Remove TargetInstrInfo::canFoldMemoryOperand

[RKSimon]

Summary

During a recent visual review of the x86 memory folding code I noticed that X86InstrInfo::canFoldMemoryOperand had bit-rotted somewhat compared to the actual foldMemoryOperand/foldMemoryOperandImpl implementation. I began investigating a fix when I realised that canFoldMemoryOperand is not actually used anywhere in the codebase.... All existing users instead call foldMemoryOperand directly when they wish to fold and can correctly deduce what they need from the return value. I don't see this state of affairs changing - do you?

This patch removes the canFoldMemoryOperand base function and the target implementations; only x86 had a real implementation, although AMDGPU had a preparatory stub that had never needed to be completed.

[bkramer]

LGTM. Nuke it!

[RKSimon]

Thanks Ben

llvm/trunk/include/llvm/Target/TargetInstrInfo.h

protected:
   virtual bool
   getInsertSubregLikeInputs(const MachineInstr &MI, unsigned DefIdx,
                             RegSubRegPair &BaseReg,
                             RegSubRegPairAndIdx &InsertedReg) const {
     return false;
   }
 
 public:
-  /// Returns true for the specified load / store if folding is possible.
-  virtual bool canFoldMemoryOperand(const MachineInstr *MI,
-                                    ArrayRef<unsigned> Ops) const;
-
   /// unfoldMemoryOperand - Separate a single instruction which folded a load or
   /// a store or a load and a store into two or more instruction. If this is
   /// possible, returns true as well as the new instructions by reference.
   virtual bool unfoldMemoryOperand(MachineFunction &MF, MachineInstr *MI,
                                 unsigned Reg, bool UnfoldLoad, bool UnfoldStore,
                                  SmallVectorImpl<MachineInstr*> &NewMIs) const{
     return false;
   }

llvm/trunk/lib/CodeGen/TargetInstrInfo.cpp

static const TargetRegisterClass *canFoldCopy(const MachineInstr *MI,
   // FIXME: Allow folding when register classes are memory compatible.
   return nullptr;
 }
 
 void TargetInstrInfo::getNoopForMachoTarget(MCInst &NopInst) const {
   llvm_unreachable("Not a MachO target");
 }
 
-bool TargetInstrInfo::canFoldMemoryOperand(const MachineInstr *MI,
-                                           ArrayRef<unsigned> Ops) const {
-  return MI->isCopy() && Ops.size() == 1 && canFoldCopy(MI, Ops[0]);
-}
-
 static MachineInstr *foldPatchpoint(MachineFunction &MF, MachineInstr *MI,
                                     ArrayRef<unsigned> Ops, int FrameIndex,
                                     const TargetInstrInfo &TII) {
   unsigned StartIdx = 0;
   switch (MI->getOpcode()) {
   case TargetOpcode::STACKMAP:
     StartIdx = 2; // Skip ID, nShadowBytes.
     break;

llvm/trunk/lib/Target/AMDGPU/AMDGPUInstrInfo.h

public:
   /// \returns the smallest register index that will be accessed by an indirect
   /// read or write or -1 if indirect addressing is not used by this program.
   int getIndirectIndexBegin(const MachineFunction &MF) const;
 
   /// \returns the largest register index that will be accessed by an indirect
   /// read or write or -1 if indirect addressing is not used by this program.
   int getIndirectIndexEnd(const MachineFunction &MF) const;
 
-  bool canFoldMemoryOperand(const MachineInstr *MI,
-                            ArrayRef<unsigned> Ops) const override;
   bool unfoldMemoryOperand(MachineFunction &MF, MachineInstr *MI,
                         unsigned Reg, bool UnfoldLoad, bool UnfoldStore,
                         SmallVectorImpl<MachineInstr *> &NewMIs) const override;
   bool unfoldMemoryOperand(SelectionDAG &DAG, SDNode *N,
                            SmallVectorImpl<SDNode *> &NewNodes) const override;
   unsigned getOpcodeAfterMemoryUnfold(unsigned Opc,
                                bool UnfoldLoad, bool UnfoldStore,
                                unsigned *LoadRegIndex = nullptr) const override;

llvm/trunk/lib/Target/AMDGPU/AMDGPUInstrInfo.cpp

// TODO: Implement this function
   return nullptr;
 }
 MachineInstr *AMDGPUInstrInfo::foldMemoryOperandImpl(
     MachineFunction &MF, MachineInstr *MI, ArrayRef<unsigned> Ops,
     MachineBasicBlock::iterator InsertPt, MachineInstr *LoadMI) const {
   // TODO: Implement this function
   return nullptr;
 }
-bool AMDGPUInstrInfo::canFoldMemoryOperand(const MachineInstr *MI,
-                                           ArrayRef<unsigned> Ops) const {
-  // TODO: Implement this function
-  return false;
-}
 bool
 AMDGPUInstrInfo::unfoldMemoryOperand(MachineFunction &MF, MachineInstr *MI,
                                  unsigned Reg, bool UnfoldLoad,
                                  bool UnfoldStore,
                                  SmallVectorImpl<MachineInstr*> &NewMIs) const {
   // TODO: Implement this function
   return false;
 }

