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 "llvm/CodeGen/MachineFrameInfo.h"
19 #include "llvm/CodeGen/MachineFunction.h"
20 #include "llvm/CodeGen/MachineInstrBuilder.h"
21 #include "llvm/CodeGen/MachineModuleInfo.h"
22 #include "llvm/CodeGen/MachineRegisterInfo.h"
23 #include "llvm/IR/DataLayout.h"
24 #include "llvm/IR/Function.h"
25 #include "llvm/Support/CommandLine.h"
26 #include "llvm/Target/TargetOptions.h"
27
28 using namespace llvm;
29
emitPrologue(MachineFunction & MF) const30 void Mips16FrameLowering::emitPrologue(MachineFunction &MF) const {
31 MachineBasicBlock &MBB = MF.front();
32 MachineFrameInfo *MFI = MF.getFrameInfo();
33 const Mips16InstrInfo &TII =
34 *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
35 MachineBasicBlock::iterator MBBI = MBB.begin();
36 DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
37 uint64_t StackSize = MFI->getStackSize();
38
39 // No need to allocate space on the stack.
40 if (StackSize == 0 && !MFI->adjustsStack()) return;
41
42 MachineModuleInfo &MMI = MF.getMMI();
43 const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
44 MachineLocation DstML, SrcML;
45
46 // Adjust stack.
47 TII.makeFrame(Mips::SP, StackSize, MBB, MBBI);
48
49 // emit ".cfi_def_cfa_offset StackSize"
50 MCSymbol *AdjustSPLabel = MMI.getContext().CreateTempSymbol();
51 BuildMI(MBB, MBBI, dl,
52 TII.get(TargetOpcode::PROLOG_LABEL)).addSym(AdjustSPLabel);
53 MMI.addFrameInst(
54 MCCFIInstruction::createDefCfaOffset(AdjustSPLabel, -StackSize));
55
56 MCSymbol *CSLabel = MMI.getContext().CreateTempSymbol();
57 BuildMI(MBB, MBBI, dl,
58 TII.get(TargetOpcode::PROLOG_LABEL)).addSym(CSLabel);
59 unsigned S2 = MRI->getDwarfRegNum(Mips::S2, true);
60 MMI.addFrameInst(MCCFIInstruction::createOffset(CSLabel, S2, -8));
61
62 unsigned S1 = MRI->getDwarfRegNum(Mips::S1, true);
63 MMI.addFrameInst(MCCFIInstruction::createOffset(CSLabel, S1, -12));
64
65 unsigned S0 = MRI->getDwarfRegNum(Mips::S0, true);
66 MMI.addFrameInst(MCCFIInstruction::createOffset(CSLabel, S0, -16));
67
68 unsigned RA = MRI->getDwarfRegNum(Mips::RA, true);
69 MMI.addFrameInst(MCCFIInstruction::createOffset(CSLabel, RA, -4));
70
71 if (hasFP(MF))
72 BuildMI(MBB, MBBI, dl, TII.get(Mips::MoveR3216), Mips::S0)
73 .addReg(Mips::SP);
74
75 }
76
emitEpilogue(MachineFunction & MF,MachineBasicBlock & MBB) const77 void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
78 MachineBasicBlock &MBB) const {
79 MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
80 MachineFrameInfo *MFI = MF.getFrameInfo();
81 const Mips16InstrInfo &TII =
82 *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
83 DebugLoc dl = MBBI->getDebugLoc();
84 uint64_t StackSize = MFI->getStackSize();
85
86 if (!StackSize)
87 return;
88
89 if (hasFP(MF))
90 BuildMI(MBB, MBBI, dl, TII.get(Mips::Move32R16), Mips::SP)
91 .addReg(Mips::S0);
92
93 // Adjust stack.
