//===-- InstSelectSimple.cpp - A simple instruction selector for x86 ------===// // // This file defines a simple peephole instruction selector for the x86 platform // //===----------------------------------------------------------------------===// #include "X86.h" #include "X86InstrInfo.h" #include "X86InstrBuilder.h" #include "llvm/Function.h" #include "llvm/iTerminators.h" #include "llvm/iOperators.h" #include "llvm/iOther.h" #include "llvm/iPHINode.h" #include "llvm/iMemory.h" #include "llvm/Type.h" #include "llvm/Constants.h" #include "llvm/Pass.h" #include "llvm/CodeGen/MachineFunction.h" #include "llvm/CodeGen/MachineInstrBuilder.h" #include "llvm/Target/TargetMachine.h" #include "llvm/Support/InstVisitor.h" #include "llvm/Target/MRegisterInfo.h" #include using namespace MOTy; // Get Use, Def, UseAndDef namespace { struct ISel : public FunctionPass, InstVisitor { TargetMachine &TM; MachineFunction *F; // The function we are compiling into MachineBasicBlock *BB; // The current MBB we are compiling unsigned CurReg; std::map RegMap; // Mapping between Val's and SSA Regs ISel(TargetMachine &tm) : TM(tm), F(0), BB(0), CurReg(MRegisterInfo::FirstVirtualRegister) {} /// runOnFunction - Top level implementation of instruction selection for /// the entire function. /// bool runOnFunction(Function &Fn) { F = &MachineFunction::construct(&Fn, TM); visit(Fn); RegMap.clear(); F = 0; return false; // We never modify the LLVM itself. } /// visitBasicBlock - This method is called when we are visiting a new basic /// block. This simply creates a new MachineBasicBlock to emit code into /// and adds it to the current MachineFunction. Subsequent visit* for /// instructions will be invoked for all instructions in the basic block. /// void visitBasicBlock(BasicBlock &LLVM_BB) { BB = new MachineBasicBlock(&LLVM_BB); // FIXME: Use the auto-insert form when it's available F->getBasicBlockList().push_back(BB); } // Visitation methods for various instructions. These methods simply emit // fixed X86 code for each instruction. // void visitReturnInst(ReturnInst &RI); void visitBranchInst(BranchInst &BI); // Arithmetic operators void visitSimpleBinary(BinaryOperator &B, unsigned OpcodeClass); void visitAdd(BinaryOperator &B) { visitSimpleBinary(B, 0); } void visitSub(BinaryOperator &B) { visitSimpleBinary(B, 1); } void visitMul(BinaryOperator &B); void visitDiv(BinaryOperator &B) { visitDivRem(B); } void visitRem(BinaryOperator &B) { visitDivRem(B); } void visitDivRem(BinaryOperator &B); // Bitwise operators void visitAnd(BinaryOperator &B) { visitSimpleBinary(B, 2); } void visitOr (BinaryOperator &B) { visitSimpleBinary(B, 3); } void visitXor(BinaryOperator &B) { visitSimpleBinary(B, 4); } // Binary comparison operators void visitSetCCInst(SetCondInst &I, unsigned OpNum); void visitSetEQ(SetCondInst &I) { visitSetCCInst(I, 0); } void visitSetNE(SetCondInst &I) { visitSetCCInst(I, 1); } void visitSetLT(SetCondInst &I) { visitSetCCInst(I, 2); } void visitSetGT(SetCondInst &I) { visitSetCCInst(I, 3); } void visitSetLE(SetCondInst &I) { visitSetCCInst(I, 4); } void visitSetGE(SetCondInst &I) { visitSetCCInst(I, 5); } // Memory Instructions void visitLoadInst(LoadInst &I); void visitStoreInst(StoreInst &I); // Other operators void visitShiftInst(ShiftInst &I); void visitPHINode(PHINode &I); void visitInstruction(Instruction &I) { std::cerr << "Cannot instruction select: " << I; abort(); } /// copyConstantToRegister - Output the instructions required to put the /// specified constant into the specified register. /// void copyConstantToRegister(Constant *C, unsigned Reg); /// getReg - This method turns an LLVM value into a register number. This /// is guaranteed to produce the same register number for a particular value /// every time it is queried. /// unsigned getReg(Value &V) { return