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 "llvm/CodeGen/MachineFrameInfo.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineInstrBuilder.h"
22 #include "llvm/CodeGen/MachineModuleInfo.h"
23 #include "llvm/CodeGen/MachineRegisterInfo.h"
24 #include "llvm/IR/DataLayout.h"
25 #include "llvm/IR/Function.h"
26 #include "llvm/Support/CommandLine.h"
27 #include "llvm/Target/TargetOptions.h"
28 
29 using namespace llvm;
30 
31 void Mips16FrameLowering::emitPrologue(MachineFunction &MF) const {
32   MachineBasicBlock &MBB = MF.front();
33   MachineFrameInfo *MFI = MF.getFrameInfo();
34   const Mips16InstrInfo &TII =
35     *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
36   MachineBasicBlock::iterator MBBI = MBB.begin();
37   DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
38   uint64_t StackSize = MFI->getStackSize();
39 
40   // No need to allocate space on the stack.
41   if (StackSize == 0 && !MFI->adjustsStack()) return;
42 
43   MachineModuleInfo &MMI = MF.getMMI();
44   const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
45   MachineLocation DstML, SrcML;
46 
47   // Adjust stack.
48   TII.makeFrame(Mips::SP, StackSize, MBB, MBBI);
49 
50   // emit ".cfi_def_cfa_offset StackSize"
51   MCSymbol *AdjustSPLabel = MMI.getContext().CreateTempSymbol();
52   BuildMI(MBB, MBBI, dl,
53           TII.get(TargetOpcode::PROLOG_LABEL)).addSym(AdjustSPLabel);
54   MMI.addFrameInst(
55       MCCFIInstruction::createDefCfaOffset(AdjustSPLabel, -StackSize));
56 
57   const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
58 
59   if (CSI.size()) {
60     MCSymbol *CSLabel = MMI.getContext().CreateTempSymbol();
61     BuildMI(MBB, MBBI, dl,
62             TII.get(TargetOpcode::PROLOG_LABEL)).addSym(CSLabel);
63 
64 
65     const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
66 
67     for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
68          E = CSI.end(); I != E; ++I) {
69       int64_t Offset = MFI->getObjectOffset(I->getFrameIdx());
70       unsigned Reg = I->getReg();
71       unsigned DReg = MRI->getDwarfRegNum(Reg, true);
72       MMI.addFrameInst(MCCFIInstruction::createOffset(CSLabel, DReg, Offset));
73     }
74   }
75   if (hasFP(MF))
76     BuildMI(MBB, MBBI, dl, TII.get(Mips::MoveR3216), Mips::S0)
77       .addReg(Mips::SP);
78 
79 }
80 
81 void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
82                                  MachineBasicBlock &MBB) const {
83   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
84   MachineFrameInfo *MFI = MF.getFrameInfo();
85   const Mips16InstrInfo &TII =
86     *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
87   DebugLoc dl = MBBI->getDebugLoc();
88   uint64_t StackSize = MFI->getStackSize();
89 
90   if (!StackSize)
91     return;
92 
93   if (hasFP(MF))
94     BuildMI(MBB, MBBI, dl, TII.get(Mips::Move32R16), Mips::SP)
95       .addReg(Mips::S0);
96 
97   // Adjust stack.
98   // assumes stacksize multiple of 8
99   TII.restoreFrame(Mips::SP, StackSize, MBB, MBBI);
100 }
101 
102 bool Mips16FrameLowering::
103 spillCalleeSavedRegisters(MachineBasicBlock &MBB,
104                           MachineBasicBlock::iterator MI,
105                           const std::vector<CalleeSavedInfo> &CSI,
106                           const TargetRegisterInfo *TRI) const {
107   MachineFunction *MF = MBB.getParent();
108   MachineBasicBlock *EntryBlock = MF->begin();
109 
110   //
111   // Registers RA, S0,S1 are the callee saved registers and they
112   // will be saved with the "save" instruction
113   // during emitPrologue
114   //
115   for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
116     // Add the callee-saved register as live-in. Do not add if the register is
117     // RA and return address is taken, because it has already been added in
118     // method MipsTargetLowering::LowerRETURNADDR.
119     // It's killed at the spill, unless the register is RA and return address
120     // is taken.
121     unsigned Reg = CSI[i].getReg();
122     bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
123       && MF->getFrameInfo()->isReturnAddressTaken();
124     if (!IsRAAndRetAddrIsTaken)
125       EntryBlock->addLiveIn(Reg);
126   }
127 
128   return true;
129 }
130 
131 bool Mips16FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
132                                           MachineBasicBlock::iterator MI,
133                                        const std::vector<CalleeSavedInfo> &CSI,
134                                        const TargetRegisterInfo *TRI) const {
135   //
136   // Registers RA,S0,S1 are the callee saved registers and they will be restored
137   // with the restore instruction during emitEpilogue.
138   // We need to override this virtual function, otherwise llvm will try and
139   // restore the registers on it's on from the stack.
140   //
141 
142   return true;
143 }
144 
145 // Eliminate ADJCALLSTACKDOWN, ADJCALLSTACKUP pseudo instructions
146 void Mips16FrameLowering::
147 eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
148                               MachineBasicBlock::iterator I) const {
149   if (!hasReservedCallFrame(MF)) {
150     int64_t Amount = I->getOperand(0).getImm();
151 
152     if (I->getOpcode() == Mips::ADJCALLSTACKDOWN)
153       Amount = -Amount;
154 
155     const Mips16InstrInfo &TII =
156       *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
157 
158     TII.adjustStackPtr(Mips::SP, Amount, MBB, I);
159   }
160 
161   MBB.erase(I);
162 }
163 
164 bool
165 Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
166   const MachineFrameInfo *MFI = MF.getFrameInfo();
167   // Reserve call frame if the size of the maximum call frame fits into 15-bit
168   // immediate field and there are no variable sized objects on the stack.
169   return isInt<15>(MFI->getMaxCallFrameSize()) && !MFI->hasVarSizedObjects();
170 }
171 
172 void Mips16FrameLowering::
173 processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
174                                      RegScavenger *RS) const {
175   const Mips16InstrInfo &TII =
176     *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
177   const MipsRegisterInfo &RI = TII.getRegisterInfo();
178   const BitVector Reserved = RI.getReservedRegs(MF);
179   bool SaveS2 = Reserved[Mips::S2];
180   if (SaveS2)
181     MF.getRegInfo().setPhysRegUsed(Mips::S2);
182   if (hasFP(MF))
183     MF.getRegInfo().setPhysRegUsed(Mips::S0);
184 }
185 
186 const MipsFrameLowering *
187 llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
188   return new Mips16FrameLowering(ST);
189 }
190