llvm/trunk/lib/Target/X86/X86InstrInfo.h

public:
   /// foldMemoryOperand - Same as the previous version except it allows folding
   /// of any load and store from / to any address, not just from a specific
   /// stack slot.
   MachineInstr *foldMemoryOperandImpl(MachineFunction &MF, MachineInstr *MI,
                                       ArrayRef<unsigned> Ops,
                                       MachineBasicBlock::iterator InsertPt,
                                       MachineInstr *LoadMI) const override;
 
-  /// canFoldMemoryOperand - Returns true if the specified load / store is
-  /// folding is possible.
-  bool canFoldMemoryOperand(const MachineInstr *,
-                            ArrayRef<unsigned>) const override;
-
   /// unfoldMemoryOperand - Separate a single instruction which folded a load or
   /// a store or a load and a store into two or more instruction. If this is
   /// possible, returns true as well as the new instructions by reference.
   bool unfoldMemoryOperand(MachineFunction &MF, MachineInstr *MI,
                          unsigned Reg, bool UnfoldLoad, bool UnfoldStore,
                          SmallVectorImpl<MachineInstr*> &NewMIs) const override;
 
   bool unfoldMemoryOperand(SelectionDAG &DAG, SDNode *N,

llvm/trunk/lib/Target/X86/X86InstrInfo.cpp

MOs.append(LoadMI->operands_begin() + NumOps - X86::AddrNumOperands,
                LoadMI->operands_begin() + NumOps);
     break;
   }
   }
   return foldMemoryOperandImpl(MF, MI, Ops[0], MOs, InsertPt,
                                /*Size=*/0, Alignment, /*AllowCommute=*/true);
 }
 
-bool X86InstrInfo::canFoldMemoryOperand(const MachineInstr *MI,
-                                        ArrayRef<unsigned> Ops) const {
-  // Check switch flag
-  if (NoFusing) return 0;
-
-  if (Ops.size() == 2 && Ops[0] == 0 && Ops[1] == 1) {
-    switch (MI->getOpcode()) {
-    default: return false;
-    case X86::TEST8rr:
-    case X86::TEST16rr:
-    case X86::TEST32rr:
-    case X86::TEST64rr:
-      return true;
-    case X86::ADD32ri:
-      // FIXME: AsmPrinter doesn't know how to handle
-      // X86II::MO_GOT_ABSOLUTE_ADDRESS after folding.
-      if (MI->getOperand(2).getTargetFlags() == X86II::MO_GOT_ABSOLUTE_ADDRESS)
-        return false;
-      break;
-    }
-  }
-
-  if (Ops.size() != 1)
-    return false;
-
-  unsigned OpNum = Ops[0];
-  unsigned Opc = MI->getOpcode();
-  unsigned NumOps = MI->getDesc().getNumOperands();
-  bool isTwoAddr = NumOps > 1 &&
-    MI->getDesc().getOperandConstraint(1, MCOI::TIED_TO) != -1;
-
-  // Folding a memory location into the two-address part of a two-address
-  // instruction is different than folding it other places.  It requires
-  // replacing the *two* registers with the memory location.
-  const DenseMap<unsigned,
-                 std::pair<unsigned,unsigned> > *OpcodeTablePtr = nullptr;
-  if (isTwoAddr && NumOps >= 2 && OpNum < 2) {
-    OpcodeTablePtr = &RegOp2MemOpTable2Addr;
-  } else if (OpNum == 0) {
-    if (Opc == X86::MOV32r0)
-      return true;
-
-    OpcodeTablePtr = &RegOp2MemOpTable0;
-  } else if (OpNum == 1) {
-    OpcodeTablePtr = &RegOp2MemOpTable1;
-  } else if (OpNum == 2) {
-    OpcodeTablePtr = &RegOp2MemOpTable2;
-  } else if (OpNum == 3) {
-    OpcodeTablePtr = &RegOp2MemOpTable3;
-  }
-
-  if (OpcodeTablePtr && OpcodeTablePtr->count(Opc))
-    return true;
-  return TargetInstrInfo::canFoldMemoryOperand(MI, Ops);
-}
-
 bool X86InstrInfo::unfoldMemoryOperand(MachineFunction &MF, MachineInstr *MI,
                                 unsigned Reg, bool UnfoldLoad, bool UnfoldStore,
                                 SmallVectorImpl<MachineInstr*> &NewMIs) const {
   DenseMap<unsigned, std::pair<unsigned,unsigned> >::const_iterator I =
     MemOp2RegOpTable.find(MI->getOpcode());
   if (I == MemOp2RegOpTable.end())
     return false;
   unsigned Opc = I->second.first;