getReg(&V); } // Allow references unsigned getReg(Value *V) { unsigned &Reg = RegMap[V]; if (Reg == 0) { Reg = CurReg++; RegMap[V] = Reg; // Add the mapping of regnumber => reg class to MachineFunction F->addRegMap(Reg, TM.getRegisterInfo()->getRegClassForType(V->getType())); } // If this operand is a constant, emit the code to copy the constant into // the register here... // if (Constant *C = dyn_cast(V)) copyConstantToRegister(C, Reg); return Reg; } }; } /// TypeClass - Used by the X86 backend to group LLVM types by their basic X86 /// Representation. /// enum TypeClass { cByte, cShort, cInt, cLong, cFloat, cDouble }; /// getClass - Turn a primitive type into a "class" number which is based on the /// size of the type, and whether or not it is floating point. /// static inline TypeClass getClass(const Type *Ty) { switch (Ty->getPrimitiveID()) { case Type::SByteTyID: case Type::UByteTyID: return cByte; // Byte operands are class #0 case Type::ShortTyID: case Type::UShortTyID: return cShort; // Short operands are class #1 case Type::IntTyID: case Type::UIntTyID: case Type::PointerTyID: return cInt; // Int's and pointers are class #2 case Type::LongTyID: case Type::ULongTyID: return cLong; // Longs are class #3 case Type::FloatTyID: return cFloat; // Float is class #4 case Type::DoubleTyID: return cDouble; // Doubles are class #5 default: assert(0 && "Invalid type to getClass!"); return cByte; // not reached } } /// copyConstantToRegister - Output the instructions required to put the /// specified constant into the specified register. /// void ISel::copyConstantToRegister(Constant *C, unsigned R) { assert (!isa(C) && "Constant expressions not yet handled!\n"); if (C->getType()->isIntegral()) { unsigned Class = getClass(C->getType()); assert(Class != 3 && "Type not handled yet!"); static const unsigned IntegralOpcodeTab[] = { X86::MOVir8, X86::MOVir16, X86::MOVir32 }; if (C->getType()->isSigned()) { ConstantSInt *CSI = cast(C); BuildMI(BB, IntegralOpcodeTab[Class], 1, R).addSImm(CSI->getValue()); } else { ConstantUInt *CUI = cast(C); BuildMI(BB, IntegralOpcodeTab[Class], 1, R).addZImm(CUI->getValue()); } } else { assert(0 && "Type not handled yet!"); } } /// SetCC instructions - Here we just emit boilerplate code to set a byte-sized /// register, then move it to wherever the result should be. /// We handle FP setcc instructions by pushing them, doing a /// compare-and-pop-twice, and then copying the concodes to the main /// processor's concodes (I didn't make this up, it's in the Intel manual) /// void ISel::visitSetCCInst(SetCondInst &I, unsigned OpNum) { // The arguments are already supposed to be of the same type. const Type *CompTy = I.getOperand(0)->getType(); unsigned reg1 = getReg(I.getOperand(0)); unsigned reg2 = getReg(I.getOperand(1)); unsigned Class = getClass(CompTy); switch (Class) { // Emit: cmp , (do the comparison). We can // compare 8-bit with 8-bit, 16-bit with 16-bit, 32-bit with // 32-bit. case cByte: BuildMI (BB, X86::CMPrr8, 2).addReg (reg1).addReg (reg2); break; case cShort: BuildMI (BB, X86::CMPrr16, 2).addReg (reg1).addReg (reg2); break; case cInt: BuildMI (BB, X86::CMPrr32, 2).addReg (reg1).addReg (reg2); break; // Push the variables on the stack with fldl opcodes. // FIXME: assuming var1, var2 are in memory, if not, spill to // stack first case cFloat: // Floats BuildMI (BB, X86::FLDr4, 1, X86::NoReg).addReg (reg1); BuildMI (BB, X86::FLDr4, 1, X86::NoReg).addReg (reg2); break; case cDouble: // Doubles BuildMI (BB, X86::FLDr8, 1, X86::NoReg).addReg (reg1); BuildMI (BB, X86::FLDr8, 1, X86::NoReg).addReg (reg2); break; case cLong: default: visitInstruction(I); } if (CompTy->isFloatingPoint()) { // (Non-trapping) compare and pop twice. BuildMI (BB, X86::FUCOMPP, 0); // Move fp status word (concodes) to ax. BuildMI (BB, X86::FNSTSWr8, 1, X86::AX); // Load