llvm/lib/Target/Mips/MipsInstrInfo.cpp - toolchain/llvm-project - Gitiles

 //===-- MipsInstrInfo.cpp - Mips Instruction Information ------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file contains the Mips implementation of the TargetInstrInfo class.
 //
 //===----------------------------------------------------------------------===//

 #include "MipsInstrInfo.h"
 #include "InstPrinter/MipsInstPrinter.h"
 #include "MipsMachineFunction.h"
 #include "MipsSubtarget.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/TargetRegistry.h"

 using namespace llvm;

 #define GET_INSTRINFO_CTOR_DTOR
 #include "MipsGenInstrInfo.inc"

 // Pin the vtable to this file.
 void MipsInstrInfo::anchor() {}

 MipsInstrInfo::MipsInstrInfo(const MipsSubtarget &STI, unsigned UncondBr)
     : MipsGenInstrInfo(Mips::ADJCALLSTACKDOWN, Mips::ADJCALLSTACKUP),
       Subtarget(STI), UncondBrOpc(UncondBr) {}

 const MipsInstrInfo *MipsInstrInfo::create(MipsSubtarget &STI) {
   if (STI.inMips16Mode())
     return llvm::createMips16InstrInfo(STI);

   return llvm::createMipsSEInstrInfo(STI);
 }

 bool MipsInstrInfo::isZeroImm(const MachineOperand &op) const {
   return op.isImm() && op.getImm() == 0;
 }

 /// insertNoop - If data hazard condition is found insert the target nop
 /// instruction.
 // FIXME: This appears to be dead code.
 void MipsInstrInfo::
 insertNoop(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI) const
 {
   DebugLoc DL;
   BuildMI(MBB, MI, DL, get(Mips::NOP));
 }

 MachineMemOperand *
 MipsInstrInfo::GetMemOperand(MachineBasicBlock &MBB, int FI,
                              MachineMemOperand::Flags Flags) const {
   MachineFunction &MF = *MBB.getParent();
   MachineFrameInfo &MFI = *MF.getFrameInfo();
   unsigned Align = MFI.getObjectAlignment(FI);

   return MF.getMachineMemOperand(MachinePointerInfo::getFixedStack(MF, FI),
                                  Flags, MFI.getObjectSize(FI), Align);
 }

 //===----------------------------------------------------------------------===//
 // Branch Analysis
 //===----------------------------------------------------------------------===//

 void MipsInstrInfo::AnalyzeCondBr(const MachineInstr *Inst, unsigned Opc,
                                   MachineBasicBlock *&BB,
                                   SmallVectorImpl<MachineOperand> &Cond) const {
   assert(getAnalyzableBrOpc(Opc) && "Not an analyzable branch");
   int NumOp = Inst->getNumExplicitOperands();

   // for both int and fp branches, the last explicit operand is the
   // MBB.
   BB = Inst->getOperand(NumOp-1).getMBB();
   Cond.push_back(MachineOperand::CreateImm(Opc));

   for (int i=0; i<NumOp-1; i++)
     Cond.push_back(Inst->getOperand(i));
 }

 bool MipsInstrInfo::analyzeBranch(MachineBasicBlock &MBB,
                                   MachineBasicBlock *&TBB,
                                   MachineBasicBlock *&FBB,
                                   SmallVectorImpl<MachineOperand> &Cond,
                                   bool AllowModify) const {
   SmallVector<MachineInstr*, 2> BranchInstrs;
   BranchType BT = analyzeBranch(MBB, TBB, FBB, Cond, AllowModify, BranchInstrs);

   return (BT == BT_None) || (BT == BT_Indirect);
 }

 void MipsInstrInfo::BuildCondBr(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
                                 const DebugLoc &DL,
                                 ArrayRef<MachineOperand> Cond) const {
   unsigned Opc = Cond[0].getImm();
   const MCInstrDesc &MCID = get(Opc);
   MachineInstrBuilder MIB = BuildMI(&MBB, DL, MCID);

   for (unsigned i = 1; i < Cond.size(); ++i) {
     if (Cond[i].isReg())
       MIB.addReg(Cond[i].getReg());
     else if (Cond[i].isImm())
       MIB.addImm(Cond[i].getImm());
     else
        assert(false && "Cannot copy operand");
   }
   MIB.addMBB(TBB);
 }

 unsigned MipsInstrInfo::InsertBranch(MachineBasicBlock &MBB,
                                      MachineBasicBlock *TBB,
                                      MachineBasicBlock *FBB,
                                      ArrayRef<MachineOperand> Cond,
                                      const DebugLoc &DL) const {
   // Shouldn't be a fall through.
   assert(TBB && "InsertBranch must not be told to insert a fallthrough");

