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 <cstdint>
34 #include <vector>
35
36 using namespace llvm;
37
Mips16FrameLowering(const MipsSubtarget & STI)38 Mips16FrameLowering::Mips16FrameLowering(const MipsSubtarget &STI)
39 : MipsFrameLowering(STI, STI.getStackAlignment()) {}
40
emitPrologue(MachineFunction & MF,MachineBasicBlock & MBB) const41 void Mips16FrameLowering::emitPrologue(MachineFunction &MF,
42 MachineBasicBlock &MBB) const {
43 MachineFrameInfo &MFI = MF.getFrameInfo();
44 const Mips16InstrInfo &TII =
45 *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
46 MachineBasicBlock::iterator MBBI = MBB.begin();
47
48 // Debug location must be unknown since the first debug location is used
49 // to determine the end of the prologue.
50 DebugLoc dl;
51
52 uint64_t StackSize = MFI.getStackSize();
53
54 // No need to allocate space on the stack.
55 if (StackSize == 0 && !MFI.adjustsStack()) return;
56
57 const MCRegisterInfo *MRI = MF.getContext().getRegisterInfo();
58
59 // Adjust stack.
60 TII.makeFrame(Mips::SP, StackSize, MBB, MBBI);
61
62 // emit ".cfi_def_cfa_offset StackSize"
63 unsigned CFIIndex =
64 MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, StackSize));
65 BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
66 .addCFIIndex(CFIIndex);
67
68 const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
69
70 if (!CSI.empty()) {
71 const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
72
73 for (const CalleeSavedInfo &I : CSI) {
74 int64_t Offset = MFI.getObjectOffset(I.getFrameIdx());
75 Register Reg = I.getReg();
76 unsigned DReg = MRI->getDwarfRegNum(Reg, true);
77 unsigned CFIIndex = MF.addFrameInst(
78 MCCFIInstruction::createOffset(nullptr, DReg, Offset));
79 BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
80 .addCFIIndex(CFIIndex);
81 }
82 }
83 if (hasFP(MF))
84 BuildMI(MBB, MBBI, dl, TII.get(Mips::MoveR3216), Mips::S0)
85 .addReg(Mips::SP).setMIFlag(MachineInstr::FrameSetup);
86 }
87
emitEpilogue(MachineFunction & MF,MachineBasicBlock & MBB) const88 void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
89 MachineBasicBlock &MBB) const {
90 MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
91 MachineFrameInfo &MFI = MF.getFrameInfo();
92 const Mips16InstrInfo &TII =
93 *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
94 DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
95 uint64_t StackSize = MFI.getStackSize();
96
97 if (!StackSize)
98 return;
99
100 if (hasFP(MF))
101 BuildMI(MBB, MBBI, dl, TII.get(Mips::Move32R16), Mips::SP)
102 .addReg(Mips::S0);
103
104 // Adjust stack.
105 // assumes stacksize multiple of 8
106 TII.restoreFrame(Mips::SP, StackSize, MBB, MBBI);
107 }
108
spillCalleeSavedRegisters(MachineBasicBlock & MBB,MachineBasicBlock::iterator MI,ArrayRef<CalleeSavedInfo> CSI,const TargetRegisterInfo * TRI) const109 bool Mips16FrameLowering::spillCalleeSavedRegisters(
110 MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
111 ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
112 MachineFunction *MF = MBB.getParent();
113
114 //
115 // Registers RA, S0,S1 are the callee saved registers and they
116 // will be saved with the "save" instruction
117 // during emitPrologue
118 //
119 for (const CalleeSavedInfo &I : CSI) {
120 // Add the callee-saved register as live-in. Do not add if the register is
121 // RA and return address is taken, because it has already been added in
122 // method MipsTargetLowering::lowerRETURNADDR.
123 // It's killed at the spill, unless the register is RA and return address
124 // is taken.
125 Register Reg = I.getReg();
126 bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
127 && MF->getFrameInfo().isReturnAddressTaken();
128 if (!IsRAAndRetAddrIsTaken)
129 MBB.addLiveIn(Reg);
130 }
131
132 return true;
133 }
134
restoreCalleeSavedRegisters(MachineBasicBlock & MBB,MachineBasicBlock::iterator MI,MutableArrayRef<CalleeSavedInfo> CSI,const TargetRegisterInfo * TRI) const135 bool Mips16FrameLowering::restoreCalleeSavedRegisters(
136 MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
137 MutableArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
138 //
139 // Registers RA,S0,S1 are the callee saved registers and they will be restored
140 // with the restore instruction during emitEpilogue.
141 // We need to override this virtual function, otherwise llvm will try and
142 // restore the registers on it's on from the stack.
143 //
144
145 return true;
146 }
147
148 bool
hasReservedCallFrame(const MachineFunction & MF) const149 Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
150 const MachineFrameInfo &MFI = MF.getFrameInfo();
151 // Reserve call frame if the size of the maximum call frame fits into 15-bit
152 // immediate field and there are no variable sized objects on the stack.
153 return isInt<15>(MFI.getMaxCallFrameSize()) && !MFI.hasVarSizedObjects();
154 }
155
determineCalleeSaves(MachineFunction & MF,BitVector & SavedRegs,RegScavenger * RS) const156 void Mips16FrameLowering::determineCalleeSaves(MachineFunction &MF,
157 BitVector &SavedRegs,
158 RegScavenger *RS) const {
159 TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
160 const Mips16InstrInfo &TII =
161 *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
162 const MipsRegisterInfo &RI = TII.getRegisterInfo();
163 const BitVector Reserved = RI.getReservedRegs(MF);
164 bool SaveS2 = Reserved[Mips::S2];
165 if (SaveS2)
166 SavedRegs.set(Mips::S2);
167 if (hasFP(MF))
168 SavedRegs.set(Mips::S0);
169 }
170
171 const MipsFrameLowering *
createMips16FrameLowering(const MipsSubtarget & ST)172 llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
173 return new Mips16FrameLowering(ST);
174 }
175