llvm.org GIT mirror llvm / 52e96d1 lib / Target / Mips / MipsFrameLowering.cpp
52e96d1

Tree @52e96d1 (Download .tar.gz)

MipsFrameLowering.cpp @52e96d1

c570711
3346491
 
 
 
 
 
4552c9a
3346491
16c29b5
3346491
4552c9a
3346491
16c29b5
d04a8d4
3346491
 
af26626
3346491
 
 
 
 
0b8c9a8
 
d04a8d4
3346491
 
 
 
4552c9a
3346491
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4552c9a
3346491
0ce4f58
 
af26626
 
 
 
 
d0c3817
330e5f1
 
 
16c29b5
f79c57a
330e5f1
 
8a8d479
f79c57a
330e5f1
 
 
 
f79c57a
330e5f1
 
f79c57a
d0c3817
265f191
d27dcd3
 
 
 
 
265f191
f79c57a
2d64c55
265f191
d27dcd3
265f191
d27dcd3
f79c57a
d27dcd3
 
265f191
 
84f7f35
d27dcd3
 
265f191
 
d27dcd3
 
 
265f191
3fabd02
 
f864a32
3fabd02
 
 
 
 
 
 
 
 
 
 
 
f864a32
3fabd02
//===-- MipsFrameLowering.cpp - Mips Frame Information --------------------===//
//
//                     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 Mips implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//

#include "MipsFrameLowering.h"
#include "MCTargetDesc/MipsBaseInfo.h"
#include "MipsInstrInfo.h"
#include "MipsMachineFunction.h"
#include "MipsTargetMachine.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/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/Target/TargetOptions.h"

using namespace llvm;


//===----------------------------------------------------------------------===//
//
// Stack Frame Processing methods
// +----------------------------+
//
// The stack is allocated decrementing the stack pointer on
// the first instruction of a function prologue. Once decremented,
// all stack references are done thought a positive offset
// from the stack/frame pointer, so the stack is considering
// to grow up! Otherwise terrible hacks would have to be made
// to get this stack ABI compliant :)
//
//  The stack frame required by the ABI (after call):
//  Offset
//
//  0                 ----------
//  4                 Args to pass
//  .                 saved $GP  (used in PIC)
//  .                 Alloca allocations
//  .                 Local Area
//  .                 CPU "Callee Saved" Registers
//  .                 saved FP
//  .                 saved RA
//  .                 FPU "Callee Saved" Registers
//  StackSize         -----------
//
// Offset - offset from sp after stack allocation on function prologue
//
// The sp is the stack pointer subtracted/added from the stack size
// at the Prologue/Epilogue
//
// References to the previous stack (to obtain arguments) are done
// with offsets that exceeds the stack size: (stacksize+(4*(num_arg-1))
//
// Examples:
// - reference to the actual stack frame
//   for any local area var there is smt like : FI >= 0, StackOffset: 4
//     sw REGX, 4(SP)
//
// - reference to previous stack frame
//   suppose there's a load to the 5th arguments : FI < 0, StackOffset: 16.
//   The emitted instruction will be something like:
//     lw REGX, 16+StackSize(SP)
//
// Since the total stack size is unknown on LowerFormalArguments, all
// stack references (ObjectOffset) created to reference the function
// arguments, are negative numbers. This way, on eliminateFrameIndex it's
// possible to detect those references and the offsets are adjusted to
// their real location.
//
//===----------------------------------------------------------------------===//

const MipsFrameLowering *MipsFrameLowering::create(const MipsSubtarget &ST) {
  if (ST.inMips16Mode())
    return llvm::createMips16FrameLowering(ST);

  return llvm::createMipsSEFrameLowering(ST);
}

// hasFP - Return true if the specified function should have a dedicated frame
// pointer register.  This is true if the function has variable sized allocas,
// if it needs dynamic stack realignment, if frame pointer elimination is
// disabled, or if the frame address is taken.
bool MipsFrameLowering::hasFP(const MachineFunction &MF) const {
  const MachineFrameInfo &MFI = MF.getFrameInfo();
  const TargetRegisterInfo *TRI = STI.getRegisterInfo();

  return MF.getTarget().Options.DisableFramePointerElim(MF) ||
      MFI.hasVarSizedObjects() || MFI.isFrameAddressTaken() ||
      TRI->needsStackRealignment(MF);
}

bool MipsFrameLowering::hasBP(const MachineFunction &MF) const {
  const MachineFrameInfo &MFI = MF.getFrameInfo();
  const TargetRegisterInfo *TRI = STI.getRegisterInfo();

  return MFI.hasVarSizedObjects() && TRI->needsStackRealignment(MF);
}

// Estimate the size of the stack, including the incoming arguments. We need to
// account for register spills, local objects, reserved call frame and incoming
// arguments. This is required to determine the largest possible positive offset
// from $sp so that it can be determined if an emergency spill slot for stack
// addresses is required.
uint64_t MipsFrameLowering::estimateStackSize(const MachineFunction &MF) const {
  const MachineFrameInfo &MFI = MF.getFrameInfo();
  const TargetRegisterInfo &TRI = *STI.getRegisterInfo();

  int64_t Size = 0;

  // Iterate over fixed sized objects which are incoming arguments.
  for (int I = MFI.getObjectIndexBegin(); I != 0; ++I)
    if (MFI.getObjectOffset(I) > 0)
      Size += MFI.getObjectSize(I);

  // Conservatively assume all callee-saved registers will be saved.
  for (const MCPhysReg *R = TRI.getCalleeSavedRegs(&MF); *R; ++R) {
    unsigned RegSize = TRI.getSpillSize(*TRI.getMinimalPhysRegClass(*R));
    Size = alignTo(Size + RegSize, RegSize);
  }

  // Get the size of the rest of the frame objects and any possible reserved
  // call frame, accounting for alignment.
  return Size + MFI.estimateStackSize(MF);
}

// Eliminate ADJCALLSTACKDOWN, ADJCALLSTACKUP pseudo instructions
MachineBasicBlock::iterator MipsFrameLowering::
eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
                              MachineBasicBlock::iterator I) const {
  unsigned SP = STI.getABI().IsN64() ? Mips::SP_64 : Mips::SP;

  if (!hasReservedCallFrame(MF)) {
    int64_t Amount = I->getOperand(0).getImm();
    if (I->getOpcode() == Mips::ADJCALLSTACKDOWN)
      Amount = -Amount;

    STI.getInstrInfo()->adjustStackPtr(SP, Amount, MBB, I);
  }

  return MBB.erase(I);
}