mirror of
https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5326 91177308-0d34-0410-b5e6-96231b3b80d8
250 lines
9.7 KiB
C++
250 lines
9.7 KiB
C++
//===-- PrologEpilogInserter.cpp - Insert Prolog/Epilog code in function --===//
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//
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// This pass is responsible for finalizing the functions frame layout, saving
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// callee saved registers, and for emitting prolog & epilog code for the
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// function.
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//
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// This pass must be run after register allocation. After this pass is
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// executed, it is illegal to construct MO_FrameIndex operands.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/MRegisterInfo.h"
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#include "llvm/Target/TargetFrameInfo.h"
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#include "llvm/Target/TargetInstrInfo.h"
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namespace {
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struct PEI : public MachineFunctionPass {
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const char *getPassName() const {
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return "Prolog/Epilog Insertion & Frame Finalization";
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}
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/// runOnMachineFunction - Insert prolog/epilog code and replace abstract
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/// frame indexes with appropriate references.
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///
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bool runOnMachineFunction(MachineFunction &Fn) {
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// Scan the function for modified caller saved registers and insert spill
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// code for any caller saved registers that are modified. Also calculate
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// the MaxCallFrameSize and HasCalls variables for the function's frame
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// information and eliminates call frame pseudo instructions.
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saveCallerSavedRegisters(Fn);
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// Allow the target machine to make final modifications to the function
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// before the frame layout is finalized.
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Fn.getTarget().getRegisterInfo()->processFunctionBeforeFrameFinalized(Fn);
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// Calculate actual frame offsets for all of the abstract stack objects...
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calculateFrameObjectOffsets(Fn);
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// Add prolog and epilog code to the function.
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insertPrologEpilogCode(Fn);
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// Replace all MO_FrameIndex operands with physical register references
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// and actual offsets.
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//
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replaceFrameIndices(Fn);
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return true;
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}
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private:
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void saveCallerSavedRegisters(MachineFunction &Fn);
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void calculateFrameObjectOffsets(MachineFunction &Fn);
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void replaceFrameIndices(MachineFunction &Fn);
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void insertPrologEpilogCode(MachineFunction &Fn);
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};
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}
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/// createPrologEpilogCodeInserter - This function returns a pass that inserts
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/// prolog and epilog code, and eliminates abstract frame references.
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///
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Pass *createPrologEpilogCodeInserter() { return new PEI(); }
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/// saveCallerSavedRegisters - Scan the function for modified caller saved
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/// registers and insert spill code for any caller saved registers that are
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/// modified. Also calculate the MaxCallFrameSize and HasCalls variables for
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/// the function's frame information and eliminates call frame pseudo
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/// instructions.
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///
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void PEI::saveCallerSavedRegisters(MachineFunction &Fn) {
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const MRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
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const TargetFrameInfo &FrameInfo = Fn.getTarget().getFrameInfo();
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// Get the callee saved register list...
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const unsigned *CSRegs = RegInfo->getCalleeSaveRegs();
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// Get the function call frame set-up and tear-down instruction opcode
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int FrameSetupOpcode = RegInfo->getCallFrameSetupOpcode();
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int FrameDestroyOpcode = RegInfo->getCallFrameDestroyOpcode();
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// Early exit for targets which have no callee saved registers and no call
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// frame setup/destroy pseudo instructions.
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if ((CSRegs == 0 || CSRegs[0] == 0) &&
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FrameSetupOpcode == -1 && FrameDestroyOpcode == -1)
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return;
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// This bitset contains an entry for each physical register for the target...
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std::vector<bool> ModifiedRegs(MRegisterInfo::FirstVirtualRegister);
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unsigned MaxCallFrameSize = 0;
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bool HasCalls = false;
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for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB)
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for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); )
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if ((*I)->getOpcode() == FrameSetupOpcode ||
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(*I)->getOpcode() == FrameDestroyOpcode) {
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assert((*I)->getNumOperands() == 1 && "Call Frame Setup/Destroy Pseudo"
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" instructions should have a single immediate argument!");
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unsigned Size = (*I)->getOperand(0).getImmedValue();
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if (Size > MaxCallFrameSize) MaxCallFrameSize = Size;
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HasCalls = true;
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RegInfo->eliminateCallFramePseudoInstr(Fn, *BB, I);
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} else {
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for (unsigned i = 0, e = (*I)->getNumOperands(); i != e; ++i) {
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MachineOperand &MO = (*I)->getOperand(i);
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assert(!MO.isVirtualRegister() &&
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"Register allocation must be performed!");
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if (MO.isPhysicalRegister() && MO.opIsDef())
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ModifiedRegs[MO.getReg()] = true; // Register is modified
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}
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++I;
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}
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MachineFrameInfo *FFI = Fn.getFrameInfo();
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FFI->setHasCalls(HasCalls);
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FFI->setMaxCallFrameSize(MaxCallFrameSize);
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// Now figure out which *callee saved* registers are modified by the current
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// function, thus needing to be saved and restored in the prolog/epilog.
