Example #1
0
/// 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, *SaveBlock);

  // Add epilogue to restore the callee-save registers in each exiting block.
  for (MachineBasicBlock *RestoreBlock : RestoreBlocks)
    TFI.emitEpilogue(Fn, *RestoreBlock);

  // 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, *SaveBlock);

  // 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, *SaveBlock);
}