[PATCH][DAGCombiner] Split up an indexed load if only the base pointer value is live

[Adam Nemet]

Thank you.  This is r208640.

Adam

On May 12, 2014, at 12:35 PM, Hal Finkel <hfinkel at anl.gov> wrote:

> LGTM.
> 
> -Hal
> 
> ----- Original Message -----
>> From: "Adam Nemet" <anemet at apple.com>
>> To: "llvm-commits" <llvm-commits at cs.uiuc.edu>
>> Sent: Monday, May 12, 2014 1:59:58 PM
>> Subject: Re: [PATCH][DAGCombiner] Split up an indexed load if only the base	pointer value is live
>> 
>> 
>> 
>> Ping^2
>> 
>> On May 5, 2014, at 11:42 AM, Adam Nemet <anemet at apple.com> wrote:
>> 
>>> Ping.
>>> 
>>> + for (SDNode *U : N->uses())
>>> + AddToWorkList(U);
>>> 
>>> For the review, please consider this written as:
>>> AddUsersToWorkList(N)
>>> 
>>> On Apr 24, 2014, at 5:09 PM, Adam Nemet <anemet at apple.com> wrote:
>>> 
>>>> Right now the load may not get DCE'd because of the side-effect of
>>>> updating
>>>> the base pointer.
>>>> 
>>>> This can happen if we lower a read-modify-write of an illegal
>>>> larger type
>>>> (e.g. i48) such that the modification only affects one of the
>>>> subparts (the
>>>> lower i32 part but not the higher i16 part). See the testcase.
>>>> 
>>>> In order to spot the dead load we need to revisit it when
>>>> SimplifyDemandedBits
>>>> decided that the value of the load is masked off. This is the
>>>> CommitTargetLoweringOpt piece.
>>>> 
>>>> I checked compile time with ARM64 by sending SPEC bitcode files
>>>> through llc.
>>>> No measurable change.
>>>> 
>>>> Fixes <rdar://problem/16031651>
>>>> 
>>>> Adam
>>>> 
>> 
>> 
>>>> 
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>>> 
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>> 
>> 
>> 
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> 
> -- 
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory