path: root/lib/Target/PowerPC/PPCFrameLowering.cpp

//=====- PPCFrameLowering.cpp - PPC Frame Information -----------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the PPC implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//

#include "PPCFrameLowering.h"
#include "PPCInstrInfo.h"
#include "PPCMachineFunctionInfo.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/Target/TargetOptions.h"

using namespace llvm;

// FIXME This disables some code that aligns the stack to a boundary bigger than
// the default (16 bytes on Darwin) when there is a stack local of greater
// alignment.  This does not currently work, because the delta between old and
// new stack pointers is added to offsets that reference incoming parameters
// after the prolog is generated, and the code that does that doesn't handle a
// variable delta.  You don't want to do that anyway; a better approach is to
// reserve another register that retains to the incoming stack pointer, and
// reference parameters relative to that.
#define ALIGN_STACK 0


/// VRRegNo - Map from a numbered VR register to its enum value.
///
static const unsigned short VRRegNo[] = {
 PPC::V0 , PPC::V1 , PPC::V2 , PPC::V3 , PPC::V4 , PPC::V5 , PPC::V6 , PPC::V7 ,
 PPC::V8 , PPC::V9 , PPC::V10, PPC::V11, PPC::V12, PPC::V13, PPC::V14, PPC::V15,
 PPC::V16, PPC::V17, PPC::V18, PPC::V19, PPC::V20, PPC::V21, PPC::V22, PPC::V23,
 PPC::V24, PPC::V25, PPC::V26, PPC::V27, PPC::V28, PPC::V29, PPC::V30, PPC::V31
};

/// RemoveVRSaveCode - We have found that this function does not need any code
/// to manipulate the VRSAVE register, even though it uses vector registers.
/// This can happen when the only registers used are known to be live in or out
/// of the function.  Remove all of the VRSAVE related code from the function.
static void RemoveVRSaveCode(MachineInstr *MI) {
  MachineBasicBlock *Entry = MI->getParent();
  MachineFunction *MF = Entry->getParent();

  // We know that the MTVRSAVE instruction immediately follows MI.  Remove it.
  MachineBasicBlock::iterator MBBI = MI;
  ++MBBI;
  assert(MBBI != Entry->end() && MBBI->getOpcode() == PPC::MTVRSAVE);
  MBBI->eraseFromParent();

  bool RemovedAllMTVRSAVEs = true;
  // See if we can find and remove the MTVRSAVE instruction from all of the
  // epilog blocks.
  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().getDesc().isReturn()) {
      bool FoundIt = false;
      for (MBBI = I->end(); MBBI != I->begin(); ) {
        --MBBI;
        if (MBBI->getOpcode() == PPC::MTVRSAVE) {
          MBBI->eraseFromParent();  // remove it.
          FoundIt = true;
          break;
        }
      }
      RemovedAllMTVRSAVEs &= FoundIt;
    }
  }

  // If we found and removed all MTVRSAVE instructions, remove the read of
  // VRSAVE as well.
  if (RemovedAllMTVRSAVEs) {
    MBBI = MI;
    assert(MBBI != Entry->begin() && "UPDATE_VRSAVE is first instr in block?");
    --MBBI;
    assert(MBBI->getOpcode() == PPC::MFVRSAVE && "VRSAVE instrs wandered?");
    MBBI->eraseFromParent();
  }

  // Finally, nuke the UPDATE_VRSAVE.
  MI->eraseFromParent();
}

// HandleVRSaveUpdate - MI is the UPDATE_VRSAVE instruction introduced by the
// instruction selector.  Based on the vector registers that have been used,
// transform this into the appropriate ORI instruction.
static void HandleVRSaveUpdate(MachineInstr *MI, const TargetInstrInfo &TII) {
  MachineFunction *MF = MI->getParent()->getParent();
  DebugLoc dl = MI->getDebugLoc();

  unsigned UsedRegMask = 0;
  for (unsigned i = 0; i != 32; ++i)
    if (MF->getRegInfo().isPhysRegUsed(VRRegNo[i]))
      UsedRegMask |= 1 << (31-i);

  // Live in and live out values already must be in the mask, so don't bother
  // marking them.
  for (MachineRegisterInfo::livein_iterator
       I = MF->getRegInfo().livein_begin(),
       E = MF->getRegInfo().livein_end(); I != E; ++I) {
    unsigned RegNo = getPPCRegisterNumbering(I->first);
    if (VRRegNo[RegNo] == I->first)        // If this really is a vector reg.