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/WebAssemblyMCTargetDesc.h"
18 #include "MCTargetDesc/WebAssemblyTargetStreamer.h"
19 #include "TargetInfo/WebAssemblyTargetInfo.h"
20 #include "Utils/WebAssemblyTypeUtilities.h"
21 #include "WebAssembly.h"
22 #include "WebAssemblyMCInstLower.h"
23 #include "WebAssemblyMachineFunctionInfo.h"
24 #include "WebAssemblyRegisterInfo.h"
25 #include "WebAssemblyRuntimeLibcallSignatures.h"
26 #include "WebAssemblyTargetMachine.h"
27 #include "WebAssemblyUtilities.h"
28 #include "llvm/ADT/MapVector.h"
29 #include "llvm/ADT/SmallSet.h"
30 #include "llvm/ADT/StringExtras.h"
31 #include "llvm/Analysis/ValueTracking.h"
32 #include "llvm/BinaryFormat/Wasm.h"
33 #include "llvm/CodeGen/Analysis.h"
34 #include "llvm/CodeGen/AsmPrinter.h"
35 #include "llvm/CodeGen/MachineConstantPool.h"
36 #include "llvm/CodeGen/MachineInstr.h"
37 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
38 #include "llvm/IR/DataLayout.h"
39 #include "llvm/IR/DebugInfoMetadata.h"
40 #include "llvm/IR/GlobalVariable.h"
41 #include "llvm/IR/Metadata.h"
42 #include "llvm/MC/MCContext.h"
43 #include "llvm/MC/MCSectionWasm.h"
44 #include "llvm/MC/MCStreamer.h"
45 #include "llvm/MC/MCSymbol.h"
46 #include "llvm/MC/MCSymbolWasm.h"
47 #include "llvm/MC/TargetRegistry.h"
48 #include "llvm/Support/Debug.h"
49 #include "llvm/Support/raw_ostream.h"
50
51 using namespace llvm;
52
53 #define DEBUG_TYPE "asm-printer"
54
55 extern cl::opt<bool> WasmKeepRegisters;
56
57 //===----------------------------------------------------------------------===//
58 // Helpers.
59 //===----------------------------------------------------------------------===//
60
getRegType(unsigned RegNo) const61 MVT WebAssemblyAsmPrinter::getRegType(unsigned RegNo) const {
62 const TargetRegisterInfo *TRI = Subtarget->getRegisterInfo();
63 const TargetRegisterClass *TRC = MRI->getRegClass(RegNo);
64 for (MVT T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64, MVT::v16i8, MVT::v8i16,
65 MVT::v4i32, MVT::v2i64, MVT::v4f32, MVT::v2f64})
66 if (TRI->isTypeLegalForClass(*TRC, T))
67 return T;
68 LLVM_DEBUG(errs() << "Unknown type for register number: " << RegNo);
69 llvm_unreachable("Unknown register type");
70 return MVT::Other;
71 }
72
regToString(const MachineOperand & MO)73 std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
74 Register RegNo = MO.getReg();
75 assert(RegNo.isVirtual() &&
76 "Unlowered physical register encountered during assembly printing");
77 assert(!MFI->isVRegStackified(RegNo));
78 unsigned WAReg = MFI->getWAReg(RegNo);
79 assert(WAReg != WebAssembly::UnusedReg);
80 return '$' + utostr(WAReg);
81 }
82
getTargetStreamer()83 WebAssemblyTargetStreamer *WebAssemblyAsmPrinter::getTargetStreamer() {
84 MCTargetStreamer *TS = OutStreamer->getTargetStreamer();
85 return static_cast<WebAssemblyTargetStreamer *>(TS);
86 }
87
88 // Emscripten exception handling helpers
89 //
90 // This converts invoke names generated by LowerEmscriptenEHSjLj to real names
91 // that are expected by JavaScript glue code. The invoke names generated by
92 // Emscripten JS glue code are based on their argument and return types; for
93 // example, for a function that takes an i32 and returns nothing, it is
94 // 'invoke_vi'. But the format of invoke generated by LowerEmscriptenEHSjLj pass
95 // contains a mangled string generated from their IR types, for example,
96 // "__invoke_void_%struct.mystruct*_int", because final wasm types are not
97 // available in the IR pass. So we convert those names to the form that
98 // Emscripten JS code expects.
