xref: /freebsd/contrib/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp (revision f976241773df2260e6170317080761d1c5814fe5)
1 //===-- WebAssemblyAsmPrinter.cpp - WebAssembly LLVM assembly writer ------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 ///
9 /// \file
10 /// This file contains a printer that converts from our internal
11 /// representation of machine-dependent LLVM code to the WebAssembly assembly
12 /// language.
13 ///
14 //===----------------------------------------------------------------------===//
15 
16 #include "WebAssemblyAsmPrinter.h"
17 #include "MCTargetDesc/WebAssemblyInstPrinter.h"
18 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
19 #include "MCTargetDesc/WebAssemblyTargetStreamer.h"
20 #include "TargetInfo/WebAssemblyTargetInfo.h"
21 #include "WebAssembly.h"
22 #include "WebAssemblyMCInstLower.h"
23 #include "WebAssemblyMachineFunctionInfo.h"
24 #include "WebAssemblyRegisterInfo.h"
25 #include "WebAssemblyTargetMachine.h"
26 #include "llvm/ADT/SmallSet.h"
27 #include "llvm/ADT/StringExtras.h"
28 #include "llvm/BinaryFormat/Wasm.h"
29 #include "llvm/CodeGen/Analysis.h"
30 #include "llvm/CodeGen/AsmPrinter.h"
31 #include "llvm/CodeGen/MachineConstantPool.h"
32 #include "llvm/CodeGen/MachineInstr.h"
33 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
34 #include "llvm/IR/DataLayout.h"
35 #include "llvm/IR/DebugInfoMetadata.h"
36 #include "llvm/IR/GlobalVariable.h"
37 #include "llvm/IR/Metadata.h"
38 #include "llvm/MC/MCContext.h"
39 #include "llvm/MC/MCSectionWasm.h"
40 #include "llvm/MC/MCStreamer.h"
41 #include "llvm/MC/MCSymbol.h"
42 #include "llvm/MC/MCSymbolWasm.h"
43 #include "llvm/Support/Debug.h"
44 #include "llvm/Support/TargetRegistry.h"
45 #include "llvm/Support/raw_ostream.h"
46 
47 using namespace llvm;
48 
49 #define DEBUG_TYPE "asm-printer"
50 
51 extern cl::opt<bool> WasmKeepRegisters;
52 
53 //===----------------------------------------------------------------------===//
54 // Helpers.
55 //===----------------------------------------------------------------------===//
56 
57 MVT WebAssemblyAsmPrinter::getRegType(unsigned RegNo) const {
58   const TargetRegisterInfo *TRI = Subtarget->getRegisterInfo();
59   const TargetRegisterClass *TRC = MRI->getRegClass(RegNo);
60   for (MVT T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64, MVT::v16i8, MVT::v8i16,
61                 MVT::v4i32, MVT::v2i64, MVT::v4f32, MVT::v2f64})
62     if (TRI->isTypeLegalForClass(*TRC, T))
63       return T;
64   LLVM_DEBUG(errs() << "Unknown type for register number: " << RegNo);
65   llvm_unreachable("Unknown register type");
66   return MVT::Other;
67 }
68 
69 std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
70   unsigned RegNo = MO.getReg();
71   assert(TargetRegisterInfo::isVirtualRegister(RegNo) &&
72          "Unlowered physical register encountered during assembly printing");
73   assert(!MFI->isVRegStackified(RegNo));
74   unsigned WAReg = MFI->getWAReg(RegNo);
75   assert(WAReg != WebAssemblyFunctionInfo::UnusedReg);
76   return '$' + utostr(WAReg);
77 }
78 
79 WebAssemblyTargetStreamer *WebAssemblyAsmPrinter::getTargetStreamer() {
80   MCTargetStreamer *TS = OutStreamer->getTargetStreamer();
81   return static_cast<WebAssemblyTargetStreamer *>(TS);
82 }
83 
84 //===----------------------------------------------------------------------===//
85 // WebAssemblyAsmPrinter Implementation.
86 //===----------------------------------------------------------------------===//
87 
88 void WebAssemblyAsmPrinter::EmitEndOfAsmFile(Module &M) {
89   for (auto &It : OutContext.getSymbols()) {
90     // Emit a .globaltype and .eventtype declaration.
