Mips16FrameLowering.cpp revision 0fdf3b029b35f495d7261fe78737e434edc84758 
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/Target/TargetData.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  const TargetInstrInfo &TII = *MF->getTarget().getInstrInfo();
72
73  //
74  // Registers RA, S0,S1 are the callee saved registers and they
75  // will be saved with the "save" instruction
76  // during emitPrologue
77  //
78  for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
79    // Add the callee-saved register as live-in. Do not add if the register is
80    // RA and return address is taken, because it has already been added in
81    // method MipsTargetLowering::LowerRETURNADDR.
82    // It's killed at the spill, unless the register is RA and return address
83    // is taken.
84    unsigned Reg = CSI[i].getReg();
85    bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
86      && MF->getFrameInfo()->isReturnAddressTaken();
87    if (!IsRAAndRetAddrIsTaken)
88      EntryBlock->addLiveIn(Reg);
89  }
90
91  return true;
92}
93
94bool Mips16FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
95                                          MachineBasicBlock::iterator MI,
96                                       const std::vector<CalleeSavedInfo> &CSI,
97                                       const TargetRegisterInfo *TRI) const {
98  //
99  // Registers RA,S0,S1 are the callee saved registers and they will be restored
100  // with the restore instruction during emitEpilogue.
101  // We need to override this virtual function, otherwise llvm will try and
102  // restore the registers on it's on from the stack.
103  //
104
105  return true;
106}
107
108bool
109Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
110  // FIXME: implement.
111  return true;
112}
113
114void Mips16FrameLowering::
115processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
116                                     RegScavenger *RS) const {
117  MF.getRegInfo().setPhysRegUsed(Mips::RA);
118  MF.getRegInfo().setPhysRegUsed(Mips::S0);
119  MF.getRegInfo().setPhysRegUsed(Mips::S1);
120}
121
122const MipsFrameLowering *
123llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
124  return new Mips16FrameLowering(ST);
125}
126