real concodes from ax. BuildMI (BB, X86::SAHF, 1).addReg(X86::AH); } // Emit setOp instruction (extract concode; clobbers ax), // using the following mapping: // LLVM -> X86 signed X86 unsigned // ----- ----- ----- // seteq -> sete sete // setne -> setne setne // setlt -> setl setb // setgt -> setg seta // setle -> setle setbe // setge -> setge setae static const unsigned OpcodeTab[2][6] = { {X86::SETEr, X86::SETNEr, X86::SETBr, X86::SETAr, X86::SETBEr, X86::SETAEr}, {X86::SETEr, X86::SETNEr, X86::SETLr, X86::SETGr, X86::SETLEr, X86::SETGEr}, }; BuildMI(BB, OpcodeTab[CompTy->isSigned()][OpNum], 0, X86::AL); // Put it in the result using a move. BuildMI (BB, X86::MOVrr8, 1, getReg(I)).addReg(X86::AL); } /// 'ret' instruction - Here we are interested in meeting the x86 ABI. As such, /// we have the following possibilities: /// /// ret void: No return value, simply emit a 'ret' instruction /// ret sbyte, ubyte : Extend value into EAX and return /// ret short, ushort: Extend value into EAX and return /// ret int, uint : Move value into EAX and return /// ret pointer : Move value into EAX and return /// ret long, ulong : Move value into EAX/EDX and return /// ret float/double : Top of FP stack /// void ISel::visitReturnInst (ReturnInst &I) { if (I.getNumOperands() == 0) { // Emit a 'ret' instruction BuildMI(BB, X86::RET, 0); return; } unsigned val = getReg(I.getOperand(0)); unsigned Class = getClass(I.getOperand(0)->getType()); bool isUnsigned = I.getOperand(0)->getType()->isUnsigned(); switch (Class) { case cByte: // ret sbyte, ubyte: Extend value into EAX and return if (isUnsigned) BuildMI (BB, X86::MOVZXr32r8, 1, X86::EAX).addReg (val); else BuildMI (BB, X86::MOVSXr32r8, 1, X86::EAX).addReg (val); break; case cShort: // ret short, ushort: Extend value into EAX and return if (isUnsigned) BuildMI (BB, X86::MOVZXr32r16, 1, X86::EAX).addReg (val); else BuildMI (BB, X86::MOVSXr32r16, 1, X86::EAX).addReg (val); break; case cInt: // ret int, uint, ptr: Move value into EAX and return // MOV EAX, BuildMI(BB, X86::MOVrr32, 1, X86::EAX).addReg(val); break; // ret float/double: top of FP stack // FLD case cFloat: // Floats BuildMI(BB, X86::FLDr4, 1).addReg(val); break; case cDouble: // Doubles BuildMI(BB, X86::FLDr8, 1).addReg(val); break; case cLong: // ret long: use EAX(least significant 32 bits)/EDX (most // significant 32)...uh, I think so Brain, but how do i call // up the two parts of the value from inside this mouse // cage? *zort* default: visitInstruction(I); } // Emit a 'ret' instruction BuildMI(BB, X86::RET, 0); } /// visitBranchInst - Handle conditional and unconditional branches here. Note /// that since code layout is frozen at this point, that if we are trying to /// jump to a block that is the immediate successor of the current block, we can /// just make a fall-through. (but we don't currently). /// void ISel::visitBranchInst (BranchInst & BI) { if (BI.isConditional ()) { BasicBlock *ifTrue = BI.getSuccessor (0); BasicBlock *ifFalse = BI.getSuccessor (1); // this is really unobvious // simplest thing I can think of: compare condition with zero, // followed by jump-if-equal to ifFalse, and jump-if-nonequal to // ifTrue unsigned int condReg = getReg (BI.getCondition ()); BuildMI (BB, X86::CMPri8, 2).addReg (condReg).addZImm (0); BuildMI (BB, X86::JNE, 1).addPCDisp (BI.getSuccessor (0)); BuildMI (BB, X86::JE, 1).addPCDisp (BI.getSuccessor (1)); } else // unconditional branch { BuildMI (BB, X86::JMP, 1).addPCDisp (BI.getSuccessor (0)); } } /// visitSimpleBinary - Implement simple binary operators for integral types... /// OperatorClass is one of: 0 for Add, 1 for Sub, 2 for And, 3 for Or, /// 4 for Xor. /// void ISel::visitSimpleBinary(BinaryOperator &B, unsigned OperatorClass) { if (B.getType() == Type::BoolTy) // FIXME: Handle bools for logicals