   // # of condition operands:
   //  Unconditional branches: 0
   //  Floating point branches: 1 (opc)
   //  Int BranchZero: 2 (opc, reg)
   //  Int Branch: 3 (opc, reg0, reg1)
   assert((Cond.size() <= 3) &&
          "# of Mips branch conditions must be <= 3!");

   // Two-way Conditional branch.
   if (FBB) {
     BuildCondBr(MBB, TBB, DL, Cond);
     BuildMI(&MBB, DL, get(UncondBrOpc)).addMBB(FBB);
     return 2;
   }

   // One way branch.
   // Unconditional branch.
   if (Cond.empty())
     BuildMI(&MBB, DL, get(UncondBrOpc)).addMBB(TBB);
   else // Conditional branch.
     BuildCondBr(MBB, TBB, DL, Cond);
   return 1;
 }

 unsigned MipsInstrInfo::RemoveBranch(MachineBasicBlock &MBB) const {
   MachineBasicBlock::reverse_iterator I = MBB.rbegin(), REnd = MBB.rend();
   MachineBasicBlock::reverse_iterator FirstBr;
   unsigned removed;

   // Skip all the debug instructions.
   while (I != REnd && I->isDebugValue())
     ++I;

   FirstBr = I;

   // Up to 2 branches are removed.
   // Note that indirect branches are not removed.
   for (removed = 0; I != REnd && removed < 2; ++I, ++removed)
     if (!getAnalyzableBrOpc(I->getOpcode()))
       break;

   MBB.erase(I.base(), FirstBr.base());

   return removed;
 }

 /// ReverseBranchCondition - Return the inverse opcode of the
 /// specified Branch instruction.
 bool MipsInstrInfo::ReverseBranchCondition(
     SmallVectorImpl<MachineOperand> &Cond) const {
   assert( (Cond.size() && Cond.size() <= 3) &&
           "Invalid Mips branch condition!");
   Cond[0].setImm(getOppositeBranchOpc(Cond[0].getImm()));
   return false;
 }

 MipsInstrInfo::BranchType MipsInstrInfo::analyzeBranch(
     MachineBasicBlock &MBB, MachineBasicBlock *&TBB, MachineBasicBlock *&FBB,
     SmallVectorImpl<MachineOperand> &Cond, bool AllowModify,
     SmallVectorImpl<MachineInstr *> &BranchInstrs) const {

   MachineBasicBlock::reverse_iterator I = MBB.rbegin(), REnd = MBB.rend();

   // Skip all the debug instructions.
   while (I != REnd && I->isDebugValue())
     ++I;

   if (I == REnd || !isUnpredicatedTerminator(*I)) {
     // This block ends with no branches (it just falls through to its succ).
     // Leave TBB/FBB null.
     TBB = FBB = nullptr;
     return BT_NoBranch;
   }

   MachineInstr *LastInst = &*I;
   unsigned LastOpc = LastInst->getOpcode();
   BranchInstrs.push_back(LastInst);

   // Not an analyzable branch (e.g., indirect jump).
   if (!getAnalyzableBrOpc(LastOpc))
     return LastInst->isIndirectBranch() ? BT_Indirect : BT_None;

   // Get the second to last instruction in the block.
   unsigned SecondLastOpc = 0;
   MachineInstr *SecondLastInst = nullptr;

   if (++I != REnd) {
     SecondLastInst = &*I;
     SecondLastOpc = getAnalyzableBrOpc(SecondLastInst->getOpcode());

     // Not an analyzable branch (must be an indirect jump).
     if (isUnpredicatedTerminator(*SecondLastInst) && !SecondLastOpc)
       return BT_None;
   }

   // If there is only one terminator instruction, process it.
   if (!SecondLastOpc) {
     // Unconditional branch.
     if (LastInst->isUnconditionalBranch()) {
       TBB = LastInst->getOperand(0).getMBB();
       return BT_Uncond;
     }

     // Conditional branch
     AnalyzeCondBr(LastInst, LastOpc, TBB, Cond);
     return BT_Cond;
   }

   // If we reached here, there are two branches.
   // If there are three terminators, we don't know what sort of block this is.
   if (++I != REnd && isUnpredicatedTerminator(*I))
     return BT_None;

   BranchInstrs.insert(BranchInstrs.begin(), SecondLastInst);

