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 "InstPrinter/WebAssemblyInstPrinter.h"
19 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
20 #include "WebAssemblyMCInstLower.h"
21 #include "WebAssemblyMachineFunctionInfo.h"
22 #include "WebAssemblyRegisterInfo.h"
23 #include "WebAssemblySubtarget.h"
24 #include "llvm/ADT/SmallString.h"
25 #include "llvm/ADT/StringExtras.h"
26 #include "llvm/CodeGen/Analysis.h"
27 #include "llvm/CodeGen/AsmPrinter.h"
28 #include "llvm/CodeGen/MachineConstantPool.h"
29 #include "llvm/CodeGen/MachineInstr.h"
30 #include "llvm/IR/DataLayout.h"
31 #include "llvm/MC/MCContext.h"
32 #include "llvm/MC/MCStreamer.h"
33 #include "llvm/MC/MCSymbol.h"
34 #include "llvm/Support/Debug.h"
35 #include "llvm/Support/TargetRegistry.h"
36 #include "llvm/Support/raw_ostream.h"
37 
38 using namespace llvm;
39 
40 #define DEBUG_TYPE "asm-printer"
41 
42 namespace {
43 
44 class WebAssemblyAsmPrinter final : public AsmPrinter {
45   const MachineRegisterInfo *MRI;
46   const WebAssemblyFunctionInfo *MFI;
47 
48 public:
49   WebAssemblyAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
50       : AsmPrinter(TM, std::move(Streamer)), MRI(nullptr), MFI(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     MRI = &MF.getRegInfo();
67     MFI = MF.getInfo<WebAssemblyFunctionInfo>();
68     return AsmPrinter::runOnMachineFunction(MF);
69   }
70 
71   //===------------------------------------------------------------------===//
72   // AsmPrinter Implementation.
73   //===------------------------------------------------------------------===//
74 
75   void EmitJumpTableInfo() override;
76   void EmitConstantPool() override;
77   void EmitFunctionBodyStart() override;
78   void EmitInstruction(const MachineInstr *MI) override;
79   void EmitEndOfAsmFile(Module &M) override;
80   bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
81                        unsigned AsmVariant, const char *ExtraCode,
82                        raw_ostream &OS) override;
83   bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
84                              unsigned AsmVariant, const char *ExtraCode,
85                              raw_ostream &OS) override;
86 
87   std::string getRegTypeName(unsigned RegNo) const;
88   const char *toString(MVT VT) const;
89   std::string regToString(const MachineOperand &MO);
90 };
91 
92 } // end anonymous namespace
93 
94 //===----------------------------------------------------------------------===//
95 // Helpers.
96 //===----------------------------------------------------------------------===//
97 
98 std::string WebAssemblyAsmPrinter::getRegTypeName(unsigned RegNo) const {
99   const TargetRegisterClass *TRC = MRI->getRegClass(RegNo);
100   for (MVT T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64})
101     if (TRC->hasType(T))
102       return EVT(T).getEVTString();
103   DEBUG(errs() << "Unknown type for register number: " << RegNo);
104   llvm_unreachable("Unknown register type");
105   return "?";
106 }
107 
108 std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
109   unsigned RegNo = MO.getReg();
110   assert(TargetRegisterInfo::isVirtualRegister(RegNo) &&
111          "Unlowered physical register encountered during assembly printing");
112   assert(!MFI->isVRegStackified(RegNo));
113   unsigned WAReg = MFI->getWAReg(RegNo);
114   assert(WAReg != WebAssemblyFunctionInfo::UnusedReg);
115   return '$' + utostr(WAReg);
116 }
117 
118 const char *WebAssemblyAsmPrinter::toString(MVT VT) const {
119   switch (VT.SimpleTy) {
120   default:
121     break;
122   case MVT::f32:
123     return "f32";
124   case MVT::f64:
125     return "f64";
126   case MVT::i32:
127     return "i32";
128   case MVT::i64:
129     return "i64";
130   }
131   DEBUG(dbgs() << "Invalid type " << EVT(VT).getEVTString() << '\n');
132   llvm_unreachable("invalid type");
133   return "<invalid>";
134 }
135 
136 //===----------------------------------------------------------------------===//
137 // WebAssemblyAsmPrinter Implementation.
138 //===----------------------------------------------------------------------===//
139 
140 void WebAssemblyAsmPrinter::EmitConstantPool() {
141   assert(MF->getConstantPool()->getConstants().empty() &&
142          "WebAssembly disables constant pools");
143 }
144 
145 void WebAssemblyAsmPrinter::EmitJumpTableInfo() {
146   // Nothing to do; jump tables are incorporated into the instruction stream.
147 }
148 
149 static void ComputeLegalValueVTs(const Function &F,
150                                  const TargetMachine &TM,
151                                  Type *Ty,
152                                  SmallVectorImpl<MVT> &ValueVTs) {
153   const DataLayout& DL(F.getParent()->getDataLayout());
154   const WebAssemblyTargetLowering &TLI =
155       *TM.getSubtarget<WebAssemblySubtarget>(F).getTargetLowering();
156   SmallVector<EVT, 4> VTs;
157   ComputeValueVTs(TLI, DL, Ty, VTs);
158 
159   for (EVT VT : VTs) {
160     unsigned NumRegs = TLI.getNumRegisters(F.getContext(), VT);
161     MVT RegisterVT = TLI.getRegisterType(F.getContext(), VT);
162     for (unsigned i = 0; i != NumRegs; ++i)
163       ValueVTs.push_back(RegisterVT);
164   }
165 }
166 
167 void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
168   SmallString<128> Str;
169   raw_svector_ostream OS(Str);
170 
171   for (MVT VT : MFI->getParams())
172     OS << "\t" ".param " << toString(VT) << '\n';
173 
174   SmallVector<MVT, 4> ResultVTs;
175   const Function &F(*MF->getFunction());
176   ComputeLegalValueVTs(F, TM, F.getReturnType(), ResultVTs);
177   // If the return type needs to be legalized it will get converted into
178   // passing a pointer.
