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 "MCTargetDesc/MipsBaseInfo.h"
16#include "Mips16InstrInfo.h"
17#include "MipsInstrInfo.h"
18#include "MipsRegisterInfo.h"
19#include "MipsSubtarget.h"
20#include "llvm/CodeGen/MachineFrameInfo.h"
21#include "llvm/CodeGen/MachineFunction.h"
22#include "llvm/CodeGen/MachineInstrBuilder.h"
23#include "llvm/CodeGen/MachineModuleInfo.h"
24#include "llvm/CodeGen/MachineRegisterInfo.h"
25#include "llvm/IR/DataLayout.h"
26#include "llvm/IR/Function.h"
27#include "llvm/Target/TargetOptions.h"
28
29using namespace llvm;
30
31Mips16FrameLowering::Mips16FrameLowering(const MipsSubtarget &STI)
32    : MipsFrameLowering(STI, STI.stackAlignment()) {}
33
34void Mips16FrameLowering::emitPrologue(MachineFunction &MF,
35                                       MachineBasicBlock &MBB) const {
36  assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported");
37  MachineFrameInfo *MFI = MF.getFrameInfo();
38  const Mips16InstrInfo &TII =
39      *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
40  MachineBasicBlock::iterator MBBI = MBB.begin();
41
42  // Debug location must be unknown since the first debug location is used
43  // to determine the end of the prologue.
44  DebugLoc dl;
45
46  uint64_t StackSize = MFI->getStackSize();
47
48  // No need to allocate space on the stack.
49  if (StackSize == 0 && !MFI->adjustsStack()) return;
50
51  MachineModuleInfo &MMI = MF.getMMI();
52  const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
53  MachineLocation DstML, SrcML;
54
55  // Adjust stack.
56  TII.makeFrame(Mips::SP, StackSize, MBB, MBBI);
57
58  // emit ".cfi_def_cfa_offset StackSize"
59  unsigned CFIIndex = MMI.addFrameInst(
60      MCCFIInstruction::createDefCfaOffset(nullptr, -StackSize));
61  BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
62      .addCFIIndex(CFIIndex);
63
64  const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
65
66  if (CSI.size()) {
67    const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
68
69    for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
70         E = CSI.end(); I != E; ++I) {
71      int64_t Offset = MFI->getObjectOffset(I->getFrameIdx());
72      unsigned Reg = I->getReg();
73      unsigned DReg = MRI->getDwarfRegNum(Reg, true);
74      unsigned CFIIndex = MMI.addFrameInst(
75          MCCFIInstruction::createOffset(nullptr, DReg, Offset));
76      BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
77          .addCFIIndex(CFIIndex);
78    }
79  }
80  if (hasFP(MF))
81    BuildMI(MBB, MBBI, dl, TII.get(Mips::MoveR3216), Mips::S0)
82      .addReg(Mips::SP).setMIFlag(MachineInstr::FrameSetup);
83
84}
85
86void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
87                                 MachineBasicBlock &MBB) const {
88  MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
89  MachineFrameInfo *MFI = MF.getFrameInfo();
90  const Mips16InstrInfo &TII =
91      *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
92  DebugLoc dl = MBBI->getDebugLoc();
93  uint64_t StackSize = MFI->getStackSize();
94
95  if (!StackSize)
96    return;
97
98  if (hasFP(MF))
99    BuildMI(MBB, MBBI, dl, TII.get(Mips::Move32R16), Mips::SP)
100      .addReg(Mips::S0);
101
102  // Adjust stack.
103  // assumes stacksize multiple of 8
104  TII.restoreFrame(Mips::SP, StackSize, MBB, MBBI);
105}
106
107bool Mips16FrameLowering::
108spillCalleeSavedRegisters(MachineBasicBlock &MBB,
109                          MachineBasicBlock::iterator MI,
110                          const std::vector<CalleeSavedInfo> &CSI,
111                          const TargetRegisterInfo *TRI) const {
112  MachineFunction *MF = MBB.getParent();
113  MachineBasicBlock *EntryBlock = &MF->front();
114
115  //
116  // Registers RA, S0,S1 are the callee saved registers and they
117  // will be saved with the "save" instruction
118  // during emitPrologue
119  //
120  for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
121    // Add the callee-saved register as live-in. Do not add if the register is
122    // RA and return address is taken, because it has already been added in
123    // method MipsTargetLowering::LowerRETURNADDR.
124    // It's killed at the spill, unless the register is RA and return address
125    // is taken.
126    unsigned Reg = CSI[i].getReg();
127    bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
128      && MF->getFrameInfo()->isReturnAddressTaken();
129    if (!IsRAAndRetAddrIsTaken)
130      EntryBlock->addLiveIn(Reg);
131  }
132
133  return true;
134}
135
136bool Mips16FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
137                                          MachineBasicBlock::iterator MI,
138                                       const std::vector<CalleeSavedInfo> &CSI,
139                                       const TargetRegisterInfo *TRI) const {
140  //
141  // Registers RA,S0,S1 are the callee saved registers and they will be restored
142  // with the restore instruction during emitEpilogue.
143  // We need to override this virtual function, otherwise llvm will try and
144  // restore the registers on it's on from the stack.
145  //
146
147  return true;
148}
149
150bool
151Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
152  const MachineFrameInfo *MFI = MF.getFrameInfo();
153  // Reserve call frame if the size of the maximum call frame fits into 15-bit
154  // immediate field and there are no variable sized objects on the stack.
155  return isInt<15>(MFI->getMaxCallFrameSize()) && !MFI->hasVarSizedObjects();
156}
157
158void Mips16FrameLowering::determineCalleeSaves(MachineFunction &MF,
159                                               BitVector &SavedRegs,
160                                               RegScavenger *RS) const {
161  TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
162  const Mips16InstrInfo &TII =
163      *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
164  const MipsRegisterInfo &RI = TII.getRegisterInfo();
165  const BitVector Reserved = RI.getReservedRegs(MF);
166  bool SaveS2 = Reserved[Mips::S2];
167  if (SaveS2)
168    SavedRegs.set(Mips::S2);
169  if (hasFP(MF))
170    SavedRegs.set(Mips::S0);
171}
172
173const MipsFrameLowering *
174llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
175  return new Mips16FrameLowering(ST);
176}
177