99 //
100 // Refer to LowerEmscriptenEHSjLj pass for more details.
101
102 // Returns true if the given function name is an invoke name generated by
103 // LowerEmscriptenEHSjLj pass.
isEmscriptenInvokeName(StringRef Name)104 static bool isEmscriptenInvokeName(StringRef Name) {
105 if (Name.front() == '"' && Name.back() == '"')
106 Name = Name.substr(1, Name.size() - 2);
107 return Name.starts_with("__invoke_");
108 }
109
110 // Returns a character that represents the given wasm value type in invoke
111 // signatures.
getInvokeSig(wasm::ValType VT)112 static char getInvokeSig(wasm::ValType VT) {
113 switch (VT) {
114 case wasm::ValType::I32:
115 return 'i';
116 case wasm::ValType::I64:
117 return 'j';
118 case wasm::ValType::F32:
119 return 'f';
120 case wasm::ValType::F64:
121 return 'd';
122 case wasm::ValType::V128:
123 return 'V';
124 case wasm::ValType::FUNCREF:
125 return 'F';
126 case wasm::ValType::EXTERNREF:
127 return 'X';
128 }
129 llvm_unreachable("Unhandled wasm::ValType enum");
130 }
131
132 // Given the wasm signature, generate the invoke name in the format JS glue code
133 // expects.
getEmscriptenInvokeSymbolName(wasm::WasmSignature * Sig)134 static std::string getEmscriptenInvokeSymbolName(wasm::WasmSignature *Sig) {
135 assert(Sig->Returns.size() <= 1);
136 std::string Ret = "invoke_";
137 if (!Sig->Returns.empty())
138 for (auto VT : Sig->Returns)
139 Ret += getInvokeSig(VT);
140 else
141 Ret += 'v';
142 // Invokes' first argument is a pointer to the original function, so skip it
143 for (unsigned I = 1, E = Sig->Params.size(); I < E; I++)
144 Ret += getInvokeSig(Sig->Params[I]);
145 return Ret;
146 }
147
148 //===----------------------------------------------------------------------===//
149 // WebAssemblyAsmPrinter Implementation.
150 //===----------------------------------------------------------------------===//
151
getMCSymbolForFunction(const Function * F,bool EnableEmEH,wasm::WasmSignature * Sig,bool & InvokeDetected)152 MCSymbolWasm *WebAssemblyAsmPrinter::getMCSymbolForFunction(
153 const Function *F, bool EnableEmEH, wasm::WasmSignature *Sig,
154 bool &InvokeDetected) {
155 MCSymbolWasm *WasmSym = nullptr;
156 if (EnableEmEH && isEmscriptenInvokeName(F->getName())) {
157 assert(Sig);
158 InvokeDetected = true;
159 if (Sig->Returns.size() > 1) {
160 std::string Msg =
161 "Emscripten EH/SjLj does not support multivalue returns: " +
162 std::string(F->getName()) + ": " +
163 WebAssembly::signatureToString(Sig);
164 report_fatal_error(Twine(Msg));
165 }
166 WasmSym = cast<MCSymbolWasm>(
167 GetExternalSymbolSymbol(getEmscriptenInvokeSymbolName(Sig)));
168 } else {
169 WasmSym = cast<MCSymbolWasm>(getSymbol(F));
170 }
171 return WasmSym;
172 }
173
emitGlobalVariable(const GlobalVariable * GV)174 void WebAssemblyAsmPrinter::emitGlobalVariable(const GlobalVariable *GV) {
175 if (!WebAssembly::isWasmVarAddressSpace(GV->getAddressSpace())) {
176 AsmPrinter::emitGlobalVariable(GV);
177 return;
178 }
179
180 assert(!GV->isThreadLocal());
181
182 MCSymbolWasm *Sym = cast<MCSymbolWasm>(getSymbol(GV));
183
184 if (!Sym->getType()) {
185 SmallVector<MVT, 1> VTs;
186 Type *GlobalVT = GV->getValueType();
187 if (Subtarget) {
188 // Subtarget is only set when a function is defined, because
189 // each function can declare a different subtarget. For example,
190 // on ARM a compilation unit might have a function on ARM and
191 // another on Thumb. Therefore only if Subtarget is non-null we
192 // can actually calculate the legal VTs.
