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/ADT/StringExtras.h"
26 #include "llvm/CodeGen/AsmPrinter.h"
27 #include "llvm/CodeGen/MachineConstantPool.h"
28 #include "llvm/CodeGen/MachineInstr.h"
29 #include "llvm/IR/DataLayout.h"
30 #include "llvm/IR/DebugInfo.h"
31 #include "llvm/MC/MCStreamer.h"
32 #include "llvm/MC/MCSymbol.h"
33 #include "llvm/Support/Debug.h"
34 #include "llvm/Support/TargetRegistry.h"
35 #include "llvm/Support/raw_ostream.h"
36 
37 using namespace llvm;
38 
39 #define DEBUG_TYPE "asm-printer"
40 
41 namespace {
42 
43 class WebAssemblyAsmPrinter final : public AsmPrinter {
44   const WebAssemblyInstrInfo *TII;
45   const MachineRegisterInfo *MRI;
46   unsigned NumArgs;
47 
48 public:
49   WebAssemblyAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
50       : AsmPrinter(TM, std::move(Streamer)), TII(nullptr), MRI(nullptr) {}
51 
52 private:
53   const char *getPassName() const override {
54     return "WebAssembly Assembly Printer";
55   }
56 
57   //===------------------------------------------------------------------===//
58   // MachineFunctionPass Implementation.
59   //===------------------------------------------------------------------===//
60 
61   void getAnalysisUsage(AnalysisUsage &AU) const override {
62     AsmPrinter::getAnalysisUsage(AU);
63   }
64 
65   bool runOnMachineFunction(MachineFunction &MF) override {
66     const auto &Subtarget = MF.getSubtarget<WebAssemblySubtarget>();
67     TII = Subtarget.getInstrInfo();
68     MRI = &MF.getRegInfo();
69     NumArgs = MF.getInfo<WebAssemblyFunctionInfo>()->getNumArguments();
70     return AsmPrinter::runOnMachineFunction(MF);
71   }
72 
73   //===------------------------------------------------------------------===//
74   // AsmPrinter Implementation.
75   //===------------------------------------------------------------------===//
76 
77   void EmitJumpTableInfo() override;
78   void EmitConstantPool() override;
79   void EmitFunctionBodyStart() override;
80   void EmitInstruction(const MachineInstr *MI) override;
81   void EmitEndOfAsmFile(Module &M) override;
82 
83   std::string getRegTypeName(unsigned RegNo) const;
84   static std::string toString(const APFloat &APF);
85   const char *toString(Type *Ty) const;
86   std::string regToString(const MachineOperand &MO);
87   std::string argToString(const MachineOperand &MO);
88 };
89 
90 } // end anonymous namespace
91 
92 //===----------------------------------------------------------------------===//
93 // Helpers.
94 //===----------------------------------------------------------------------===//
95 
96 // Operand type (if any), followed by the lower-case version of the opcode's
97 // name matching the names WebAssembly opcodes are expected to have. The
98 // tablegen names are uppercase and suffixed with their type (after an
99 // underscore). Conversions are additionally prefixed with their input type
100 // (before a double underscore).
101 static std::string OpcodeName(const WebAssemblyInstrInfo *TII,
102                               const MachineInstr *MI) {
103   std::string N(StringRef(TII->getName(MI->getOpcode())).lower());
104   std::string::size_type Len = N.length();
105   std::string::size_type Under = N.rfind('_');
106   bool HasType = std::string::npos != Under;
107   std::string::size_type NameEnd = HasType ? Under : Len;
108   std::string Name(&N[0], &N[NameEnd]);
109   if (!HasType)
110     return Name;
111   for (const char *typelessOpcode : { "return", "call", "br_if" })
112     if (Name == typelessOpcode)
113       return Name;
114   std::string Type(&N[NameEnd + 1], &N[Len]);
115   std::string::size_type DoubleUnder = Name.find("__");
116   bool IsConv = std::string::npos != DoubleUnder;
117   if (!IsConv)
118     return Type + '.' + Name;
119   std::string InType(&Name[0], &Name[DoubleUnder]);
120   return Type + '.' + std::string(&Name[DoubleUnder + 2], &Name[NameEnd]) +
121       '/' + InType;
122 }
123 
124 static std::string toSymbol(StringRef S) { return ("$" + S).str(); }
125 
126 std::string WebAssemblyAsmPrinter::getRegTypeName(unsigned RegNo) const {
127   const TargetRegisterClass *TRC = MRI->getRegClass(RegNo);
128   for (MVT T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64})
129     if (TRC->hasType(T))
130       return EVT(T).getEVTString();
131   DEBUG(errs() << "Unknown type for register number: " << RegNo);
132   llvm_unreachable("Unknown register type");
133   return "?";
134 }
135 
136 std::string WebAssemblyAsmPrinter::toString(const APFloat &FP) {
137   static const size_t BufBytes = 128;
138   char buf[BufBytes];
139   if (FP.isNaN())
140     assert((FP.bitwiseIsEqual(APFloat::getQNaN(FP.getSemantics())) ||
141             FP.bitwiseIsEqual(
142                 APFloat::getQNaN(FP.getSemantics(), /*Negative=*/true))) &&
143            "convertToHexString handles neither SNaN nor NaN payloads");
144   // Use C99's hexadecimal floating-point representation.
