path: root/lib/Target/X86/X86FrameInfo.cpp

//=======- X86FrameInfo.cpp - X86 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 X86 implementation of TargetFrameInfo class.
//
//===----------------------------------------------------------------------===//

#include "X86FrameInfo.h"
#include "X86InstrBuilder.h"
#include "X86InstrInfo.h"
#include "X86MachineFunctionInfo.h"
#include "X86TargetMachine.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/Target/TargetData.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Support/CommandLine.h"

using namespace llvm;

// FIXME: completely move here.
extern cl::opt<bool> ForceStackAlign;

bool X86FrameInfo::hasReservedCallFrame(const MachineFunction &MF) const {
  return !MF.getFrameInfo()->hasVarSizedObjects();
}

/// hasFP - Return true if the specified function should have a dedicated frame
/// pointer register.  This is true if the function has variable sized allocas
/// or if frame pointer elimination is disabled.
bool X86FrameInfo::hasFP(const MachineFunction &MF) const {
  const MachineFrameInfo *MFI = MF.getFrameInfo();
  const MachineModuleInfo &MMI = MF.getMMI();
  const TargetRegisterInfo *RI = TM.getRegisterInfo();

  return (DisableFramePointerElim(MF) ||
          RI->needsStackRealignment(MF) ||
          MFI->hasVarSizedObjects() ||
          MFI->isFrameAddressTaken() ||
          MF.getInfo<X86MachineFunctionInfo>()->getForceFramePointer() ||
          MMI.callsUnwindInit());
}

static unsigned getSUBriOpcode(unsigned is64Bit, int64_t Imm) {
  if (is64Bit) {
    if (isInt<8>(Imm))
      return X86::SUB64ri8;
    return X86::SUB64ri32;
  } else {
    if (isInt<8>(Imm))
      return X86::SUB32ri8;
    return X86::SUB32ri;
  }
}

static unsigned getADDriOpcode(unsigned is64Bit, int64_t Imm) {
  if (is64Bit) {
    if (isInt<8>(Imm))
      return X86::ADD64ri8;
    return X86::ADD64ri32;
  } else {
    if (isInt<8>(Imm))
      return X86::ADD32ri8;
    return X86::ADD32ri;
  }
}

/// emitSPUpdate - Emit a series of instructions to increment / decrement the
/// stack pointer by a constant value.
static
void emitSPUpdate(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
                  unsigned StackPtr, int64_t NumBytes, bool Is64Bit,
                  const TargetInstrInfo &TII) {
  bool isSub = NumBytes < 0;
  uint64_t Offset = isSub ? -NumBytes : NumBytes;
  unsigned Opc = isSub ?
    getSUBriOpcode(Is64Bit, Offset) :
    getADDriOpcode(Is64Bit, Offset);
  uint64_t Chunk = (1LL << 31) - 1;
  DebugLoc DL = MBB.findDebugLoc(MBBI);

  while (Offset) {
    uint64_t ThisVal = (Offset > Chunk) ? Chunk : Offset;
    MachineInstr *MI =
      BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr)
        .addReg(StackPtr)
        .addImm(ThisVal);
    MI->getOperand(3).setIsDead(); // The EFLAGS implicit def is dead.
    Offset -= ThisVal;
  }
}

/// mergeSPUpdatesUp - Merge two stack-manipulating instructions upper iterator.
static
void mergeSPUpdatesUp(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
                      unsigned StackPtr, uint64_t *NumBytes = NULL) {
  if (MBBI == MBB.begin()) return;

  MachineBasicBlock::iterator PI = prior(MBBI);
  unsigned Opc = PI->getOpcode();
  if ((Opc == X86::ADD64ri32 || Opc == X86::ADD64ri8 ||
       Opc == X86::ADD32ri || Opc == X86::ADD32ri8) &&
      PI->getOperand(0).getReg() == StackPtr) {
    if (NumBytes)
      *NumBytes += PI->getOperand(2).getImm();
    MBB.erase(PI);
  } else if ((Opc == X86::SUB64ri32 || Opc == X86::SUB64ri8 ||
              Opc == X86::SUB32ri || Opc == X86::SUB32ri8) &&
             PI->getOperand(0).getReg() == StackPtr) {
    if (NumBytes)
      *NumBytes -= PI->getOperand(2).getImm();
    MBB.erase(PI);
  }