   // If second to last instruction is an unconditional branch,
   // analyze it and remove the last instruction.
   if (SecondLastInst->isUnconditionalBranch()) {
     // Return if the last instruction cannot be removed.
     if (!AllowModify)
       return BT_None;

     TBB = SecondLastInst->getOperand(0).getMBB();
     LastInst->eraseFromParent();
     BranchInstrs.pop_back();
     return BT_Uncond;
   }

   // Conditional branch followed by an unconditional branch.
   // The last one must be unconditional.
   if (!LastInst->isUnconditionalBranch())
     return BT_None;

   AnalyzeCondBr(SecondLastInst, SecondLastOpc, TBB, Cond);
   FBB = LastInst->getOperand(0).getMBB();

   return BT_CondUncond;
 }

 /// Return the corresponding compact (no delay slot) form of a branch.
 unsigned MipsInstrInfo::getEquivalentCompactForm(
     const MachineBasicBlock::iterator I) const {
   unsigned Opcode = I->getOpcode();
   bool canUseShortMicroMipsCTI = false;

   if (Subtarget.inMicroMipsMode()) {
     switch (Opcode) {
     case Mips::BNE:
     case Mips::BNE_MM:
     case Mips::BEQ:
     case Mips::BEQ_MM:
     // microMIPS has NE,EQ branches that do not have delay slots provided one
     // of the operands is zero.
       if (I->getOperand(1).getReg() == Subtarget.getABI().GetZeroReg())
         canUseShortMicroMipsCTI = true;
       break;
     // For microMIPS the PseudoReturn and PseudoIndirectBranch are always
     // expanded to JR_MM, so they can be replaced with JRC16_MM.
     case Mips::JR:
     case Mips::PseudoReturn:
     case Mips::PseudoIndirectBranch:
       canUseShortMicroMipsCTI = true;
       break;
     }
   }

   // MIPSR6 forbids both operands being the zero register.
   if (Subtarget.hasMips32r6() && (I->getNumOperands() > 1) &&
       (I->getOperand(0).isReg() &&
        (I->getOperand(0).getReg() == Mips::ZERO ||
         I->getOperand(0).getReg() == Mips::ZERO_64)) &&
       (I->getOperand(1).isReg() &&
        (I->getOperand(1).getReg() == Mips::ZERO ||
         I->getOperand(1).getReg() == Mips::ZERO_64)))
     return 0;

   if (Subtarget.hasMips32r6() || canUseShortMicroMipsCTI) {
     switch (Opcode) {
     case Mips::B:
       return Mips::BC;
     case Mips::BAL:
       return Mips::BALC;
     case Mips::BEQ:
     case Mips::BEQ_MM:
       if (canUseShortMicroMipsCTI)
         return Mips::BEQZC_MM;
       else if (I->getOperand(0).getReg() == I->getOperand(1).getReg())
         return 0;
       return Mips::BEQC;
     case Mips::BNE:
     case Mips::BNE_MM:
       if (canUseShortMicroMipsCTI)
         return Mips::BNEZC_MM;
       else if (I->getOperand(0).getReg() == I->getOperand(1).getReg())
         return 0;
       return Mips::BNEC;
     case Mips::BGE:
       if (I->getOperand(0).getReg() == I->getOperand(1).getReg())
         return 0;
       return Mips::BGEC;
     case Mips::BGEU:
       if (I->getOperand(0).getReg() == I->getOperand(1).getReg())
         return 0;
       return Mips::BGEUC;
     case Mips::BGEZ:
       return Mips::BGEZC;
     case Mips::BGTZ:
       return Mips::BGTZC;
     case Mips::BLEZ:
       return Mips::BLEZC;
     case Mips::BLT:
       if (I->getOperand(0).getReg() == I->getOperand(1).getReg())
         return 0;
       return Mips::BLTC;
     case Mips::BLTU:
       if (I->getOperand(0).getReg() == I->getOperand(1).getReg())
         return 0;
       return Mips::BLTUC;
     case Mips::BLTZ:
       return Mips::BLTZC;
     // For MIPSR6, the instruction 'jic' can be used for these cases. Some
     // tools will accept 'jrc reg' as an alias for 'jic 0, $reg'.
     case Mips::JR:
     case Mips::PseudoReturn:
     case Mips::PseudoIndirectBranch:
       if (canUseShortMicroMipsCTI)
         return Mips::JRC16_MM;
       return Mips::JIC;
     case Mips::JALRPseudo:
       return Mips::JIALC;
     case Mips::JR64:
     case Mips::PseudoReturn64:
     case Mips::PseudoIndirectBranch64:
       return Mips::JIC64;
     case Mips::JALR64Pseudo:
       return Mips::JIALC64;
     default:
       return 0;
     }
   }

   return 0;
 }

 /// Predicate for distingushing between control transfer instructions and all
 /// other instructions for handling forbidden slots. Consider inline assembly
 /// as unsafe as well.
 bool MipsInstrInfo::SafeInForbiddenSlot(const MachineInstr &MI) const {
   if (MI.isInlineAsm())
     return false;

   return (MI.getDesc().TSFlags & MipsII::IsCTI) == 0;

