[llvm-dev] Status of llvm.experimental.vector.reduce.* intrinsics

[Haidl, Michael via llvm-dev]

Hi Amara,

thank you for the clarification. I tested the intrinsics x86_64 and it
seemed to work pretty well. Looking forward to try this intrinsics with
the AArch64 backend. Maybe I find the time to look into codegen to get
this intrinsics out of experimental stage. They seem pretty useful.

Cheers,
Michael

-----Original Message-----
From: Amara Emerson [amara.emerson at gmail.com]
Received: Donnerstag, 03 Aug. 2017, 14:50
To: michael.haidl at uni-muenster.de [michael.haidl at uni-muenster.de]
CC: llvm-dev at lists.llvm.org [llvm-dev at lists.llvm.org]
Subject: Re: [llvm-dev] Status of llvm.experimental.vector.reduce.* intrinsics

​Hi Michael,

​The intrinsics are still technically in an experimental state as we need to have a further discussion to build consensus before marking them as fully supported.

The AArch64 backend has been using them for all *natively supported* vector reductions for a few months now, with no issues as far as I'm aware. There are some rough edges which need some further work. For example, we're currently relying on a TTI hook to determine whether or not we create an intrinsic call or degenerate into a shuffevector sequence based on the reduction type. This was intended as a transitional stage. To mark the intrinsics as being first class operations we probably need to add support in codegen to expand the VECREDUCE_* nodes into the shufflevector reduction pattern, so that targets can generate the intrinsics in all cases without having to rely on TTI.

Amara


On 3 August 2017 at 12:03, Haidl, Michael via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
Hi,

I was wandering about the status of the
llvm.experimental.vector.reduce.* intrinsics. Are all back-ends
supporting those intrinsics or are they still in a very "experimental"
state?

Thanks,
Michael
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