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[x64] Add GFNI and AVX512VBMI optimization for `VECTOR_SHL`(int8) 

Uses `{v}gf2p8mulb` as a general int8-multiplication instruction to simulate bit-shifts.
This commit is contained in:
Wunkolo 2024-02-05 23:58:24 -08:00
parent 887fda55c2
commit 179ee7618d
1 changed files with 35 additions and 0 deletions
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35
src/xenia/cpu/backend/x64/x64_seq_vector.cc
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@ -816,6 +816,41 @@ struct VECTOR_SHL_V128
}
e.lea(e.GetNativeParam(1), e.StashConstantXmm(1, i.src2.constant()));
} else {
// gf2p8mulb's "x8 + x4 + x3 + x + 1"-polynomial-reduction only
// applies when the multiplication overflows. Masking away any bits
// that would have overflowed turns the polynomial-multiplication into
// regular modulo-multiplication
const uint64_t shift_mask = UINT64_C(0x01'03'07'0f'1f'3f'7f'ff);
// n << 0 == n * 1 | n << 1 == n * 2 | n << 2 == n * 4 | etc
const uint64_t multiply_table = UINT64_C(0x80'40'20'10'08'04'02'01);
if (e.IsFeatureEnabled(kX64EmitGFNI | kX64EmitAVX512Ortho |
kX64EmitAVX512VBMI)) {
e.LoadConstantXmm(e.xmm0, vec128q(shift_mask, shift_mask));
e.vpermb(e.xmm0, i.src2, e.xmm0);
e.vpand(e.xmm0, i.src1, e.xmm0);
e.LoadConstantXmm(e.xmm1, vec128q(multiply_table, multiply_table));
e.vpermb(e.xmm1, i.src2, e.xmm1);
e.vgf2p8mulb(i.dest, e.xmm0, e.xmm1);
return;
} else if (e.IsFeatureEnabled(kX64EmitGFNI)) {
// Only use the lower 4 bits
// This also protects from vpshufb from writing zero when the MSB is set
e.LoadConstantXmm(e.xmm0, vec128b(0x0F));
e.vpand(e.xmm2, i.src2, e.xmm0);
e.LoadConstantXmm(e.xmm0, vec128q(shift_mask, shift_mask));
e.vpshufb(e.xmm0, e.xmm0, e.xmm2);
e.vpand(e.xmm0, i.src1, e.xmm0);
e.LoadConstantXmm(e.xmm1, vec128q(multiply_table, multiply_table));
e.vpshufb(e.xmm1, e.xmm1, e.xmm2);
e.vgf2p8mulb(i.dest, e.xmm0, e.xmm1);
return;
}
e.lea(e.GetNativeParam(1), e.StashXmm(1, i.src2));
}
e.lea(e.GetNativeParam(0), e.StashXmm(0, i.src1));