1 //===- Mips16FrameLowering.cpp - Mips16 Frame Information -----------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file contains the Mips16 implementation of TargetFrameLowering class.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "Mips16FrameLowering.h"
14 #include "MCTargetDesc/MipsBaseInfo.h"
15 #include "Mips16InstrInfo.h"
16 #include "MipsInstrInfo.h"
17 #include "MipsRegisterInfo.h"
18 #include "MipsSubtarget.h"
19 #include "llvm/ADT/BitVector.h"
20 #include "llvm/CodeGen/MachineBasicBlock.h"
21 #include "llvm/CodeGen/MachineFrameInfo.h"
22 #include "llvm/CodeGen/MachineFunction.h"
23 #include "llvm/CodeGen/MachineInstr.h"
24 #include "llvm/CodeGen/MachineInstrBuilder.h"
25 #include "llvm/CodeGen/MachineModuleInfo.h"
26 #include "llvm/IR/DebugLoc.h"
27 #include "llvm/MC/MCContext.h"
28 #include "llvm/MC/MCDwarf.h"
29 #include "llvm/MC/MCRegisterInfo.h"
30 #include "llvm/MC/MachineLocation.h"
31 #include "llvm/Support/MathExtras.h"
32 #include "llvm/CodeGen/TargetFrameLowering.h"
33 #include <cassert>
34 #include <cstdint>
35 #include <vector>
36
37 using namespace llvm;
38
Mips16FrameLowering(const MipsSubtarget & STI)39 Mips16FrameLowering::Mips16FrameLowering(const MipsSubtarget &STI)
40 : MipsFrameLowering(STI, STI.getStackAlignment()) {}
41
emitPrologue(MachineFunction & MF,MachineBasicBlock & MBB) const42 void Mips16FrameLowering::emitPrologue(MachineFunction &MF,
43 MachineBasicBlock &MBB) const {
44 MachineFrameInfo &MFI = MF.getFrameInfo();
45 const Mips16InstrInfo &TII =
46 *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
47 MachineBasicBlock::iterator MBBI = MBB.begin();
48
49 // Debug location must be unknown since the first debug location is used
50 // to determine the end of the prologue.
51 DebugLoc dl;
52
53 uint64_t StackSize = MFI.getStackSize();
54
55 // No need to allocate space on the stack.
56 if (StackSize == 0 && !MFI.adjustsStack()) return;
57
58 MachineModuleInfo &MMI = MF.getMMI();
59 const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
60
61 // Adjust stack.
62 TII.makeFrame(Mips::SP, StackSize, MBB, MBBI);
63
64 // emit ".cfi_def_cfa_offset StackSize"
65 unsigned CFIIndex =
66 MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, StackSize));
67 BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
68 .addCFIIndex(CFIIndex);
69
70 const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
71
72 if (!CSI.empty()) {
73 const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
74
75 for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
76 E = CSI.end(); I != E; ++I) {
77 int64_t Offset = MFI.getObjectOffset(I->getFrameIdx());
78 unsigned Reg = I->getReg();
79 unsigned DReg = MRI->getDwarfRegNum(Reg, true);
80 unsigned CFIIndex = MF.addFrameInst(
81 MCCFIInstruction::createOffset(nullptr, DReg, Offset));
82 BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
83 .addCFIIndex(CFIIndex);
84 }
85 }
86 if (hasFP(MF))
87 BuildMI(MBB, MBBI, dl, TII.get(Mips::MoveR3216), Mips::S0)
88 .addReg(Mips::SP).setMIFlag(MachineInstr::FrameSetup);
89 }
90
emitEpilogue(MachineFunction & MF,MachineBasicBlock & MBB) const91 void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
92 MachineBasicBlock &MBB) const {
93 MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
94 MachineFrameInfo &MFI = MF.getFrameInfo();
95 const Mips16InstrInfo &TII =
96 *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
97 DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
98 uint64_t StackSize = MFI.getStackSize();
99
100 if (!StackSize)
101 return;
102
103 if (hasFP(MF))
104 BuildMI(MBB, MBBI, dl, TII.get(Mips::Move32R16), Mips::SP)
105 .addReg(Mips::S0);
106
107 // Adjust stack.
108 // assumes stacksize multiple of 8
109 TII.restoreFrame(Mips::SP, StackSize, MBB, MBBI);
110 }
111
spillCalleeSavedRegisters(MachineBasicBlock & MBB,MachineBasicBlock::iterator MI,ArrayRef<CalleeSavedInfo> CSI,const TargetRegisterInfo * TRI) const112 bool Mips16FrameLowering::spillCalleeSavedRegisters(
113 MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
114 ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
115 MachineFunction *MF = MBB.getParent();
116
117 //
118 // Registers RA, S0,S1 are the callee saved registers and they
119 // will be saved with the "save" instruction
120 // during emitPrologue
121 //
122 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
123 // Add the callee-saved register as live-in. Do not add if the register is
124 // RA and return address is taken, because it has already been added in
125 // method MipsTargetLowering::lowerRETURNADDR.
126 // It's killed at the spill, unless the register is RA and return address
127 // is taken.
128 unsigned Reg = CSI[i].getReg();
129 bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
130 && MF->getFrameInfo().isReturnAddressTaken();
131 if (!IsRAAndRetAddrIsTaken)
132 MBB.addLiveIn(Reg);
133 }
134
135 return true;
136 }
137
restoreCalleeSavedRegisters(MachineBasicBlock & MBB,MachineBasicBlock::iterator MI,MutableArrayRef<CalleeSavedInfo> CSI,const TargetRegisterInfo * TRI) const138 bool Mips16FrameLowering::restoreCalleeSavedRegisters(
139 MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
140 MutableArrayRef<CalleeSavedInfo> CSI, 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