LLVM  4.0.0
BPFISelDAGToDAG.cpp
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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"
25 #include "llvm/IR/IntrinsicInst.h"
26 #include "llvm/Support/Debug.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:
39  explicit BPFDAGToDAGISel(BPFTargetMachine &TM) : SelectionDAGISel(TM) {}
40 
41  StringRef 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
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 ||
69  return false;
70 
71  // Addresses of the form Addr+const or Addr|const
72  if (CurDAG->isBaseWithConstantOffset(Addr)) {
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
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
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 
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 
185  return new BPFDAGToDAGISel(TM);
186 }
raw_ostream & errs()
This returns a reference to a raw_ostream for standard error.
bool hasOneUse() const
Return true if there is exactly one use of this node.
unsigned getOpcode() const
Return the SelectionDAG opcode value for this node.
TargetGlobalAddress - Like GlobalAddress, but the DAG does no folding or anything else with this node...
Definition: ISDOpcodes.h:131
A debug info location.
Definition: DebugLoc.h:34
const SDValue & getOperand(unsigned Num) const
RESULT,OUTCHAIN = INTRINSIC_W_CHAIN(INCHAIN, INTRINSICID, arg1, ...) This node represents a target in...
Definition: ISDOpcodes.h:159
This file declares the MachineConstantPool class which is an abstract constant pool to keep track of ...
EVT getValueType(unsigned ResNo) const
Return the type of a specified result.
unsigned getLine() const
Definition: DebugLoc.cpp:25
const SDValue & getOperand(unsigned i) const
uint32_t Offset
unsigned getOpcode() const
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:298
EVT - Extended Value Type.
Definition: ValueTypes.h:31
#define R6(n)
void dump() const
Dump this node, for debugging.
constexpr bool isInt< 32 >(int64_t x)
Definition: MathExtras.h:274
Wrapper class for IR location info (IR ordering and DebugLoc) to be passed into SDNode creation funct...
Represents one node in the SelectionDAG.
SelectionDAGISel - This is the common base class used for SelectionDAG-based pattern-matching instruc...
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
int64_t getSExtValue() const
#define N
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:287
const DebugLoc & getDebugLoc() const
Return the source location info.
#define DEBUG(X)
Definition: Debug.h:100
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:47
Unlike LLVM values, Selection DAG nodes may return multiple values as the result of a computation...
FunctionPass * createBPFISelDag(BPFTargetMachine &TM)
bool isMachineOpcode() const
Test if this node has a post-isel opcode, directly corresponding to a MachineInstr opcode...