[PATCH] Optimize andl $0xffffffff, %eax

Jakub Jelinek jakub@redhat.com
Fri May 22 09:38:00 GMT 2009


On Thu, May 21, 2009 at 05:44:09PM +0200, Richard Guenther wrote:
> > Bootstrapped/regtested on x86_64-linux, ok for trunk?
> 
> Hm, isn't that something simplify-rtx should do?  Transform
> (and:SI reg 0xfffff) to (zero-extend:SI (subreg ...))?

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.

	Jakub



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