplify-rtx canonicalizes that to zero-extend, we
> risk oscillating forever between the two.

As I said this is already done by make_compound_operation; you're probably not
combining two instructions to get to this pattern on x86 so this never kicks
in.  But anyway you wouldn't oscillate because the fact that zero_extend is
implemented with an and is not exposed to the backend but it's hidden in the
pattern.

Adam


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