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[PowerPC] Replace PPCISD::VABSD cases with generic ISD::ABDU(X,Y) node
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A move towards using the generic ISD::ABDU nodes on more backends

Also support ISD::ABDS for v4i32 types using the existing signbit flip trick

PowerPC has a select(icmp_ugt(x,y),sub(x,y),sub(y,x)) -> abdu(x,y) combine that I intend to move to DAGCombiner in a future patch.

The ABS(SUB(X,Y)) -> PPCISD::VABSD(X,Y,1) v4i32 combine wasn't legal (https://alive2.llvm.org/ce/z/jc2hLU) - so I've removed it, having already added the legal sub nsw tests equivalent.

Differential Revision: https://reviews.llvm.org/D142313
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@RKSimon
RKSimon committed Feb 25, 2023
1 parent 465a48f commit 8757ce4
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Showing 3 changed files with 24 additions and 100 deletions.
85 changes: 13 additions & 72 deletions llvm/lib/Target/PowerPC/PPCISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1299,6 +1299,11 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::v2i16, Legal);
setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::v2i32, Legal);
setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::v2i64, Legal);

setOperationAction(ISD::ABDU, MVT::v16i8, Legal);
setOperationAction(ISD::ABDU, MVT::v8i16, Legal);
setOperationAction(ISD::ABDU, MVT::v4i32, Legal);
setOperationAction(ISD::ABDS, MVT::v4i32, Legal);
}

if (Subtarget.hasP10Vector()) {
Expand Down Expand Up @@ -1386,7 +1391,7 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
}

if (Subtarget.hasP9Altivec()) {
setTargetDAGCombine({ISD::ABS, ISD::VSELECT});
setTargetDAGCombine({ISD::VSELECT});
}

setLibcallName(RTLIB::LOG_F128, "logf128");
Expand Down Expand Up @@ -1750,7 +1755,6 @@ const char *PPCTargetLowering::getTargetNodeName(unsigned Opcode) const {
case PPCISD::RFEBB: return "PPCISD::RFEBB";
case PPCISD::XXSWAPD: return "PPCISD::XXSWAPD";
case PPCISD::SWAP_NO_CHAIN: return "PPCISD::SWAP_NO_CHAIN";
case PPCISD::VABSD: return "PPCISD::VABSD";
case PPCISD::BUILD_FP128: return "PPCISD::BUILD_FP128";
case PPCISD::BUILD_SPE64: return "PPCISD::BUILD_SPE64";
case PPCISD::EXTRACT_SPE: return "PPCISD::EXTRACT_SPE";
Expand Down Expand Up @@ -16034,8 +16038,6 @@ SDValue PPCTargetLowering::PerformDAGCombine(SDNode *N,
}
case ISD::BUILD_VECTOR:
return DAGCombineBuildVector(N, DCI);
case ISD::ABS:
return combineABS(N, DCI);
case ISD::VSELECT:
return combineVSelect(N, DCI);
}
Expand Down Expand Up @@ -17463,24 +17465,6 @@ SDValue PPCTargetLowering::combineTRUNCATE(SDNode *N,
SDLoc dl(N);
SDValue Op0 = N->getOperand(0);

// fold (truncate (abs (sub (zext a), (zext b)))) -> (vabsd a, b)
if (Subtarget.hasP9Altivec() && Op0.getOpcode() == ISD::ABS) {
EVT VT = N->getValueType(0);
if (VT != MVT::v4i32 && VT != MVT::v8i16 && VT != MVT::v16i8)
return SDValue();
SDValue Sub = Op0.getOperand(0);
if (Sub.getOpcode() == ISD::SUB) {
SDValue SubOp0 = Sub.getOperand(0);
SDValue SubOp1 = Sub.getOperand(1);
if ((SubOp0.getOpcode() == ISD::ZERO_EXTEND) &&
(SubOp1.getOpcode() == ISD::ZERO_EXTEND)) {
return DCI.DAG.getNode(PPCISD::VABSD, dl, VT, SubOp0.getOperand(0),
SubOp1.getOperand(0),
DCI.DAG.getTargetConstant(0, dl, MVT::i32));
}
}
}

// Looking for a truncate of i128 to i64.
if (Op0.getValueType() != MVT::i128 || N->getValueType(0) != MVT::i64)
return SDValue();
Expand Down Expand Up @@ -17681,54 +17665,12 @@ isMaskAndCmp0FoldingBeneficial(const Instruction &AndI) const {
return true;
}

