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) const {
36  MachineBasicBlock &MBB = MF.front();
37  MachineFrameInfo *MFI = MF.getFrameInfo();
38  const Mips16InstrInfo &TII =
39    *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
40  MachineBasicBlock::iterator MBBI = MBB.begin();
41  DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
42  uint64_t StackSize = MFI->getStackSize();
43
44  // No need to allocate space on the stack.
45  if (StackSize == 0 && !MFI->adjustsStack()) return;
46
47  MachineModuleInfo &MMI = MF.getMMI();
48  const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
49  MachineLocation DstML, SrcML;
50
51  // Adjust stack.
52  TII.makeFrame(Mips::SP, StackSize, MBB, MBBI);
53
54  // emit ".cfi_def_cfa_offset StackSize"
55  unsigned CFIIndex = MMI.addFrameInst(
56      MCCFIInstruction::createDefCfaOffset(nullptr, -StackSize));
57  BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
58      .addCFIIndex(CFIIndex);
59
60  const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
61
62  if (CSI.size()) {
63    const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
64
65    for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
66         E = CSI.end(); I != E; ++I) {
67      int64_t Offset = MFI->getObjectOffset(I->getFrameIdx());
68      unsigned Reg = I->getReg();
69      unsigned DReg = MRI->getDwarfRegNum(Reg, true);
70      unsigned CFIIndex = MMI.addFrameInst(
71          MCCFIInstruction::createOffset(nullptr, DReg, Offset));
72      BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
73          .addCFIIndex(CFIIndex);
74    }
75  }
76  if (hasFP(MF))
77    BuildMI(MBB, MBBI, dl, TII.get(Mips::MoveR3216), Mips::S0)
78      .addReg(Mips::SP).setMIFlag(MachineInstr::FrameSetup);
79
80}
81
82void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
83                                 MachineBasicBlock &MBB) const {
84  MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
85  MachineFrameInfo *MFI = MF.getFrameInfo();
86  const Mips16InstrInfo &TII =
87    *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
88  DebugLoc dl = MBBI->getDebugLoc();
89  uint64_t StackSize = MFI->getStackSize();
90
91  if (!StackSize)
92    return;
93
94  if (hasFP(MF))
95    BuildMI(MBB, MBBI, dl, TII.get(Mips::Move32R16), Mips::SP)
96      .addReg(Mips::S0);
97
98  // Adjust stack.
99  // assumes stacksize multiple of 8
100  TII.restoreFrame(Mips::SP, StackSize, MBB, MBBI);
101}
102
103bool Mips16FrameLowering::
104spillCalleeSavedRegisters(MachineBasicBlock &MBB,
105                          MachineBasicBlock::iterator MI,
106                          const std::vector<CalleeSavedInfo> &CSI,
107                          const TargetRegisterInfo *TRI) const {
108  MachineFunction *MF = MBB.getParent();
109  MachineBasicBlock *EntryBlock = MF->begin();
110
111  //
112  // Registers RA, S0,S1 are the callee saved registers and they
113  // will be saved with the "save" instruction
114  // during emitPrologue
115  //
116  for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
117    // Add the callee-saved register as live-in. Do not add if the register is
118    // RA and return address is taken, because it has already been added in
119    // method MipsTargetLowering::LowerRETURNADDR.
120    // It's killed at the spill, unless the register is RA and return address
121    // is taken.
122    unsigned Reg = CSI[i].getReg();
123    bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
124      && MF->getFrameInfo()->isReturnAddressTaken();
125    if (!IsRAAndRetAddrIsTaken)
126      EntryBlock->addLiveIn(Reg);
127  }
128
129  return true;
130}
131
132bool Mips16FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
133                                          MachineBasicBlock::iterator MI,
134                                       const std::vector<CalleeSavedInfo> &CSI,
135                                       const TargetRegisterInfo *TRI) const {
136  //
137  // Registers RA,S0,S1 are the callee saved registers and they will be restored
138  // with the restore instruction during emitEpilogue.
139  // We need to override this virtual function, otherwise llvm will try and
140  // restore the registers on it's on from the stack.
141  //
142
143  return true;
144}
145
146// Eliminate ADJCALLSTACKDOWN, ADJCALLSTACKUP pseudo instructions
147void Mips16FrameLowering::
148eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
149                              MachineBasicBlock::iterator I) const {
150  if (!hasReservedCallFrame(MF)) {
151    int64_t Amount = I->getOperand(0).getImm();
152
153    if (I->getOpcode() == Mips::ADJCALLSTACKDOWN)
154      Amount = -Amount;
155
156    const Mips16InstrInfo &TII =
157      *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
158
159    TII.adjustStackPtr(Mips::SP, Amount, MBB, I);
160  }
161
162  MBB.erase(I);
163}
164
165bool
166Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
167  const MachineFrameInfo *MFI = MF.getFrameInfo();
168  // Reserve call frame if the size of the maximum call frame fits into 15-bit
169  // immediate field and there are no variable sized objects on the stack.
170  return isInt<15>(MFI->getMaxCallFrameSize()) && !MFI->hasVarSizedObjects();
171}
172
173void Mips16FrameLowering::
174processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
175                                     RegScavenger *RS) const {
176  const Mips16InstrInfo &TII =
177    *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
178  const MipsRegisterInfo &RI = TII.getRegisterInfo();
179  const BitVector Reserved = RI.getReservedRegs(MF);
180  bool SaveS2 = Reserved[Mips::S2];
181  if (SaveS2)
182    MF.getRegInfo().setPhysRegUsed(Mips::S2);
183  if (hasFP(MF))
184    MF.getRegInfo().setPhysRegUsed(Mips::S0);
185}
186
187const MipsFrameLowering *
188llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
189  return new Mips16FrameLowering(ST);
190}
191