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Differential D136059 Diff 469476 llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp

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llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp

Show First 20 Lines • Show All 3,239 Lines • ▼ Show 20 LinesSDValue AMDGPUTargetLowering::performTruncateCombine(
if (VT.getScalarSizeInBits() < 32) { if (VT.getScalarSizeInBits() < 32) {
EVT SrcVT = Src.getValueType(); EVT SrcVT = Src.getValueType();
if (SrcVT.getScalarSizeInBits() > 32 && if (SrcVT.getScalarSizeInBits() > 32 &&
(Src.getOpcode() == ISD::SRL || (Src.getOpcode() == ISD::SRL ||
Src.getOpcode() == ISD::SRA || Src.getOpcode() == ISD::SRA ||
Src.getOpcode() == ISD::SHL)) { Src.getOpcode() == ISD::SHL)) {
SDValue Amt = Src.getOperand(1); SDValue Amt = Src.getOperand(1);
KnownBits Known = DAG.computeKnownBits(Amt); KnownBits Known = DAG.computeKnownBits(Amt);
unsigned Size = VT.getScalarSizeInBits();
if ((Known.isConstant() && Known.getConstant().ule(Size)) || // - For left shifts, do the transform as long as the shift
(Known.countMaxActiveBits() <= Log2_32(Size))) { // amount is still legal for i32, so when ShiftAmt < 32 (<= 31)
// - For right shift, do it if ShiftAmt <= (32 - Size) to avoid
// losing information stored in the high bits when truncating.
const unsigned MaxCstSize =
(Src.getOpcode() == ISD::SHL) ? 31 : (32 - VT.getScalarSizeInBits());
foadUnsubmitted
Done
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For left shifts you can do it so long as the new shift amount is still valid, so ShiftAmt < 32 (aka <= 31).

So this can be: ... ? 31 : 32 - Size

foad: For left shifts you can do it so long as the new shift amount is still valid, so ShiftAmt < 32…
if (Known.getMaxValue().ule(MaxCstSize)) {
foadUnsubmitted
Done
ReplyInline Actions

The whole if condition can be replaced with: Known.getMaxValue().ule(MaxCstSize)

foad: The whole `if` condition can be replaced with: `Known.getMaxValue().ule(MaxCstSize)`
EVT MidVT = VT.isVector() ? EVT MidVT = VT.isVector() ?
EVT::getVectorVT(*DAG.getContext(), MVT::i32, EVT::getVectorVT(*DAG.getContext(), MVT::i32,
VT.getVectorNumElements()) : MVT::i32; VT.getVectorNumElements()) : MVT::i32;
EVT NewShiftVT = getShiftAmountTy(MidVT, DAG.getDataLayout()); EVT NewShiftVT = getShiftAmountTy(MidVT, DAG.getDataLayout());
SDValue Trunc = DAG.getNode(ISD::TRUNCATE, SL, MidVT, SDValue Trunc = DAG.getNode(ISD::TRUNCATE, SL, MidVT,
Src.getOperand(0)); Src.getOperand(0));
DCI.AddToWorklist(Trunc.getNode()); DCI.AddToWorklist(Trunc.getNode());
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