| //===-- PrologEpilogInserter.cpp - Insert Prolog/Epilog code in function --===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This pass is responsible for finalizing the functions frame layout, saving |
| // callee saved registers, and for emitting prolog & epilog code for the |
| // function. |
| // |
| // This pass must be run after register allocation. After this pass is |
| // executed, it is illegal to construct MO_FrameIndex operands. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/CodeGen/Passes.h" |
| #include "llvm/CodeGen/MachineFunctionPass.h" |
| #include "llvm/CodeGen/MachineInstr.h" |
| #include "llvm/CodeGen/MachineFrameInfo.h" |
| #include "llvm/Target/TargetMachine.h" |
| #include "llvm/Target/MRegisterInfo.h" |
| #include "llvm/Target/TargetFrameInfo.h" |
| #include "llvm/Target/TargetInstrInfo.h" |
| |
| namespace { |
| struct PEI : public MachineFunctionPass { |
| const char *getPassName() const { |
| return "Prolog/Epilog Insertion & Frame Finalization"; |
| } |
| |
| /// runOnMachineFunction - Insert prolog/epilog code and replace abstract |
| /// frame indexes with appropriate references. |
| /// |
| bool runOnMachineFunction(MachineFunction &Fn) { |
| // Scan the function for modified caller saved registers and insert spill |
| // code for any caller saved registers that are modified. Also calculate |
| // the MaxCallFrameSize and HasCalls variables for the function's frame |
| // information and eliminates call frame pseudo instructions. |
| saveCallerSavedRegisters(Fn); |
| |
| // Allow the target machine to make final modifications to the function |
| // before the frame layout is finalized. |
| Fn.getTarget().getRegisterInfo()->processFunctionBeforeFrameFinalized(Fn); |
| |
| // Calculate actual frame offsets for all of the abstract stack objects... |
| calculateFrameObjectOffsets(Fn); |
| |
| // Add prolog and epilog code to the function. |
| insertPrologEpilogCode(Fn); |
| |
| // Replace all MO_FrameIndex operands with physical register references |
| // and actual offsets. |
| // |
| replaceFrameIndices(Fn); |
| return true; |
| } |
| |
| private: |
| void saveCallerSavedRegisters(MachineFunction &Fn); |
| void calculateFrameObjectOffsets(MachineFunction &Fn); |
| void replaceFrameIndices(MachineFunction &Fn); |
| void insertPrologEpilogCode(MachineFunction &Fn); |
| }; |
| } |
| |
| /// createPrologEpilogCodeInserter - This function returns a pass that inserts |
| /// prolog and epilog code, and eliminates abstract frame references. |
| /// |
| FunctionPass *createPrologEpilogCodeInserter() { return new PEI(); } |
| |
| |
| /// saveCallerSavedRegisters - Scan the function for modified caller saved |
| /// registers and insert spill code for any caller saved registers that are |
| /// modified. Also calculate the MaxCallFrameSize and HasCalls variables for |
| /// the function's frame information and eliminates call frame pseudo |
| /// instructions. |
| /// |
| void PEI::saveCallerSavedRegisters(MachineFunction &Fn) { |
| const MRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo(); |
| const TargetFrameInfo &FrameInfo = Fn.getTarget().getFrameInfo(); |
| |
| // Get the callee saved register list... |
| const unsigned *CSRegs = RegInfo->getCalleeSaveRegs(); |
| |
| // Get the function call frame set-up and tear-down instruction opcode |
| int FrameSetupOpcode = RegInfo->getCallFrameSetupOpcode(); |
| int FrameDestroyOpcode = RegInfo->getCallFrameDestroyOpcode(); |
| |
| // Early exit for targets which have no callee saved registers and no call |
| // frame setup/destroy pseudo instructions. |
| if ((CSRegs == 0 || CSRegs[0] == 0) && |
| FrameSetupOpcode == -1 && FrameDestroyOpcode == -1) |
| return; |
| |
| // This bitset contains an entry for each physical register for the target... |
| std::vector<bool> ModifiedRegs(MRegisterInfo::FirstVirtualRegister); |
| unsigned MaxCallFrameSize = 0; |
| bool HasCalls = false; |
| |
| for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) |
| for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) |
| if ((*I)->getOpcode() == FrameSetupOpcode || |
| (*I)->getOpcode() == FrameDestroyOpcode) { |
| assert((*I)->getNumOperands() == 1 && "Call Frame Setup/Destroy Pseudo" |
| " instructions should have a single immediate argument!"); |
| unsigned Size = (*I)->getOperand(0).getImmedValue(); |
| if (Size > MaxCallFrameSize) MaxCallFrameSize = Size; |
| HasCalls = true; |
| RegInfo->eliminateCallFramePseudoInstr(Fn, *BB, I); |
| } else { |
| for (unsigned i = 0, e = (*I)->getNumOperands(); i != e; ++i) { |
| MachineOperand &MO = (*I)->getOperand(i); |
| assert(!MO.isVirtualRegister() && |
| "Register allocation must be performed!"); |
| if (MO.isPhysicalRegister() && |
| (MO.opIsDefOnly() || MO.opIsDefAndUse())) |
| ModifiedRegs[MO.getReg()] = true; // Register is modified |
| } |
| ++I; |
| } |
| |
| MachineFrameInfo *FFI = Fn.getFrameInfo(); |
| FFI->setHasCalls(HasCalls); |
| FFI->setMaxCallFrameSize(MaxCallFrameSize); |
| |
| // Now figure out which *callee saved* registers are modified by the current |
| // function, thus needing to be saved and restored in the prolog/epilog. |
