llvm dev - Apr 2018 - Aliasing of pointers from different address spaces

Hi,

       Can I configure address spaces aliasing for my specific target?
       I found this discussion
(https://groups.google.com/forum/#!topic/llvm-dev/0ZbzzN6t05o) , where James
says "pointers in different address spaces cannot alias",
       but it is not what I see in the code.
       I looked for a way to customize address spaces separation in Target, but
I can't find.
       Any thoughts?
       Thanks.

-        Elena



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Hi, Elena,

You're correct. We do assume that pointers in different address spaces
can alias.

Targets can add their own AA pass into the AA query chain, and one of
the things such analysis passes can do account for target-specific
knowledge of address-space semantics. For example, see
lib/Target/AMDGPU/AMDGPUAliasAnalysis.cpp

 -Hal


On 04/26/2018 07:56 AM, Demikhovsky, Elena via llvm-dev
wrote:
> Hi,
>  
> Can I configure address spaces aliasing for my specific target?
> I found this discussion
> (_https://groups.google.com/forum/#!topic/llvm-dev/0ZbzzN6t05o_
> <https://groups.google.com/forum/#%21topic/llvm-dev/0ZbzzN6t05o>) ,
> where James says “pointers in different address spaces cannot alias”,
> but it is not what I see in the code.
> I looked for a way to customize address spaces separation in Target,
> but I can’t find.
> Any thoughts?
> Thanks.
>  
>
>   * */Elena/*
>
>  
>  
>  
>
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> Intel Israel (74) Limited
>
> This e-mail and any attachments may contain confidential material for
> the sole use of the intended recipient(s). Any review or distribution
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>
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-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

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Thank you. That's, probably, what I was looking for.
In this case
  &getAnalysis<AAResultsWrapperPass>().getAAResults()
will return the target-configured AAResults, right?

I'm asking, because I want to use this analysis within a standard pass,
LICM, for example.

-           Elena

From: Hal Finkel [mailto:hfinkel at anl.gov]
Sent: Thursday, April 26, 2018 20:50
To: Demikhovsky, Elena <elena.demikhovsky at intel.com>; llvm-dev at
lists.llvm.org
Subject: Re: [llvm-dev] Aliasing of pointers from different address spaces


Hi, Elena,

You're correct. We do assume that pointers in different address spaces can
alias.

Targets can add their own AA pass into the AA query chain, and one of the things
such analysis passes can do account for target-specific knowledge of
address-space semantics. For example, see
lib/Target/AMDGPU/AMDGPUAliasAnalysis.cpp

 -Hal

On 04/26/2018 07:56 AM, Demikhovsky, Elena via llvm-dev wrote:
Hi,

Can I configure address spaces aliasing for my specific target?
I found this discussion
(https://groups.google.com/forum/#!topic/llvm-dev/0ZbzzN6t05o<https://groups.google.com/forum/#%21topic/llvm-dev/0ZbzzN6t05o>)
, where James says "pointers in different address spaces cannot
alias",
but it is not what I see in the code.
I looked for a way to customize address spaces separation in Target, but I
can't find.
Any thoughts?
Thanks.

*         Elena




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Intel Israel (74) Limited

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--

Hal Finkel

Lead, Compiler Technology and Programming Languages

Leadership Computing Facility

Argonne National Laboratory
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