 }

 /// Predicate for distingushing instructions that have forbidden slots.
 bool MipsInstrInfo::HasForbiddenSlot(const MachineInstr &MI) const {
   return (MI.getDesc().TSFlags & MipsII::HasForbiddenSlot) != 0;
 }

 /// Return the number of bytes of code the specified instruction may be.
 unsigned MipsInstrInfo::GetInstSizeInBytes(const MachineInstr &MI) const {
   switch (MI.getOpcode()) {
   default:
     return MI.getDesc().getSize();
   case  TargetOpcode::INLINEASM: {       // Inline Asm: Variable size.
     const MachineFunction *MF = MI.getParent()->getParent();
     const char *AsmStr = MI.getOperand(0).getSymbolName();
     return getInlineAsmLength(AsmStr, *MF->getTarget().getMCAsmInfo());
   }
   case Mips::CONSTPOOL_ENTRY:
     // If this machine instr is a constant pool entry, its size is recorded as
     // operand #2.
     return MI.getOperand(2).getImm();
   }
 }

 MachineInstrBuilder
 MipsInstrInfo::genInstrWithNewOpc(unsigned NewOpc,
                                   MachineBasicBlock::iterator I) const {
   MachineInstrBuilder MIB;

   // Certain branches have two forms: e.g beq $1, $zero, dst vs beqz $1, dest
   // Pick the zero form of the branch for readable assembly and for greater
   // branch distance in non-microMIPS mode.
   // FIXME: Certain atomic sequences on mips64 generate 32bit references to
   // Mips::ZERO, which is incorrect. This test should be updated to use
   // Subtarget.getABI().GetZeroReg() when those atomic sequences and others
   // are fixed.
   bool BranchWithZeroOperand =
       (I->isBranch() && !I->isPseudo() && I->getOperand(1).isReg() &&
        (I->getOperand(1).getReg() == Mips::ZERO ||
         I->getOperand(1).getReg() == Mips::ZERO_64));

   if (BranchWithZeroOperand) {
     switch (NewOpc) {
     case Mips::BEQC:
       NewOpc = Mips::BEQZC;
       break;
     case Mips::BNEC:
       NewOpc = Mips::BNEZC;
       break;
     case Mips::BGEC:
       NewOpc = Mips::BGEZC;
       break;
     case Mips::BLTC:
       NewOpc = Mips::BLTZC;
       break;
     }
   }

   MIB = BuildMI(*I->getParent(), I, I->getDebugLoc(), get(NewOpc));

   // For MIPSR6 JI*C requires an immediate 0 as an operand, JIALC(64) an
   // immediate 0 as an operand and requires the removal of it's %RA<imp-def>
   // implicit operand as copying the implicit operations of the instructio we're
   // looking at will give us the correct flags.
   if (NewOpc == Mips::JIC || NewOpc == Mips::JIALC || NewOpc == Mips::JIC64 ||
       NewOpc == Mips::JIALC64) {

     if (NewOpc == Mips::JIALC || NewOpc == Mips::JIALC64)
       MIB->RemoveOperand(0);

     for (unsigned J = 0, E = I->getDesc().getNumOperands(); J < E; ++J) {
       MIB.addOperand(I->getOperand(J));
     }

     MIB.addImm(0);

  } else if (BranchWithZeroOperand) {
     // For MIPSR6 and microMIPS branches with an explicit zero operand, copy
     // everything after the zero.
      MIB.addOperand(I->getOperand(0));

     for (unsigned J = 2, E = I->getDesc().getNumOperands(); J < E; ++J) {
       MIB.addOperand(I->getOperand(J));
     }
   } else {
     // All other cases copy all other operands.
     for (unsigned J = 0, E = I->getDesc().getNumOperands(); J < E; ++J) {
       MIB.addOperand(I->getOperand(J));
     }
   }

   MIB.copyImplicitOps(*I);

   MIB.setMemRefs(I->memoperands_begin(), I->memoperands_end());
   return MIB;
 }
	//===-- MipsInstrInfo.cpp - Mips Instruction Information ------------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// This file contains the Mips implementation of the TargetInstrInfo class.
	//
	//===----------------------------------------------------------------------===//

