//===- X86RegisterInfo.cpp - X86 Register Information -----------*- C++ -*-===// // // This file contains the X86 implementation of the MRegisterInfo class. This // file is responsible for the frame pointer elimination optimization on X86. // //===----------------------------------------------------------------------===// #include "X86.h" #include "X86RegisterInfo.h" #include "X86InstrBuilder.h" #include "llvm/Constants.h" #include "llvm/Type.h" #include "llvm/CodeGen/MachineInstrBuilder.h" #include "llvm/CodeGen/MachineFunction.h" #include "llvm/CodeGen/MachineFrameInfo.h" #include "llvm/Target/TargetMachine.h" #include "llvm/Target/TargetFrameInfo.h" #include "Support/CommandLine.h" namespace { cl::opt NoFPElim("no-fp-elim", cl::desc("Disable frame pointer elimination optimization")); } static unsigned getIdx(const TargetRegisterClass *RC) { switch (RC->getSize()) { default: assert(0 && "Invalid data size!"); case 1: return 0; case 2: return 1; case 4: return 2; case 10: return 3; } } void X86RegisterInfo::storeRegToStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI, unsigned SrcReg, int FrameIdx, const TargetRegisterClass *RC) const { static const unsigned Opcode[] = { X86::MOVrm8, X86::MOVrm16, X86::MOVrm32, X86::FSTPr80 }; MachineInstr *MI = addFrameReference(BuildMI(Opcode[getIdx(RC)], 5), FrameIdx).addReg(SrcReg); MBBI = MBB.insert(MBBI, MI)+1; } void X86RegisterInfo::loadRegFromStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI, unsigned DestReg, int FrameIdx, const TargetRegisterClass *RC) const{ static const unsigned Opcode[] = { X86::MOVmr8, X86::MOVmr16, X86::MOVmr32, X86::FLDr80 }; MachineInstr *MI = addFrameReference(BuildMI(Opcode[getIdx(RC)], 4, DestReg), FrameIdx); MBBI = MBB.insert(MBBI, MI)+1; } void X86RegisterInfo::copyRegToReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI, unsigned DestReg, unsigned SrcReg, const TargetRegisterClass *RC) const { static const unsigned Opcode[] = { X86::MOVrr8, X86::MOVrr16, X86::MOVrr32, X86::FpMOV }; MachineInstr *MI = BuildMI(Opcode[getIdx(RC)],1,DestReg).addReg(SrcReg); MBBI = MBB.insert(MBBI, MI)+1; } const unsigned* X86RegisterInfo::getCalleeSaveRegs() const { static const unsigned CalleeSaveRegs[] = { X86::ESI, X86::EDI, X86::EBX, X86::EBP, 0 }; return CalleeSaveRegs; } //===----------------------------------------------------------------------===// // Stack Frame Processing methods //===----------------------------------------------------------------------===// // hasFP - Return true if the specified function should have a dedicated frame // pointer register. This is true if the function has variable sized allocas or // if frame pointer elimination is disabled. // static bool hasFP(MachineFunction &MF) { return NoFPElim || MF.getFrameInfo()->hasVarSizedObjects(); } // hasSPAdjust - Return true if this function has ESP adjustment instructions in // the prolog and epilog which allocate local stack space. This is neccesary // because we elide these instructions if there are no function calls in the // current function (ie, this is a leaf function). In this case, we can refer // beyond the stack pointer because we know that nothing will trample on that // part of the stack. // static bool hasSPAdjust(MachineFunction &MF) { assert(!hasFP(MF) && "Can only eliminate SP adjustment if no frame-pointer!"); return MF.getFrameInfo()->hasCalls(); } void X86RegisterInfo::eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB, MachineBasicBlock::iterator &I) const { MachineInstr *New = 0, *Old = *I;; if (hasFP(MF)) { // If we have a frame pointer, turn the adjcallstackup instruction into a // 'sub ESP, ' and the adjcallstackdown instruction into 'add ESP, // ' unsigned Amount = Old->getOperand(0).getImmedValue(); if (Amount != 0) { // We need to keep the stack aligned properly. To do this, we round the // amount of space needed for the outgoing arguments up to the next // alignment boundary. unsigned Align = MF.getTarget().getFrameInfo().getStackAlignment(); Amount = (Amount+Align-1)/Align*Align; if (Old->getOpcode() == X86::ADJCALLSTACKDOWN) { New=BuildMI(X86::SUBri32, 2, X86::ESP).addReg(X86::ESP).addZImm(Amount); } else { assert(Old->getOpcode() == X86::ADJCALLSTACKUP); New=BuildMI(X86::ADDri32, 2, X86::ESP).addReg(X86::ESP).addZImm(Amount); } } } if (New) *I = New; // Replace the pseudo instruction with a new instruction... else I = MBB.erase(I);// Just delete the pseudo instruction... delete Old; } void X86RegisterInfo::eliminateFrameIndex(MachineFunction &MF, MachineBasicBlock::iterator &II) const { unsigned i = 0; MachineInstr &MI = **II; while (!MI.getOperand(i).isFrameIndex()) { ++i; assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!"); } int FrameIndex = MI.getOperand(i).getFrameIndex(); // This must be part of a four operand memory reference. Replace the // FrameIndex with base register with EBP. Add add an offset to the offset. MI.SetMachineOperandReg(i, hasFP(MF) ? X86::EBP : X86::ESP); // Now add the frame object offset to the offset from EBP. int Offset = MF.getFrameInfo()->getObjectOffset(FrameIndex) + MI.getOperand(i+3).getImmedValue()+4; if (!hasFP(MF) && hasSPAdjust(MF)) { const MachineFrameInfo *MFI = MF.getFrameInfo(); Offset += MFI->getStackSize(); } MI.SetMachineOperandConst(i+3, MachineOperand::MO_SignExtendedImmed, Offset); } void X86RegisterInfo::processFunctionBeforeFrameFinalized(MachineFunction &MF) const { if (hasFP(MF)) { // Create a frame entry for the EBP register that must be saved. int FrameIdx = MF.getFrameInfo()->CreateStackObject(4, 4); assert(FrameIdx == MF.getFrameInfo()->getObjectIndexEnd()-1 && "Slot for EBP register must be last in order to be found!"); } } void X86RegisterInfo::emitPrologue(MachineFunction &MF) const { MachineBasicBlock &MBB = MF.front(); // Prolog goes in entry BB MachineBasicBlock::iterator MBBI = MBB.begin(); MachineFrameInfo *MFI = MF.getFrameInfo(); MachineInstr *MI; // Get the number of bytes to allocate from the FrameInfo unsigned NumBytes = MFI->getStackSize(); if (hasFP(MF)) { // Get the offset of the stack slot for the EBP register... which is // guaranteed to be the last slot by processFunctionBeforeFrameFinalized. int EBPOffset = MFI->getObjectOffset(MFI->getObjectIndexEnd()-1)+4; MI = addRegOffset(BuildMI(X86::MOVrm32, 5), // mov [ESP-], EBP X86::ESP, EBPOffset).addReg(X86::EBP); MBBI = MBB.insert(MBBI, MI)+1; MI = BuildMI(X86::MOVrr32, 2, X86::EBP).addReg(X86::ESP); MBBI = MBB.insert(MBBI, MI)+1; } else { // If we don't have a frame pointer, and the function contains no call sites // (it's a leaf function), we don't have to emit ANY stack adjustment // instructions at all, we can just refer to the area beyond the stack // pointer. This can be important for small functions. // if (!hasSPAdjust(MF)) return; // When we have no frame pointer, we reserve argument space for call sites // in the function immediately on entry to the current function. This // eliminates the need for add/sub ESP brackets around call sites. // NumBytes += MFI->getMaxCallFrameSize(); // Round the size to a multiple of the alignment (don't forget the 4 byte // offset though). unsigned Align = MF.getTarget().getFrameInfo().getStackAlignment(); NumBytes = ((NumBytes+4)+Align-1)/Align*Align - 4; // Update frame info to pretend that this is part of the stack... MFI->setStackSize(NumBytes); } if (NumBytes) { // adjust stack pointer: ESP -= numbytes MI = BuildMI(X86::SUBri32, 2, X86::ESP).addReg(X86::ESP).addZImm(NumBytes); MBBI = 1+MBB.insert(MBBI, MI); } } void X86RegisterInfo::emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const { const MachineFrameInfo *MFI = MF.getFrameInfo(); MachineBasicBlock::iterator MBBI = MBB.end()-1; MachineInstr *MI; assert((*MBBI)->getOpcode() == X86::RET && "Can only insert epilog into returning blocks"); if (hasFP(MF)) { // Get the offset of the stack slot for the EBP register... which is // guaranteed to be the last slot by processFunctionBeforeFrameFinalized. int EBPOffset = MFI->getObjectOffset(MFI->getObjectIndexEnd()-1)+4; // mov ESP, EBP MI = BuildMI(X86::MOVrr32, 1,X86::ESP).addReg(X86::EBP); MBBI = 1+MBB.insert(MBBI, MI); // mov