[ARM] Remove unused enable-arm-3-addr-conv (#141850)

This code is not enabled by default and has no tests, having been added
back in 10043e2. It can be safely removed to help keep things
simpler, not needing to maintain code that is never used.

Author: davemgreen

llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp

@@ -76,10 +76,6 @@ using namespace llvm;
 #define GET_INSTRINFO_CTOR_DTOR
 #include "ARMGenInstrInfo.inc"
 
-static cl::opt<bool>
-EnableARM3Addr("enable-arm-3-addr-conv", cl::Hidden,
-               cl::desc("Enable ARM 2-addr to 3-addr conv"));
-
 /// ARM_MLxEntry - Record information about MLA / MLS instructions.
 struct ARM_MLxEntry {
   uint16_t MLxOpc;     // MLA / MLS opcode
@@ -175,175 +171,6 @@ CreateTargetPostRAHazardRecognizer(const InstrItineraryData *II,
   return MHR;
 }
 
-MachineInstr *
-ARMBaseInstrInfo::convertToThreeAddress(MachineInstr &MI, LiveVariables *LV,
-                                        LiveIntervals *LIS) const {
-  // FIXME: Thumb2 support.
-
-  if (!EnableARM3Addr)
-    return nullptr;
-
-  MachineFunction &MF = *MI.getParent()->getParent();
-  uint64_t TSFlags = MI.getDesc().TSFlags;
-  bool isPre = false;
-  switch ((TSFlags & ARMII::IndexModeMask) >> ARMII::IndexModeShift) {
-  default: return nullptr;
-  case ARMII::IndexModePre:
-    isPre = true;
-    break;
-  case ARMII::IndexModePost:
-    break;
-  }
-
-  // Try splitting an indexed load/store to an un-indexed one plus an add/sub
-  // operation.
-  unsigned MemOpc = getUnindexedOpcode(MI.getOpcode());
-  if (MemOpc == 0)
-    return nullptr;
-
-  MachineInstr *UpdateMI = nullptr;
-  MachineInstr *MemMI = nullptr;
-  unsigned AddrMode = (TSFlags & ARMII::AddrModeMask);
-  const MCInstrDesc &MCID = MI.getDesc();
-  unsigned NumOps = MCID.getNumOperands();
-  bool isLoad = !MI.mayStore();
-  const MachineOperand &WB = isLoad ? MI.getOperand(1) : MI.getOperand(0);
-  const MachineOperand &Base = MI.getOperand(2);
-  const MachineOperand &Offset = MI.getOperand(NumOps - 3);
-  Register WBReg = WB.getReg();
-  Register BaseReg = Base.getReg();
-  Register OffReg = Offset.getReg();
-  unsigned OffImm = MI.getOperand(NumOps - 2).getImm();
-  ARMCC::CondCodes Pred = (ARMCC::CondCodes)MI.getOperand(NumOps - 1).getImm();
-  switch (AddrMode) {
-  default: llvm_unreachable("Unknown indexed op!");
-  case ARMII::AddrMode2: {
-    bool isSub = ARM_AM::getAM2Op(OffImm) == ARM_AM::sub;
-    unsigned Amt = ARM_AM::getAM2Offset(OffImm);
-    if (OffReg == 0) {
-      if (ARM_AM::getSOImmVal(Amt) == -1)
-        // Can't encode it in a so_imm operand. This transformation will
-        // add more than 1 instruction. Abandon!
-        return nullptr;
-      UpdateMI = BuildMI(MF, MI.getDebugLoc(),
-                         get(isSub ? ARM::SUBri : ARM::ADDri), WBReg)
-                     .addReg(BaseReg)
-                     .addImm(Amt)
-                     .add(predOps(Pred))
-                     .add(condCodeOp());
-    } else if (Amt != 0) {
-      ARM_AM::ShiftOpc ShOpc = ARM_AM::getAM2ShiftOpc(OffImm);
-      unsigned SOOpc = ARM_AM::getSORegOpc(ShOpc, Amt);
-      UpdateMI = BuildMI(MF, MI.getDebugLoc(),
-                         get(isSub ? ARM::SUBrsi : ARM::ADDrsi), WBReg)
-                     .addReg(BaseReg)
-                     .addReg(OffReg)
-                     .addReg(0)
-                     .addImm(SOOpc)
-                     .add(predOps(Pred))
-                     .add(condCodeOp());
-    } else
-      UpdateMI = BuildMI(MF, MI.getDebugLoc(),
-                         get(isSub ? ARM::SUBrr : ARM::ADDrr), WBReg)
-                     .addReg(BaseReg)
-                     .addReg(OffReg)
-                     .add(predOps(Pred))
-                     .add(condCodeOp());
-    break;
-  }
-  case ARMII::AddrMode3 : {
-    bool isSub = ARM_AM::getAM3Op(OffImm) == ARM_AM::sub;
-    unsigned Amt = ARM_AM::getAM3Offset(OffImm);
-    if (OffReg == 0)
-      // Immediate is 8-bits. It's guaranteed to fit in a so_imm operand.
-      UpdateMI = BuildMI(MF, MI.getDebugLoc(),
-                         get(isSub ? ARM::SUBri : ARM::ADDri), WBReg)
-                     .addReg(BaseReg)
-                     .addImm(Amt)
-                     .add(predOps(Pred))
-                     .add(condCodeOp());
-    else
-      UpdateMI = BuildMI(MF, MI.getDebugLoc(),
-                         get(isSub ? ARM::SUBrr : ARM::ADDrr), WBReg)
-                     .addReg(BaseReg)
-                     .addReg(OffReg)
-                     .add(predOps(Pred))
-                     .add(condCodeOp());
-    break;
-  }
-  }
-
-  std::vector<MachineInstr*> NewMIs;
-  if (isPre) {
-    if (isLoad)
-      MemMI =
-          BuildMI(MF, MI.getDebugLoc(), get(MemOpc), MI.getOperand(0).getReg())
-              .addReg(WBReg)
-              .addImm(0)
-              .addImm(Pred);
-    else
-      MemMI = BuildMI(MF, MI.getDebugLoc(), get(MemOpc))
-                  .addReg(MI.getOperand(1).getReg())
-                  .addReg(WBReg)
-                  .addReg(0)
-                  .addImm(0)
-                  .addImm(Pred);
-    NewMIs.push_back(MemMI);
-    NewMIs.push_back(UpdateMI);
-  } else {
-    if (isLoad)
-      MemMI =
-          BuildMI(MF, MI.getDebugLoc(), get(MemOpc), MI.getOperand(0).getReg())
-              .addReg(BaseReg)
-              .addImm(0)
-              .addImm(Pred);
-    else
-      MemMI = BuildMI(MF, MI.getDebugLoc(), get(MemOpc))
-                  .addReg(MI.getOperand(1).getReg())
-                  .addReg(BaseReg)
-                  .addReg(0)
-                  .addImm(0)
-                  .addImm(Pred);
-    if (WB.isDead())
-      UpdateMI->getOperand(0).setIsDead();
-    NewMIs.push_back(UpdateMI);
-    NewMIs.push_back(MemMI);
-  }
-
-  // Transfer LiveVariables states, kill / dead info.
-  if (LV) {
-    for (const MachineOperand &MO : MI.operands()) {
-      if (MO.isReg() && MO.getReg().isVirtual()) {
-        Register Reg = MO.getReg();
-
-        LiveVariables::VarInfo &VI = LV->getVarInfo(Reg);
-        if (MO.isDef()) {
-          MachineInstr *NewMI = (Reg == WBReg) ? UpdateMI : MemMI;
-          if (MO.isDead())
-            LV->addVirtualRegisterDead(Reg, *NewMI);
-        }
-        if (MO.isUse() && MO.isKill()) {
-          for (unsigned j = 0; j < 2; ++j) {
-            // Look at the two new MI's in reverse order.
-            MachineInstr *NewMI = NewMIs[j];
-            if (!NewMI->readsRegister(Reg, /*TRI=*/nullptr))
-              continue;
-            LV->addVirtualRegisterKilled(Reg, *NewMI);
-            if (VI.removeKill(MI))
-              VI.Kills.push_back(NewMI);
-            break;
-          }
-        }
-      }
-    }
-  }
-
-  MachineBasicBlock &MBB = *MI.getParent();
-  MBB.insert(MI, NewMIs[1]);
-  MBB.insert(MI, NewMIs[0]);
-  return NewMIs[0];
-}
-
 // Branch analysis.
 // Cond vector output format:
 //   0 elements indicates an unconditional branch

llvm/lib/Target/ARM/ARMBaseInstrInfo.h

@@ -125,9 +125,6 @@ class ARMBaseInstrInfo : public ARMGenInstrInfo {
   // if there is not such an opcode.
   virtual unsigned getUnindexedOpcode(unsigned Opc) const = 0;
 
-  MachineInstr *convertToThreeAddress(MachineInstr &MI, LiveVariables *LV,
-                                      LiveIntervals *LIS) const override;
-
   virtual const ARMBaseRegisterInfo &getRegisterInfo() const = 0;
   const ARMSubtarget &getSubtarget() const { return Subtarget; }