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[PowerPC] Use rldimi/rlwimi to optimize build_vector #67640

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[PowerPC] Use rldimi/rlwimi to optimize build_vector #67640

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50 changes: 50 additions & 0 deletions llvm/lib/Target/PowerPC/PPCISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9276,6 +9276,49 @@ bool llvm::checkConvertToNonDenormSingle(APFloat &ArgAPFloat) {
return (!LosesInfo && !APFloatToConvert.isDenormal());
}

// Use rldimi/rlwimi to construct vectors:
// i32 = (i8 << 24) | (i8 << 16) | (i8 << 8) | i
// i32 = (i16 << 16) | i16
// i64 = (i32 << 32) | i32
// And put two i64 together to get a vector.
static SDValue tryMaskInsertVector(SDValue Op, SelectionDAG &DAG,
bool LittleEndian) {
EVT VT = Op.getValueType();
SDLoc dl(Op);

// There are already patterns for v4i32 and v2i64 construction.
if (VT == MVT::v16i8 || VT == MVT::v8i16) {
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Please flip the condition and make this an early exit.

int NumElt = VT.getVectorNumElements();
int ScalarSize = VT.getScalarSizeInBits();
int EltsFor32 = NumElt / 4;
SDValue NewVecElts[4];
SDValue Parts[4];
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < EltsFor32; ++j) {
SDValue Elt = LittleEndian
? Op.getOperand(i * EltsFor32 + EltsFor32 - j - 1)
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These expressions are far from obvious. Please initialize variables with these expressions with comments explaining the expressions and then use the variables. The reader should not be forced to work out the details of this math without context.

: Op.getOperand(i * EltsFor32 + j);
Parts[j] = DAG.getZExtOrTrunc(Elt, dl, MVT::i32);

// Left-shift elements to insert, except the last, because offset is 0.
if (j != EltsFor32 - 1)
Parts[j] =
DAG.getNode(ISD::SHL, dl, MVT::i32, Parts[j],
DAG.getTargetConstant(
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You should not use target constants with arbitrary nodes

ScalarSize * (EltsFor32 - j - 1), dl, MVT::i32));
if (j > 0)
Parts[j] = DAG.getNode(ISD::OR, dl, MVT::i32, Parts[j - 1], Parts[j]);
}
NewVecElts[i] = Parts[EltsFor32 - 1];
}

// Count on v4i32 to get optimized BUILD_VECTOR pattern.
return DAG.getBitcast(VT, DAG.getBuildVector(MVT::v4i32, dl, NewVecElts));
}

return SDValue();
}

static bool isValidSplatLoad(const PPCSubtarget &Subtarget, const SDValue &Op,
unsigned &Opcode) {
LoadSDNode *InputNode = dyn_cast<LoadSDNode>(Op.getOperand(0));
Expand Down Expand Up @@ -9457,6 +9500,13 @@ SDValue PPCTargetLowering::LowerBUILD_VECTOR(SDValue Op,
haveEfficientBuildVectorPattern(BVN, Subtarget.hasDirectMove(),
Subtarget.hasP8Vector()))
return Op;

// Try to construct vector using masked insert.
if (!BVN->isConstant() && !DAG.isSplatValue(Op, true))
if (SDValue Res =
tryMaskInsertVector(Op, DAG, Subtarget.isLittleEndian()))
return Res;

return SDValue();
}

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