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[TargetLowering] Extract simplifySetCCs ctpop into a separate function. NFCI 

As requested in D89346. This allows us to add some early outs.

I reordered some checks a little bit to make the more common bail outs happen earlier. Like checking opcode before checking hasOneUse. And I moved the bit width check to make sure it was safe to look through a truncate to the spot where we look through truncates instead of after.

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D89494
This commit is contained in:
Craig Topper 2020-10-16 15:42:49 -07:00
parent dc97138123
commit 278bd06891
1 changed files with 51 additions and 38 deletions
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89
llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
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@ -3379,6 +3379,54 @@ SDValue TargetLowering::foldSetCCWithBinOp(EVT VT, SDValue N0, SDValue N1,
return DAG.getSetCC(DL, VT, X, YShl1, Cond);
}
static SDValue simplifySetCCWithCTPOP(const TargetLowering &TLI, EVT VT,
SDValue N0, const APInt &C1,
ISD::CondCode Cond, const SDLoc &dl,
SelectionDAG &DAG) {
assert(!VT.isVector() && "Vectors are not supported yet!");
// Look through truncs that don't change the value of a ctpop.
SDValue CTPOP = N0;
if (N0.getOpcode() == ISD::TRUNCATE && N0.hasOneUse() &&
N0.getValueSizeInBits() > Log2_32(N0.getOperand(0).getValueSizeInBits()))
CTPOP = N0.getOperand(0);
if (CTPOP.getOpcode() != ISD::CTPOP || !CTPOP.hasOneUse())
return SDValue();
EVT CTVT = CTPOP.getValueType();
SDValue CTOp = CTPOP.getOperand(0);
// (ctpop x) u< 2 -> (x & x-1) == 0
// (ctpop x) u> 1 -> (x & x-1) != 0
if ((Cond == ISD::SETULT && C1 == 2) || (Cond == ISD::SETUGT && C1 == 1)) {
SDValue NegOne = DAG.getAllOnesConstant(dl, CTVT);
SDValue Add = DAG.getNode(ISD::ADD, dl, CTVT, CTOp, NegOne);
SDValue And = DAG.getNode(ISD::AND, dl, CTVT, CTOp, Add);
ISD::CondCode CC = Cond == ISD::SETULT ? ISD::SETEQ : ISD::SETNE;
return DAG.getSetCC(dl, VT, And, DAG.getConstant(0, dl, CTVT), CC);
}
// If ctpop is not supported, expand a power-of-2 comparison based on it.
if ((Cond == ISD::SETEQ || Cond == ISD::SETNE) && C1 == 1 &&
!TLI.isOperationLegalOrCustom(ISD::CTPOP, CTVT)) {
// (ctpop x) == 1 --> (x != 0) && ((x & x-1) == 0)
// (ctpop x) != 1 --> (x == 0) || ((x & x-1) != 0)
SDValue Zero = DAG.getConstant(0, dl, CTVT);
SDValue NegOne = DAG.getAllOnesConstant(dl, CTVT);
assert(CTVT.isInteger());
ISD::CondCode InvCond = ISD::getSetCCInverse(Cond, CTVT);
SDValue Add = DAG.getNode(ISD::ADD, dl, CTVT, CTOp, NegOne);
SDValue And = DAG.getNode(ISD::AND, dl, CTVT, CTOp, Add);
SDValue LHS = DAG.getSetCC(dl, VT, CTOp, Zero, InvCond);
SDValue RHS = DAG.getSetCC(dl, VT, And, Zero, Cond);
unsigned LogicOpcode = Cond == ISD::SETEQ ? ISD::AND : ISD::OR;
return DAG.getNode(LogicOpcode, dl, VT, LHS, RHS);
}
return SDValue();
}
/// Try to simplify a setcc built with the specified operands and cc. If it is
/// unable to simplify it, return a null SDValue.
SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
@ -3439,44 +3487,9 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
}
}
SDValue CTPOP = N0;
// Look through truncs that don't change the value of a ctpop.
if (N0.hasOneUse() && N0.getOpcode() == ISD::TRUNCATE)
CTPOP = N0.getOperand(0);
if (CTPOP.hasOneUse() && CTPOP.getOpcode() == ISD::CTPOP &&
(N0 == CTPOP ||
N0.getValueSizeInBits() > Log2_32(CTPOP.getValueSizeInBits()))) {
EVT CTVT = CTPOP.getValueType();
SDValue CTOp = CTPOP.getOperand(0);
// (ctpop x) u< 2 -> (x & x-1) == 0
// (ctpop x) u> 1 -> (x & x-1) != 0
if ((Cond == ISD::SETULT && C1 == 2) || (Cond == ISD::SETUGT && C1 == 1)){
SDValue NegOne = DAG.getAllOnesConstant(dl, CTVT);
SDValue Add = DAG.getNode(ISD::ADD, dl, CTVT, CTOp, NegOne);
SDValue And = DAG.getNode(ISD::AND, dl, CTVT, CTOp, Add);
ISD::CondCode CC = Cond == ISD::SETULT ? ISD::SETEQ : ISD::SETNE;
return DAG.getSetCC(dl, VT, And, DAG.getConstant(0, dl, CTVT), CC);
}
// If ctpop is not supported, expand a power-of-2 comparison based on it.
if (C1 == 1 && !isOperationLegalOrCustom(ISD::CTPOP, CTVT) &&
(Cond == ISD::SETEQ || Cond == ISD::SETNE)) {
// (ctpop x) == 1 --> (x != 0) && ((x & x-1) == 0)
// (ctpop x) != 1 --> (x == 0) || ((x & x-1) != 0)
SDValue Zero = DAG.getConstant(0, dl, CTVT);
SDValue NegOne = DAG.getAllOnesConstant(dl, CTVT);
assert(CTVT.isInteger());
ISD::CondCode InvCond = ISD::getSetCCInverse(Cond, CTVT);
SDValue Add = DAG.getNode(ISD::ADD, dl, CTVT, CTOp, NegOne);
SDValue And = DAG.getNode(ISD::AND, dl, CTVT, CTOp, Add);
SDValue LHS = DAG.getSetCC(dl, VT, CTOp, Zero, InvCond);
SDValue RHS = DAG.getSetCC(dl, VT, And, Zero, Cond);
unsigned LogicOpcode = Cond == ISD::SETEQ ? ISD::AND : ISD::OR;
return DAG.getNode(LogicOpcode, dl, VT, LHS, RHS);
}
}
// Optimize some CTPOP cases.
if (SDValue V = simplifySetCCWithCTPOP(*this, VT, N0, C1, Cond, dl, DAG))
return V;
// (zext x) == C --> x == (trunc C)
// (sext x) == C --> x == (trunc C)