91     auto Sym = cast<MCSymbolWasm>(It.getValue());
92     if (Sym->getType() == wasm::WASM_SYMBOL_TYPE_GLOBAL)
93       getTargetStreamer()->emitGlobalType(Sym);
94     else if (Sym->getType() == wasm::WASM_SYMBOL_TYPE_EVENT)
95       getTargetStreamer()->emitEventType(Sym);
96   }
97 
98   for (const auto &F : M) {
99     // Emit function type info for all undefined functions
100     if (F.isDeclarationForLinker() && !F.isIntrinsic()) {
101       SmallVector<MVT, 4> Results;
102       SmallVector<MVT, 4> Params;
103       computeSignatureVTs(F.getFunctionType(), F, TM, Params, Results);
104       auto *Sym = cast<MCSymbolWasm>(getSymbol(&F));
105       Sym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
106       if (!Sym->getSignature()) {
107         auto Signature = signatureFromMVTs(Results, Params);
108         Sym->setSignature(Signature.get());
109         addSignature(std::move(Signature));
110       }
111       // FIXME: this was originally intended for post-linking and was only used
112       // for imports that were only called indirectly (i.e. s2wasm could not
113       // infer the type from a call). With object files it applies to all
114       // imports. so fix the names and the tests, or rethink how import
115       // delcarations work in asm files.
116       getTargetStreamer()->emitFunctionType(Sym);
117 
118       if (TM.getTargetTriple().isOSBinFormatWasm() &&
119           F.hasFnAttribute("wasm-import-module")) {
120         StringRef Name =
121             F.getFnAttribute("wasm-import-module").getValueAsString();
122         Sym->setImportModule(Name);
123         getTargetStreamer()->emitImportModule(Sym, Name);
124       }
125       if (TM.getTargetTriple().isOSBinFormatWasm() &&
126           F.hasFnAttribute("wasm-import-name")) {
127         StringRef Name =
128             F.getFnAttribute("wasm-import-name").getValueAsString();
129         Sym->setImportName(Name);
130         getTargetStreamer()->emitImportName(Sym, Name);
131       }
132     }
133   }
134 
135   for (const auto &G : M.globals()) {
136     if (!G.hasInitializer() && G.hasExternalLinkage()) {
137       if (G.getValueType()->isSized()) {
138         uint16_t Size = M.getDataLayout().getTypeAllocSize(G.getValueType());
139         OutStreamer->emitELFSize(getSymbol(&G),
140                                  MCConstantExpr::create(Size, OutContext));
141       }
142     }
143   }
144 
145   if (const NamedMDNode *Named = M.getNamedMetadata("wasm.custom_sections")) {
146     for (const Metadata *MD : Named->operands()) {
147       const auto *Tuple = dyn_cast<MDTuple>(MD);
148       if (!Tuple || Tuple->getNumOperands() != 2)
149         continue;
150       const MDString *Name = dyn_cast<MDString>(Tuple->getOperand(0));
151       const MDString *Contents = dyn_cast<MDString>(Tuple->getOperand(1));
152       if (!Name || !Contents)
153         continue;
154 
155       OutStreamer->PushSection();
156       std::string SectionName = (".custom_section." + Name->getString()).str();
157       MCSectionWasm *MySection =
158           OutContext.getWasmSection(SectionName, SectionKind::getMetadata());
159       OutStreamer->SwitchSection(MySection);
160       OutStreamer->EmitBytes(Contents->getString());
161       OutStreamer->PopSection();
162     }
163   }
164 
165   EmitProducerInfo(M);
166   EmitTargetFeatures(M);
167 }
168 
169 void WebAssemblyAsmPrinter::EmitProducerInfo(Module &M) {
170   llvm::SmallVector<std::pair<std::string, std::string>, 4> Languages;
171   if (const NamedMDNode *Debug = M.getNamedMetadata("llvm.dbg.cu")) {
172     llvm::SmallSet<StringRef, 4> SeenLanguages;
173     for (size_t I = 0, E = Debug->getNumOperands(); I < E; ++I) {
174       const auto *CU = cast<DICompileUnit>(Debug->getOperand(I));
175       StringRef Language = dwarf::LanguageString(CU->getSourceLanguage());
176       Language.consume_front("DW_LANG_");
177       if (SeenLanguages.insert(Language).second)