	#include "MipsInstrInfo.h"
	#include "InstPrinter/MipsInstPrinter.h"
	#include "MipsMachineFunction.h"
	#include "MipsSubtarget.h"
	#include "llvm/ADT/STLExtras.h"
	#include "llvm/CodeGen/MachineInstrBuilder.h"
	#include "llvm/CodeGen/MachineRegisterInfo.h"
	#include "llvm/Support/ErrorHandling.h"
	#include "llvm/Support/TargetRegistry.h"

	using namespace llvm;

	#define GET_INSTRINFO_CTOR_DTOR
	#include "MipsGenInstrInfo.inc"

	// Pin the vtable to this file.
	void MipsInstrInfo::anchor() {}

	MipsInstrInfo::MipsInstrInfo(const MipsSubtarget &STI, unsigned UncondBr)
	: MipsGenInstrInfo(Mips::ADJCALLSTACKDOWN, Mips::ADJCALLSTACKUP),
	Subtarget(STI), UncondBrOpc(UncondBr) {}

	const MipsInstrInfo *MipsInstrInfo::create(MipsSubtarget &STI) {
	if (STI.inMips16Mode())
	return llvm::createMips16InstrInfo(STI);

	return llvm::createMipsSEInstrInfo(STI);
	}

	bool MipsInstrInfo::isZeroImm(const MachineOperand &op) const {
	return op.isImm() && op.getImm() == 0;
	}

	/// insertNoop - If data hazard condition is found insert the target nop
	/// instruction.
	// FIXME: This appears to be dead code.
	void MipsInstrInfo::
	insertNoop(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI) const
	{
	DebugLoc DL;
	BuildMI(MBB, MI, DL, get(Mips::NOP));
	}

	MachineMemOperand *
	MipsInstrInfo::GetMemOperand(MachineBasicBlock &MBB, int FI,
	MachineMemOperand::Flags Flags) const {
	MachineFunction &MF = *MBB.getParent();
	MachineFrameInfo &MFI = *MF.getFrameInfo();
	unsigned Align = MFI.getObjectAlignment(FI);

	return MF.getMachineMemOperand(MachinePointerInfo::getFixedStack(MF, FI),
	Flags, MFI.getObjectSize(FI), Align);
	}

	//===----------------------------------------------------------------------===//
	// Branch Analysis
	//===----------------------------------------------------------------------===//

	void MipsInstrInfo::AnalyzeCondBr(const MachineInstr *Inst, unsigned Opc,
	MachineBasicBlock *&BB,
	SmallVectorImpl<MachineOperand> &Cond) const {
	assert(getAnalyzableBrOpc(Opc) && "Not an analyzable branch");
	int NumOp = Inst->getNumExplicitOperands();

	// for both int and fp branches, the last explicit operand is the
	// MBB.
	BB = Inst->getOperand(NumOp-1).getMBB();
	Cond.push_back(MachineOperand::CreateImm(Opc));

	for (int i=0; i<NumOp-1; i++)
	Cond.push_back(Inst->getOperand(i));
	}

	bool MipsInstrInfo::analyzeBranch(MachineBasicBlock &MBB,
	MachineBasicBlock *&TBB,
	MachineBasicBlock *&FBB,
	SmallVectorImpl<MachineOperand> &Cond,
	bool AllowModify) const {
	SmallVector<MachineInstr*, 2> BranchInstrs;
	BranchType BT = analyzeBranch(MBB, TBB, FBB, Cond, AllowModify, BranchInstrs);

	return (BT == BT_None) \|\| (BT == BT_Indirect);
	}

	void MipsInstrInfo::BuildCondBr(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
	const DebugLoc &DL,
	ArrayRef<MachineOperand> Cond) const {
	unsigned Opc = Cond[0].getImm();
	const MCInstrDesc &MCID = get(Opc);
	MachineInstrBuilder MIB = BuildMI(&MBB, DL, MCID);

	for (unsigned i = 1; i < Cond.size(); ++i) {
	if (Cond[i].isReg())
	MIB.addReg(Cond[i].getReg());
	else if (Cond[i].isImm())
	MIB.addImm(Cond[i].getImm());
	else
	assert(false && "Cannot copy operand");
	}
	MIB.addMBB(TBB);
	}

	unsigned MipsInstrInfo::InsertBranch(MachineBasicBlock &MBB,
	MachineBasicBlock *TBB,
	MachineBasicBlock *FBB,
	ArrayRef<MachineOperand> Cond,
	const DebugLoc &DL) const {
	// Shouldn't be a fall through.
	assert(TBB && "InsertBranch must not be told to insert a fallthrough");

