RFR: 8256973: Intrinsic creation for VectorMask query (lastTrue, firstTrue, trueCount) APIs [v4]

[Vladimir Ivanov]

On Mon, 17 May 2021 14:13:16 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

> This is being enforced by Matcher::match_rule_supported_vector(), for a 512 bit vector of sub-word type is supported only if target supports AVX512BW.
For other types apart from sub-word types a 512 bit vector mask will be handled by the second instruction selection pattern which is predicated by !VM_Version::supports_avx512vlbw() since for them maximum vector size needed to hold the byte vector containing mask will always be <= 32 bytes.

Ah, now I get it! Thanks for the clarifications. 
It's the consequence of canonical mask representation being consumed by the operations. Worth putting a comment stressing that aspect.

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PR: https://git.openjdk.java.net/jdk/pull/3916