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   void 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 void 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;
128   }
129 
130   // tablegen selection should be handled here.
131   switch (Opcode) {
132   default: break;
133   case ISD::SDIV: {
134     DebugLoc Empty;
135     const DebugLoc &DL = Node->getDebugLoc();
136     if (DL != Empty)
137       errs() << "Error at line " << DL.getLine() << ": ";
138     else
139       errs() << "Error: ";
140     errs() << "Unsupport signed division for DAG: ";
141     Node->dump(CurDAG);
142     errs() << "Please convert to unsigned div/mod.\n";
143     break;
144   }
145   case ISD::INTRINSIC_W_CHAIN: {
146     unsigned IntNo = cast<ConstantSDNode>(Node->getOperand(1))->getZExtValue();
147     switch (IntNo) {
148     case Intrinsic::bpf_load_byte:
149     case Intrinsic::bpf_load_half:
150     case Intrinsic::bpf_load_word: {
151       SDLoc DL(Node);
152       SDValue Chain = Node->getOperand(0);
153       SDValue N1 = Node->getOperand(1);
154       SDValue Skb = Node->getOperand(2);
155       SDValue N3 = Node->getOperand(3);
156 
157       SDValue R6Reg = CurDAG->getRegister(BPF::R6, MVT::i64);
158       Chain = CurDAG->getCopyToReg(Chain, DL, R6Reg, Skb, SDValue());
159       Node = CurDAG->UpdateNodeOperands(Node, Chain, N1, R6Reg, N3);
160       break;
161     }
162     }
163     break;
164   }
165 
166   case ISD::FrameIndex: {
167     int FI = cast<FrameIndexSDNode>(Node)->getIndex();
168     EVT VT = Node->getValueType(0);
169     SDValue TFI = CurDAG->getTargetFrameIndex(FI, VT);
170     unsigned Opc = BPF::MOV_rr;
171     if (Node->hasOneUse()) {
172       CurDAG->SelectNodeTo(Node, Opc, VT, TFI);
173       return;
174     }
175     ReplaceNode(Node, CurDAG->getMachineNode(Opc, SDLoc(Node), VT, TFI));
176     return;
177   }
178   }
179 
180   // Select the default instruction
181   SelectCode(Node);
182 }
183 
createBPFISelDag(BPFTargetMachine & TM)184 FunctionPass *llvm::createBPFISelDag(BPFTargetMachine &TM) {
185   return new BPFDAGToDAGISel(TM);
186 }
187