	// # of condition operands:
	// Unconditional branches: 0
	// Floating point branches: 1 (opc)
	// Int BranchZero: 2 (opc, reg)
	// Int Branch: 3 (opc, reg0, reg1)
	assert((Cond.size() <= 3) &&
	"# of Mips branch conditions must be <= 3!");

	// Two-way Conditional branch.
	if (FBB) {
	BuildCondBr(MBB, TBB, DL, Cond);
	BuildMI(&MBB, DL, get(UncondBrOpc)).addMBB(FBB);
	return 2;
	}

	// One way branch.
	// Unconditional branch.
	if (Cond.empty())
	BuildMI(&MBB, DL, get(UncondBrOpc)).addMBB(TBB);
	else // Conditional branch.
	BuildCondBr(MBB, TBB, DL, Cond);
	return 1;
	}

	unsigned MipsInstrInfo::RemoveBranch(MachineBasicBlock &MBB) const {
	MachineBasicBlock::reverse_iterator I = MBB.rbegin(), REnd = MBB.rend();
	MachineBasicBlock::reverse_iterator FirstBr;
	unsigned removed;

	// Skip all the debug instructions.
	while (I != REnd && I->isDebugValue())
	++I;

	FirstBr = I;

	// Up to 2 branches are removed.
	// Note that indirect branches are not removed.
	for (removed = 0; I != REnd && removed < 2; ++I, ++removed)
	if (!getAnalyzableBrOpc(I->getOpcode()))
	break;

	MBB.erase(I.base(), FirstBr.base());

	return removed;
	}

	/// ReverseBranchCondition - Return the inverse opcode of the
	/// specified Branch instruction.
	bool MipsInstrInfo::ReverseBranchCondition(
	SmallVectorImpl<MachineOperand> &Cond) const {
	assert( (Cond.size() && Cond.size() <= 3) &&
	"Invalid Mips branch condition!");
	Cond[0].setImm(getOppositeBranchOpc(Cond[0].getImm()));
	return false;
	}

	MipsInstrInfo::BranchType MipsInstrInfo::analyzeBranch(
	MachineBasicBlock &MBB, MachineBasicBlock &TBB, MachineBasicBlock &FBB,
	SmallVectorImpl<MachineOperand> &Cond, bool AllowModify,
	SmallVectorImpl<MachineInstr *> &BranchInstrs) const {

	MachineBasicBlock::reverse_iterator I = MBB.rbegin(), REnd = MBB.rend();

	// Skip all the debug instructions.
	while (I != REnd && I->isDebugValue())
	++I;

	if (I == REnd \|\| !isUnpredicatedTerminator(*I)) {
	// This block ends with no branches (it just falls through to its succ).
	// Leave TBB/FBB null.
	TBB = FBB = nullptr;
	return BT_NoBranch;
	}

	MachineInstr LastInst = &I;
	unsigned LastOpc = LastInst->getOpcode();
	BranchInstrs.push_back(LastInst);

	// Not an analyzable branch (e.g., indirect jump).
	if (!getAnalyzableBrOpc(LastOpc))
	return LastInst->isIndirectBranch() ? BT_Indirect : BT_None;

	// Get the second to last instruction in the block.
	unsigned SecondLastOpc = 0;
	MachineInstr *SecondLastInst = nullptr;

	if (++I != REnd) {
	SecondLastInst = &*I;
	SecondLastOpc = getAnalyzableBrOpc(SecondLastInst->getOpcode());

	// Not an analyzable branch (must be an indirect jump).
	if (isUnpredicatedTerminator(*SecondLastInst) && !SecondLastOpc)
	return BT_None;
	}

	// If there is only one terminator instruction, process it.
	if (!SecondLastOpc) {
	// Unconditional branch.
	if (LastInst->isUnconditionalBranch()) {
	TBB = LastInst->getOperand(0).getMBB();
	return BT_Uncond;
	}

	// Conditional branch
	AnalyzeCondBr(LastInst, LastOpc, TBB, Cond);
	return BT_Cond;
	}

	// If we reached here, there are two branches.
	// If there are three terminators, we don't know what sort of block this is.
	if (++I != REnd && isUnpredicatedTerminator(*I))
	return BT_None;

	BranchInstrs.insert(BranchInstrs.begin(), SecondLastInst);