// Transform (abs (sub (zext a), (zext b))) to (vabsd a b 0)
// Transform (abs (sub (zext a), (zext_invec b))) to (vabsd a b 0)
// Transform (abs (sub (zext_invec a), (zext_invec b))) to (vabsd a b 0)
// Transform (abs (sub (zext_invec a), (zext b))) to (vabsd a b 0)
// Transform (abs (sub a, b) to (vabsd a b 1)) if a & b of type v4i32
SDValue PPCTargetLowering::combineABS(SDNode *N, DAGCombinerInfo &DCI) const {
assert((N->getOpcode() == ISD::ABS) && "Need ABS node here");
assert(Subtarget.hasP9Altivec() &&
"Only combine this when P9 altivec supported!");
EVT VT = N->getValueType(0);
if (VT != MVT::v4i32 && VT != MVT::v8i16 && VT != MVT::v16i8)
return SDValue();

SelectionDAG &DAG = DCI.DAG;
SDLoc dl(N);
if (N->getOperand(0).getOpcode() == ISD::SUB) {
// Even for signed integers, if it's known to be positive (as signed
// integer) due to zero-extended inputs.
unsigned SubOpcd0 = N->getOperand(0)->getOperand(0).getOpcode();
unsigned SubOpcd1 = N->getOperand(0)->getOperand(1).getOpcode();
if ((SubOpcd0 == ISD::ZERO_EXTEND ||
SubOpcd0 == ISD::ZERO_EXTEND_VECTOR_INREG) &&
(SubOpcd1 == ISD::ZERO_EXTEND ||
SubOpcd1 == ISD::ZERO_EXTEND_VECTOR_INREG)) {
return DAG.getNode(PPCISD::VABSD, dl, N->getOperand(0).getValueType(),
N->getOperand(0)->getOperand(0),
N->getOperand(0)->getOperand(1),
DAG.getTargetConstant(0, dl, MVT::i32));
}

// For type v4i32, it can be optimized with xvnegsp + vabsduw
if (N->getOperand(0).getValueType() == MVT::v4i32 &&
N->getOperand(0).hasOneUse()) {
return DAG.getNode(PPCISD::VABSD, dl, N->getOperand(0).getValueType(),
N->getOperand(0)->getOperand(0),
N->getOperand(0)->getOperand(1),
DAG.getTargetConstant(1, dl, MVT::i32));
}
}

return SDValue();
}

// For type v4i32/v8ii16/v16i8, transform
// from (vselect (setcc a, b, setugt), (sub a, b), (sub b, a)) to (vabsd a, b)
// from (vselect (setcc a, b, setuge), (sub a, b), (sub b, a)) to (vabsd a, b)
// from (vselect (setcc a, b, setult), (sub b, a), (sub a, b)) to (vabsd a, b)
// from (vselect (setcc a, b, setule), (sub b, a), (sub a, b)) to (vabsd a, b)
// from (vselect (setcc a, b, setugt), (sub a, b), (sub b, a)) to (abdu a, b)
// from (vselect (setcc a, b, setuge), (sub a, b), (sub b, a)) to (abdu a, b)
// from (vselect (setcc a, b, setult), (sub b, a), (sub a, b)) to (abdu a, b)
// from (vselect (setcc a, b, setule), (sub b, a), (sub a, b)) to (abdu a, b)
// TODO: Move this to DAGCombiner?
SDValue PPCTargetLowering::combineVSelect(SDNode *N,
DAGCombinerInfo &DCI) const {
assert((N->getOpcode() == ISD::VSELECT) && "Need VSELECT node here");
Expand Down Expand Up @@ -17779,9 +17721,8 @@ SDValue PPCTargetLowering::combineVSelect(SDNode *N,
TrueOpnd.getOperand(1) == CmpOpnd2 &&
FalseOpnd.getOperand(0) == CmpOpnd2 &&
FalseOpnd.getOperand(1) == CmpOpnd1) {
return DAG.getNode(PPCISD::VABSD, dl, N->getOperand(1).getValueType(),
CmpOpnd1, CmpOpnd2,
DAG.getTargetConstant(0, dl, MVT::i32));
return DAG.getNode(ISD::ABDU, dl, N->getOperand(1).getValueType(), CmpOpnd1,
CmpOpnd2, DAG.getTargetConstant(0, dl, MVT::i32));
}

return SDValue();
Expand Down
16 changes: 0 additions & 16 deletions llvm/lib/Target/PowerPC/PPCISelLowering.h
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Original file line number Diff line number Diff line change
Expand Up @@ -440,21 +440,6 @@ namespace llvm {
/// and thereby have no chain.
SWAP_NO_CHAIN,

/// An SDNode for Power9 vector absolute value difference.
/// operand #0 vector
/// operand #1 vector
/// operand #2 constant i32 0 or 1, to indicate whether needs to patch
/// the most significant bit for signed i32
///
/// Power9 VABSD* instructions are designed to support unsigned integer
/// vectors (byte/halfword/word), if we want to make use of them for signed
/// integer vectors, we have to flip their sign bits first. To flip sign bit
/// for byte/halfword integer vector would become inefficient, but for word
/// integer vector, we can leverage XVNEGSP to make it efficiently. eg:
/// abs(sub(a,b)) => VABSDUW(a+0x80000000, b+0x80000000)
/// => VABSDUW((XVNEGSP a), (XVNEGSP b))
VABSD,