94 // assumes stacksize multiple of 8
95 TII.restoreFrame(Mips::SP, StackSize, MBB, MBBI);
96 }
97
98 bool Mips16FrameLowering::
spillCalleeSavedRegisters(MachineBasicBlock & MBB,MachineBasicBlock::iterator MI,const std::vector<CalleeSavedInfo> & CSI,const TargetRegisterInfo * TRI) const99 spillCalleeSavedRegisters(MachineBasicBlock &MBB,
100 MachineBasicBlock::iterator MI,
101 const std::vector<CalleeSavedInfo> &CSI,
102 const TargetRegisterInfo *TRI) const {
103 MachineFunction *MF = MBB.getParent();
104 MachineBasicBlock *EntryBlock = MF->begin();
105
106 //
107 // Registers RA, S0,S1 are the callee saved registers and they
108 // will be saved with the "save" instruction
109 // during emitPrologue
110 //
111 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
112 // Add the callee-saved register as live-in. Do not add if the register is
113 // RA and return address is taken, because it has already been added in
114 // method MipsTargetLowering::LowerRETURNADDR.
115 // It's killed at the spill, unless the register is RA and return address
116 // is taken.
117 unsigned Reg = CSI[i].getReg();
118 bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
119 && MF->getFrameInfo()->isReturnAddressTaken();
120 if (!IsRAAndRetAddrIsTaken)
121 EntryBlock->addLiveIn(Reg);
122 }
123
124 return true;
125 }
126
restoreCalleeSavedRegisters(MachineBasicBlock & MBB,MachineBasicBlock::iterator MI,const std::vector<CalleeSavedInfo> & CSI,const TargetRegisterInfo * TRI) const127 bool Mips16FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
128 MachineBasicBlock::iterator MI,
129 const std::vector<CalleeSavedInfo> &CSI,
130 const TargetRegisterInfo *TRI) const {
131 //
132 // Registers RA,S0,S1 are the callee saved registers and they will be restored
133 // with the restore instruction during emitEpilogue.
134 // We need to override this virtual function, otherwise llvm will try and
135 // restore the registers on it's on from the stack.
136 //
137
138 return true;
139 }
140
141 // Eliminate ADJCALLSTACKDOWN, ADJCALLSTACKUP pseudo instructions
142 void Mips16FrameLowering::
eliminateCallFramePseudoInstr(MachineFunction & MF,MachineBasicBlock & MBB,MachineBasicBlock::iterator I) const143 eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
144 MachineBasicBlock::iterator I) const {
145 if (!hasReservedCallFrame(MF)) {
146 int64_t Amount = I->getOperand(0).getImm();
147
148 if (I->getOpcode() == Mips::ADJCALLSTACKDOWN)
149 Amount = -Amount;
150
151 const Mips16InstrInfo &TII =
152 *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
153
154 TII.adjustStackPtr(Mips::SP, Amount, MBB, I);
155 }
156
157 MBB.erase(I);
158 }
159
160 bool
hasReservedCallFrame(const MachineFunction & MF) const161 Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
162 const MachineFrameInfo *MFI = MF.getFrameInfo();
163 // Reserve call frame if the size of the maximum call frame fits into 15-bit
164 // immediate field and there are no variable sized objects on the stack.
165 return isInt<15>(MFI->getMaxCallFrameSize()) && !MFI->hasVarSizedObjects();
166 }
167
168 void Mips16FrameLowering::
processFunctionBeforeCalleeSavedScan(MachineFunction & MF,RegScavenger * RS) const169 processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
170 RegScavenger *RS) const {
171 MF.getRegInfo().setPhysRegUsed(Mips::RA);
172 MF.getRegInfo().setPhysRegUsed(Mips::S0);
173 MF.getRegInfo().setPhysRegUsed(Mips::S1);
174 MF.getRegInfo().setPhysRegUsed(Mips::S2);
175 }
176
177 const MipsFrameLowering *
createMips16FrameLowering(const MipsSubtarget & ST)178 llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
179 return new Mips16FrameLowering(ST);
180 }
181