	// If second to last instruction is an unconditional branch,
	// analyze it and remove the last instruction.
	if (SecondLastInst->isUnconditionalBranch()) {
	// Return if the last instruction cannot be removed.
	if (!AllowModify)
	return BT_None;

	TBB = SecondLastInst->getOperand(0).getMBB();
	LastInst->eraseFromParent();
	BranchInstrs.pop_back();
	return BT_Uncond;
	}

	// Conditional branch followed by an unconditional branch.
	// The last one must be unconditional.
	if (!LastInst->isUnconditionalBranch())
	return BT_None;

	AnalyzeCondBr(SecondLastInst, SecondLastOpc, TBB, Cond);
	FBB = LastInst->getOperand(0).getMBB();

	return BT_CondUncond;
	}

	/// Return the corresponding compact (no delay slot) form of a branch.
	unsigned MipsInstrInfo::getEquivalentCompactForm(
	const MachineBasicBlock::iterator I) const {
	unsigned Opcode = I->getOpcode();
	bool canUseShortMicroMipsCTI = false;

	if (Subtarget.inMicroMipsMode()) {
	switch (Opcode) {
	case Mips::BNE:
	case Mips::BNE_MM:
	case Mips::BEQ:
	case Mips::BEQ_MM:
	// microMIPS has NE,EQ branches that do not have delay slots provided one
	// of the operands is zero.
	if (I->getOperand(1).getReg() == Subtarget.getABI().GetZeroReg())
	canUseShortMicroMipsCTI = true;
	break;
	// For microMIPS the PseudoReturn and PseudoIndirectBranch are always
	// expanded to JR_MM, so they can be replaced with JRC16_MM.
	case Mips::JR:
	case Mips::PseudoReturn:
	case Mips::PseudoIndirectBranch:
	canUseShortMicroMipsCTI = true;
	break;
	}
	}

	// MIPSR6 forbids both operands being the zero register.
	if (Subtarget.hasMips32r6() && (I->getNumOperands() > 1) &&
	(I->getOperand(0).isReg() &&
	(I->getOperand(0).getReg() == Mips::ZERO \|\|
	I->getOperand(0).getReg() == Mips::ZERO_64)) &&
	(I->getOperand(1).isReg() &&
	(I->getOperand(1).getReg() == Mips::ZERO \|\|
	I->getOperand(1).getReg() == Mips::ZERO_64)))
	return 0;

	if (Subtarget.hasMips32r6() \|\| canUseShortMicroMipsCTI) {
	switch (Opcode) {
	case Mips::B:
	return Mips::BC;
	case Mips::BAL:
	return Mips::BALC;
	case Mips::BEQ:
	case Mips::BEQ_MM:
	if (canUseShortMicroMipsCTI)
	return Mips::BEQZC_MM;
	else if (I->getOperand(0).getReg() == I->getOperand(1).getReg())
	return 0;
	return Mips::BEQC;
	case Mips::BNE:
	case Mips::BNE_MM:
	if (canUseShortMicroMipsCTI)
	return Mips::BNEZC_MM;
	else if (I->getOperand(0).getReg() == I->getOperand(1).getReg())
	return 0;
	return Mips::BNEC;
	case Mips::BGE:
	if (I->getOperand(0).getReg() == I->getOperand(1).getReg())
	return 0;
	return Mips::BGEC;
	case Mips::BGEU:
	if (I->getOperand(0).getReg() == I->getOperand(1).getReg())
	return 0;
	return Mips::BGEUC;
	case Mips::BGEZ:
	return Mips::BGEZC;
	case Mips::BGTZ:
	return Mips::BGTZC;
	case Mips::BLEZ:
	return Mips::BLEZC;
	case Mips::BLT:
	if (I->getOperand(0).getReg() == I->getOperand(1).getReg())
	return 0;
	return Mips::BLTC;
	case Mips::BLTU:
	if (I->getOperand(0).getReg() == I->getOperand(1).getReg())
	return 0;
	return Mips::BLTUC;
	case Mips::BLTZ:
	return Mips::BLTZC;
	// For MIPSR6, the instruction 'jic' can be used for these cases. Some
	// tools will accept 'jrc reg' as an alias for 'jic 0, $reg'.
	case Mips::JR:
	case Mips::PseudoReturn:
	case Mips::PseudoIndirectBranch:
	if (canUseShortMicroMipsCTI)
	return Mips::JRC16_MM;
	return Mips::JIC;
	case Mips::JALRPseudo:
	return Mips::JIALC;
	case Mips::JR64:
	case Mips::PseudoReturn64:
	case Mips::PseudoIndirectBranch64:
	return Mips::JIC64;
	case Mips::JALR64Pseudo:
	return Mips::JIALC64;
	default:
	return 0;
	}
	}

	return 0;
	}

	/// Predicate for distingushing between control transfer instructions and all
	/// other instructions for handling forbidden slots. Consider inline assembly
	/// as unsafe as well.
	bool MipsInstrInfo::SafeInForbiddenSlot(const MachineInstr &MI) const {
	if (MI.isInlineAsm())
	return false;

	return (MI.getDesc().TSFlags & MipsII::IsCTI) == 0;

