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/MachineConstantPool.h"
27 #include "llvm/CodeGen/MachineInstr.h"
28 #include "llvm/IR/DataLayout.h"
29 #include "llvm/IR/DebugInfo.h"
30 #include "llvm/MC/MCStreamer.h"
31 #include "llvm/MC/MCSymbol.h"
32 #include "llvm/Support/Debug.h"
33 #include "llvm/Support/TargetRegistry.h"
34 #include "llvm/Support/raw_ostream.h"
35 
36 using namespace llvm;
37 
38 #define DEBUG_TYPE "asm-printer"
39 
40 namespace {
41 
42 class WebAssemblyAsmPrinter final : public AsmPrinter {
43   const WebAssemblyInstrInfo *TII;
44 
45 public:
46   WebAssemblyAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
47       : AsmPrinter(TM, std::move(Streamer)), TII(nullptr) {}
48 
49 private:
50   const char *getPassName() const override {
51     return "WebAssembly Assembly Printer";
52   }
53 
54   //===------------------------------------------------------------------===//
55   // MachineFunctionPass Implementation.
56   //===------------------------------------------------------------------===//
57 
58   void getAnalysisUsage(AnalysisUsage &AU) const override {
59     AsmPrinter::getAnalysisUsage(AU);
60   }
61 
62   bool runOnMachineFunction(MachineFunction &MF) override {
63     TII = MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
64     return AsmPrinter::runOnMachineFunction(MF);
65   }
66 
67   //===------------------------------------------------------------------===//
68   // AsmPrinter Implementation.
69   //===------------------------------------------------------------------===//
70 
71   void EmitConstantPool() override;
72   void EmitFunctionEntryLabel() override;
73   void EmitFunctionBodyStart() override;
74   void EmitFunctionBodyEnd() override;
75 
76   void EmitInstruction(const MachineInstr *MI) override;
77 };
78 
79 } // end anonymous namespace
80 
81 //===----------------------------------------------------------------------===//
82 
83 // Untyped, lower-case version of the opcode's name matching the names
84 // WebAssembly opcodes are expected to have. The tablegen names are uppercase
85 // and suffixed with their type (after an underscore).
86 static SmallString<32> Name(const WebAssemblyInstrInfo *TII,
87                             const MachineInstr *MI) {
88   std::string N(StringRef(TII->getName(MI->getOpcode())).lower());
89   std::string::size_type End = N.rfind('_');
90   End = std::string::npos == End ? N.length() : End;
91   return SmallString<32>(&N[0], &N[End]);
92 }
93 
94 static std::string toSymbol(StringRef S) { return ("$" + S).str(); }
95 
96 static const char *toType(const Type *Ty) {
97   switch (Ty->getTypeID()) {
98   default: break;
99   case Type::FloatTyID:  return "f32";
100   case Type::DoubleTyID: return "f64";
101   case Type::IntegerTyID:
102     switch (Ty->getIntegerBitWidth()) {
103     case 32: return "i32";
104     case 64: return "i64";
105     default: break;
106     }
107   }
108   DEBUG(dbgs() << "Invalid type "; Ty->print(dbgs()); dbgs() << '\n');
109   llvm_unreachable("invalid type");
110   return "<invalid>";
111 }
112 
113 void WebAssemblyAsmPrinter::EmitConstantPool() {
114   assert(MF->getConstantPool()->getConstants().empty() &&
115          "WebAssembly disables constant pools");
116 }
117 
118 void WebAssemblyAsmPrinter::EmitFunctionEntryLabel() {
119   SmallString<128> Str;
120   raw_svector_ostream OS(Str);
121 
122   CurrentFnSym->redefineIfPossible();
123 
124   // The function label could have already been emitted if two symbols end up
125   // conflicting due to asm renaming.  Detect this and emit an error.
126   if (CurrentFnSym->isVariable())
127     report_fatal_error("'" + Twine(CurrentFnSym->getName()) +
128                        "' is a protected alias");
129   if (CurrentFnSym->isDefined())
130     report_fatal_error("'" + Twine(CurrentFnSym->getName()) +
131                        "' label emitted multiple times to assembly file");
132 
133   OS << "(func " << toSymbol(CurrentFnSym->getName());
134   OutStreamer->EmitRawText(OS.str());
135 }
136 
137 void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
138   SmallString<128> Str;
139   raw_svector_ostream OS(Str);
140   const Function *F = MF->getFunction();
141   for (const Argument &A : F->args())
142     OS << " (param " << toType(A.getType()) << ')';
143   const Type *Rt = F->getReturnType();
144   if (!Rt->isVoidTy())
145     OS << " (result " << toType(Rt) << ')';
146   OS << '\n';
147   OutStreamer->EmitRawText(OS.str());
148 }
149 
150 void WebAssemblyAsmPrinter::EmitFunctionBodyEnd() {
151   SmallString<128> Str;
152   raw_svector_ostream OS(Str);
153   OS << ") ;; end func " << toSymbol(CurrentFnSym->getName()) << '\n';
154   OutStreamer->EmitRawText(OS.str());
155 }
156 
157 void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
158   DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
159   SmallString<128> Str;
160   raw_svector_ostream OS(Str);
161 
162   unsigned NumDefs = MI->getDesc().getNumDefs();
163   assert(NumDefs <= 1 &&
164          "Instructions with multiple result values not implemented");
165 
166   OS << '\t';
167 
168   if (NumDefs != 0) {
169     const MachineOperand &MO = MI->getOperand(0);
170     unsigned Reg = MO.getReg();
171     OS << "(setlocal @" << TargetRegisterInfo::virtReg2Index(Reg) << ' ';
172   }
173 
174   OS << '(' << Name(TII, MI);
175   for (const MachineOperand &MO : MI->uses())
176     switch (MO.getType()) {
177     default:
178       llvm_unreachable("unexpected machine operand type");
179     case MachineOperand::MO_Register: {
180       if (MO.isImplicit())
181         continue;
182       unsigned Reg = MO.getReg();
183       OS << " @" << TargetRegisterInfo::virtReg2Index(Reg);
184     } break;
185     case MachineOperand::MO_Immediate: {
186       OS << ' ' << MO.getImm();
187     } break;
188     case MachineOperand::MO_FPImmediate: {
189       static const size_t BufBytes = 128;
190       char buf[BufBytes];
191       APFloat FP = MO.getFPImm()->getValueAPF();
192       if (FP.isNaN())
193         assert((FP.bitwiseIsEqual(APFloat::getQNaN(FP.getSemantics())) ||
194                 FP.bitwiseIsEqual(
195                     APFloat::getQNaN(FP.getSemantics(), /*Negative=*/true))) &&
196                "convertToHexString handles neither SNaN nor NaN payloads");
197       // Use C99's hexadecimal floating-point representation.
198       auto Written =
199           FP.convertToHexString(buf, /*hexDigits=*/0, /*upperCase=*/false,
200                                 APFloat::rmNearestTiesToEven);
201       (void)Written;
202       assert(Written != 0);
203       assert(Written < BufBytes);
204       OS << ' ' << buf;
205     } break;
206     case MachineOperand::MO_GlobalAddress: {
207       OS << ' ' << toSymbol(MO.getGlobal()->getName());
208     } break;
209     }
210   OS << ')';
211 
212   if (NumDefs != 0)
213     OS << ')';
214 
215   OS << '\n';
216 
217   OutStreamer->EmitRawText(OS.str());
218 }
219 
220 // Force static initialization.
221 extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
222   RegisterAsmPrinter<WebAssemblyAsmPrinter> X(TheWebAssemblyTarget32);
223   RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(TheWebAssemblyTarget64);
224 }
225