/// FP_EXTEND_HALF(VECTOR, IDX) - Custom extend upper (IDX=0) half or
/// lower (IDX=1) half of v4f32 to v2f64.
FP_EXTEND_HALF,
Expand Down Expand Up @@ -1430,7 +1415,6 @@ namespace llvm {
SDValue combineFMALike(SDNode *N, DAGCombinerInfo &DCI) const;
SDValue combineTRUNCATE(SDNode *N, DAGCombinerInfo &DCI) const;
SDValue combineSetCC(SDNode *N, DAGCombinerInfo &DCI) const;
SDValue combineABS(SDNode *N, DAGCombinerInfo &DCI) const;
SDValue combineVSelect(SDNode *N, DAGCombinerInfo &DCI) const;
SDValue combineVectorShuffle(ShuffleVectorSDNode *SVN,
SelectionDAG &DAG) const;
Expand Down
23 changes: 11 additions & 12 deletions llvm/lib/Target/PowerPC/PPCInstrVSX.td
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Original file line number Diff line number Diff line change
Expand Up @@ -76,9 +76,6 @@ def SDT_PPCxxswapd : SDTypeProfile<1, 1, [
def SDTVecConv : SDTypeProfile<1, 2, [
SDTCisVec<0>, SDTCisVec<1>, SDTCisPtrTy<2>
]>;
def SDTVabsd : SDTypeProfile<1, 3, [
SDTCisVec<0>, SDTCisSameAs<0, 1>, SDTCisSameAs<0, 2>, SDTCisVT<3, i32>
]>;
def SDT_PPCld_vec_be : SDTypeProfile<1, 1, [
SDTCisVec<0>, SDTCisPtrTy<1>
]>;
Expand All @@ -105,7 +102,6 @@ def PPCmtvsrz : SDNode<"PPCISD::MTVSRZ", SDTUnaryOp, []>;
def PPCsvec2fp : SDNode<"PPCISD::SINT_VEC_TO_FP", SDTVecConv, []>;
def PPCuvec2fp: SDNode<"PPCISD::UINT_VEC_TO_FP", SDTVecConv, []>;
def PPCswapNoChain : SDNode<"PPCISD::SWAP_NO_CHAIN", SDT_PPCxxswapd>;
def PPCvabsd : SDNode<"PPCISD::VABSD", SDTVabsd, []>;

def PPCfpexth : SDNode<"PPCISD::FP_EXTEND_HALF", SDT_PPCfpexth, []>;
def PPCldvsxlh : SDNode<"PPCISD::LD_VSX_LH", SDT_PPCldvsxlh,
Expand Down Expand Up @@ -4821,20 +4817,23 @@ def : Pat<(f128 (uint_to_fp (i32 (PPCmfvsr f64:$src)))),

// Any Power9 VSX subtarget that supports Power9 Altivec.
let Predicates = [HasVSX, HasP9Altivec] in {
// Put this P9Altivec related definition here since it's possible to be
// selected to VSX instruction xvnegsp, avoid possible undef.
def : Pat<(v4i32 (PPCvabsd v4i32:$A, v4i32:$B, (i32 0))),
// Unsigned absolute-difference.
def : Pat<(v4i32 (abdu v4i32:$A, v4i32:$B)),
(v4i32 (VABSDUW $A, $B))>;

def : Pat<(v8i16 (PPCvabsd v8i16:$A, v8i16:$B, (i32 0))),
def : Pat<(v8i16 (abdu v8i16:$A, v8i16:$B)),
(v8i16 (VABSDUH $A, $B))>;

def : Pat<(v16i8 (PPCvabsd v16i8:$A, v16i8:$B, (i32 0))),
def : Pat<(v16i8 (abdu v16i8:$A, v16i8:$B)),
(v16i8 (VABSDUB $A, $B))>;

// As PPCVABSD description, the last operand indicates whether do the
// sign bit flip.
def : Pat<(v4i32 (PPCvabsd v4i32:$A, v4i32:$B, (i32 1))),
// Signed absolute-difference.
// Power9 VABSD* instructions are designed to support unsigned integer
// vectors (byte/halfword/word), if we want to make use of them for signed
// integer vectors, we have to flip their sign bits first. To flip sign bit
// for byte/halfword integer vector would become inefficient, but for word
// integer vector, we can leverage XVNEGSP to make it efficiently.
def : Pat<(v4i32 (abds v4i32:$A, v4i32:$B)),
(v4i32 (VABSDUW (XVNEGSP $A), (XVNEGSP $B)))>;
} // HasVSX, HasP9Altivec

Expand Down

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