1 //===-- BPFISelDAGToDAG.cpp - A dag to dag inst selector for BPF ----------===//
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 defines a DAG pattern matching instruction selector for BPF,
11 // converting from a legalized dag to a BPF dag.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "BPF.h"
16 #include "BPFRegisterInfo.h"
17 #include "BPFSubtarget.h"
18 #include "BPFTargetMachine.h"
19 #include "llvm/CodeGen/MachineConstantPool.h"
20 #include "llvm/CodeGen/MachineFrameInfo.h"
21 #include "llvm/CodeGen/MachineFunction.h"
22 #include "llvm/CodeGen/MachineInstrBuilder.h"
23 #include "llvm/CodeGen/MachineRegisterInfo.h"
24 #include "llvm/CodeGen/SelectionDAGISel.h"
25 #include "llvm/IR/IntrinsicInst.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include "llvm/Target/TargetMachine.h"
30 using namespace llvm;
31
32 #define DEBUG_TYPE "bpf-isel"
33
34 // Instruction Selector Implementation
35 namespace {
36
37 class BPFDAGToDAGISel : public SelectionDAGISel {
38 public:
BPFDAGToDAGISel(BPFTargetMachine & TM)39 explicit BPFDAGToDAGISel(BPFTargetMachine &TM) : SelectionDAGISel(TM) {}
40
getPassName() const41 const char *getPassName() const override {
42 return "BPF DAG->DAG Pattern Instruction Selection";
43 }
44
45 private:
46 // Include the pieces autogenerated from the target description.
47 #include "BPFGenDAGISel.inc"
48
49 SDNode *Select(SDNode *N) override;
50
51 // Complex Pattern for address selection.
52 bool SelectAddr(SDValue Addr, SDValue &Base, SDValue &Offset);
53 bool SelectFIAddr(SDValue Addr, SDValue &Base, SDValue &Offset);
54 };
55 }
56
57 // ComplexPattern used on BPF Load/Store instructions
SelectAddr(SDValue Addr,SDValue & Base,SDValue & Offset)58 bool BPFDAGToDAGISel::SelectAddr(SDValue Addr, SDValue &Base, SDValue &Offset) {
59 // if Address is FI, get the TargetFrameIndex.
60 SDLoc DL(Addr);
61 if (FrameIndexSDNode *FIN = dyn_cast<FrameIndexSDNode>(Addr)) {
62 Base = CurDAG->getTargetFrameIndex(FIN->getIndex(), MVT::i64);
63 Offset = CurDAG->getTargetConstant(0, DL, MVT::i64);
64 return true;
65 }
66
67 if (Addr.getOpcode() == ISD::TargetExternalSymbol ||
68 Addr.getOpcode() == ISD::TargetGlobalAddress)
69 return false;
70
71 // Addresses of the form Addr+const or Addr|const
72 if (CurDAG->isBaseWithConstantOffset(Addr)) {
73 ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Addr.getOperand(1));
74 if (isInt<32>(CN->getSExtValue())) {
75
76 // If the first operand is a FI, get the TargetFI Node
77 if (FrameIndexSDNode *FIN =
78 dyn_cast<FrameIndexSDNode>(Addr.getOperand(0)))
79 Base = CurDAG->getTargetFrameIndex(FIN->getIndex(), MVT::i64);
80 else
81 Base = Addr.getOperand(0);
82
83 Offset = CurDAG->getTargetConstant(CN->getSExtValue(), DL, MVT::i64);
84 return true;
85 }
86 }
87
88 Base = Addr;
89 Offset = CurDAG->getTargetConstant(0, DL, MVT::i64);
90 return true;
91 }
92
93 // ComplexPattern used on BPF FI instruction
SelectFIAddr(SDValue Addr,SDValue & Base,SDValue & Offset)94 bool BPFDAGToDAGISel::SelectFIAddr(SDValue Addr, SDValue &Base, SDValue &Offset) {
95 SDLoc DL(Addr);
96
97 if (!CurDAG->isBaseWithConstantOffset(Addr))
98 return false;
99
100 // Addresses of the form Addr+const or Addr|const
101 ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Addr.getOperand(1));
102 if (isInt<32>(CN->getSExtValue())) {
103
104 // If the first operand is a FI, get the TargetFI Node
105 if (FrameIndexSDNode *FIN =
106 dyn_cast<FrameIndexSDNode>(Addr.getOperand(0)))
107 Base = CurDAG->getTargetFrameIndex(FIN->getIndex(), MVT::i64);
108 else
109 return false;
110
111 Offset = CurDAG->getTargetConstant(CN->getSExtValue(), DL, MVT::i64);
112 return true;
113 }
114
115 return false;
116 }
117
Select(SDNode * Node)118 SDNode *BPFDAGToDAGISel::Select(SDNode *Node) {
119 unsigned Opcode = Node->getOpcode();
120
121 // Dump information about the Node being selected
122 DEBUG(dbgs() << "Selecting: "; Node->dump(CurDAG); dbgs() << '\n');
123
124 // If we have a custom node, we already have selected!
125 if (Node->isMachineOpcode()) {
126 DEBUG(dbgs() << "== "; Node->dump(CurDAG); dbgs() << '\n');
127 return NULL;
128 }
129
130 // tablegen selection should be handled here.
131 switch (Opcode) {
132 default: break;
133 case ISD::INTRINSIC_W_CHAIN: {
134 unsigned IntNo = cast<ConstantSDNode>(Node->getOperand(1))->getZExtValue();
135 switch (IntNo) {
136 case Intrinsic::bpf_load_byte:
137 case Intrinsic::bpf_load_half:
138 case Intrinsic::bpf_load_word: {
139 SDLoc DL(Node);
140 SDValue Chain = Node->getOperand(0);
141 SDValue N1 = Node->getOperand(1);
142 SDValue Skb = Node->getOperand(2);
143 SDValue N3 = Node->getOperand(3);
144
145 SDValue R6Reg = CurDAG->getRegister(BPF::R6, MVT::i64);
146 Chain = CurDAG->getCopyToReg(Chain, DL, R6Reg, Skb, SDValue());
147 Node = CurDAG->UpdateNodeOperands(Node, Chain, N1, R6Reg, N3);
148 break;
149 }
150 }
151 break;
152 }
153
154 case ISD::FrameIndex: {
155 int FI = cast<FrameIndexSDNode>(Node)->getIndex();
156 EVT VT = Node->getValueType(0);
157 SDValue TFI = CurDAG->getTargetFrameIndex(FI, VT);
158 unsigned Opc = BPF::MOV_rr;
159 if (Node->hasOneUse())
160 return CurDAG->SelectNodeTo(Node, Opc, VT, TFI);
161 return CurDAG->getMachineNode(Opc, SDLoc(Node), VT, TFI);
162 }
163 }
164
165 // Select the default instruction
166 SDNode *ResNode = SelectCode(Node);
167
168 DEBUG(dbgs() << "=> ";
169 if (ResNode == nullptr || ResNode == Node)
170 Node->dump(CurDAG);
171 else
172 ResNode->dump(CurDAG);
173 dbgs() << '\n');
174 return ResNode;
175 }
176
createBPFISelDag(BPFTargetMachine & TM)177 FunctionPass *llvm::createBPFISelDag(BPFTargetMachine &TM) {
178 return new BPFDAGToDAGISel(TM);
179 }
180