EBP, [ESP-] MI = addRegOffset(BuildMI(X86::MOVmr32, 5, X86::EBP), X86::ESP, EBPOffset); MBBI = 1+MBB.insert(MBBI, MI); } else { if (!hasSPAdjust(MF)) return; // Get the number of bytes allocated from the FrameInfo... unsigned NumBytes = MFI->getStackSize(); if (NumBytes) { // adjust stack pointer back: ESP += numbytes MI =BuildMI(X86::ADDri32, 2, X86::ESP).addReg(X86::ESP).addZImm(NumBytes); MBBI = 1+MBB.insert(MBBI, MI); } } } //===----------------------------------------------------------------------===// // Register Class Implementation Code //===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===// // 8 Bit Integer Registers // namespace { const unsigned ByteRegClassRegs[] = { X86::AL, X86::CL, X86::DL, X86::BL, X86::AH, X86::CH, X86::DH, X86::BH, }; TargetRegisterClass X86ByteRegisterClassInstance(1, 1, ByteRegClassRegs, ByteRegClassRegs+sizeof(ByteRegClassRegs)/sizeof(ByteRegClassRegs[0])); //===----------------------------------------------------------------------===// // 16 Bit Integer Registers // const unsigned ShortRegClassRegs[] = { X86::AX, X86::CX, X86::DX, X86::BX, X86::SI, X86::DI, X86::BP, X86::SP }; struct R16CL : public TargetRegisterClass { R16CL():TargetRegisterClass(2, 2, ShortRegClassRegs, ShortRegClassRegs+8) {} iterator allocation_order_end(MachineFunction &MF) const { if (hasFP(MF)) // Does the function dedicate EBP to being a frame ptr? return end()-2; // Don't allocate SP or BP else return end()-1; // Don't allocate SP } } X86ShortRegisterClassInstance; //===----------------------------------------------------------------------===// // 32 Bit Integer Registers // const unsigned IntRegClassRegs[] = { X86::EAX, X86::ECX, X86::EDX, X86::EBX, X86::ESI, X86::EDI, X86::EBP, X86::ESP }; struct R32CL : public TargetRegisterClass { R32CL() : TargetRegisterClass(4, 4, IntRegClassRegs, IntRegClassRegs+8) {} iterator allocation_order_end(MachineFunction &MF) const { if (hasFP(MF)) // Does the function dedicate EBP to being a frame ptr? return end()-2; // Don't allocate ESP or EBP else return end()-1; // Don't allocate ESP } } X86IntRegisterClassInstance; //===----------------------------------------------------------------------===// // Pseudo Floating Point Registers // const unsigned PFPRegClassRegs[] = { #define PFP(ENUM, NAME, FLAGS, TSFLAGS, ALIAS_SET) X86::ENUM, #include "X86RegisterInfo.def" }; TargetRegisterClass X86FPRegisterClassInstance(10, 4, PFPRegClassRegs, PFPRegClassRegs+sizeof(PFPRegClassRegs)/sizeof(PFPRegClassRegs[0])); //===----------------------------------------------------------------------===// // Register class array... // const TargetRegisterClass * const X86RegClasses[] = { &X86ByteRegisterClassInstance, &X86ShortRegisterClassInstance, &X86IntRegisterClassInstance, &X86FPRegisterClassInstance, }; } // Create static lists to contain register alias sets... #define ALIASLIST(NAME, ...) \ static const unsigned NAME[] = { __VA_ARGS__ }; #include "X86RegisterInfo.def" // X86Regs - Turn the X86RegisterInfo.def file into a bunch of register // descriptors // static const MRegisterDesc X86Regs[] = { #define R(ENUM, NAME, FLAGS, TSFLAGS, ALIAS_SET) \ { NAME, ALIAS_SET, FLAGS, TSFLAGS }, #include "X86RegisterInfo.def" }; X86RegisterInfo::X86RegisterInfo() : MRegisterInfo(X86Regs, sizeof(X86Regs)/sizeof(X86Regs[0]), X86RegClasses, X86RegClasses+sizeof(X86RegClasses)/sizeof(X86RegClasses[0]), X86::ADJCALLSTACKDOWN, X86::ADJCALLSTACKUP) { } const TargetRegisterClass* X86RegisterInfo::getRegClassForType(const Type* Ty) const { switch (Ty->getPrimitiveID()) { case Type::LongTyID: case Type::ULongTyID: assert(0 && "Long values can't fit in registers!"); default: assert(0 && "Invalid type to getClass!"); case Type::BoolTyID: case Type::SByteTyID: case Type::UByteTyID: return &X86ByteRegisterClassInstance; case Type::ShortTyID: case Type::UShortTyID: return &X86ShortRegisterClassInstance; case Type::IntTyID: case Type::UIntTyID: case Type::PointerTyID: return &X86IntRegisterClassInstance; case Type::FloatTyID: case Type::DoubleTyID: return &X86FPRegisterClassInstance; } }