visitInstruction(B); unsigned Class = getClass(B.getType()); if (Class > 2) // FIXME: Handle longs visitInstruction(B); static const unsigned OpcodeTab[][4] = { // Arithmetic operators { X86::ADDrr8, X86::ADDrr16, X86::ADDrr32, 0 }, // ADD { X86::SUBrr8, X86::SUBrr16, X86::SUBrr32, 0 }, // SUB // Bitwise operators { X86::ANDrr8, X86::ANDrr16, X86::ANDrr32, 0 }, // AND { X86:: ORrr8, X86:: ORrr16, X86:: ORrr32, 0 }, // OR { X86::XORrr8, X86::XORrr16, X86::XORrr32, 0 }, // XOR }; unsigned Opcode = OpcodeTab[OperatorClass][Class]; unsigned Op0r = getReg(B.getOperand(0)); unsigned Op1r = getReg(B.getOperand(1)); BuildMI(BB, Opcode, 2, getReg(B)).addReg(Op0r).addReg(Op1r); } /// visitMul - Multiplies are not simple binary operators because they must deal /// with the EAX register explicitly. /// void ISel::visitMul(BinaryOperator &I) { unsigned Class = getClass(I.getType()); if (Class > 2) // FIXME: Handle longs visitInstruction(I); static const unsigned Regs[] ={ X86::AL , X86::AX , X86::EAX }; static const unsigned Clobbers[] ={ X86::AH , X86::DX , X86::EDX }; static const unsigned MulOpcode[]={ X86::MULrr8, X86::MULrr16, X86::MULrr32 }; static const unsigned MovOpcode[]={ X86::MOVrr8, X86::MOVrr16, X86::MOVrr32 }; unsigned Reg = Regs[Class]; unsigned Clobber = Clobbers[Class]; unsigned Op0Reg = getReg(I.getOperand(0)); unsigned Op1Reg = getReg(I.getOperand(1)); // Put the first operand into one of the A registers... BuildMI(BB, MovOpcode[Class], 1, Reg).addReg(Op0Reg); // Emit the appropriate multiply instruction... BuildMI(BB, MulOpcode[Class], 3) .addReg(Reg, UseAndDef).addReg(Op1Reg).addClobber(Clobber); // Put the result into the destination register... BuildMI(BB, MovOpcode[Class], 1, getReg(I)).addReg(Reg); } /// visitDivRem - Handle division and remainder instructions... these /// instruction both require the same instructions to be generated, they just /// select the result from a different register. Note that both of these /// instructions work differently for signed and unsigned operands. /// void ISel::visitDivRem(BinaryOperator &I) { unsigned Class = getClass(I.getType()); if (Class > 2) // FIXME: Handle longs visitInstruction(I); static const unsigned Regs[] ={ X86::AL , X86::AX , X86::EAX }; static const unsigned MovOpcode[]={ X86::MOVrr8, X86::MOVrr16, X86::MOVrr32 }; static const unsigned ExtOpcode[]={ X86::CBW , X86::CWD , X86::CDQ }; static const unsigned ClrOpcode[]={ X86::XORrr8, X86::XORrr16, X86::XORrr32 }; static const unsigned ExtRegs[] ={ X86::AH , X86::DX , X86::EDX }; static const unsigned DivOpcode[][4] = { { X86::DIVrr8 , X86::DIVrr16 , X86::DIVrr32 , 0 }, // Unsigned division { X86::IDIVrr8, X86::IDIVrr16, X86::IDIVrr32, 0 }, // Signed division }; bool isSigned = I.getType()->isSigned(); unsigned Reg = Regs[Class]; unsigned ExtReg = ExtRegs[Class]; unsigned Op0Reg = getReg(I.getOperand(0)); unsigned Op1Reg = getReg(I.getOperand(1)); // Put the first operand into one of the A registers... BuildMI(BB, MovOpcode[Class], 1, Reg).addReg(Op0Reg); if (isSigned) { // Emit a sign extension instruction... BuildMI(BB, ExtOpcode[Class], 1, ExtReg).addReg(Reg); } else { // If unsigned, emit a zeroing instruction... (reg = xor reg, reg) BuildMI(BB, ClrOpcode[Class], 2, ExtReg).addReg(ExtReg).addReg(ExtReg); } // Emit the appropriate divide or remainder instruction... BuildMI(BB, DivOpcode[isSigned][Class], 2) .addReg(Reg, UseAndDef).addReg(ExtReg, UseAndDef).addReg(Op1Reg); // Figure out which register we want to pick the result out of... unsigned DestReg = (I.getOpcode() == Instruction::Div) ? Reg : ExtReg; // Put the result into the destination register... BuildMI(BB, MovOpcode[Class], 1, getReg(I)).addReg(DestReg); } /// Shift instructions: 'shl', 'sar', 'shr' - Some special cases here /// for constant immediate shift values, and for constant immediate /// shift