[vectorIntrinsics] RFR: 8265312: Unsigned comparison operators

[Jatin Bhateja]

On Fri, 16 Apr 2021 17:10:33 GMT, Paul Sandoz <psandoz at openjdk.org> wrote:

> Add unsigned comparison operators to VectorOperators and add intrinsic support on x64.

src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 2143:

> 2141:     vpmovzxbw(vtmp2, src2, vlen_enc);
> 2142:     vpcmpCCW(dst, vtmp1, vtmp2, comparison, Assembler::W, vlen_enc, scratch);
> 2143:     vpand(dst, dst, ExternalAddress(StubRoutines::x86::vector_short_to_byte_mask()), vlen_enc, scratch);

Hi @sviswa7 , zero extension for unsigned comparison for signed numbers looks fine, post extension comparison result will be all 1s or all 0s in corresponding lanes, by doing a signed saturation packing (vpacksswb) can we not avoid extra vector AND.

src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 2183:

> 2181:     vpand(vtmp3, vtmp3, ExternalAddress(StubRoutines::x86::vector_short_to_byte_mask()), vlen_enc, scratch);
> 2182:     vpackuswb(dst, dst, vtmp3, vlen_enc);
> 2183:     vpermpd(dst, dst, 0xd8, vlen_enc);

since comparison is performed at lane level (x86 definition 128 bits) and later on we are packing the results of two lanes I am not sure about the need for last permute instruction.

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PR: https://git.openjdk.java.net/panama-vector/pull/68