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Re: [GCC][PATCH][AArch64] Add negative tests for dotprod and set minimum version to v8.2 in the target bit.
- From: James Greenhalgh <james dot greenhalgh at arm dot com>
- To: Tamar Christina <Tamar dot Christina at arm dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, nd <nd at arm dot com>, Richard Earnshaw <Richard dot Earnshaw at arm dot com>, Marcus Shawcroft <Marcus dot Shawcroft at arm dot com>
- Date: Fri, 17 Nov 2017 22:06:40 +0000
- Subject: Re: [GCC][PATCH][AArch64] Add negative tests for dotprod and set minimum version to v8.2 in the target bit.
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On Tue, Nov 14, 2017 at 03:54:56PM +0000, Tamar Christina wrote:
> Hi All,
>
> Dot Product is intended to only be available for Armv8.2-a and newer.
> While this restriction is reflected in the intrinsics, the patterns
> themselves were missing the Armv8.2-a bit.
>
> This means that using -march=armv8.1-a+dotprod incorrectly got the
> auto-vectorizer to generate dot product instructions.
>
> Regtested on aarch64-none-elf and no issues.
>
> Ok for trunk?
What is the design here? That -march=armv8.1-a+dotprod is valid, but that
the +dotprod is silently ignored? Is that really less surprising than
a hard error?
How does this interact with -march=native ? If I remember right, we don't
get any good indication from the kernel that we are Armv8.2-A rather than
Armv8.1-A? Maybe I'm misremembering.
Thanks,
James
>
> Thanks,
> Tamar
>
> gcc/
> 2017-11-14 Tamar Christina <tamar.christina@arm.com>
>
> * config/aarch64/aarch64.h (TARGET_DOTPROD): Add AARCH64_ISA_V8_2.
>
> gcc/testsuite/
> 2017-11-14 Tamar Christina <tamar.christina@arm.com>
>
> * gcc.target/aarch64/advsimd-intrinsics/vect-dot-s8_1.c: New.
> * gcc.target/aarch64/advsimd-intrinsics/vect-dot-s8_2.c: New.