193 const WebAssemblyTargetLowering &TLI = *Subtarget->getTargetLowering();
194 computeLegalValueVTs(TLI, GV->getParent()->getContext(),
195 GV->getParent()->getDataLayout(), GlobalVT, VTs);
196 }
197 WebAssembly::wasmSymbolSetType(Sym, GlobalVT, VTs);
198 }
199
200 emitVisibility(Sym, GV->getVisibility(), !GV->isDeclaration());
201 emitSymbolType(Sym);
202 if (GV->hasInitializer()) {
203 assert(getSymbolPreferLocal(*GV) == Sym);
204 emitLinkage(GV, Sym);
205 OutStreamer->emitLabel(Sym);
206 // TODO: Actually emit the initializer value. Otherwise the global has the
207 // default value for its type (0, ref.null, etc).
208 OutStreamer->addBlankLine();
209 }
210 }
211
getOrCreateWasmSymbol(StringRef Name)212 MCSymbol *WebAssemblyAsmPrinter::getOrCreateWasmSymbol(StringRef Name) {
213 auto *WasmSym = cast<MCSymbolWasm>(GetExternalSymbolSymbol(Name));
214
215 // May be called multiple times, so early out.
216 if (WasmSym->getType())
217 return WasmSym;
218
219 const WebAssemblySubtarget &Subtarget = getSubtarget();
220
221 // Except for certain known symbols, all symbols used by CodeGen are
222 // functions. It's OK to hardcode knowledge of specific symbols here; this
223 // method is precisely there for fetching the signatures of known
224 // Clang-provided symbols.
225 if (Name == "__stack_pointer" || Name == "__tls_base" ||
226 Name == "__memory_base" || Name == "__table_base" ||
227 Name == "__tls_size" || Name == "__tls_align") {
228 bool Mutable =
229 Name == "__stack_pointer" || Name == "__tls_base";
230 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
231 WasmSym->setGlobalType(wasm::WasmGlobalType{
232 uint8_t(Subtarget.hasAddr64() ? wasm::WASM_TYPE_I64
233 : wasm::WASM_TYPE_I32),
234 Mutable});
235 return WasmSym;
236 }
237
238 if (Name.starts_with("GCC_except_table")) {
239 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_DATA);
240 return WasmSym;
241 }
242
243 SmallVector<wasm::ValType, 4> Returns;
244 SmallVector<wasm::ValType, 4> Params;
245 if (Name == "__cpp_exception" || Name == "__c_longjmp") {
246 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_TAG);
247 // In static linking we define tag symbols in WasmException::endModule().
248 // But we may have multiple objects to be linked together, each of which
249 // defines the tag symbols. To resolve them, we declare them as weak. In
250 // dynamic linking we make tag symbols undefined in the backend, define it
251 // in JS, and feed them to each importing module.
252 if (!isPositionIndependent())
253 WasmSym->setWeak(true);
254 WasmSym->setExternal(true);
255
256 // Currently both C++ exceptions and C longjmps have a single pointer type
257 // param. For C++ exceptions it is a pointer to an exception object, and for
258 // C longjmps it is pointer to a struct that contains a setjmp buffer and a
259 // longjmp return value. We may consider using multiple value parameters for
260 // longjmps later when multivalue support is ready.
261 wasm::ValType AddrType =
262 Subtarget.hasAddr64() ? wasm::ValType::I64 : wasm::ValType::I32;
263 Params.push_back(AddrType);
264 } else { // Function symbols
265 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
266 getLibcallSignature(Subtarget, Name, Returns, Params);
267 }
268 auto Signature = std::make_unique<wasm::WasmSignature>(std::move(Returns),
269 std::move(Params));
270 WasmSym->setSignature(Signature.get());
271 addSignature(std::move(Signature));
272
273 return WasmSym;
274 }
275
emitSymbolType(const MCSymbolWasm * Sym)276 void WebAssemblyAsmPrinter::emitSymbolType(const MCSymbolWasm *Sym) {
277 std::optional<wasm::WasmSymbolType> WasmTy = Sym->getType();
278 if (!WasmTy)
279 return;
280
281 switch (*WasmTy) {
282 case wasm::WASM_SYMBOL_TYPE_GLOBAL:
283 getTargetStreamer()->emitGlobalType(Sym);
284 break;
285 case wasm::WASM_SYMBOL_TYPE_TAG:
286 getTargetStreamer()->emitTagType(Sym);
287 break;
288 case wasm::WASM_SYMBOL_TYPE_TABLE:
289 getTargetStreamer()->emitTableType(Sym);
290 break;
291 default:
292 break; // We only handle globals, tags and tables here
293 }
294 }
295
emitDecls(const Module & M)296 void WebAssemblyAsmPrinter::emitDecls(const Module &M) {
297 if (signaturesEmitted)
298 return;
299 signaturesEmitted = true;
300
301 // Normally symbols for globals get discovered as the MI gets lowered,
302 // but we need to know about them ahead of time. This will however,
303 // only find symbols that have been used. Unused symbols from globals will
304 // not be found here.