	}

	/// Predicate for distingushing instructions that have forbidden slots.
	bool MipsInstrInfo::HasForbiddenSlot(const MachineInstr &MI) const {
	return (MI.getDesc().TSFlags & MipsII::HasForbiddenSlot) != 0;
	}

	/// Return the number of bytes of code the specified instruction may be.
	unsigned MipsInstrInfo::GetInstSizeInBytes(const MachineInstr &MI) const {
	switch (MI.getOpcode()) {
	default:
	return MI.getDesc().getSize();
	case TargetOpcode::INLINEASM: { // Inline Asm: Variable size.
	const MachineFunction *MF = MI.getParent()->getParent();
	const char *AsmStr = MI.getOperand(0).getSymbolName();
	return getInlineAsmLength(AsmStr, *MF->getTarget().getMCAsmInfo());
	}
	case Mips::CONSTPOOL_ENTRY:
	// If this machine instr is a constant pool entry, its size is recorded as
	// operand #2.
	return MI.getOperand(2).getImm();
	}
	}

	MachineInstrBuilder
	MipsInstrInfo::genInstrWithNewOpc(unsigned NewOpc,
	MachineBasicBlock::iterator I) const {
	MachineInstrBuilder MIB;

	// Certain branches have two forms: e.g beq $1, $zero, dst vs beqz $1, dest
	// Pick the zero form of the branch for readable assembly and for greater
	// branch distance in non-microMIPS mode.
	// FIXME: Certain atomic sequences on mips64 generate 32bit references to
	// Mips::ZERO, which is incorrect. This test should be updated to use
	// Subtarget.getABI().GetZeroReg() when those atomic sequences and others
	// are fixed.
	bool BranchWithZeroOperand =
	(I->isBranch() && !I->isPseudo() && I->getOperand(1).isReg() &&
	(I->getOperand(1).getReg() == Mips::ZERO \|\|
	I->getOperand(1).getReg() == Mips::ZERO_64));

	if (BranchWithZeroOperand) {
	switch (NewOpc) {
	case Mips::BEQC:
	NewOpc = Mips::BEQZC;
	break;
	case Mips::BNEC:
	NewOpc = Mips::BNEZC;
	break;
	case Mips::BGEC:
	NewOpc = Mips::BGEZC;
	break;
	case Mips::BLTC:
	NewOpc = Mips::BLTZC;
	break;
	}
	}

	MIB = BuildMI(*I->getParent(), I, I->getDebugLoc(), get(NewOpc));

	// For MIPSR6 JI*C requires an immediate 0 as an operand, JIALC(64) an
	// immediate 0 as an operand and requires the removal of it's %RA<imp-def>
	// implicit operand as copying the implicit operations of the instructio we're
	// looking at will give us the correct flags.
	if (NewOpc == Mips::JIC \|\| NewOpc == Mips::JIALC \|\| NewOpc == Mips::JIC64 \|\|
	NewOpc == Mips::JIALC64) {

	if (NewOpc == Mips::JIALC \|\| NewOpc == Mips::JIALC64)
	MIB->RemoveOperand(0);

	for (unsigned J = 0, E = I->getDesc().getNumOperands(); J < E; ++J) {
	MIB.addOperand(I->getOperand(J));
	}

	MIB.addImm(0);

	} else if (BranchWithZeroOperand) {
	// For MIPSR6 and microMIPS branches with an explicit zero operand, copy
	// everything after the zero.
	MIB.addOperand(I->getOperand(0));

	for (unsigned J = 2, E = I->getDesc().getNumOperands(); J < E; ++J) {
	MIB.addOperand(I->getOperand(J));
	}
	} else {
	// All other cases copy all other operands.
	for (unsigned J = 0, E = I->getDesc().getNumOperands(); J < E; ++J) {
	MIB.addOperand(I->getOperand(J));
	}
	}

	MIB.copyImplicitOps(*I);

	MIB.setMemRefs(I->memoperands_begin(), I->memoperands_end());
	return MIB;
	}