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[CodeGen] Remove dead hack for MIPS #148039

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[CodeGen] Remove dead hack for MIPS #148039

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4 changes: 0 additions & 4 deletions llvm/lib/CodeGen/LiveVariables.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -534,10 +534,6 @@ void LiveVariables::runOnInstr(MachineInstr &MI,
UseRegs.push_back(MOReg);
} else {
assert(MO.isDef());
// FIXME: We should not remove any dead flags. However the MIPS RDDSP
// instruction needs it at the moment: http://llvm.org/PR27116.
if (MOReg.isPhysical() && !MRI->isReserved(MOReg))
MO.setIsDead(false);
DefRegs.push_back(MOReg);
}
}
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8 changes: 8 additions & 0 deletions llvm/lib/Target/Mips/MipsDSPInstrInfo.td
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Expand Up @@ -1470,3 +1470,11 @@ let AddedComplexity = 20 in {
let AdditionalPredicates = [NotInMicroMips] in {
def : DSPInstAlias<"wrdsp $rt", (WRDSP GPR32Opnd:$rt, 0x1F), 1>;
}

def RDDSP_Pseudo : Pseudo<(outs GPR32Opnd:$rd), (ins uimm10:$mask), []> {
let usesCustomInserter = 1;
}

def WRDSP_Pseudo : Pseudo<(outs), (ins GPR32Opnd:$rs, uimm10:$mask), []> {
let usesCustomInserter = 1;
}
51 changes: 51 additions & 0 deletions llvm/lib/Target/Mips/MipsISelLowering.cpp
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Expand Up @@ -1411,6 +1411,53 @@ static MachineBasicBlock *insertDivByZeroTrap(MachineInstr &MI,
return &MBB;
}

MachineBasicBlock::iterator
MipsTargetLowering::emitRDDSP(MachineInstr &MI, MachineBasicBlock *BB) const {
const TargetInstrInfo &TII = *Subtarget.getInstrInfo();
unsigned DestReg = MI.getOperand(0).getReg();
unsigned Mask = MI.getOperand(1).getImm();
auto MIB = BuildMI(*BB, MI, MI.getDebugLoc(), TII.get(Mips::RDDSP), DestReg)
.addImm(Mask);
if (Mask & 1)
MIB.addReg(Mips::DSPPos, RegState::Implicit);
if (Mask & 2)
MIB.addReg(Mips::DSPSCount, RegState::Implicit);
if (Mask & 4)
MIB.addReg(Mips::DSPCarry, RegState::Implicit);
if (Mask & 8)
MIB.addReg(Mips::DSPOutFlag, RegState::Implicit);
if (Mask & 16)
MIB.addReg(Mips::DSPCCond, RegState::Implicit);
if (Mask & 32)
MIB.addReg(Mips::DSPEFI, RegState::Implicit);
MI.eraseFromParent();
return MIB;
}

MachineBasicBlock::iterator
MipsTargetLowering::emitWRDSP(MachineInstr &MI, MachineBasicBlock *BB) const {
const TargetInstrInfo &TII = *Subtarget.getInstrInfo();
unsigned SrcReg = MI.getOperand(0).getReg();
unsigned Mask = MI.getOperand(1).getImm();
auto MIB = BuildMI(*BB, MI, MI.getDebugLoc(), TII.get(Mips::WRDSP))
.addReg(SrcReg)
.addImm(Mask);
if (Mask & 1)
MIB.addReg(Mips::DSPPos, RegState::ImplicitDefine);
if (Mask & 2)
MIB.addReg(Mips::DSPSCount, RegState::ImplicitDefine);
if (Mask & 4)
MIB.addReg(Mips::DSPCarry, RegState::ImplicitDefine);
if (Mask & 8)
MIB.addReg(Mips::DSPOutFlag, RegState::ImplicitDefine);
if (Mask & 16)
MIB.addReg(Mips::DSPCCond, RegState::ImplicitDefine);
if (Mask & 32)
MIB.addReg(Mips::DSPEFI, RegState::ImplicitDefine);
MI.eraseFromParent();
return MIB;
}

MachineBasicBlock *
MipsTargetLowering::EmitInstrWithCustomInserter(MachineInstr &MI,
MachineBasicBlock *BB) const {
Expand Down Expand Up @@ -1579,6 +1626,10 @@ MipsTargetLowering::EmitInstrWithCustomInserter(MachineInstr &MI,
return emitSTR_W(MI, BB);
case Mips::STR_D:
return emitSTR_D(MI, BB);
case Mips::RDDSP_Pseudo:
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@topperc topperc Jul 16, 2025 •
edited
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EmitInstrWithCustomerInsert runs later than processFunctionAfterISel. How does this fix the problem?