305 MachineModuleInfoWasm &MMIW = MMI->getObjFileInfo<MachineModuleInfoWasm>();
306 for (StringRef Name : MMIW.MachineSymbolsUsed) {
307 auto *WasmSym = cast<MCSymbolWasm>(getOrCreateWasmSymbol(Name));
308 if (WasmSym->isFunction()) {
309 // TODO(wvo): is there any case where this overlaps with the call to
310 // emitFunctionType in the loop below?
311 getTargetStreamer()->emitFunctionType(WasmSym);
312 }
313 }
314
315 for (auto &It : OutContext.getSymbols()) {
316 // Emit .globaltype, .tagtype, or .tabletype declarations for extern
317 // declarations, i.e. those that have only been declared (but not defined)
318 // in the current module
319 auto Sym = cast<MCSymbolWasm>(It.getValue());
320 if (!Sym->isDefined())
321 emitSymbolType(Sym);
322 }
323
324 DenseSet<MCSymbol *> InvokeSymbols;
325 for (const auto &F : M) {
326 if (F.isIntrinsic())
327 continue;
328
329 // Emit function type info for all functions. This will emit duplicate
330 // information for defined functions (which already have function type
331 // info emitted alongside their definition), but this is necessary in
332 // order to enable the single-pass WebAssemblyAsmTypeCheck to succeed.
333 SmallVector<MVT, 4> Results;
334 SmallVector<MVT, 4> Params;
335 computeSignatureVTs(F.getFunctionType(), &F, F, TM, Params, Results);
336 // At this point these MCSymbols may or may not have been created already
337 // and thus also contain a signature, but we need to get the signature
338 // anyway here in case it is an invoke that has not yet been created. We
339 // will discard it later if it turns out not to be necessary.
340 auto Signature = signatureFromMVTs(Results, Params);
341 bool InvokeDetected = false;
342 auto *Sym = getMCSymbolForFunction(
343 &F, WebAssembly::WasmEnableEmEH || WebAssembly::WasmEnableEmSjLj,
344 Signature.get(), InvokeDetected);
345
346 // Multiple functions can be mapped to the same invoke symbol. For
347 // example, two IR functions '__invoke_void_i8*' and '__invoke_void_i32'
348 // are both mapped to '__invoke_vi'. We keep them in a set once we emit an
349 // Emscripten EH symbol so we don't emit the same symbol twice.
350 if (InvokeDetected && !InvokeSymbols.insert(Sym).second)
351 continue;
352
353 Sym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
354 if (!Sym->getSignature()) {
355 Sym->setSignature(Signature.get());
356 addSignature(std::move(Signature));
357 } else {
358 // This symbol has already been created and had a signature. Discard it.
359 Signature.reset();
360 }
361
362 getTargetStreamer()->emitFunctionType(Sym);
363
364 if (F.hasFnAttribute("wasm-import-module")) {
365 StringRef Name =
366 F.getFnAttribute("wasm-import-module").getValueAsString();
367 Sym->setImportModule(storeName(Name));
368 getTargetStreamer()->emitImportModule(Sym, Name);
369 }
370 if (F.hasFnAttribute("wasm-import-name")) {
371 // If this is a converted Emscripten EH/SjLj symbol, we shouldn't use
372 // the original function name but the converted symbol name.
