RFR: 8321648: Integral gather optimized mask computation.

[Jatin Bhateja]

On Wed, 13 Dec 2023 14:31:14 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

> Thanks for the clarification, Jatin. So the incorrect encoding has no real (negative) effect on code generation?

Instruction attributes VL allows EVEX to VEX demotions, iff participating vectors are allocated from lower register bank and are less than 512 bit wide. On the contrary, if RA makes an allocation from higher register bank then we may need EVEX bits to accomodate encoding for a reigister in higher register bank even if vectors are lesser than 512 bit wide.

However, there are some instructions which are constrained to use VEX encoding and AVX2 gather belong to that class. Patch also strength reduces mask computation which is currently using memory operands.

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

PR Comment: https://git.openjdk.org/jdk/pull/17048#issuecomment-1854082915