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Re: [PATCH] Improve andq $0xffffffff, %reg handling (PR target/53110)


On Thu, Apr 26, 2012 at 5:28 PM, Jakub Jelinek <jakub@redhat.com> wrote:

>> > We have a splitter for reg1 = reg2 & 0xffffffff, but only if regnums
>> > are different. ?But movl %edi, %edi is a cheaper variant of
>> > andq $0xffffffff, %rdi even with the same register and doesn't clobber
>> > flags, so this patch attempts to expand it as a zero extension early.
>> >
>> > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>> >
>> > 2012-04-25 ?Jakub Jelinek ?<jakub@redhat.com>
>> >
>> > ? ? ? ?PR target/53110
>> > ? ? ? ?* config/i386/i386.md (and<mode>3): For andq $0xffffffff, reg
>> > ? ? ? ?instead expand it as zero extension.
>>
>> Perhaps we can go all the way and also convert ANDs with $0xff and
>> $0xffff to relevant zero_extend patterns, like in the referred
>> splitter.
>
> I wasn't sure about 0xffff, on which CPUs it would be a win and on which it
> would not. ?0xffffffff is a win always.

My recent changes to zero_extend expanders should handle this
automatically, and will undo generation of zero_extend pattern. Please
see zero_extend<mode>si2_and expander, and how it handles
TARGET_ZERO_EXTEND_WITH_AND targets.

Uros.


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