RFR: 8284813: x86 Code cleanup related to move instructions. [v2]

[Sandhya Viswanathan]

On Fri, 29 Apr 2022 05:10:44 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Summary of changes:
>> 
>> - Correct feature checks in some assembler move instruction.
>> - Explicitly pass opmask register in routines accepting merge argument.
>> - Code re-organization related to move instruction, pull out the merge argument up to instruction pattern or top level caller.
>> - Add missing encoding based move elision checks in some macro assembly routines.
>> 
>> Kindly review and share your feedback.
>> 
>> Regards,
>> Jatin
>
> Jatin Bhateja has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:
> 
>  - Merge branch 'master' of http://github.com/openjdk/jdk into JDK-8284813
>  - 8284813: x86 Code cleanup related to move instructions.

src/hotspot/cpu/x86/assembler_x86.cpp line 3032:

> 3030:     attributes.reset_is_clear_context();
> 3031:   }
> 3032:   int encode = vex_prefix_and_encode(dst->encoding(), 0, src->encoding(), VEX_SIMD_F2, VEX_OPCODE_0F, &attributes);

The existing version (with no mask) was using VEX_SIMD_F2 or VEX_SIMD_F3 based on  avx512bw supported or not. With this change now the calling place need to be fixed. One place I see this being used is loadIotaIndices(). Please fix loadIotaIndices to use appropriate instruction for the platform. Is there any other place in array copy/clear?

src/hotspot/cpu/x86/macroAssembler_x86_arrayCopy_avx3.cpp line 202:

> 200:     bzhiq(temp, temp, length);
> 201:     kmovql(mask, temp);
> 202:     evmovdqu(type[shift], mask, xmm, Address(src, index, scale, offset), true, Assembler::AVX_512bit);

Should the merge parameter be set to false for load here?

src/hotspot/cpu/x86/macroAssembler_x86_arrayCopy_avx3.cpp line 217:

> 215:   bzhiq(temp, temp, length);
> 216:   kmovql(mask, temp);
> 217:   evmovdqu(type[shift], mask, xmm, Address(src, index, scale, offset), true, Assembler::AVX_256bit);

Should the merge parameter be set to false for load here?

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PR: https://git.openjdk.java.net/jdk/pull/8230