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//
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std::vector<unsigned> RegsToSave;
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for (unsigned i = 0; CSRegs[i]; ++i) {
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unsigned Reg = CSRegs[i];
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if (ModifiedRegs[Reg]) {
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RegsToSave.push_back(Reg); // If modified register...
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} else if (const unsigned *AliasSet = RegInfo->getAliasSet(Reg))
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for (unsigned j = 0; AliasSet[j]; ++j) // Check alias registers too...
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if (ModifiedRegs[AliasSet[j]]) {
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RegsToSave.push_back(Reg);
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break;
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}
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}
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if (RegsToSave.empty())
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return; // Early exit if no caller saved registers are modified!
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// Now that we know which registers need to be saved and restored, allocate
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// stack slots for them.
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std::vector<int> StackSlots;
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for (unsigned i = 0, e = RegsToSave.size(); i != e; ++i) {
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int FrameIdx = FFI->CreateStackObject(RegInfo->getRegClass(RegsToSave[i]));
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StackSlots.push_back(FrameIdx);
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}
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// Now that we have a stack slot for each register to be saved, insert spill
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// code into the entry block...
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MachineBasicBlock *MBB = Fn.begin();
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MachineBasicBlock::iterator I = MBB->begin();
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for (unsigned i = 0, e = RegsToSave.size(); i != e; ++i) {
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const TargetRegisterClass *RC = RegInfo->getRegClass(RegsToSave[i]);
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// Insert the spill to the stack frame...
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RegInfo->storeRegToStackSlot(*MBB, I, RegsToSave[i], StackSlots[i], RC);
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}
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// Add code to restore the callee-save registers in each exiting block.
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const TargetInstrInfo &TII = Fn.getTarget().getInstrInfo();
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for (MachineFunction::iterator FI = Fn.begin(), E = Fn.end(); FI != E; ++FI) {
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// If last instruction is a return instruction, add an epilogue
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if (TII.isReturn(FI->back()->getOpcode())) {
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MBB = FI; I = MBB->end()-1;
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for (unsigned i = 0, e = RegsToSave.size(); i != e; ++i) {
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const TargetRegisterClass *RC = RegInfo->getRegClass(RegsToSave[i]);
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RegInfo->loadRegFromStackSlot(*MBB, I, RegsToSave[i],StackSlots[i], RC);
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--I; // Insert in reverse order
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}
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}
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}
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}
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/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
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/// abstract stack objects...
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///
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void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
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const TargetFrameInfo &TFI = Fn.getTarget().getFrameInfo();
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bool StackGrowsDown =
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TFI.getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown;
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assert(StackGrowsDown && "Only tested on stack down growing targets!");
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// Loop over all of the stack objects, assigning sequential addresses...
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MachineFrameInfo *FFI = Fn.getFrameInfo();
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unsigned StackAlignment = TFI.getStackAlignment();
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// Start at the beginning of the local area...
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int Offset = TFI.getOffsetOfLocalArea();
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for (unsigned i = 0, e = FFI->getObjectIndexEnd(); i != e; ++i) {
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Offset += FFI->getObjectSize(i); // Allocate Size bytes...
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unsigned Align = FFI->getObjectAlignment(i);
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assert(Align <= StackAlignment && "Cannot align stack object to higher "
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"alignment boundary than the stack itself!");
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Offset = (Offset+Align-1)/Align*Align; // Adjust to Alignment boundary...
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FFI->setObjectOffset(i, -Offset); // Set the computed offset
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}
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// Align the final stack pointer offset...
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Offset = (Offset+StackAlignment-1)/StackAlignment*StackAlignment;
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// Set the final value of the stack pointer...
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FFI->setStackSize(Offset-TFI.getOffsetOfLocalArea());
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}
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/// insertPrologEpilogCode - Scan the function for modified caller saved
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/// registers, insert spill code for these caller saved registers, then add
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/// prolog and epilog code to the function.
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///
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void PEI::insertPrologEpilogCode(MachineFunction &Fn) {
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// Add prologue to the function...
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Fn.getTarget().getRegisterInfo()->emitPrologue(Fn);
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// Add epilogue to restore the callee-save registers in each exiting block
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const TargetInstrInfo &TII = Fn.getTarget().getInstrInfo();
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for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
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// If last instruction is a return instruction, add an epilogue
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if (!I->empty() && TII.isReturn(I->back()->getOpcode()))
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Fn.getTarget().getRegisterInfo()->emitEpilogue(Fn, *I);
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}
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}
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/// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
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/// register references and actual offsets.
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///
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void PEI::replaceFrameIndices(MachineFunction &Fn) {
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if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do?
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const TargetMachine &TM = Fn.getTarget();
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assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!");
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const MRegisterInfo &MRI = *TM.getRegisterInfo();
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for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB)
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for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I)
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for (unsigned i = 0, e = (*I)->getNumOperands(); i != e; ++i)
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if ((*I)->getOperand(i).isFrameIndex()) {
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// If this instruction has a FrameIndex operand, we need to use that
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// target machine register info object to eliminate it.
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MRI.eliminateFrameIndex(Fn, I);
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break;
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}
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}
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