1 //===-- BPFInstrInfo.cpp - BPF Instruction Information ----------*- C++ -*-===//
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 BPF implementation of the TargetInstrInfo class.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "BPFInstrInfo.h"
15 #include "BPF.h"
16 #include "llvm/ADT/SmallVector.h"
17 #include "llvm/CodeGen/MachineBasicBlock.h"
18 #include "llvm/CodeGen/MachineInstrBuilder.h"
19 #include "llvm/IR/DebugLoc.h"
20 #include "llvm/Support/ErrorHandling.h"
21 #include <cassert>
22 #include <iterator>
23
24 #define GET_INSTRINFO_CTOR_DTOR
25 #include "BPFGenInstrInfo.inc"
26
27 using namespace llvm;
28
BPFInstrInfo()29 BPFInstrInfo::BPFInstrInfo()
30 : BPFGenInstrInfo(BPF::ADJCALLSTACKDOWN, BPF::ADJCALLSTACKUP) {}
31
copyPhysReg(MachineBasicBlock & MBB,MachineBasicBlock::iterator I,const DebugLoc & DL,unsigned DestReg,unsigned SrcReg,bool KillSrc) const32 void BPFInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
33 MachineBasicBlock::iterator I,
34 const DebugLoc &DL, unsigned DestReg,
35 unsigned SrcReg, bool KillSrc) const {
36 if (BPF::GPRRegClass.contains(DestReg, SrcReg))
37 BuildMI(MBB, I, DL, get(BPF::MOV_rr), DestReg)
38 .addReg(SrcReg, getKillRegState(KillSrc));
39 else if (BPF::GPR32RegClass.contains(DestReg, SrcReg))
40 BuildMI(MBB, I, DL, get(BPF::MOV_rr_32), DestReg)
41 .addReg(SrcReg, getKillRegState(KillSrc));
42 else
43 llvm_unreachable("Impossible reg-to-reg copy");
44 }
45
expandMEMCPY(MachineBasicBlock::iterator MI) const46 void BPFInstrInfo::expandMEMCPY(MachineBasicBlock::iterator MI) const {
47 unsigned DstReg = MI->getOperand(0).getReg();
48 unsigned SrcReg = MI->getOperand(1).getReg();
49 uint64_t CopyLen = MI->getOperand(2).getImm();
50 uint64_t Alignment = MI->getOperand(3).getImm();
51 unsigned ScratchReg = MI->getOperand(4).getReg();
52 MachineBasicBlock *BB = MI->getParent();
53 DebugLoc dl = MI->getDebugLoc();
54 unsigned LdOpc, StOpc;
55
56 switch (Alignment) {
57 case 1:
58 LdOpc = BPF::LDB;
59 StOpc = BPF::STB;
60 break;
61 case 2:
62 LdOpc = BPF::LDH;
63 StOpc = BPF::STH;
64 break;
65 case 4:
66 LdOpc = BPF::LDW;
67 StOpc = BPF::STW;
68 break;
69 case 8:
70 LdOpc = BPF::LDD;
71 StOpc = BPF::STD;
72 break;
73 default:
74 llvm_unreachable("unsupported memcpy alignment");
75 }
76
77 unsigned IterationNum = CopyLen >> Log2_64(Alignment);
78 for(unsigned I = 0; I < IterationNum; ++I) {
79 BuildMI(*BB, MI, dl, get(LdOpc))
80 .addReg(ScratchReg, RegState::Define).addReg(SrcReg)
81 .addImm(I * Alignment);
82 BuildMI(*BB, MI, dl, get(StOpc))
83 .addReg(ScratchReg, RegState::Kill).addReg(DstReg)
84 .addImm(I * Alignment);
85 }
86
87 unsigned BytesLeft = CopyLen & (Alignment - 1);
88 unsigned Offset = IterationNum * Alignment;
89 bool Hanging4Byte = BytesLeft & 0x4;
90 bool Hanging2Byte = BytesLeft & 0x2;
91 bool Hanging1Byte = BytesLeft & 0x1;
92 if (Hanging4Byte) {
93 BuildMI(*BB, MI, dl, get(BPF::LDW))
94 .addReg(ScratchReg, RegState::Define).addReg(SrcReg).addImm(Offset);
95 BuildMI(*BB, MI, dl, get(BPF::STW))
96 .addReg(ScratchReg, RegState::Kill).addReg(DstReg).addImm(Offset);
97 Offset += 4;
98 }
99 if (Hanging2Byte) {
100 BuildMI(*BB, MI, dl, get(BPF::LDH))
101 .addReg(ScratchReg, RegState::Define).addReg(SrcReg).addImm(Offset);
102 BuildMI(*BB, MI, dl, get(BPF::STH))
103 .addReg(ScratchReg, RegState::Kill).addReg(DstReg).addImm(Offset);
104 Offset += 2;
105 }
106 if (Hanging1Byte) {
107 BuildMI(*BB, MI, dl, get(BPF::LDB))
108 .addReg(ScratchReg, RegState::Define).addReg(SrcReg).addImm(Offset);
109 BuildMI(*BB, MI, dl, get(BPF::STB))
110 .addReg(ScratchReg, RegState::Kill).addReg(DstReg).addImm(Offset);
111 }
112
113 BB->erase(MI);
114 }
115
expandPostRAPseudo(MachineInstr & MI) const116 bool BPFInstrInfo::expandPostRAPseudo(MachineInstr &MI) const {
117 if (MI.getOpcode() == BPF::MEMCPY) {
118 expandMEMCPY(MI);
119 return true;
120 }
121
122 return false;
123 }
124
storeRegToStackSlot(MachineBasicBlock & MBB,MachineBasicBlock::iterator I,unsigned SrcReg,bool IsKill,int FI,const TargetRegisterClass * RC,const TargetRegisterInfo * TRI) const125 void BPFInstrInfo::storeRegToStackSlot(MachineBasicBlock &MBB,
126 MachineBasicBlock::iterator I,
127 unsigned SrcReg, bool IsKill, int FI,
128 const TargetRegisterClass *RC,
