RFR: 8279668: x86: AVX2 versions of vpxor should be asserted

Mon Jan 10 11:02:29 UTC 2022

On Mon, 10 Jan 2022 10:31:30 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Got the SIGILLs on some machines when testing JDK-8279621. That patch started using shorter `vpxor` versions on `UseAVX = 1` path, which tried to use `VEX.256`-encoded `vpxor` instruction that is only available on AVX2. This should be at very least asserted in assembler code. 
> 
> Also fixed the implicit `bool` -> `int` conversion to `vector_len`.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug `tier1` with `-XX:UseAVX=1`

Hi, I think the assert should be inserted in the assembler instead. Also, I would prefer `AVX_256bit` instead of `1`.
Thanks.

-------------

PR: https://git.openjdk.java.net/jdk/pull/7005