373 StringRef Name =
374 InvokeDetected
375 ? Sym->getName()
376 : F.getFnAttribute("wasm-import-name").getValueAsString();
377 Sym->setImportName(storeName(Name));
378 getTargetStreamer()->emitImportName(Sym, Name);
379 }
380
381 if (F.hasFnAttribute("wasm-export-name")) {
382 auto *Sym = cast<MCSymbolWasm>(getSymbol(&F));
383 StringRef Name = F.getFnAttribute("wasm-export-name").getValueAsString();
384 Sym->setExportName(storeName(Name));
385 getTargetStreamer()->emitExportName(Sym, Name);
386 }
387 }
388 }
389
emitEndOfAsmFile(Module & M)390 void WebAssemblyAsmPrinter::emitEndOfAsmFile(Module &M) {
391 // This is required to emit external declarations (like .functypes) when
392 // no functions are defined in the compilation unit and therefore,
393 // emitDecls() is not called until now.
394 emitDecls(M);
395
396 // When a function's address is taken, a TABLE_INDEX relocation is emitted
397 // against the function symbol at the use site. However the relocation
398 // doesn't explicitly refer to the table. In the future we may want to
399 // define a new kind of reloc against both the function and the table, so
400 // that the linker can see that the function symbol keeps the table alive,
401 // but for now manually mark the table as live.
402 for (const auto &F : M) {
403 if (!F.isIntrinsic() && F.hasAddressTaken()) {
404 MCSymbolWasm *FunctionTable =
405 WebAssembly::getOrCreateFunctionTableSymbol(OutContext, Subtarget);
406 OutStreamer->emitSymbolAttribute(FunctionTable, MCSA_NoDeadStrip);
407 break;
408 }
409 }
410
411 for (const auto &G : M.globals()) {
412 if (!G.hasInitializer() && G.hasExternalLinkage() &&
413 !WebAssembly::isWasmVarAddressSpace(G.getAddressSpace()) &&
414 G.getValueType()->isSized()) {
415 uint16_t Size = M.getDataLayout().getTypeAllocSize(G.getValueType());
416 OutStreamer->emitELFSize(getSymbol(&G),
417 MCConstantExpr::create(Size, OutContext));
418 }
419 }
420
421 if (const NamedMDNode *Named = M.getNamedMetadata("wasm.custom_sections")) {
422 for (const Metadata *MD : Named->operands()) {
423 const auto *Tuple = dyn_cast<MDTuple>(MD);
424 if (!Tuple || Tuple->getNumOperands() != 2)
425 continue;
426 const MDString *Name = dyn_cast<MDString>(Tuple->getOperand(0));
427 const MDString *Contents = dyn_cast<MDString>(Tuple->getOperand(1));
428 if (!Name || !Contents)
429 continue;
430
431 OutStreamer->pushSection();
432 std::string SectionName = (".custom_section." + Name->getString()).str();
433 MCSectionWasm *MySection =
434 OutContext.getWasmSection(SectionName, SectionKind::getMetadata());
435 OutStreamer->switchSection(MySection);
436 OutStreamer->emitBytes(Contents->getString());
437 OutStreamer->popSection();
438 }
439 }
440
441 EmitProducerInfo(M);
442 EmitTargetFeatures(M);
443 EmitFunctionAttributes(M);
444 }
445
EmitProducerInfo(Module & M)446 void WebAssemblyAsmPrinter::EmitProducerInfo(Module &M) {
447 llvm::SmallVector<std::pair<std::string, std::string>, 4> Languages;
448 if (const NamedMDNode *Debug = M.getNamedMetadata("llvm.dbg.cu")) {
449 llvm::SmallSet<StringRef, 4> SeenLanguages;
450 for (size_t I = 0, E = Debug->getNumOperands(); I < E; ++I) {
451 const auto *CU = cast<DICompileUnit>(Debug->getOperand(I));
452 StringRef Language = dwarf::LanguageString(CU->getSourceLanguage());
453 Language.consume_front("DW_LANG_");
454 if (SeenLanguages.insert(Language).second)
455 Languages.emplace_back(Language.str(), "");
456 }
457 }
458
459 llvm::SmallVector<std::pair<std::string, std::string>, 4> Tools;
460 if (const NamedMDNode *Ident = M.getNamedMetadata("llvm.ident")) {
461 llvm::SmallSet<StringRef, 4> SeenTools;
462 for (size_t I = 0, E = Ident->getNumOperands(); I < E; ++I) {
463 const auto *S = cast<MDString>(Ident->getOperand(I)->getOperand(0));
