C++ iterator::back方法代码示例

/// insertPrologEpilogCode - Scan the function for modified callee saved
/// registers, insert spill code for these callee saved registers, then add
/// prolog and epilog code to the function.
///
void PEI::insertPrologEpilogCode(MachineFunction &Fn) {
  const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();

  // Add prologue to the function...
  TFI.emitPrologue(Fn);

  // Add epilogue to restore the callee-save registers in each exiting block
  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() && I->back().isReturn())
      TFI.emitEpilogue(Fn, *I);
  }

  // Emit additional code that is required to support segmented stacks, if
  // we've been asked for it.  This, when linked with a runtime with support
  // for segmented stacks (libgcc is one), will result in allocating stack
  // space in small chunks instead of one large contiguous block.
  if (Fn.getTarget().Options.EnableSegmentedStacks)
    TFI.adjustForSegmentedStacks(Fn);

  // Emit additional code that is required to support Erlang HiPE native code,
  // if we've been asked for it.
  if (Fn.getTarget().Options.EnableHiPEPrologue)
    TFI.adjustForHiPEPrologue(Fn);
}

/// insertPrologEpilogCode - Scan the function for modified callee saved
/// registers, insert spill code for these callee saved registers, then add
/// prolog and epilog code to the function.
///
void PEI::insertPrologEpilogCode(MachineFunction &Fn) {
  const TargetFrameLowering &TFI = *Fn.getSubtarget().getFrameLowering();

  // Add prologue to the function...
  TFI.emitPrologue(Fn);

  // Add epilogue to restore the callee-save registers in each exiting block
  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() && I->back().isReturn())
      TFI.emitEpilogue(Fn, *I);
  }

  // Emit additional code that is required to support segmented stacks, if
  // we've been asked for it.  This, when linked with a runtime with support
  // for segmented stacks (libgcc is one), will result in allocating stack
  // space in small chunks instead of one large contiguous block.
  if (Fn.shouldSplitStack())
    TFI.adjustForSegmentedStacks(Fn);

  // Emit additional code that is required to explicitly handle the stack in
  // HiPE native code (if needed) when loaded in the Erlang/OTP runtime. The
  // approach is rather similar to that of Segmented Stacks, but it uses a
  // different conditional check and another BIF for allocating more stack
  // space.
  if (Fn.getFunction()->getCallingConv() == CallingConv::HiPE)
    TFI.adjustForHiPEPrologue(Fn);
}

bool NVPTXPrologEpilogPass::runOnMachineFunction(MachineFunction &MF) {
  const TargetMachine &TM = MF.getTarget();
  const TargetFrameLowering &TFI = *TM.getFrameLowering();
  const TargetRegisterInfo &TRI = *TM.getRegisterInfo();
  bool Modified = false;

  calculateFrameObjectOffsets(MF);

  for (MachineFunction::iterator BB = MF.begin(), E = MF.end(); BB != E; ++BB) {
    for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
      MachineInstr *MI = I;
      for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
        if (!MI->getOperand(i).isFI())
          continue;
        TRI.eliminateFrameIndex(MI, 0, i, nullptr);
        Modified = true;
      }
    }
  }

  // Add function prolog/epilog
  TFI.emitPrologue(MF);

  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
    // If last instruction is a return instruction, add an epilogue
    if (!I->empty() && I->back().isReturn())
      TFI.emitEpilogue(MF, *I);
  }

  return Modified;
}

/// insertPrologEpilogCode - Scan the function for modified callee saved
/// registers, insert spill code for these callee saved registers, then add
/// prolog and epilog code to the function.
///
void PEI::insertPrologEpilogCode(MachineFunction &Fn) {
  const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();

  // Add prologue to the function...
  TFI.emitPrologue(Fn);

  // Add epilogue to restore the callee-save registers in each exiting block
  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() && I->back().getDesc().isReturn())
      TFI.emitEpilogue(Fn, *I);
  }
}