178         Languages.emplace_back(Language.str(), "");
179     }
180   }
181 
182   llvm::SmallVector<std::pair<std::string, std::string>, 4> Tools;
183   if (const NamedMDNode *Ident = M.getNamedMetadata("llvm.ident")) {
184     llvm::SmallSet<StringRef, 4> SeenTools;
185     for (size_t I = 0, E = Ident->getNumOperands(); I < E; ++I) {
186       const auto *S = cast<MDString>(Ident->getOperand(I)->getOperand(0));
187       std::pair<StringRef, StringRef> Field = S->getString().split("version");
188       StringRef Name = Field.first.trim();
189       StringRef Version = Field.second.trim();
190       if (SeenTools.insert(Name).second)
191         Tools.emplace_back(Name.str(), Version.str());
192     }
193   }
194 
195   int FieldCount = int(!Languages.empty()) + int(!Tools.empty());
196   if (FieldCount != 0) {
197     MCSectionWasm *Producers = OutContext.getWasmSection(
198         ".custom_section.producers", SectionKind::getMetadata());
199     OutStreamer->PushSection();
200     OutStreamer->SwitchSection(Producers);
201     OutStreamer->EmitULEB128IntValue(FieldCount);
202     for (auto &Producers : {std::make_pair("language", &Languages),
203             std::make_pair("processed-by", &Tools)}) {
204       if (Producers.second->empty())
205         continue;
206       OutStreamer->EmitULEB128IntValue(strlen(Producers.first));
207       OutStreamer->EmitBytes(Producers.first);
208       OutStreamer->EmitULEB128IntValue(Producers.second->size());
209       for (auto &Producer : *Producers.second) {
210         OutStreamer->EmitULEB128IntValue(Producer.first.size());
211         OutStreamer->EmitBytes(Producer.first);
212         OutStreamer->EmitULEB128IntValue(Producer.second.size());
213         OutStreamer->EmitBytes(Producer.second);
214       }
215     }
216     OutStreamer->PopSection();
217   }
218 }
219 
220 void WebAssemblyAsmPrinter::EmitTargetFeatures(Module &M) {
221   struct FeatureEntry {
222     uint8_t Prefix;
223     StringRef Name;
224   };
225 
226   // Read target features and linkage policies from module metadata
227   SmallVector<FeatureEntry, 4> EmittedFeatures;
228   for (const SubtargetFeatureKV &KV : WebAssemblyFeatureKV) {
229     std::string MDKey = (StringRef("wasm-feature-") + KV.Key).str();
230     Metadata *Policy = M.getModuleFlag(MDKey);
231     if (Policy == nullptr)
232       continue;
233 
234     FeatureEntry Entry;
235     Entry.Prefix = 0;
236     Entry.Name = KV.Key;
237 
238     if (auto *MD = cast<ConstantAsMetadata>(Policy))
239       if (auto *I = cast<ConstantInt>(MD->getValue()))
240         Entry.Prefix = I->getZExtValue();
241 
242     // Silently ignore invalid metadata
243     if (Entry.Prefix != wasm::WASM_FEATURE_PREFIX_USED &&
244         Entry.Prefix != wasm::WASM_FEATURE_PREFIX_REQUIRED &&
245         Entry.Prefix != wasm::WASM_FEATURE_PREFIX_DISALLOWED)
246       continue;
247 
248     EmittedFeatures.push_back(Entry);
249   }
250 
251   if (EmittedFeatures.size() == 0)
252     return;
253 
254   // Emit features and linkage policies into the "target_features" section
255   MCSectionWasm *FeaturesSection = OutContext.getWasmSection(
256       ".custom_section.target_features", SectionKind::getMetadata());
257   OutStreamer->PushSection();
258   OutStreamer->SwitchSection(FeaturesSection);
259 
260   OutStreamer->EmitULEB128IntValue(EmittedFeatures.size());
261   for (auto &F : EmittedFeatures) {
262     OutStreamer->EmitIntValue(F.Prefix, 1);
263     OutStreamer->EmitULEB128IntValue(F.Name.size());
264     OutStreamer->EmitBytes(F.Name);
265   }
266 
267   OutStreamer->PopSection();
268 }
269 
270 void WebAssemblyAsmPrinter::EmitConstantPool() {
271   assert(MF->getConstantPool()->getConstants().empty() &&
272          "WebAssembly disables constant pools");
273 }
274 
275 void WebAssemblyAsmPrinter::EmitJumpTableInfo() {
276   // Nothing to do; jump tables are incorporated into the instruction stream.
