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emit_x64_vector: Simplify "position == 0" case for EmitVectorExtractLower()

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In the event position == 0, we can just treat it as a simple movq,
clearing the upper half of the XMM register. This also makes that case
use only one register.
This commit is contained in:
Lioncash 2018-09-08 01:51:50 -04:00 committed by MerryMage
parent f5fb496e7e
commit 87372917f9
1 changed files with 6 additions and 3 deletions
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9
src/backend/x64/emit_x64_vector.cpp
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@ -780,13 +780,16 @@ void EmitX64::EmitVectorExtractLower(EmitContext& ctx, IR::Inst* inst) {
auto args = ctx.reg_alloc.GetArgumentInfo(inst);
const Xbyak::Xmm xmm_a = ctx.reg_alloc.UseScratchXmm(args[0]);
const Xbyak::Xmm xmm_b = ctx.reg_alloc.UseXmm(args[1]);
const u8 position = args[2].GetImmediateU8();
ASSERT(position % 8 == 0);
code.punpcklqdq(xmm_a, xmm_b);
code.psrldq(xmm_a, position / 8);
if (position != 0) {
const Xbyak::Xmm xmm_b = ctx.reg_alloc.UseXmm(args[1]);
code.punpcklqdq(xmm_a, xmm_b);
code.psrldq(xmm_a, position / 8);
}
code.movq(xmm_a, xmm_a);
ctx.reg_alloc.DefineValue(inst, xmm_a);