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emit_x64_vector: Simplify EmitVectorLogicalLeftShift8()

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Similar to EmitVectorLogicalRightShift8(), we can determine a mask ahead
of time and just and the results of a halfword left shift.
This commit is contained in:
Lioncash 2018-08-31 11:14:51 -04:00 committed by MerryMage
parent 135107279d
commit 2cac6ad129
1 changed files with 8 additions and 3 deletions
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11
src/backend/x64/emit_x64_vector.cpp
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@ -1055,12 +1055,17 @@ void EmitX64::EmitVectorInterleaveUpper64(EmitContext& ctx, IR::Inst* inst) {
void EmitX64::EmitVectorLogicalShiftLeft8(EmitContext& ctx, IR::Inst* inst) {
auto args = ctx.reg_alloc.GetArgumentInfo(inst);
Xbyak::Xmm result = ctx.reg_alloc.UseScratchXmm(args[0]);
const Xbyak::Xmm result = ctx.reg_alloc.UseScratchXmm(args[0]);
const u8 shift_amount = args[1].GetImmediateU8();
// TODO: Optimize
for (size_t i = 0; i < shift_amount; ++i) {
if (shift_amount == 1) {
code.paddb(result, result);
} else if (shift_amount > 0) {
const u64 replicand = (0xFFULL << shift_amount) & 0xFF;
const u64 mask = Common::Replicate(replicand, Common::BitSize<u8>());
code.psllw(result, shift_amount);
code.pand(result, code.MConst(xword, mask, mask));
}
ctx.reg_alloc.DefineValue(inst, result);