RFR: 8318650: Optimized subword gather for x86 targets. [v10]

[Emanuel Peter]

On Tue, 16 Jan 2024 06:17:43 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 1900:
>> 
>>> 1898:       vgather8b(elem_ty, xtmp3, base, idx_base, rtmp, vlen_enc);
>>> 1899:     } else {
>>> 1900:       LP64_ONLY(vgather8b_masked(elem_ty, xtmp3, base, idx_base, mask, midx, rtmp, vlen_enc));
>> 
>> What happens if if not `LP64_ONLY`?
>
> 32bit skip over check is part of match_rule_supported_vector, https://github.com/openjdk/jdk/pull/16354/files#diff-d6a3624f0f0af65a98a47378a5c146eed5016ca09b4de1acd0a3acc823242e82R1921

An assert might still be nice. Or just call the method anyway but then hit an assert there?

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PR Review Comment: https://git.openjdk.org/jdk/pull/16354#discussion_r1453005169