179   if (ResultVTs.size() == 1)
180     OS << "\t" ".result " << toString(ResultVTs.front()) << '\n';
181 
182   bool FirstWAReg = true;
183   for (unsigned Idx = 0, IdxE = MRI->getNumVirtRegs(); Idx != IdxE; ++Idx) {
184     unsigned VReg = TargetRegisterInfo::index2VirtReg(Idx);
185     unsigned WAReg = MFI->getWAReg(VReg);
186     // Don't declare unused registers.
187     if (WAReg == WebAssemblyFunctionInfo::UnusedReg)
188       continue;
189     // Don't redeclare parameters.
190     if (WAReg < MFI->getParams().size())
191       continue;
192     // Don't declare stackified registers.
193     if (int(WAReg) < 0)
194       continue;
195     if (FirstWAReg)
196       OS << "\t" ".local ";
197     else
198       OS << ", ";
199     OS << getRegTypeName(VReg);
200     FirstWAReg = false;
201   }
202   if (!FirstWAReg)
203     OS << '\n';
204 
205   // EmitRawText appends a newline, so strip off the last newline.
206   StringRef Text = OS.str();
207   if (!Text.empty())
208     OutStreamer->EmitRawText(Text.substr(0, Text.size() - 1));
209   AsmPrinter::EmitFunctionBodyStart();
210 }
211 
212 void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
213   DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
214 
215   switch (MI->getOpcode()) {
216   case WebAssembly::ARGUMENT_I32:
217   case WebAssembly::ARGUMENT_I64:
218   case WebAssembly::ARGUMENT_F32:
219   case WebAssembly::ARGUMENT_F64:
220     // These represent values which are live into the function entry, so there's
221     // no instruction to emit.
222     break;
223   default: {
224     WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
225     MCInst TmpInst;
226     MCInstLowering.Lower(MI, TmpInst);
227     EmitToStreamer(*OutStreamer, TmpInst);
228     break;
229   }
230   }
231 }
232 
233 void WebAssemblyAsmPrinter::EmitEndOfAsmFile(Module &M) {
234   const DataLayout &DL = M.getDataLayout();
235 
236   SmallString<128> Str;
237   raw_svector_ostream OS(Str);
238   for (const Function &F : M)
239     if (F.isDeclarationForLinker()) {
240       assert(F.hasName() && "imported functions must have a name");
241       if (F.isIntrinsic())
242         continue;
243       if (Str.empty())
244         OS << "\t.imports\n";
245 
246       MCSymbol *Sym = OutStreamer->getContext().getOrCreateSymbol(F.getName());
247       OS << "\t.import " << *Sym << " \"\" " << *Sym;
248 
249       const WebAssemblyTargetLowering &TLI =
250           *TM.getSubtarget<WebAssemblySubtarget>(F).getTargetLowering();
251 
252       // If we need to legalize the return type, it'll get converted into
253       // passing a pointer.
254       bool SawParam = false;
255       SmallVector<MVT, 4> ResultVTs;
256       ComputeLegalValueVTs(F, TM, F.getReturnType(), ResultVTs);
257       if (ResultVTs.size() > 1) {
258         ResultVTs.clear();
259         OS << " (param " << toString(TLI.getPointerTy(DL));
260         SawParam = true;
261       }
262 
263       for (const Argument &A : F.args()) {
264         SmallVector<MVT, 4> ParamVTs;
265         ComputeLegalValueVTs(F, TM, A.getType(), ParamVTs);
266         for (MVT VT : ParamVTs) {
267           if (!SawParam) {
268             OS << " (param";
269             SawParam = true;
270           }
271           OS << ' ' << toString(VT);
272         }
273       }
274       if (SawParam)
275         OS << ')';
276 
277       for (MVT VT : ResultVTs)
278         OS << " (result " << toString(VT) << ')';
279 
280       OS << '\n';
281     }
282 
283   StringRef Text = OS.str();
284   if (!Text.empty())
285     OutStreamer->EmitRawText(Text.substr(0, Text.size() - 1));
286 }
287 
288 bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
289                                             unsigned OpNo, unsigned AsmVariant,
290                                             const char *ExtraCode,
291                                             raw_ostream &OS) {
292   if (AsmVariant != 0)
293     report_fatal_error("There are no defined alternate asm variants");
294 
295   if (!ExtraCode) {
296     const MachineOperand &MO = MI->getOperand(OpNo);
297     if (MO.isImm())
298       OS << MO.getImm();
299     else
300       OS << regToString(MO);
301     return false;
302   }
303 
304   return AsmPrinter::PrintAsmOperand(MI, OpNo, AsmVariant, ExtraCode, OS);
305 }
306 
307 bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
308                                                   unsigned OpNo,
309                                                   unsigned AsmVariant,
310                                                   const char *ExtraCode,
311                                                   raw_ostream &OS) {
312   if (AsmVariant != 0)
313     report_fatal_error("There are no defined alternate asm variants");
314 
315   if (!ExtraCode) {
316     OS << regToString(MI->getOperand(OpNo));
317     return false;
318   }
319 
320   return AsmPrinter::PrintAsmMemoryOperand(MI, OpNo, AsmVariant, ExtraCode, OS);
321 }
322 
323 // Force static initialization.
324 extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
325   RegisterAsmPrinter<WebAssemblyAsmPrinter> X(TheWebAssemblyTarget32);
326   RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(TheWebAssemblyTarget64);
327 }
328