[jdk17] Integrated: 8269528: VectorAPI Long512VectorTest fails on X86 KNL target

[Jatin Bhateja]

On Tue, 29 Jun 2021 16:25:29 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

> Long512VectorTest shows assertion failure on fastdebug build and incorrectness issue in release build.
> 
> Problem is seen on targets missing AVX512BW feature, load_vector_mask operation loads the mask boolean array into a vector followed by signed expansion operation to match the vector width of the operation. 
> 
> load_vector_mask macro assembly routine uses a vpsubb instruction which necessities existence of AVX512BW feature while operating over 64 byte operands.
> 
> Load mask over Byte512 and Short512 species does not get intrinsified since Matcher::match_rule_supported_vector
> check for legality of vector size against the maximum vector size supported by the target, in case of 64 byte subword type operation, an AVX512 target must support AVX512BW feature else vector size is reduced to 32 bytes. 
> 
> For a load mask operation over all other species i.e. Int512,Float512,Double512,Long512 underlined mask boolean array is 16 bytes or less, thus a 256bit AVX2 byte vpsubb should suffice, also subsequent unpacking instruction (VPMOVSD, VPMOVSQ) needs AVX512F feature.
> 
> legVec register class constrains the allocation set of operands of new loadmask instruction pattern for non-AVX512BW targets to lower register bank ([X/Y]MM0-15 registers).

This pull request has now been integrated.

Changeset: 90eb1189
Author:    Jatin Bhateja <jbhateja at openjdk.org>
URL:       https://git.openjdk.java.net/jdk17/commit/90eb1189aeebbf6a5a285ff88a504c162471d04c
Stats:     22 lines in 3 files changed: 17 ins; 0 del; 5 mod

8269528: VectorAPI Long512VectorTest fails on X86 KNL target

Reviewed-by: kvn, sviswanathan

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PR: https://git.openjdk.java.net/jdk17/pull/174