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
30 using namespace llvm;
31
Mips16FrameLowering(const MipsSubtarget & STI)32 Mips16FrameLowering::Mips16FrameLowering(const MipsSubtarget &STI)
33 : MipsFrameLowering(STI, STI.stackAlignment()) {}
34
emitPrologue(MachineFunction & MF,MachineBasicBlock & MBB) const35 void 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
emitEpilogue(MachineFunction & MF,MachineBasicBlock & MBB) const87 void 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
108 bool Mips16FrameLowering::
spillCalleeSavedRegisters(MachineBasicBlock & MBB,MachineBasicBlock::iterator MI,const std::vector<CalleeSavedInfo> & CSI,const TargetRegisterInfo * TRI) const109 spillCalleeSavedRegisters(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
restoreCalleeSavedRegisters(MachineBasicBlock & MBB,MachineBasicBlock::iterator MI,const std::vector<CalleeSavedInfo> & CSI,const TargetRegisterInfo * TRI) const137 bool 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
151 bool
hasReservedCallFrame(const MachineFunction & MF) const152 Mips16FrameLowering::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
determineCalleeSaves(MachineFunction & MF,BitVector & SavedRegs,RegScavenger * RS) const159 void 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
174 const MipsFrameLowering *
createMips16FrameLowering(const MipsSubtarget & ST)175 llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
176 return new Mips16FrameLowering(ST);
177 }
178