[llvm-commits] InstCombine patch to improve combining of nested ShuffleVectorInst's

[Guo, Xiaoyi]

Ping?

-----Original Message-----
From: llvm-commits-bounces at cs.uiuc.edu [mailto:llvm-commits-bounces at cs.uiuc.edu] On Behalf Of Eli Friedman
Sent: Tuesday, October 11, 2011 4:34 PM
To: Guo, Xiaoyi
Cc: llvm-commits at cs.uiuc.edu
Subject: Re: [llvm-commits] InstCombine patch to improve combining of nested ShuffleVectorInst's

On Tue, Oct 11, 2011 at 4:16 PM, Guo, Xiaoyi <Xiaoyi.Guo at amd.com> wrote:
> From the comment in the original code I understood that we want to be very conservative when doing the shuffle transformations. So I also tried to be careful and only do the transformation if no new mask is created, so the net effect is just removing some instructions, which I think should be as safe as the original code.

Oh, I missed that part.  Now I follow what you're doing. :)

The concept is fine; I want to look over the mask transform logic a bit more closely before committing, though.

-Eli

>
> Xiaoyi
>
> -----Original Message-----
> From: llvm-commits-bounces at cs.uiuc.edu 
> [mailto:llvm-commits-bounces at cs.uiuc.edu] On Behalf Of Eli Friedman
> Sent: Tuesday, October 11, 2011 4:10 PM
> To: Guo, Xiaoyi
> Cc: llvm-commits at cs.uiuc.edu
> Subject: Re: [llvm-commits] InstCombine patch to improve combining of 
> nested ShuffleVectorInst's
>
> On Tue, Oct 11, 2011 at 3:54 PM, Guo, Xiaoyi <Xiaoyi.Guo at amd.com> wrote:
>> Sorry. Try again...
>
> We intentionally don't do generalized shuffle transformations in instcombine at the moment because, at least at the time the shufflevector instruction was introduced, we didn't really trust the quality of the shuffle-matching code in the backends for shuffles which don't have an obvious single-instruction mapping.  I'm not sure that situation has improved...
>
> -Eli
>
>> -----Original Message-----
>> From: Bruno Cardoso Lopes [mailto:bruno.cardoso at gmail.com]
>> Sent: Tuesday, October 11, 2011 3:06 PM
>> To: Guo, Xiaoyi
>> Cc: llvm-commits at cs.uiuc.edu
>> Subject: Re: [llvm-commits] InstCombine patch to improve combining of 
>> nested ShuffleVectorInst's
>>
>> The attached patch only contain testcases! You probably missed 
>> something! :)
>>
>> On Tue, Oct 11, 2011 at 6:58 PM, Guo, Xiaoyi <Xiaoyi.Guo at amd.com> wrote:
>>> The attached patch is to improve InstCombine to handle more cases of 
>>> nested ShuffleVectorInst's. New test cases are added to vec_shuffle.ll.
>>>
>>>
>>>
>>> It would be much appreciated if someone can review it and if ok help 
>>> to commit it.
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Xiaoyi
>>>
>>> _______________________________________________
>>> llvm-commits mailing list
>>> llvm-commits at cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>>
>>>
>>
>>
>>
>> --
>> Bruno Cardoso Lopes
>> http://www.brunocardoso.cc
>>
>>
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