464 std::pair<StringRef, StringRef> Field = S->getString().split("version");
465 StringRef Name = Field.first.trim();
466 StringRef Version = Field.second.trim();
467 if (SeenTools.insert(Name).second)
468 Tools.emplace_back(Name.str(), Version.str());
469 }
470 }
471
472 int FieldCount = int(!Languages.empty()) + int(!Tools.empty());
473 if (FieldCount != 0) {
474 MCSectionWasm *Producers = OutContext.getWasmSection(
475 ".custom_section.producers", SectionKind::getMetadata());
476 OutStreamer->pushSection();
477 OutStreamer->switchSection(Producers);
478 OutStreamer->emitULEB128IntValue(FieldCount);
479 for (auto &Producers : {std::make_pair("language", &Languages),
480 std::make_pair("processed-by", &Tools)}) {
481 if (Producers.second->empty())
482 continue;
483 OutStreamer->emitULEB128IntValue(strlen(Producers.first));
484 OutStreamer->emitBytes(Producers.first);
485 OutStreamer->emitULEB128IntValue(Producers.second->size());
486 for (auto &Producer : *Producers.second) {
487 OutStreamer->emitULEB128IntValue(Producer.first.size());
488 OutStreamer->emitBytes(Producer.first);
489 OutStreamer->emitULEB128IntValue(Producer.second.size());
490 OutStreamer->emitBytes(Producer.second);
491 }
492 }
493 OutStreamer->popSection();
494 }
495 }
496
EmitTargetFeatures(Module & M)497 void WebAssemblyAsmPrinter::EmitTargetFeatures(Module &M) {
498 struct FeatureEntry {
499 uint8_t Prefix;
500 std::string Name;
501 };
502
503 // Read target features and linkage policies from module metadata
504 SmallVector<FeatureEntry, 4> EmittedFeatures;
505 auto EmitFeature = [&](std::string Feature) {
506 std::string MDKey = (StringRef("wasm-feature-") + Feature).str();
507 Metadata *Policy = M.getModuleFlag(MDKey);
508 if (Policy == nullptr)
509 return;
510
511 FeatureEntry Entry;
512 Entry.Prefix = 0;
513 Entry.Name = Feature;
514
515 if (auto *MD = cast<ConstantAsMetadata>(Policy))
516 if (auto *I = cast<ConstantInt>(MD->getValue()))
517 Entry.Prefix = I->getZExtValue();
518
519 // Silently ignore invalid metadata
520 if (Entry.Prefix != wasm::WASM_FEATURE_PREFIX_USED &&
521 Entry.Prefix != wasm::WASM_FEATURE_PREFIX_REQUIRED &&
522 Entry.Prefix != wasm::WASM_FEATURE_PREFIX_DISALLOWED)
523 return;
524
525 EmittedFeatures.push_back(Entry);
526 };
527
528 for (const SubtargetFeatureKV &KV : WebAssemblyFeatureKV) {
529 EmitFeature(KV.Key);
530 }
531 // This pseudo-feature tells the linker whether shared memory would be safe
532 EmitFeature("shared-mem");
533
534 // This is an "architecture", not a "feature", but we emit it as such for
535 // the benefit of tools like Binaryen and consistency with other producers.
536 // FIXME: Subtarget is null here, so can't Subtarget->hasAddr64() ?
537 if (M.getDataLayout().getPointerSize() == 8) {
538 // Can't use EmitFeature since "wasm-feature-memory64" is not a module
539 // flag.
540 EmittedFeatures.push_back({wasm::WASM_FEATURE_PREFIX_USED, "memory64"});
541 }
542
543 if (EmittedFeatures.size() == 0)
544 return;
545
546 // Emit features and linkage policies into the "target_features" section
547 MCSectionWasm *FeaturesSection = OutContext.getWasmSection(
548 ".custom_section.target_features", SectionKind::getMetadata());
549 OutStreamer->pushSection();
550 OutStreamer->switchSection(FeaturesSection);
551
552 OutStreamer->emitULEB128IntValue(EmittedFeatures.size());
553 for (auto &F : EmittedFeatures) {
554 OutStreamer->emitIntValue(F.Prefix, 1);
555 OutStreamer->emitULEB128IntValue(F.Name.size());
556 OutStreamer->emitBytes(F.Name);
557 }
558
559 OutStreamer->popSection();
560 }
561
EmitFunctionAttributes(Module & M)562 void WebAssemblyAsmPrinter::EmitFunctionAttributes(Module &M) {
563 auto V = M.getNamedGlobal("llvm.global.annotations");
564 if (!V)
565 return;
566
567 // Group all the custom attributes by name.
