[llvm-dev] how to force llvm generate gather intrinsic

[Demikhovsky, Elena via llvm-dev]

Ø  Can we legalize the same set of masked load/store operations for AVX1 as AVX2?
Yes, of course.

-           Elena

From: Sanjay Patel [mailto:spatel at rotateright.com]
Sent: Saturday, January 23, 2016 18:42
To: Nema, Ashutosh <Ashutosh.Nema at amd.com>
Cc: Demikhovsky, Elena <elena.demikhovsky at intel.com>; zhi chen <zchenhn at gmail.com>; llvm-dev <llvm-dev at lists.llvm.org>
Subject: Re: [llvm-dev] how to force llvm generate gather intrinsic


On Sat, Jan 23, 2016 at 6:45 AM, Nema, Ashutosh <Ashutosh.Nema at amd.com<mailto:Ashutosh.Nema at amd.com>> wrote:
Thanks Sanjay for highlighting this, few days back I also faced similar problem
while generating masked store in avx1 mode, found its only supported under
avx2 else we scalarize it.

>  1)   I did not switch-on masked_load/store to AVX1, I can do this.

Yes Elena, This should be supported for FP type in avx1 mode (for INT type, I doubt X86 has masked_load/store instruction in avx1 mode).


Thanks everyone for the answers. My immediate motivation is to improve the masked load/store ops for an AVX target. If we can fix scatter/gather similarly, that would be great.

Can we legalize the same set of masked load/store operations for AVX1 as AVX2? If I'm understanding them correctly, the AVX1 FP instructions (vmaskmovps/pd) can be used in place of the AVX2 int instructions (vpmaskmovd/q), just with domain crossing penalties thrown in. I think we do this for other missing integer ops for an AVX1 target either in x86 lowering or in the tablegen patterns.
 Elena - I'm not too familiar with the vectorizers or scatter/gather, but I'll certainly take a look at D15690. Thanks for pointing out the patch!

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