145   auto Written = FP.convertToHexString(
146       buf, /*hexDigits=*/0, /*upperCase=*/false, APFloat::rmNearestTiesToEven);
147   (void)Written;
148   assert(Written != 0);
149   assert(Written < BufBytes);
150   return buf;
151 }
152 
153 std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
154   unsigned RegNo = MO.getReg();
155   if (TargetRegisterInfo::isPhysicalRegister(RegNo))
156     return WebAssemblyInstPrinter::getRegisterName(RegNo);
157 
158   // WebAssembly arguments and local variables are in the same index space, and
159   // there are no explicit varargs, so we just add the number of arguments to
160   // the virtual register number to get the local variable number.
161   return utostr(TargetRegisterInfo::virtReg2Index(RegNo) + NumArgs);
162 }
163 
164 std::string WebAssemblyAsmPrinter::argToString(const MachineOperand &MO) {
165   unsigned ArgNo = MO.getImm();
166   // Same as above, but we don't need to add NumArgs here.
167   return utostr(ArgNo);
168 }
169 
170 const char *WebAssemblyAsmPrinter::toString(Type *Ty) const {
171   switch (Ty->getTypeID()) {
172   default:
173     break;
174   // Treat all pointers as the underlying integer into linear memory.
175   case Type::PointerTyID:
176     switch (getPointerSize()) {
177     case 4:
178       return "i32";
179     case 8:
180       return "i64";
181     default:
182       llvm_unreachable("unsupported pointer size");
183     }
184     break;
185   case Type::FloatTyID:
186     return "f32";
187   case Type::DoubleTyID:
188     return "f64";
189   case Type::IntegerTyID:
190     switch (Ty->getIntegerBitWidth()) {
191     case 8:
192       return "i8";
193     case 16:
194       return "i16";
195     case 32:
196       return "i32";
197     case 64:
198       return "i64";
199     default:
200       break;
201     }
202   }
203   DEBUG(dbgs() << "Invalid type "; Ty->print(dbgs()); dbgs() << '\n');
204   llvm_unreachable("invalid type");
205   return "<invalid>";
206 }
207 
208 //===----------------------------------------------------------------------===//
209 // WebAssemblyAsmPrinter Implementation.
210 //===----------------------------------------------------------------------===//
211 
212 void WebAssemblyAsmPrinter::EmitConstantPool() {
213   assert(MF->getConstantPool()->getConstants().empty() &&
214          "WebAssembly disables constant pools");
215 }
216 
217 void WebAssemblyAsmPrinter::EmitJumpTableInfo() {
218   // Nothing to do; jump tables are incorporated into the instruction stream.
219 }
220 
221 void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
222   const Function *F = MF->getFunction();
223   Type *Rt = F->getReturnType();
224   SmallString<128> Str;
225   raw_svector_ostream OS(Str);
226   bool First = true;
227 
228   if (!Rt->isVoidTy() || !F->arg_empty()) {
229     for (const Argument &A : F->args()) {
230       OS << (First ? "" : "\n") << "\t.param " << toString(A.getType());
231       First = false;
232     }
233     if (!Rt->isVoidTy()) {
234       OS << (First ? "" : "\n") << "\t.result " << toString(Rt);
235       First = false;
236     }
237   }
238 
239   bool FirstVReg = true;
240   for (unsigned Idx = 0, IdxE = MRI->getNumVirtRegs(); Idx != IdxE; ++Idx) {
241     unsigned VReg = TargetRegisterInfo::index2VirtReg(Idx);
242     // FIXME: Don't skip dead virtual registers for now: that would require
243     //        remapping all locals' numbers.
