[llvm] r257875 - [InstCombine] Rewrite bswap/bitreverse handling completely.

[Hans Wennborg via llvm-commits]

Thanks! r258180.

On Tue, Jan 19, 2016 at 9:42 AM, David Majnemer
<david.majnemer at gmail.com> wrote:
> Yes.
>
> On Tue, Jan 19, 2016 at 9:33 AM, Hans Wennborg <hans at chromium.org> wrote:
>>
>> This should have baked on the buildbots for a while now.
>>
>> David, OK to merge?
>>
>> On Fri, Jan 15, 2016 at 10:25 AM, James Molloy <James.Molloy at arm.com>
>> wrote:
>> > Hi Hans,
>> >
>> > Yes, as long as David is happy please merge this, along with the
>> > followup that fixes msan.
>> >
>> > I was waiting for it to soak through the stage2 bots before suggesting
>> > it myself.
>> >
>> > James
>> >
>> >
>> >
>> >> On 15 Jan 2016, at 17:59, Hans Wennborg <hans at chromium.org> wrote:
>> >>
>> >> It was suggested that this be merged to 3.8. David, I think you're the
>> >> code owner here; OK for merge?
>> >>
>> >> On Fri, Jan 15, 2016 at 1:20 AM, James Molloy via llvm-commits
>> >> <llvm-commits at lists.llvm.org> wrote:
>> >>> Author: jamesm
>> >>> Date: Fri Jan 15 03:20:19 2016
>> >>> New Revision: 257875
>> >>>
>> >>> URL: http://llvm.org/viewvc/llvm-project?rev=257875&view=rev
>> >>> Log:
>> >>> [InstCombine] Rewrite bswap/bitreverse handling completely.
>> >>>
>> >>> There are several requirements that ended up with this design;
>> >>>  1. Matching bitreversals is too heavyweight for InstCombine and
>> >>> doesn't really need to be done so early.
>> >>>  2. Bitreversals and byteswaps are very related in their matching
>> >>> logic.
>> >>>  3. We want to implement support for matching more advanced
>> >>> bswap/bitreverse patterns like partial bswaps/bitreverses.
>> >>>  4. Bswaps are best matched early in InstCombine.
>> >>>
>> >>> The result of these is that a new utility function is created in
>> >>> Transforms/Utils/Local.h that can be configured to search for bswaps,
>> >>> bitreverses or both. InstCombine uses it to find only bswaps, CGP uses it to
>> >>> find only bitreversals.
>> >>>
>> >>> We can then extend the matching logic in one place only.
>> >>
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>