| // |
| std::vector<unsigned> RegsToSave; |
| for (unsigned i = 0; CSRegs[i]; ++i) { |
| unsigned Reg = CSRegs[i]; |
| if (ModifiedRegs[Reg]) { |
| RegsToSave.push_back(Reg); // If modified register... |
| } else { |
| for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg); |
| *AliasSet; ++AliasSet) { // Check alias registers too... |
| if (ModifiedRegs[*AliasSet]) { |
| RegsToSave.push_back(Reg); |
| break; |
| } |
| } |
| } |
| } |
| |
| if (RegsToSave.empty()) |
| return; // Early exit if no caller saved registers are modified! |
| |
| // Now that we know which registers need to be saved and restored, allocate |
| // stack slots for them. |
| std::vector<int> StackSlots; |
| for (unsigned i = 0, e = RegsToSave.size(); i != e; ++i) { |
| int FrameIdx = FFI->CreateStackObject(RegInfo->getRegClass(RegsToSave[i])); |
| StackSlots.push_back(FrameIdx); |
| } |
| |
| // Now that we have a stack slot for each register to be saved, insert spill |
| // code into the entry block... |
| MachineBasicBlock *MBB = Fn.begin(); |
| MachineBasicBlock::iterator I = MBB->begin(); |
| for (unsigned i = 0, e = RegsToSave.size(); i != e; ++i) { |
| const TargetRegisterClass *RC = RegInfo->getRegClass(RegsToSave[i]); |
| |
| // Insert the spill to the stack frame... |
| RegInfo->storeRegToStackSlot(*MBB, I, RegsToSave[i], StackSlots[i], RC); |
| } |
| |
| // Add code to restore the callee-save registers in each exiting block. |
| const TargetInstrInfo &TII = Fn.getTarget().getInstrInfo(); |
| for (MachineFunction::iterator FI = Fn.begin(), E = Fn.end(); FI != E; ++FI) { |
| // If last instruction is a return instruction, add an epilogue |
| if (!FI->empty() && TII.isReturn(FI->back()->getOpcode())) { |
| MBB = FI; I = MBB->end()-1; |
| |
| for (unsigned i = 0, e = RegsToSave.size(); i != e; ++i) { |
| const TargetRegisterClass *RC = RegInfo->getRegClass(RegsToSave[i]); |
| RegInfo->loadRegFromStackSlot(*MBB, I, RegsToSave[i],StackSlots[i], RC); |
| --I; // Insert in reverse order |
| } |
| } |
| } |
| } |
| |
| |
| /// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the |
| /// abstract stack objects... |
| /// |
| void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) { |
| const TargetFrameInfo &TFI = Fn.getTarget().getFrameInfo(); |
| |
| bool StackGrowsDown = |
| TFI.getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown; |
| assert(StackGrowsDown && "Only tested on stack down growing targets!"); |
| |
| // Loop over all of the stack objects, assigning sequential addresses... |
| MachineFrameInfo *FFI = Fn.getFrameInfo(); |
| |
| unsigned StackAlignment = TFI.getStackAlignment(); |
| |
| // Start at the beginning of the local area... |
| int Offset = TFI.getOffsetOfLocalArea(); |
| for (unsigned i = 0, e = FFI->getObjectIndexEnd(); i != e; ++i) { |
| Offset += FFI->getObjectSize(i); // Allocate Size bytes... |
| |
| unsigned Align = FFI->getObjectAlignment(i); |
| assert(Align <= StackAlignment && "Cannot align stack object to higher " |
| "alignment boundary than the stack itself!"); |
| Offset = (Offset+Align-1)/Align*Align; // Adjust to Alignment boundary... |
| |
| FFI->setObjectOffset(i, -Offset); // Set the computed offset |
| } |
| |
| // Align the final stack pointer offset... |
| Offset = (Offset+StackAlignment-1)/StackAlignment*StackAlignment; |
| |
| // Set the final value of the stack pointer... |
| FFI->setStackSize(Offset-TFI.getOffsetOfLocalArea()); |
| } |
| |
| |
| /// insertPrologEpilogCode - Scan the function for modified caller saved |
| /// registers, insert spill code for these caller saved registers, then add |
| /// prolog and epilog code to the function. |
| /// |
| void PEI::insertPrologEpilogCode(MachineFunction &Fn) { |
| // Add prologue to the function... |
| Fn.getTarget().getRegisterInfo()->emitPrologue(Fn); |
| |
| // Add epilogue to restore the callee-save registers in each exiting block |
| const TargetInstrInfo &TII = Fn.getTarget().getInstrInfo(); |
| for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) { |
| // If last instruction is a return instruction, add an epilogue |
| if (!I->empty() && TII.isReturn(I->back()->getOpcode())) |
| Fn.getTarget().getRegisterInfo()->emitEpilogue(Fn, *I); |
| } |
| } |
| |
| |
| /// replaceFrameIndices - Replace all MO_FrameIndex operands with physical |
| /// register references and actual offsets. |
| /// |
| void PEI::replaceFrameIndices(MachineFunction &Fn) { |
| if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do? |
| |
| const TargetMachine &TM = Fn.getTarget(); |
| assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!"); |
| const MRegisterInfo &MRI = *TM.getRegisterInfo(); |
| |
| for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) |
| for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) |
| for (unsigned i = 0, e = (*I)->getNumOperands(); i != e; ++i) |
| if ((*I)->getOperand(i).isFrameIndex()) { |
| // If this instruction has a FrameIndex operand, we need to use that |
| // target machine register info object to eliminate it. |
| MRI.eliminateFrameIndex(Fn, I); |
| break; |
| } |
| } |