244     //if (!MRI->use_empty(VReg)) {
245       if (FirstVReg) {
246         OS << (First ? "" : "\n") << "\t.local ";
247         First = false;
248       }
249       OS << (FirstVReg ? "" : ", ") << getRegTypeName(VReg);
250       FirstVReg = false;
251     //}
252   }
253 
254   if (!First)
255     OutStreamer->EmitRawText(OS.str());
256   AsmPrinter::EmitFunctionBodyStart();
257 }
258 
259 void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
260   DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
261   SmallString<128> Str;
262   raw_svector_ostream OS(Str);
263 
264   unsigned NumDefs = MI->getDesc().getNumDefs();
265   assert(NumDefs <= 1 &&
266          "Instructions with multiple result values not implemented");
267 
268   OS << '\t';
269 
270   switch (MI->getOpcode()) {
271   case TargetOpcode::COPY:
272     OS << "get_local push, " << regToString(MI->getOperand(1));
273     break;
274   case WebAssembly::GLOBAL:
275     // TODO: wasm64
276     OS << "i32.const push, " << toSymbol(MI->getOperand(1).getGlobal()->getName());
277     break;
278   case WebAssembly::ARGUMENT_I32:
279   case WebAssembly::ARGUMENT_I64:
280   case WebAssembly::ARGUMENT_F32:
281   case WebAssembly::ARGUMENT_F64:
282     OS << "get_local push, " << argToString(MI->getOperand(1));
283     break;
284   case WebAssembly::Const_I32:
285     OS << "i32.const push, " << MI->getOperand(1).getImm();
286     break;
287   case WebAssembly::Const_I64:
288     OS << "i64.const push, " << MI->getOperand(1).getImm();
289     break;
290   case WebAssembly::Const_F32:
291     OS << "f32.const push, " << toString(MI->getOperand(1).getFPImm()->getValueAPF());
292     break;
293   case WebAssembly::Const_F64:
294     OS << "f64.const push, " << toString(MI->getOperand(1).getFPImm()->getValueAPF());
295     break;
296   default: {
297     OS << OpcodeName(TII, MI);
298     bool NeedComma = false;
299     bool DefsPushed = false;
300     if (NumDefs != 0 && !MI->isCall()) {
301       OS << " push";
302       NeedComma = true;
303       DefsPushed = true;
304     }
305     for (const MachineOperand &MO : MI->uses()) {
306       if (MO.isReg() && MO.isImplicit())
307         continue;
308       if (NeedComma)
309         OS << ',';
310       NeedComma = true;
311       OS << ' ';
312       switch (MO.getType()) {
313       default:
314         llvm_unreachable("unexpected machine operand type");
315       case MachineOperand::MO_Register:
316         OS << "(get_local " << regToString(MO) << ')';
317         break;
318       case MachineOperand::MO_Immediate:
319         OS << MO.getImm();
320         break;
321       case MachineOperand::MO_FPImmediate:
322         OS << toString(MO.getFPImm()->getValueAPF());
323         break;
324       case MachineOperand::MO_GlobalAddress:
325         OS << toSymbol(MO.getGlobal()->getName());
326         break;
327       case MachineOperand::MO_MachineBasicBlock:
328         OS << toSymbol(MO.getMBB()->getSymbol()->getName());
329         break;
330       }
331       if (NumDefs != 0 && !DefsPushed) {
332         // Special-case for calls; print the push after the callee.
333         assert(MI->isCall());
334         OS << ", push";
335         DefsPushed = true;
336       }
337     }
338     break;
339   }
340   }
341 
342   OutStreamer->EmitRawText(OS.str());
343 
344   if (NumDefs != 0) {
345     SmallString<128> Str;
346     raw_svector_ostream OS(Str);
347     const MachineOperand &Operand = MI->getOperand(0);
348     OS << "\tset_local " << regToString(Operand) << ", pop";
349     OutStreamer->EmitRawText(OS.str());
350   }
351 }
352 
353 void WebAssemblyAsmPrinter::EmitEndOfAsmFile(Module &M) {
354   SmallString<128> Str;
355   raw_svector_ostream OS(Str);
356   for (const Function &F : M)
357     if (F.isDeclarationForLinker()) {
358       assert(F.hasName() && "imported functions must have a name");
359       if (F.getName().startswith("llvm."))
360         continue;
361       if (Str.empty())
362         OS << "\t.imports\n";
363       Type *Rt = F.getReturnType();
364       OS << "\t.import " << toSymbol(F.getName()) << " \"\" \"" << F.getName()
365          << "\" (param";
366       for (const Argument &A : F.args())
367         OS << ' ' << toString(A.getType());
368       OS << ')';
369       if (!Rt->isVoidTy())
370         OS << " (result " << toString(Rt) << ')';
371       OS << '\n';
372     }
373   OutStreamer->EmitRawText(OS.str());
374 }
375 
376 // Force static initialization.
377 extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
378   RegisterAsmPrinter<WebAssemblyAsmPrinter> X(TheWebAssemblyTarget32);
379   RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(TheWebAssemblyTarget64);
380 }
381