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 MachineModuleInfo &MMI = MF.getMMI();
58 const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
59
60 // Adjust stack.
61 TII.makeFrame(Mips::SP, StackSize, MBB, MBBI);
62
63 // emit ".cfi_def_cfa_offset StackSize"
64 unsigned CFIIndex =
65 MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, StackSize));
66 BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
67 .addCFIIndex(CFIIndex);
68
69 const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
70
71 if (!CSI.empty()) {
72 const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
73
74 for (const CalleeSavedInfo &I : CSI) {
75 int64_t Offset = MFI.getObjectOffset(I.getFrameIdx());
76 Register Reg = I.getReg();
77 unsigned DReg = MRI->getDwarfRegNum(Reg, true);
78 unsigned CFIIndex = MF.addFrameInst(
79 MCCFIInstruction::createOffset(nullptr, DReg, Offset));
80 BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
81 .addCFIIndex(CFIIndex);
82 }
83 }
84 if (hasFP(MF))
85 BuildMI(MBB, MBBI, dl, TII.get(Mips::MoveR3216), Mips::S0)
86 .addReg(Mips::SP).setMIFlag(MachineInstr::FrameSetup);
87 }
88
emitEpilogue(MachineFunction & MF,MachineBasicBlock & MBB) const89 void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
90 MachineBasicBlock &MBB) const {
91 MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
92 MachineFrameInfo &MFI = MF.getFrameInfo();
93 const Mips16InstrInfo &TII =
94 *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
95 DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
96 uint64_t StackSize = MFI.getStackSize();
97
98 if (!StackSize)
99 return;
100
101 if (hasFP(MF))
102 BuildMI(MBB, MBBI, dl, TII.get(Mips::Move32R16), Mips::SP)
103 .addReg(Mips::S0);
104
105 // Adjust stack.
106 // assumes stacksize multiple of 8
107 TII.restoreFrame(Mips::SP, StackSize, MBB, MBBI);
108 }
109
spillCalleeSavedRegisters(MachineBasicBlock & MBB,MachineBasicBlock::iterator MI,ArrayRef<CalleeSavedInfo> CSI,const TargetRegisterInfo * TRI) const110 bool Mips16FrameLowering::spillCalleeSavedRegisters(
111 MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
112 ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
113 MachineFunction *MF = MBB.getParent();
114
115 //
116 // Registers RA, S0,S1 are the callee saved registers and they
117 // will be saved with the "save" instruction
118 // during emitPrologue
119 //
120 for (const CalleeSavedInfo &I : CSI) {
121 // Add the callee-saved register as live-in. Do not add if the register is
122 // RA and return address is taken, because it has already been added in
123 // method MipsTargetLowering::lowerRETURNADDR.
124 // It's killed at the spill, unless the register is RA and return address
125 // is taken.
126 Register Reg = I.getReg();
127 bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
128 && MF->getFrameInfo().isReturnAddressTaken();
129 if (!IsRAAndRetAddrIsTaken)
130 MBB.addLiveIn(Reg);
131 }
132
133 return true;
134 }
135
restoreCalleeSavedRegisters(MachineBasicBlock & MBB,MachineBasicBlock::iterator MI,MutableArrayRef<CalleeSavedInfo> CSI,const TargetRegisterInfo * TRI) const136 bool Mips16FrameLowering::restoreCalleeSavedRegisters(
137 MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
138 MutableArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
139 //
140 // Registers RA,S0,S1 are the callee saved registers and they will be restored
141 // with the restore instruction during emitEpilogue.
142 // We need to override this virtual function, otherwise llvm will try and
143 // restore the registers on it's on from the stack.
144 //
145
146 return true;
147 }
148
149 bool
hasReservedCallFrame(const MachineFunction & MF) const150 Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
151 const MachineFrameInfo &MFI = MF.getFrameInfo();
152 // Reserve call frame if the size of the maximum call frame fits into 15-bit
153 // immediate field and there are no variable sized objects on the stack.
154 return isInt<15>(MFI.getMaxCallFrameSize()) && !MFI.hasVarSizedObjects();
155 }
156
determineCalleeSaves(MachineFunction & MF,BitVector & SavedRegs,RegScavenger * RS) const157 void Mips16FrameLowering::determineCalleeSaves(MachineFunction &MF,
158 BitVector &SavedRegs,
159 RegScavenger *RS) const {
160 TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
161 const Mips16InstrInfo &TII =
162 *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
163 const MipsRegisterInfo &RI = TII.getRegisterInfo();
164 const BitVector Reserved = RI.getReservedRegs(MF);
165 bool SaveS2 = Reserved[Mips::S2];
166 if (SaveS2)
167 SavedRegs.set(Mips::S2);
168 if (hasFP(MF))
169 SavedRegs.set(Mips::S0);
170 }
171
172 const MipsFrameLowering *
createMips16FrameLowering(const MipsSubtarget & ST)173 llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
174 return new Mips16FrameLowering(ST);
175 }
176