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/Support/CommandLine.h"
28#include "llvm/Target/TargetOptions.h"
29
30using namespace llvm;
31
32Mips16FrameLowering::Mips16FrameLowering(const MipsSubtarget &STI)
33    : MipsFrameLowering(STI, STI.stackAlignment()) {}
34
35void Mips16FrameLowering::emitPrologue(MachineFunction &MF,
36                                       MachineBasicBlock &MBB) const {
37  assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported");
38  MachineFrameInfo *MFI = MF.getFrameInfo();
39  const Mips16InstrInfo &TII =
40      *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
41  MachineBasicBlock::iterator MBBI = MBB.begin();
42
43  // Debug location must be unknown since the first debug location is used
44  // to determine the end of the prologue.
45  DebugLoc dl;
46
47  uint64_t StackSize = MFI->getStackSize();
48
49  // No need to allocate space on the stack.
50  if (StackSize == 0 && !MFI->adjustsStack()) return;
51
52  MachineModuleInfo &MMI = MF.getMMI();
53  const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
54  MachineLocation DstML, SrcML;
55
56  // Adjust stack.
57  TII.makeFrame(Mips::SP, StackSize, MBB, MBBI);
58
59  // emit ".cfi_def_cfa_offset StackSize"
60  unsigned CFIIndex = MMI.addFrameInst(
61      MCCFIInstruction::createDefCfaOffset(nullptr, -StackSize));
62  BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
63      .addCFIIndex(CFIIndex);
64
65  const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
66
67  if (CSI.size()) {
68    const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
69
70    for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
71         E = CSI.end(); I != E; ++I) {
72      int64_t Offset = MFI->getObjectOffset(I->getFrameIdx());
73      unsigned Reg = I->getReg();
74      unsigned DReg = MRI->getDwarfRegNum(Reg, true);
75      unsigned CFIIndex = MMI.addFrameInst(
76          MCCFIInstruction::createOffset(nullptr, DReg, Offset));
77      BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
78          .addCFIIndex(CFIIndex);
79    }
80  }
81  if (hasFP(MF))
82    BuildMI(MBB, MBBI, dl, TII.get(Mips::MoveR3216), Mips::S0)
83      .addReg(Mips::SP).setMIFlag(MachineInstr::FrameSetup);
84
85}
86
87void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
88                                 MachineBasicBlock &MBB) const {
89  MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
90  MachineFrameInfo *MFI = MF.getFrameInfo();
91  const Mips16InstrInfo &TII =
92      *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
93  DebugLoc dl = MBBI->getDebugLoc();
94  uint64_t StackSize = MFI->getStackSize();
95
96  if (!StackSize)
97    return;
98
99  if (hasFP(MF))
100    BuildMI(MBB, MBBI, dl, TII.get(Mips::Move32R16), Mips::SP)
101      .addReg(Mips::S0);
102
103  // Adjust stack.
104  // assumes stacksize multiple of 8
105  TII.restoreFrame(Mips::SP, StackSize, MBB, MBBI);
106}
107
108bool Mips16FrameLowering::
109spillCalleeSavedRegisters(MachineBasicBlock &MBB,
110                          MachineBasicBlock::iterator MI,
111                          const std::vector<CalleeSavedInfo> &CSI,
112                          const TargetRegisterInfo *TRI) const {
113  MachineFunction *MF = MBB.getParent();
114  MachineBasicBlock *EntryBlock = &MF->front();
115
116  //
117  // Registers RA, S0,S1 are the callee saved registers and they
118  // will be saved with the "save" instruction
119  // during emitPrologue
120  //
121  for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
122    // Add the callee-saved register as live-in. Do not add if the register is
123    // RA and return address is taken, because it has already been added in
124    // method MipsTargetLowering::LowerRETURNADDR.
125    // It's killed at the spill, unless the register is RA and return address
126    // is taken.
127    unsigned Reg = CSI[i].getReg();
128    bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
129      && MF->getFrameInfo()->isReturnAddressTaken();
130    if (!IsRAAndRetAddrIsTaken)
131      EntryBlock->addLiveIn(Reg);
132  }
133
134  return true;
135}
136
137bool Mips16FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
138                                          MachineBasicBlock::iterator MI,
139                                       const std::vector<CalleeSavedInfo> &CSI,
140                                       const TargetRegisterInfo *TRI) const {
141  //
142  // Registers RA,S0,S1 are the callee saved registers and they will be restored
143  // with the restore instruction during emitEpilogue.
144  // We need to override this virtual function, otherwise llvm will try and
145  // restore the registers on it's on from the stack.
146  //
147
148  return true;
149}
150
151bool
152Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
153  const MachineFrameInfo *MFI = MF.getFrameInfo();
154  // Reserve call frame if the size of the maximum call frame fits into 15-bit
155  // immediate field and there are no variable sized objects on the stack.
156  return isInt<15>(MFI->getMaxCallFrameSize()) && !MFI->hasVarSizedObjects();
157}
158
159void Mips16FrameLowering::determineCalleeSaves(MachineFunction &MF,
160                                               BitVector &SavedRegs,
161                                               RegScavenger *RS) const {
162  TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
163  const Mips16InstrInfo &TII =
164      *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
165  const MipsRegisterInfo &RI = TII.getRegisterInfo();
166  const BitVector Reserved = RI.getReservedRegs(MF);
167  bool SaveS2 = Reserved[Mips::S2];
168  if (SaveS2)
169    SavedRegs.set(Mips::S2);
170  if (hasFP(MF))
171    SavedRegs.set(Mips::S0);
172}
173
174const MipsFrameLowering *
175llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
176  return new Mips16FrameLowering(ST);
177}
178