[LLVMdev] Adding masked vector load and store intrinsics

[Demikhovsky, Elena]

Thank you Hal,

meanwhile, I implemented something quick to be sure that it works and estimate what pieces of LLVM code should be touched.
I'll prepare a patch soon.

-  Elena


-----Original Message-----
From: Hal Finkel [mailto:hfinkel at anl.gov] 
Sent: Saturday, October 25, 2014 00:02
To: Demikhovsky, Elena
Cc: dag at cray.com; llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] Adding masked vector load and store intrinsics

Elena,

As far as I can tell, consensus is strongly in favor. Please submit a patch :-)

Thanks again,
Hal

----- Original Message -----
> From: "Elena Demikhovsky" <elena.demikhovsky at intel.com>
> To: llvmdev at cs.uiuc.edu
> Cc: dag at cray.com
> Sent: Friday, October 24, 2014 6:24:15 AM
> Subject: [LLVMdev] Adding masked vector load and store intrinsics
> 
> 
> 
> Hi,
> 
> We would like to add support for masked vector loads and stores by 
> introducing new target-independent intrinsics. The loop vectorizer 
> will then be enhanced to optimize loops containing conditional memory 
> accesses by generating these intrinsics for existing targets such as 
> AVX2 and AVX-512. The vectorizer will first ask the target about 
> availability of masked vector loads and stores. The SLP vectorizer can 
> potentially be enhanced to use these intrinsics as well.
> 
> The intrinsics would be legal for all targets; targets that do not 
> support masked vector loads or stores will scalarize them.
> The addressed memory will not be touched for masked-off lanes. In 
> particular, if all lanes are masked off no address will be accessed.
> 
> call void @llvm.masked.store (i32* %addr, <16 x i32> %data, i32 4,
> <16 x i1> %mask)
> 
> %data = call <8 x i32> @llvm.masked.load (i32* %addr, <8 x i32> 
> %passthru, i32 4, <8 x i1> %mask)
> 
> where %passthru is used to fill the elements of %data that are 
> masked-off (if any; can be zeroinitializer or undef).
> 
> Comments so far, before we dive into more details?
> 
> Thank you.
> 
> - Elena and Ayal
> 
> 
> 
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--
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory
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