277 }
278 
279 void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
280   const Function &F = MF->getFunction();
281   SmallVector<MVT, 1> ResultVTs;
282   SmallVector<MVT, 4> ParamVTs;
283   computeSignatureVTs(F.getFunctionType(), F, TM, ParamVTs, ResultVTs);
284   auto Signature = signatureFromMVTs(ResultVTs, ParamVTs);
285   auto *WasmSym = cast<MCSymbolWasm>(CurrentFnSym);
286   WasmSym->setSignature(Signature.get());
287   addSignature(std::move(Signature));
288   WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
289 
290   // FIXME: clean up how params and results are emitted (use signatures)
291   getTargetStreamer()->emitFunctionType(WasmSym);
292 
293   // Emit the function index.
294   if (MDNode *Idx = F.getMetadata("wasm.index")) {
295     assert(Idx->getNumOperands() == 1);
296 
297     getTargetStreamer()->emitIndIdx(AsmPrinter::lowerConstant(
298         cast<ConstantAsMetadata>(Idx->getOperand(0))->getValue()));
299   }
300 
301   SmallVector<wasm::ValType, 16> Locals;
302   valTypesFromMVTs(MFI->getLocals(), Locals);
303   getTargetStreamer()->emitLocal(Locals);
304 
305   AsmPrinter::EmitFunctionBodyStart();
306 }
307 
308 void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
309   LLVM_DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
310 
311   switch (MI->getOpcode()) {
312   case WebAssembly::ARGUMENT_i32:
313   case WebAssembly::ARGUMENT_i32_S:
314   case WebAssembly::ARGUMENT_i64:
315   case WebAssembly::ARGUMENT_i64_S:
316   case WebAssembly::ARGUMENT_f32:
317   case WebAssembly::ARGUMENT_f32_S:
318   case WebAssembly::ARGUMENT_f64:
319   case WebAssembly::ARGUMENT_f64_S:
320   case WebAssembly::ARGUMENT_v16i8:
321   case WebAssembly::ARGUMENT_v16i8_S:
322   case WebAssembly::ARGUMENT_v8i16:
323   case WebAssembly::ARGUMENT_v8i16_S:
324   case WebAssembly::ARGUMENT_v4i32:
325   case WebAssembly::ARGUMENT_v4i32_S:
326   case WebAssembly::ARGUMENT_v2i64:
327   case WebAssembly::ARGUMENT_v2i64_S:
328   case WebAssembly::ARGUMENT_v4f32:
329   case WebAssembly::ARGUMENT_v4f32_S:
330   case WebAssembly::ARGUMENT_v2f64:
331   case WebAssembly::ARGUMENT_v2f64_S:
332     // These represent values which are live into the function entry, so there's
333     // no instruction to emit.
334     break;
335   case WebAssembly::FALLTHROUGH_RETURN_I32:
336   case WebAssembly::FALLTHROUGH_RETURN_I32_S:
337   case WebAssembly::FALLTHROUGH_RETURN_I64:
338   case WebAssembly::FALLTHROUGH_RETURN_I64_S:
339   case WebAssembly::FALLTHROUGH_RETURN_F32:
340   case WebAssembly::FALLTHROUGH_RETURN_F32_S:
341   case WebAssembly::FALLTHROUGH_RETURN_F64:
342   case WebAssembly::FALLTHROUGH_RETURN_F64_S:
343   case WebAssembly::FALLTHROUGH_RETURN_v16i8:
344   case WebAssembly::FALLTHROUGH_RETURN_v16i8_S:
345   case WebAssembly::FALLTHROUGH_RETURN_v8i16:
346   case WebAssembly::FALLTHROUGH_RETURN_v8i16_S:
347   case WebAssembly::FALLTHROUGH_RETURN_v4i32:
348   case WebAssembly::FALLTHROUGH_RETURN_v4i32_S:
349   case WebAssembly::FALLTHROUGH_RETURN_v2i64:
350   case WebAssembly::FALLTHROUGH_RETURN_v2i64_S:
351   case WebAssembly::FALLTHROUGH_RETURN_v4f32:
352   case WebAssembly::FALLTHROUGH_RETURN_v4f32_S:
353   case WebAssembly::FALLTHROUGH_RETURN_v2f64:
354   case WebAssembly::FALLTHROUGH_RETURN_v2f64_S: {
355     // These instructions represent the implicit return at the end of a
356     // function body. Always pops one value off the stack.
