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) const35 void 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
emitEpilogue(MachineFunction & MF,MachineBasicBlock & MBB) const82 void 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
103 bool Mips16FrameLowering::
spillCalleeSavedRegisters(MachineBasicBlock & MBB,MachineBasicBlock::iterator MI,const std::vector<CalleeSavedInfo> & CSI,const TargetRegisterInfo * TRI) const104 spillCalleeSavedRegisters(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
restoreCalleeSavedRegisters(MachineBasicBlock & MBB,MachineBasicBlock::iterator MI,const std::vector<CalleeSavedInfo> & CSI,const TargetRegisterInfo * TRI) const132 bool 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
147 void Mips16FrameLowering::
eliminateCallFramePseudoInstr(MachineFunction & MF,MachineBasicBlock & MBB,MachineBasicBlock::iterator I) const148 eliminateCallFramePseudoInstr(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
165 bool
hasReservedCallFrame(const MachineFunction & MF) const166 Mips16FrameLowering::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
173 void Mips16FrameLowering::
processFunctionBeforeCalleeSavedScan(MachineFunction & MF,RegScavenger * RS) const174 processFunctionBeforeCalleeSavedScan(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
187 const MipsFrameLowering *
createMips16FrameLowering(const MipsSubtarget & ST)188 llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
189 return new Mips16FrameLowering(ST);
190 }
191