values equal to 1. Even the general case is sort of special, /// because the shift amount has to be in CL, not just any old register. /// void ISel::visitShiftInst (ShiftInst &I) { unsigned Op0r = getReg (I.getOperand(0)); unsigned DestReg = getReg(I); bool isLeftShift = I.getOpcode() == Instruction::Shl; bool isOperandSigned = I.getType()->isUnsigned(); unsigned OperandClass = getClass(I.getType()); if (OperandClass > 2) visitInstruction(I); // Can't handle longs yet! if (ConstantUInt *CUI = dyn_cast (I.getOperand (1))) { // The shift amount is constant, guaranteed to be a ubyte. Get its value. assert(CUI->getType() == Type::UByteTy && "Shift amount not a ubyte?"); unsigned char shAmt = CUI->getValue(); static const unsigned ConstantOperand[][4] = { { X86::SHRir8, X86::SHRir16, X86::SHRir32, 0 }, // SHR { X86::SARir8, X86::SARir16, X86::SARir32, 0 }, // SAR { X86::SHLir8, X86::SHLir16, X86::SHLir32, 0 }, // SHL { X86::SHLir8, X86::SHLir16, X86::SHLir32, 0 }, // SAL = SHL }; const unsigned *OpTab = // Figure out the operand table to use ConstantOperand[isLeftShift*2+isOperandSigned]; // Emit: reg, shamt (shift-by-immediate opcode "ir" form.) BuildMI(BB, OpTab[OperandClass], 2, DestReg).addReg(Op0r).addZImm(shAmt); } else { // The shift amount is non-constant. // // In fact, you can only shift with a variable shift amount if // that amount is already in the CL register, so we have to put it // there first. // // Emit: move cl, shiftAmount (put the shift amount in CL.) BuildMI(BB, X86::MOVrr8, 1, X86::CL).addReg(getReg(I.getOperand(1))); // This is a shift right (SHR). static const unsigned NonConstantOperand[][4] = { { X86::SHRrr8, X86::SHRrr16, X86::SHRrr32, 0 }, // SHR { X86::SARrr8, X86::SARrr16, X86::SARrr32, 0 }, // SAR { X86::SHLrr8, X86::SHLrr16, X86::SHLrr32, 0 }, // SHL { X86::SHLrr8, X86::SHLrr16, X86::SHLrr32, 0 }, // SAL = SHL }; const unsigned *OpTab = // Figure out the operand table to use NonConstantOperand[isLeftShift*2+isOperandSigned]; BuildMI(BB, OpTab[OperandClass], 2, DestReg).addReg(Op0r).addReg(X86::CL); } } /// visitLoadInst - Implement LLVM load instructions in terms of the x86 'mov' /// instruction. /// void ISel::visitLoadInst(LoadInst &I) { unsigned Class = getClass(I.getType()); if (Class > 2) // FIXME: Handle longs and others... visitInstruction(I); static const unsigned Opcode[] = { X86::MOVmr8, X86::MOVmr16, X86::MOVmr32 }; unsigned AddressReg = getReg(I.getOperand(0)); addDirectMem(BuildMI(BB, Opcode[Class], 4, getReg(I)), AddressReg); } /// visitStoreInst - Implement LLVM store instructions in terms of the x86 'mov' /// instruction. /// void ISel::visitStoreInst(StoreInst &I) { unsigned Class = getClass(I.getOperand(0)->getType()); if (Class > 2) // FIXME: Handle longs and others... visitInstruction(I); static const unsigned Opcode[] = { X86::MOVrm8, X86::MOVrm16, X86::MOVrm32 }; unsigned ValReg = getReg(I.getOperand(0)); unsigned AddressReg = getReg(I.getOperand(1)); addDirectMem(BuildMI(BB, Opcode[Class], 1+4), AddressReg).addReg(ValReg); } /// visitPHINode - Turn an LLVM PHI node into an X86 PHI node... /// void ISel::visitPHINode(PHINode &PN) { MachineInstr *MI = BuildMI(BB, X86::PHI, PN.getNumOperands(), getReg(PN)); for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) { // FIXME: This will put constants after the PHI nodes in the block, which // is invalid. They should be put inline into the PHI node eventually. // MI->addRegOperand(getReg(PN.getIncomingValue(i))); MI->addPCDispOperand(PN.getIncomingBlock(i)); } } /// createSimpleX86InstructionSelector - This pass converts an LLVM function /// into a machine code representation is a very simple peep-hole fashion. The /// generated code sucks but the implementation is nice and simple. /// Pass *createSimpleX86InstructionSelector(TargetMachine &TM) { return new ISel(TM); }