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[X86][SSSE3] Added PSHUFB LUT implementation of BITREVERSE

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PSHUFB can speed up BITREVERSE of byte vectors by performing LUT on the low/high nibbles separately and ORing the results. Wider integer vector types are already BSWAP'd beforehand so also make use of this approach.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272477 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Simon Pilgrim 2016-06-11 15:44:13 +00:00
parent 87cd6e6baa
commit fd46fc3322
2 changed files with 440 additions and 948 deletions
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62
lib/Target/X86/X86ISelLowering.cpp
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@ -869,6 +869,7 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
}
if (!Subtarget.useSoftFloat() && Subtarget.hasSSSE3()) {
setOperationAction(ISD::BITREVERSE, MVT::v16i8, Custom);
setOperationAction(ISD::CTLZ, MVT::v16i8, Custom);
setOperationAction(ISD::CTLZ, MVT::v8i16, Custom);
// ISD::CTLZ v4i32 - scalarization is faster.
@ -1005,6 +1006,7 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
setOperationAction(ISD::TRUNCATE, MVT::v16i8, Custom);
setOperationAction(ISD::TRUNCATE, MVT::v8i16, Custom);
setOperationAction(ISD::TRUNCATE, MVT::v4i32, Custom);
setOperationAction(ISD::BITREVERSE, MVT::v32i8, Custom);
for (auto VT : { MVT::v32i8, MVT::v16i16, MVT::v8i32, MVT::v4i64 }) {
setOperationAction(ISD::CTPOP, VT, Custom);
@ -20910,7 +20912,7 @@ static SDValue LowerCTPOP(SDValue Op, const X86Subtarget &Subtarget,
return LowerVectorCTPOP(Op, Subtarget, DAG);
}
static SDValue LowerBITREVERSE(SDValue Op, SelectionDAG &DAG) {
static SDValue LowerBITREVERSE_XOP(SDValue Op, SelectionDAG &DAG) {
MVT VT = Op.getSimpleValueType();
SDValue In = Op.getOperand(0);
SDLoc DL(Op);
@ -20963,6 +20965,62 @@ static SDValue LowerBITREVERSE(SDValue Op, SelectionDAG &DAG) {
return DAG.getBitcast(VT, Res);
}
static SDValue LowerBITREVERSE(SDValue Op, const X86Subtarget &Subtarget,
SelectionDAG &DAG) {
if (Subtarget.hasXOP())
return LowerBITREVERSE_XOP(Op, DAG);
assert(Subtarget.hasSSSE3() && "SSSE3 required for BITREVERSE");
MVT VT = Op.getSimpleValueType();
SDValue In = Op.getOperand(0);
SDLoc DL(Op);
unsigned NumElts = VT.getVectorNumElements();
assert(VT.getScalarType() == MVT::i8 &&
"Only byte vector BITREVERSE supported");
// Decompose 256-bit ops into smaller 128-bit ops on pre-AVX2.
if (VT.is256BitVector() && !Subtarget.hasInt256()) {
MVT HalfVT = MVT::getVectorVT(MVT::i8, NumElts / 2);
SDValue Lo = extract128BitVector(In, 0, DAG, DL);
SDValue Hi = extract128BitVector(In, NumElts / 2, DAG, DL);
Lo = DAG.getNode(ISD::BITREVERSE, DL, HalfVT, Lo);
Hi = DAG.getNode(ISD::BITREVERSE, DL, HalfVT, Hi);
return DAG.getNode(ISD::CONCAT_VECTORS, DL, VT, Lo, Hi);
}
// Perform BITREVERSE using PSHUFB lookups. Each byte is split into
// two nibbles and a PSHUFB lookup to find the bitreverse of each
// 0-15 value (moved to the other nibble).
SDValue NibbleMask = DAG.getConstant(0xF, DL, VT);
SDValue Lo = DAG.getNode(ISD::AND, DL, VT, In, NibbleMask);
SDValue Hi = DAG.getNode(ISD::SRL, DL, VT, In, DAG.getConstant(4, DL, VT));
const int LoLUT[16] = {
/* 0 */ 0x00, /* 1 */ 0x80, /* 2 */ 0x40, /* 3 */ 0xC0,
/* 4 */ 0x20, /* 5 */ 0xA0, /* 6 */ 0x60, /* 7 */ 0xE0,
/* 8 */ 0x10, /* 9 */ 0x90, /* a */ 0x50, /* b */ 0xD0,
/* c */ 0x30, /* d */ 0xB0, /* e */ 0x70, /* f */ 0xF0};
const int HiLUT[16] = {
/* 0 */ 0x00, /* 1 */ 0x08, /* 2 */ 0x04, /* 3 */ 0x0C,
/* 4 */ 0x02, /* 5 */ 0x0A, /* 6 */ 0x06, /* 7 */ 0x0E,
/* 8 */ 0x01, /* 9 */ 0x09, /* a */ 0x05, /* b */ 0x0D,
/* c */ 0x03, /* d */ 0x0B, /* e */ 0x07, /* f */ 0x0F};
SmallVector<SDValue, 16> LoMaskElts, HiMaskElts;
for (unsigned i = 0; i < NumElts; ++i) {
LoMaskElts.push_back(DAG.getConstant(LoLUT[i % 16], DL, MVT::i8));
HiMaskElts.push_back(DAG.getConstant(HiLUT[i % 16], DL, MVT::i8));
}
SDValue LoMask = DAG.getBuildVector(VT, DL, LoMaskElts);
SDValue HiMask = DAG.getBuildVector(VT, DL, HiMaskElts);
Lo = DAG.getNode(X86ISD::PSHUFB, DL, VT, LoMask, Lo);
Hi = DAG.getNode(X86ISD::PSHUFB, DL, VT, HiMask, Hi);
return DAG.getNode(ISD::OR, DL, VT, Lo, Hi);
}
static SDValue lowerAtomicArithWithLOCK(SDValue N, SelectionDAG &DAG) {
unsigned NewOpc = 0;
switch (N->getOpcode()) {
@ -21462,7 +21520,7 @@ SDValue X86TargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
case ISD::ATOMIC_LOAD_XOR:
case ISD::ATOMIC_LOAD_AND: return lowerAtomicArith(Op, DAG, Subtarget);
case ISD::ATOMIC_STORE: return LowerATOMIC_STORE(Op, DAG);
case ISD::BITREVERSE: return LowerBITREVERSE(Op, DAG);
case ISD::BITREVERSE: return LowerBITREVERSE(Op, Subtarget, DAG);
case ISD::BUILD_VECTOR: return LowerBUILD_VECTOR(Op, DAG);
case ISD::CONCAT_VECTORS: return LowerCONCAT_VECTORS(Op, Subtarget, DAG);
case ISD::VECTOR_SHUFFLE: return lowerVectorShuffle(Op, Subtarget, DAG);

1326
test/CodeGen/X86/vector-bitreverse.ll
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