357     if (isVerbose()) {
358       OutStreamer->AddComment("fallthrough-return-value");
359       OutStreamer->AddBlankLine();
360     }
361     break;
362   }
363   case WebAssembly::FALLTHROUGH_RETURN_VOID:
364   case WebAssembly::FALLTHROUGH_RETURN_VOID_S:
365     // This instruction represents the implicit return at the end of a
366     // function body with no return value.
367     if (isVerbose()) {
368       OutStreamer->AddComment("fallthrough-return-void");
369       OutStreamer->AddBlankLine();
370     }
371     break;
372   case WebAssembly::COMPILER_FENCE:
373     // This is a compiler barrier that prevents instruction reordering during
374     // backend compilation, and should not be emitted.
375     break;
376   case WebAssembly::EXTRACT_EXCEPTION_I32:
377   case WebAssembly::EXTRACT_EXCEPTION_I32_S:
378     // These are pseudo instructions that simulates popping values from stack.
379     // We print these only when we have -wasm-keep-registers on for assembly
380     // readability.
381     if (!WasmKeepRegisters)
382       break;
383     LLVM_FALLTHROUGH;
384   default: {
385     WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
386     MCInst TmpInst;
387     MCInstLowering.lower(MI, TmpInst);
388     EmitToStreamer(*OutStreamer, TmpInst);
389     break;
390   }
391   }
392 }
393 
394 bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
395                                             unsigned OpNo,
396                                             const char *ExtraCode,
397                                             raw_ostream &OS) {
398   // First try the generic code, which knows about modifiers like 'c' and 'n'.
399   if (!AsmPrinter::PrintAsmOperand(MI, OpNo, ExtraCode, OS))
400     return false;
401 
402   if (!ExtraCode) {
403     const MachineOperand &MO = MI->getOperand(OpNo);
404     switch (MO.getType()) {
405     case MachineOperand::MO_Immediate:
406       OS << MO.getImm();
407       return false;
408     case MachineOperand::MO_Register:
409       // FIXME: only opcode that still contains registers, as required by
410       // MachineInstr::getDebugVariable().
411       assert(MI->getOpcode() == WebAssembly::INLINEASM);
412       OS << regToString(MO);
413       return false;
414     case MachineOperand::MO_GlobalAddress:
415       PrintSymbolOperand(MO, OS);
416       return false;
417     case MachineOperand::MO_ExternalSymbol:
418       GetExternalSymbolSymbol(MO.getSymbolName())->print(OS, MAI);
419       printOffset(MO.getOffset(), OS);
420       return false;
421     case MachineOperand::MO_MachineBasicBlock:
422       MO.getMBB()->getSymbol()->print(OS, MAI);
423       return false;
424     default:
425       break;
426     }
427   }
428 
429   return true;
430 }
431 
432 bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
433                                                   unsigned OpNo,
434                                                   const char *ExtraCode,
435                                                   raw_ostream &OS) {
436   // The current approach to inline asm is that "r" constraints are expressed
437   // as local indices, rather than values on the operand stack. This simplifies
438   // using "r" as it eliminates the need to push and pop the values in a
439   // particular order, however it also makes it impossible to have an "m"
440   // constraint. So we don't support it.
441 
442   return AsmPrinter::PrintAsmMemoryOperand(MI, OpNo, ExtraCode, OS);
443 }
444 
445 // Force static initialization.
446 extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
447   RegisterAsmPrinter<WebAssemblyAsmPrinter> X(getTheWebAssemblyTarget32());
448   RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(getTheWebAssemblyTarget64());
449 }
450