return emitRDDSP(MI, BB);
case Mips::WRDSP_Pseudo:
return emitWRDSP(MI, BB);
}
}

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2 changes: 2 additions & 0 deletions llvm/lib/Target/Mips/MipsISelLowering.h
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Expand Up @@ -744,6 +744,8 @@ class TargetRegisterClass;
MachineBasicBlock *emitLDR_D(MachineInstr &MI, MachineBasicBlock *BB) const;
MachineBasicBlock *emitSTR_W(MachineInstr &MI, MachineBasicBlock *BB) const;
MachineBasicBlock *emitSTR_D(MachineInstr &MI, MachineBasicBlock *BB) const;
MachineBasicBlock *emitRDDSP(MachineInstr &MI, MachineBasicBlock *BB) const;
MachineBasicBlock *emitWRDSP(MachineInstr &MI, MachineBasicBlock *BB) const;
};

/// Create MipsTargetLowering objects.
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38 changes: 3 additions & 35 deletions llvm/lib/Target/Mips/MipsSEISelDAGToDAG.cpp
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Expand Up @@ -44,32 +44,6 @@ void MipsSEDAGToDAGISelLegacy::getAnalysisUsage(AnalysisUsage &AU) const {
SelectionDAGISelLegacy::getAnalysisUsage(AU);
}

void MipsSEDAGToDAGISel::addDSPCtrlRegOperands(bool IsDef, MachineInstr &MI,
MachineFunction &MF) {
MachineInstrBuilder MIB(MF, &MI);
unsigned Mask = MI.getOperand(1).getImm();
unsigned Flag =
IsDef ? RegState::ImplicitDefine : RegState::Implicit | RegState::Undef;

if (Mask & 1)
MIB.addReg(Mips::DSPPos, Flag);

if (Mask & 2)
MIB.addReg(Mips::DSPSCount, Flag);

if (Mask & 4)
MIB.addReg(Mips::DSPCarry, Flag);

if (Mask & 8)
MIB.addReg(Mips::DSPOutFlag, Flag);

if (Mask & 16)
MIB.addReg(Mips::DSPCCond, Flag);

if (Mask & 32)
MIB.addReg(Mips::DSPEFI, Flag);
}

MCRegister MipsSEDAGToDAGISel::getMSACtrlReg(const SDValue RegIdx) const {
uint64_t RegNum = RegIdx->getAsZExtVal();
return Mips::MSACtrlRegClass.getRegister(RegNum);
Expand Down Expand Up @@ -155,12 +129,6 @@ void MipsSEDAGToDAGISel::processFunctionAfterISel(MachineFunction &MF) {
for (auto &MBB: MF) {
for (auto &MI: MBB) {
switch (MI.getOpcode()) {
case Mips::RDDSP:
addDSPCtrlRegOperands(false, MI, MF);
break;
case Mips::WRDSP:
addDSPCtrlRegOperands(true, MI, MF);
break;
case Mips::BuildPairF64_64:
case Mips::ExtractElementF64_64:
if (!Subtarget->useOddSPReg()) {
Expand Down Expand Up @@ -231,8 +199,8 @@ void MipsSEDAGToDAGISel::selectAddE(SDNode *Node, const SDLoc &DL) const {

SDValue OuFlag = CurDAG->getTargetConstant(20, DL, MVT::i32);

SDNode *DSPCtrlField = CurDAG->getMachineNode(Mips::RDDSP, DL, MVT::i32,
MVT::Glue, CstOne, InGlue);
SDNode *DSPCtrlField = CurDAG->getMachineNode(
Mips::RDDSP_Pseudo, DL, MVT::i32, MVT::Glue, CstOne, InGlue);

SDNode *Carry = CurDAG->getMachineNode(
Mips::EXT, DL, MVT::i32, SDValue(DSPCtrlField, 0), OuFlag, CstOne);
Expand All @@ -253,7 +221,7 @@ void MipsSEDAGToDAGISel::selectAddE(SDNode *Node, const SDLoc &DL) const {
SDNode *DSPCtrlFinal =
CurDAG->getMachineNode(Mips::INS, DL, MVT::i32, InsOps);

SDNode *WrDSP = CurDAG->getMachineNode(Mips::WRDSP, DL, MVT::Glue,
SDNode *WrDSP = CurDAG->getMachineNode(Mips::WRDSP_Pseudo, DL, MVT::Glue,
SDValue(DSPCtrlFinal, 0), CstOne);

SDValue Operands[3] = {LHS, RHS, SDValue(WrDSP, 0)};
Expand Down
3 changes: 0 additions & 3 deletions llvm/lib/Target/Mips/MipsSEISelDAGToDAG.h
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Expand Up @@ -27,9 +27,6 @@ class MipsSEDAGToDAGISel : public MipsDAGToDAGISel {

bool runOnMachineFunction(MachineFunction &MF) override;

void addDSPCtrlRegOperands(bool IsDef, MachineInstr &MI,
MachineFunction &MF);

MCRegister getMSACtrlReg(const SDValue RegIdx) const;

bool replaceUsesWithZeroReg(MachineRegisterInfo *MRI, const MachineInstr&);
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