1 //===-- WebAssemblyAsmPrinter.cpp - WebAssembly LLVM assembly writer ------===//
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 contains a printer that converts from our internal
12 /// representation of machine-dependent LLVM code to the WebAssembly assembly
13 /// language.
14 ///
15 //===----------------------------------------------------------------------===//
16 
17 #include "WebAssembly.h"
18 #include "WebAssemblyMachineFunctionInfo.h"
19 #include "WebAssemblyRegisterInfo.h"
20 #include "WebAssemblySubtarget.h"
21 #include "InstPrinter/WebAssemblyInstPrinter.h"
22 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
23 
24 #include "llvm/ADT/SmallString.h"
25 #include "llvm/CodeGen/AsmPrinter.h"
26 #include "llvm/CodeGen/MachineInstr.h"
27 #include "llvm/IR/DataLayout.h"
28 #include "llvm/IR/DebugInfo.h"
29 #include "llvm/MC/MCStreamer.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/TargetRegistry.h"
32 #include "llvm/Support/raw_ostream.h"
33 
34 using namespace llvm;
35 
36 #define DEBUG_TYPE "asm-printer"
37 
38 namespace {
39 
40 class WebAssemblyAsmPrinter final : public AsmPrinter {
41   const WebAssemblyInstrInfo *TII;
42 
43 public:
44   WebAssemblyAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
45       : AsmPrinter(TM, std::move(Streamer)), TII(nullptr) {}
46 
47 private:
48   const char *getPassName() const override {
49     return "WebAssembly Assembly Printer";
50   }
51 
52   //===------------------------------------------------------------------===//
53   // MachineFunctionPass Implementation.
54   //===------------------------------------------------------------------===//
55 
56   void getAnalysisUsage(AnalysisUsage &AU) const override {
57     AsmPrinter::getAnalysisUsage(AU);
58   }
59 
60   bool runOnMachineFunction(MachineFunction &MF) override {
61     TII = static_cast<const WebAssemblyInstrInfo *>(
62         MF.getSubtarget().getInstrInfo());
63     return AsmPrinter::runOnMachineFunction(MF);
64   }
65 
66   //===------------------------------------------------------------------===//
67   // AsmPrinter Implementation.
68   //===------------------------------------------------------------------===//
69 
70   void EmitInstruction(const MachineInstr *MI) override;
71 };
72 
73 } // end anonymous namespace
74 
75 //===----------------------------------------------------------------------===//
76 
77 // Untyped, lower-case version of the opcode's name matching the names
78 // WebAssembly opcodes are expected to have. The tablegen names are uppercase
79 // and suffixed with their type (after an underscore).
80 static SmallString<32> Name(const WebAssemblyInstrInfo *TII,
81                             const MachineInstr *MI) {
82   std::string N(StringRef(TII->getName(MI->getOpcode())).lower());
83   std::string::size_type End = N.find('_');
84   End = std::string::npos == End ? N.length() : End;
85   return SmallString<32>(&N[0], &N[End]);
86 }
87 
88 void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
89   SmallString<128> Str;
90   raw_svector_ostream OS(Str);
91 
92   unsigned NumDefs = MI->getDesc().getNumDefs();
93   assert(NumDefs <= 1 &&
94          "Instructions with multiple result values not implemented");
95 
96   if (NumDefs != 0) {
97     const MachineOperand &MO = MI->getOperand(0);
98     unsigned Reg = MO.getReg();
99     OS << "(setlocal @" << TargetRegisterInfo::virtReg2Index(Reg) << ' ';
100   }
101 
102   OS << '(' << Name(TII, MI);
103   for (const MachineOperand &MO : MI->uses())
104     switch (MO.getType()) {
105     default:
106       llvm_unreachable("unexpected machine operand type");
107     case MachineOperand::MO_Register: {
108       if (MO.isImplicit())
109         continue;
110       unsigned Reg = MO.getReg();
111       OS << " @" << TargetRegisterInfo::virtReg2Index(Reg);
112     } break;
113     case MachineOperand::MO_Immediate: {
114       OS << ' ' << MO.getImm();
115     } break;
116     case MachineOperand::MO_FPImmediate: {
117       static const size_t BufBytes = 128;
118       char buf[BufBytes];
119       APFloat FP = MO.getFPImm()->getValueAPF();
120       if (FP.isNaN())
121         assert((FP.bitwiseIsEqual(APFloat::getQNaN(FP.getSemantics())) ||
122                 FP.bitwiseIsEqual(
123                     APFloat::getQNaN(FP.getSemantics(), /*Negative=*/true))) &&
124                "convertToHexString handles neither SNaN nor NaN payloads");
125       // Use C99's hexadecimal floating-point representation.
126       auto Written =
127           FP.convertToHexString(buf, /*hexDigits=*/0, /*upperCase=*/false,
128                                 APFloat::rmNearestTiesToEven);
129       (void)Written;
130       assert(Written != 0);
131       assert(Written < BufBytes);
132       OS << ' ' << buf;
133     } break;
134     }
135   OS << ')';
136 
137   if (NumDefs != 0)
138     OS << ')';
139 
140   OS << '\n';
141 
142   OutStreamer->EmitRawText(OS.str());
143 }
144 
145 // Force static initialization.
146 extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
147   RegisterAsmPrinter<WebAssemblyAsmPrinter> X(TheWebAssemblyTarget32);
148   RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(TheWebAssemblyTarget64);
149 }
150