568 MapVector<StringRef, SmallVector<MCSymbol *, 4>> CustomSections;
569 const ConstantArray *CA = cast<ConstantArray>(V->getOperand(0));
570 for (Value *Op : CA->operands()) {
571 auto *CS = cast<ConstantStruct>(Op);
572 // The first field is a pointer to the annotated variable.
573 Value *AnnotatedVar = CS->getOperand(0)->stripPointerCasts();
574 // Only annotated functions are supported for now.
575 if (!isa<Function>(AnnotatedVar))
576 continue;
577 auto *F = cast<Function>(AnnotatedVar);
578
579 // The second field is a pointer to a global annotation string.
580 auto *GV = cast<GlobalVariable>(CS->getOperand(1)->stripPointerCasts());
581 StringRef AnnotationString;
582 getConstantStringInfo(GV, AnnotationString);
583 auto *Sym = cast<MCSymbolWasm>(getSymbol(F));
584 CustomSections[AnnotationString].push_back(Sym);
585 }
586
587 // Emit a custom section for each unique attribute.
588 for (const auto &[Name, Symbols] : CustomSections) {
589 MCSectionWasm *CustomSection = OutContext.getWasmSection(
590 ".custom_section.llvm.func_attr.annotate." + Name, SectionKind::getMetadata());
591 OutStreamer->pushSection();
592 OutStreamer->switchSection(CustomSection);
593
594 for (auto &Sym : Symbols) {
595 OutStreamer->emitValue(
596 MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_WASM_FUNCINDEX,
597 OutContext),
598 4);
599 }
600 OutStreamer->popSection();
601 }
602 }
603
emitConstantPool()604 void WebAssemblyAsmPrinter::emitConstantPool() {
605 emitDecls(*MMI->getModule());
606 assert(MF->getConstantPool()->getConstants().empty() &&
607 "WebAssembly disables constant pools");
608 }
609
emitJumpTableInfo()610 void WebAssemblyAsmPrinter::emitJumpTableInfo() {
611 // Nothing to do; jump tables are incorporated into the instruction stream.
612 }
613
emitFunctionBodyStart()614 void WebAssemblyAsmPrinter::emitFunctionBodyStart() {
615 const Function &F = MF->getFunction();
616 SmallVector<MVT, 1> ResultVTs;
617 SmallVector<MVT, 4> ParamVTs;
618 computeSignatureVTs(F.getFunctionType(), &F, F, TM, ParamVTs, ResultVTs);
619
620 auto Signature = signatureFromMVTs(ResultVTs, ParamVTs);
621 auto *WasmSym = cast<MCSymbolWasm>(CurrentFnSym);
622 WasmSym->setSignature(Signature.get());
623 addSignature(std::move(Signature));
624 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
625
626 getTargetStreamer()->emitFunctionType(WasmSym);
627
628 // Emit the function index.
629 if (MDNode *Idx = F.getMetadata("wasm.index")) {
630 assert(Idx->getNumOperands() == 1);
631
632 getTargetStreamer()->emitIndIdx(AsmPrinter::lowerConstant(
633 cast<ConstantAsMetadata>(Idx->getOperand(0))->getValue()));
634 }
635
636 SmallVector<wasm::ValType, 16> Locals;
637 valTypesFromMVTs(MFI->getLocals(), Locals);
638 getTargetStreamer()->emitLocal(Locals);
639
640 AsmPrinter::emitFunctionBodyStart();
641 }
642
emitInstruction(const MachineInstr * MI)643 void WebAssemblyAsmPrinter::emitInstruction(const MachineInstr *MI) {
644 LLVM_DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
645 WebAssembly_MC::verifyInstructionPredicates(MI->getOpcode(),
646 Subtarget->getFeatureBits());
647
648 switch (MI->getOpcode()) {
649 case WebAssembly::ARGUMENT_i32:
650 case WebAssembly::ARGUMENT_i32_S:
651 case WebAssembly::ARGUMENT_i64:
652 case WebAssembly::ARGUMENT_i64_S:
653 case WebAssembly::ARGUMENT_f32:
654 case WebAssembly::ARGUMENT_f32_S:
655 case WebAssembly::ARGUMENT_f64:
656 case WebAssembly::ARGUMENT_f64_S:
657 case WebAssembly::ARGUMENT_v16i8:
658 case WebAssembly::ARGUMENT_v16i8_S:
659 case WebAssembly::ARGUMENT_v8i16:
660 case WebAssembly::ARGUMENT_v8i16_S:
661 case WebAssembly::ARGUMENT_v4i32:
662 case WebAssembly::ARGUMENT_v4i32_S:
663 case WebAssembly::ARGUMENT_v2i64:
664 case WebAssembly::ARGUMENT_v2i64_S:
665 case WebAssembly::ARGUMENT_v4f32:
666 case WebAssembly::ARGUMENT_v4f32_S:
667 case WebAssembly::ARGUMENT_v2f64:
668 case WebAssembly::ARGUMENT_v2f64_S:
669 // These represent values which are live into the function entry, so there's
670 // no instruction to emit.
