1 //- WebAssemblyISelDAGToDAG.cpp - A dag to dag inst selector for WebAssembly -//
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 /// \file
11 /// \brief This file defines an instruction selector for the WebAssembly target.
12 ///
13 //===----------------------------------------------------------------------===//
14
15 #include "WebAssembly.h"
16 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
17 #include "WebAssemblyTargetMachine.h"
18 #include "llvm/CodeGen/SelectionDAGISel.h"
19 #include "llvm/IR/Function.h" // To access function attributes.
20 #include "llvm/Support/Debug.h"
21 #include "llvm/Support/MathExtras.h"
22 #include "llvm/Support/raw_ostream.h"
23 using namespace llvm;
24
25 #define DEBUG_TYPE "wasm-isel"
26
27 //===--------------------------------------------------------------------===//
28 /// WebAssembly-specific code to select WebAssembly machine instructions for
29 /// SelectionDAG operations.
30 ///
31 namespace {
32 class WebAssemblyDAGToDAGISel final : public SelectionDAGISel {
33 /// Keep a pointer to the WebAssemblySubtarget around so that we can make the
34 /// right decision when generating code for different targets.
35 const WebAssemblySubtarget *Subtarget;
36
37 bool ForCodeSize;
38
39 public:
WebAssemblyDAGToDAGISel(WebAssemblyTargetMachine & tm,CodeGenOpt::Level OptLevel)40 WebAssemblyDAGToDAGISel(WebAssemblyTargetMachine &tm,
41 CodeGenOpt::Level OptLevel)
42 : SelectionDAGISel(tm, OptLevel), Subtarget(nullptr), ForCodeSize(false) {
43 }
44
getPassName() const45 const char *getPassName() const override {
46 return "WebAssembly Instruction Selection";
47 }
48
runOnMachineFunction(MachineFunction & MF)49 bool runOnMachineFunction(MachineFunction &MF) override {
50 ForCodeSize =
51 MF.getFunction()->hasFnAttribute(Attribute::OptimizeForSize) ||
52 MF.getFunction()->hasFnAttribute(Attribute::MinSize);
53 Subtarget = &MF.getSubtarget<WebAssemblySubtarget>();
54 return SelectionDAGISel::runOnMachineFunction(MF);
55 }
56
57 void Select(SDNode *Node) override;
58
59 bool SelectInlineAsmMemoryOperand(const SDValue &Op, unsigned ConstraintID,
60 std::vector<SDValue> &OutOps) override;
61
62 // Include the pieces autogenerated from the target description.
63 #include "WebAssemblyGenDAGISel.inc"
64
65 private:
66 // add select functions here...
67 };
68 } // end anonymous namespace
69
Select(SDNode * Node)70 void WebAssemblyDAGToDAGISel::Select(SDNode *Node) {
71 // Dump information about the Node being selected.
72 DEBUG(errs() << "Selecting: ");
73 DEBUG(Node->dump(CurDAG));
74 DEBUG(errs() << "\n");
75
76 // If we have a custom node, we already have selected!
77 if (Node->isMachineOpcode()) {
78 DEBUG(errs() << "== "; Node->dump(CurDAG); errs() << "\n");
79 Node->setNodeId(-1);
80 return;
81 }
82
83 // Few custom selection stuff.
84 EVT VT = Node->getValueType(0);
85
86 switch (Node->getOpcode()) {
87 default:
88 break;
89 // If we need WebAssembly-specific selection, it would go here.
90 (void)VT;
91 }
92
93 // Select the default instruction.
94 SelectCode(Node);
95 }
96
SelectInlineAsmMemoryOperand(const SDValue & Op,unsigned ConstraintID,std::vector<SDValue> & OutOps)97 bool WebAssemblyDAGToDAGISel::SelectInlineAsmMemoryOperand(
98 const SDValue &Op, unsigned ConstraintID, std::vector<SDValue> &OutOps) {
99 switch (ConstraintID) {
100 case InlineAsm::Constraint_i:
101 case InlineAsm::Constraint_m:
102 // We just support simple memory operands that just have a single address
103 // operand and need no special handling.
104 OutOps.push_back(Op);
105 return false;
106 default:
107 break;
108 }
109
110 return true;
111 }
112
113 /// This pass converts a legalized DAG into a WebAssembly-specific DAG, ready
114 /// for instruction scheduling.
createWebAssemblyISelDag(WebAssemblyTargetMachine & TM,CodeGenOpt::Level OptLevel)115 FunctionPass *llvm::createWebAssemblyISelDag(WebAssemblyTargetMachine &TM,
116 CodeGenOpt::Level OptLevel) {
117 return new WebAssemblyDAGToDAGISel(TM, OptLevel);
118 }
119