129 const TargetRegisterInfo *TRI) const {
130 DebugLoc DL;
131 if (I != MBB.end())
132 DL = I->getDebugLoc();
133
134 if (RC == &BPF::GPRRegClass)
135 BuildMI(MBB, I, DL, get(BPF::STD))
136 .addReg(SrcReg, getKillRegState(IsKill))
137 .addFrameIndex(FI)
138 .addImm(0);
139 else if (RC == &BPF::GPR32RegClass)
140 BuildMI(MBB, I, DL, get(BPF::STW32))
141 .addReg(SrcReg, getKillRegState(IsKill))
142 .addFrameIndex(FI)
143 .addImm(0);
144 else
145 llvm_unreachable("Can't store this register to stack slot");
146 }
147
loadRegFromStackSlot(MachineBasicBlock & MBB,MachineBasicBlock::iterator I,unsigned DestReg,int FI,const TargetRegisterClass * RC,const TargetRegisterInfo * TRI) const148 void BPFInstrInfo::loadRegFromStackSlot(MachineBasicBlock &MBB,
149 MachineBasicBlock::iterator I,
150 unsigned DestReg, int FI,
151 const TargetRegisterClass *RC,
152 const TargetRegisterInfo *TRI) const {
153 DebugLoc DL;
154 if (I != MBB.end())
155 DL = I->getDebugLoc();
156
157 if (RC == &BPF::GPRRegClass)
158 BuildMI(MBB, I, DL, get(BPF::LDD), DestReg).addFrameIndex(FI).addImm(0);
159 else if (RC == &BPF::GPR32RegClass)
160 BuildMI(MBB, I, DL, get(BPF::LDW32), DestReg).addFrameIndex(FI).addImm(0);
161 else
162 llvm_unreachable("Can't load this register from stack slot");
163 }
164
analyzeBranch(MachineBasicBlock & MBB,MachineBasicBlock * & TBB,MachineBasicBlock * & FBB,SmallVectorImpl<MachineOperand> & Cond,bool AllowModify) const165 bool BPFInstrInfo::analyzeBranch(MachineBasicBlock &MBB,
166 MachineBasicBlock *&TBB,
167 MachineBasicBlock *&FBB,
168 SmallVectorImpl<MachineOperand> &Cond,
169 bool AllowModify) const {
170 // Start from the bottom of the block and work up, examining the
171 // terminator instructions.
172 MachineBasicBlock::iterator I = MBB.end();
173 while (I != MBB.begin()) {
174 --I;
175 if (I->isDebugInstr())
176 continue;
177
178 // Working from the bottom, when we see a non-terminator
179 // instruction, we're done.
180 if (!isUnpredicatedTerminator(*I))
181 break;
182
183 // A terminator that isn't a branch can't easily be handled
184 // by this analysis.
185 if (!I->isBranch())
186 return true;
187
188 // Handle unconditional branches.
189 if (I->getOpcode() == BPF::JMP) {
190 if (!AllowModify) {
191 TBB = I->getOperand(0).getMBB();
192 continue;
193 }
194
195 // If the block has any instructions after a J, delete them.
196 while (std::next(I) != MBB.end())
197 std::next(I)->eraseFromParent();
198 Cond.clear();
199 FBB = nullptr;
200
201 // Delete the J if it's equivalent to a fall-through.
202 if (MBB.isLayoutSuccessor(I->getOperand(0).getMBB())) {
203 TBB = nullptr;
204 I->eraseFromParent();
205 I = MBB.end();
206 continue;
207 }
208
209 // TBB is used to indicate the unconditinal destination.
210 TBB = I->getOperand(0).getMBB();
211 continue;
212 }
213 // Cannot handle conditional branches
214 return true;
215 }
216
217 return false;
218 }
219
insertBranch(MachineBasicBlock & MBB,MachineBasicBlock * TBB,MachineBasicBlock * FBB,ArrayRef<MachineOperand> Cond,const DebugLoc & DL,int * BytesAdded) const220 unsigned BPFInstrInfo::insertBranch(MachineBasicBlock &MBB,
221 MachineBasicBlock *TBB,
222 MachineBasicBlock *FBB,
223 ArrayRef<MachineOperand> Cond,
224 const DebugLoc &DL,
225 int *BytesAdded) const {
226 assert(!BytesAdded && "code size not handled");
227
228 // Shouldn't be a fall through.
229 assert(TBB && "insertBranch must not be told to insert a fallthrough");
230
231 if (Cond.empty()) {
232 // Unconditional branch
233 assert(!FBB && "Unconditional branch with multiple successors!");
234 BuildMI(&MBB, DL, get(BPF::JMP)).addMBB(TBB);
235 return 1;
236 }
237
238 llvm_unreachable("Unexpected conditional branch");
239 }
240
removeBranch(MachineBasicBlock & MBB,int * BytesRemoved) const241 unsigned BPFInstrInfo::removeBranch(MachineBasicBlock &MBB,
242 int *BytesRemoved) const {
243 assert(!BytesRemoved && "code size not handled");
244
245 MachineBasicBlock::iterator I = MBB.end();
246 unsigned Count = 0;
247
248 while (I != MBB.begin()) {
249 --I;
250 if (I->isDebugInstr())
251 continue;
252 if (I->getOpcode() != BPF::JMP)
253 break;
254 // Remove the branch.
255 I->eraseFromParent();
256 I = MBB.end();
257 ++Count;
258 }
259
260 return Count;
261 }
262