671 break;
672 case WebAssembly::FALLTHROUGH_RETURN: {
673 // These instructions represent the implicit return at the end of a
674 // function body.
675 if (isVerbose()) {
676 OutStreamer->AddComment("fallthrough-return");
677 OutStreamer->addBlankLine();
678 }
679 break;
680 }
681 case WebAssembly::COMPILER_FENCE:
682 // This is a compiler barrier that prevents instruction reordering during
683 // backend compilation, and should not be emitted.
684 break;
685 default: {
686 WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
687 MCInst TmpInst;
688 MCInstLowering.lower(MI, TmpInst);
689 EmitToStreamer(*OutStreamer, TmpInst);
690 break;
691 }
692 }
693 }
694
PrintAsmOperand(const MachineInstr * MI,unsigned OpNo,const char * ExtraCode,raw_ostream & OS)695 bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
696 unsigned OpNo,
697 const char *ExtraCode,
698 raw_ostream &OS) {
699 // First try the generic code, which knows about modifiers like 'c' and 'n'.
700 if (!AsmPrinter::PrintAsmOperand(MI, OpNo, ExtraCode, OS))
701 return false;
702
703 if (!ExtraCode) {
704 const MachineOperand &MO = MI->getOperand(OpNo);
705 switch (MO.getType()) {
706 case MachineOperand::MO_Immediate:
707 OS << MO.getImm();
708 return false;
709 case MachineOperand::MO_Register:
710 // FIXME: only opcode that still contains registers, as required by
711 // MachineInstr::getDebugVariable().
712 assert(MI->getOpcode() == WebAssembly::INLINEASM);
713 OS << regToString(MO);
714 return false;
715 case MachineOperand::MO_GlobalAddress:
716 PrintSymbolOperand(MO, OS);
717 return false;
718 case MachineOperand::MO_ExternalSymbol:
719 GetExternalSymbolSymbol(MO.getSymbolName())->print(OS, MAI);
720 printOffset(MO.getOffset(), OS);
721 return false;
722 case MachineOperand::MO_MachineBasicBlock:
723 MO.getMBB()->getSymbol()->print(OS, MAI);
724 return false;
725 default:
726 break;
727 }
728 }
729
730 return true;
731 }
732
PrintAsmMemoryOperand(const MachineInstr * MI,unsigned OpNo,const char * ExtraCode,raw_ostream & OS)733 bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
734 unsigned OpNo,
735 const char *ExtraCode,
736 raw_ostream &OS) {
737 // The current approach to inline asm is that "r" constraints are expressed
738 // as local indices, rather than values on the operand stack. This simplifies
739 // using "r" as it eliminates the need to push and pop the values in a
740 // particular order, however it also makes it impossible to have an "m"
741 // constraint. So we don't support it.
742
743 return AsmPrinter::PrintAsmMemoryOperand(MI, OpNo, ExtraCode, OS);
744 }
745
746 // Force static initialization.
LLVMInitializeWebAssemblyAsmPrinter()747 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyAsmPrinter() {
748 RegisterAsmPrinter<WebAssemblyAsmPrinter> X(getTheWebAssemblyTarget32());
749 RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(getTheWebAssemblyTarget64());
750 }
751