Mips16FrameLowering.cpp revision 3574eca1b02600bac4e625297f4ecf745f4c4f32 
1//===-- Mips16FrameLowering.cpp - Mips16 Frame Information ----------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file contains the Mips16 implementation of TargetFrameLowering class.
11//
12//===----------------------------------------------------------------------===//
13
14#include "Mips16FrameLowering.h"
15#include "MipsInstrInfo.h"
16#include "MCTargetDesc/MipsBaseInfo.h"
17#include "llvm/Function.h"
18#include "llvm/CodeGen/MachineFrameInfo.h"
19#include "llvm/CodeGen/MachineFunction.h"
20#include "llvm/CodeGen/MachineInstrBuilder.h"
21#include "llvm/CodeGen/MachineModuleInfo.h"
22#include "llvm/CodeGen/MachineRegisterInfo.h"
23#include "llvm/DataLayout.h"
24#include "llvm/Target/TargetOptions.h"
25#include "llvm/Support/CommandLine.h"
26
27using namespace llvm;
28
29void Mips16FrameLowering::emitPrologue(MachineFunction &MF) const {
30  MachineBasicBlock &MBB = MF.front();
31  MachineFrameInfo *MFI = MF.getFrameInfo();
32  const MipsInstrInfo &TII =
33    *static_cast<const MipsInstrInfo*>(MF.getTarget().getInstrInfo());
34  MachineBasicBlock::iterator MBBI = MBB.begin();
35  DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
36  uint64_t StackSize = MFI->getStackSize();
37
38  // No need to allocate space on the stack.
39  if (StackSize == 0 && !MFI->adjustsStack()) return;
40
41  // Adjust stack.
42  if (isInt<16>(-StackSize))
43    BuildMI(MBB, MBBI, dl, TII.get(Mips::SaveRaF16)).addImm(StackSize);
44}
45
46void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
47                                 MachineBasicBlock &MBB) const {
48  MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
49  MachineFrameInfo *MFI = MF.getFrameInfo();
50  const MipsInstrInfo &TII =
51    *static_cast<const MipsInstrInfo*>(MF.getTarget().getInstrInfo());
52  DebugLoc dl = MBBI->getDebugLoc();
53  uint64_t StackSize = MFI->getStackSize();
54
55  if (!StackSize)
56    return;
57
58  // Adjust stack.
59  if (isInt<16>(StackSize))
60    // assumes stacksize multiple of 8
61    BuildMI(MBB, MBBI, dl, TII.get(Mips::RestoreRaF16)).addImm(StackSize);
62}
63
64bool Mips16FrameLowering::
65spillCalleeSavedRegisters(MachineBasicBlock &MBB,
66                          MachineBasicBlock::iterator MI,
67                          const std::vector<CalleeSavedInfo> &CSI,
68                          const TargetRegisterInfo *TRI) const {
69  MachineFunction *MF = MBB.getParent();
70  MachineBasicBlock *EntryBlock = MF->begin();
71
72  //
73  // Registers RA, S0,S1 are the callee saved registers and they
74  // will be saved with the "save" instruction
75  // during emitPrologue
76  //
77  for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
78    // Add the callee-saved register as live-in. Do not add if the register is
79    // RA and return address is taken, because it has already been added in
80    // method MipsTargetLowering::LowerRETURNADDR.
81    // It's killed at the spill, unless the register is RA and return address
82    // is taken.
83    unsigned Reg = CSI[i].getReg();
84    bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
85      && MF->getFrameInfo()->isReturnAddressTaken();
86    if (!IsRAAndRetAddrIsTaken)
87      EntryBlock->addLiveIn(Reg);
88  }
89
90  return true;
91}
92
93bool Mips16FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
94                                          MachineBasicBlock::iterator MI,
95                                       const std::vector<CalleeSavedInfo> &CSI,
96                                       const TargetRegisterInfo *TRI) const {
97  //
98  // Registers RA,S0,S1 are the callee saved registers and they will be restored
99  // with the restore instruction during emitEpilogue.
100  // We need to override this virtual function, otherwise llvm will try and
101  // restore the registers on it's on from the stack.
102  //
103
104  return true;
105}
106
107bool
108Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
109  // FIXME: implement.
110  return true;
111}
112
113void Mips16FrameLowering::
114processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
115                                     RegScavenger *RS) const {
116  MF.getRegInfo().setPhysRegUsed(Mips::RA);
117  MF.getRegInfo().setPhysRegUsed(Mips::S0);
118  MF.getRegInfo().setPhysRegUsed(Mips::S1);
119}
120
121const MipsFrameLowering *
122llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
123  return new Mips16FrameLowering(ST);
124}
125