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/IR/Module.h"
43#include "llvm/MC/MCContext.h"
44#include "llvm/MC/MCSectionWasm.h"
45#include "llvm/MC/MCStreamer.h"
46#include "llvm/MC/MCSymbol.h"
47#include "llvm/MC/MCSymbolWasm.h"
48#include "llvm/MC/TargetRegistry.h"
49#include "llvm/Support/Debug.h"
50#include "llvm/Support/raw_ostream.h"
51
52using namespace llvm;
53
54#define DEBUG_TYPE "asm-printer"
55
56extern cl::opt<bool> WasmKeepRegisters;
57
58//===----------------------------------------------------------------------===//
59// Helpers.
60//===----------------------------------------------------------------------===//
61
62MVT WebAssemblyAsmPrinter::getRegType(unsigned RegNo) const {
63 const TargetRegisterInfo *TRI = Subtarget->getRegisterInfo();
64 const TargetRegisterClass *TRC = MRI->getRegClass(Reg: RegNo);
65 for (MVT T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64, MVT::v16i8, MVT::v8i16,
66 MVT::v4i32, MVT::v2i64, MVT::v4f32, MVT::v2f64, MVT::v8f16})
67 if (TRI->isTypeLegalForClass(RC: *TRC, T))
68 return T;
69 LLVM_DEBUG(errs() << "Unknown type for register number: " << RegNo);
70 llvm_unreachable("Unknown register type");
71 return MVT::Other;
72}
73
74std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
75 Register RegNo = MO.getReg();
76 assert(RegNo.isVirtual() &&
77 "Unlowered physical register encountered during assembly printing");
78 assert(!MFI->isVRegStackified(RegNo));
79 unsigned WAReg = MFI->getWAReg(VReg: RegNo);
80 assert(WAReg != WebAssembly::UnusedReg);
81 return '$' + utostr(X: WAReg);
82}
83
84WebAssemblyTargetStreamer *WebAssemblyAsmPrinter::getTargetStreamer() {
85 MCTargetStreamer *TS = OutStreamer->getTargetStreamer();
86 return static_cast<WebAssemblyTargetStreamer *>(TS);
87}
88
89// Emscripten exception handling helpers
90//
91// This converts invoke names generated by LowerEmscriptenEHSjLj to real names
92// that are expected by JavaScript glue code. The invoke names generated by
93// Emscripten JS glue code are based on their argument and return types; for
94// example, for a function that takes an i32 and returns nothing, it is
95// 'invoke_vi'. But the format of invoke generated by LowerEmscriptenEHSjLj pass
96// contains a mangled string generated from their IR types, for example,
97// "__invoke_void_%struct.mystruct*_int", because final wasm types are not
98// available in the IR pass. So we convert those names to the form that
99// Emscripten JS code expects.
100//
101// Refer to LowerEmscriptenEHSjLj pass for more details.
102
103// Returns true if the given function name is an invoke name generated by
104// LowerEmscriptenEHSjLj pass.
105static bool isEmscriptenInvokeName(StringRef Name) {
106 if (Name.front() == '"' && Name.back() == '"')
107 Name = Name.substr(Start: 1, N: Name.size() - 2);
108 return Name.starts_with(Prefix: "__invoke_");
109}
110
111// Returns a character that represents the given wasm value type in invoke
112// signatures.
113static char getInvokeSig(wasm::ValType VT) {
114 switch (VT) {
115 case wasm::ValType::I32:
116 return 'i';
117 case wasm::ValType::I64:
118 return 'j';
119 case wasm::ValType::F32:
120 return 'f';
121 case wasm::ValType::F64:
122 return 'd';
123 case wasm::ValType::V128:
124 return 'V';
125 case wasm::ValType::FUNCREF:
126 return 'F';
127 case wasm::ValType::EXTERNREF:
128 return 'X';
129 case wasm::ValType::EXNREF:
130 return 'E';
131 default:
132 llvm_unreachable("Unhandled wasm::ValType enum");
133 }
134}
135
136// Given the wasm signature, generate the invoke name in the format JS glue code
137// expects.
138static std::string getEmscriptenInvokeSymbolName(wasm::WasmSignature *Sig) {
139 assert(Sig->Returns.size() <= 1);
140 std::string Ret = "invoke_";
141 if (!Sig->Returns.empty())
142 for (auto VT : Sig->Returns)
143 Ret += getInvokeSig(VT);
144 else
145 Ret += 'v';
146 // Invokes' first argument is a pointer to the original function, so skip it
147 for (unsigned I = 1, E = Sig->Params.size(); I < E; I++)
148 Ret += getInvokeSig(VT: Sig->Params[I]);
149 return Ret;
150}
151
152//===----------------------------------------------------------------------===//
153// WebAssemblyAsmPrinter Implementation.
154//===----------------------------------------------------------------------===//
155
156MCSymbolWasm *WebAssemblyAsmPrinter::getMCSymbolForFunction(
157 const Function *F, bool EnableEmEH, wasm::WasmSignature *Sig,
158 bool &InvokeDetected) {
159 MCSymbolWasm *WasmSym = nullptr;
160 if (EnableEmEH && isEmscriptenInvokeName(Name: F->getName())) {
161 assert(Sig);
162 InvokeDetected = true;
163 if (Sig->Returns.size() > 1) {
164 std::string Msg =
165 "Emscripten EH/SjLj does not support multivalue returns: " +
166 std::string(F->getName()) + ": " +
167 WebAssembly::signatureToString(Sig);
168 report_fatal_error(reason: Twine(Msg));
169 }
170 WasmSym = cast<MCSymbolWasm>(
171 Val: GetExternalSymbolSymbol(Sym: getEmscriptenInvokeSymbolName(Sig)));
172 } else {
173 WasmSym = cast<MCSymbolWasm>(Val: getSymbol(GV: F));
174 }
175 return WasmSym;
176}
177
178void WebAssemblyAsmPrinter::emitGlobalVariable(const GlobalVariable *GV) {
179 if (!WebAssembly::isWasmVarAddressSpace(AS: GV->getAddressSpace())) {
180 AsmPrinter::emitGlobalVariable(GV);
181 return;
182 }
183
184 assert(!GV->isThreadLocal());
185
186 MCSymbolWasm *Sym = cast<MCSymbolWasm>(Val: getSymbol(GV));
187
188 if (!Sym->getType()) {
189 SmallVector<MVT, 1> VTs;
190 Type *GlobalVT = GV->getValueType();
191 if (Subtarget) {
192 // Subtarget is only set when a function is defined, because
193 // each function can declare a different subtarget. For example,
194 // on ARM a compilation unit might have a function on ARM and
195 // another on Thumb. Therefore only if Subtarget is non-null we
196 // can actually calculate the legal VTs.
197 const WebAssemblyTargetLowering &TLI = *Subtarget->getTargetLowering();
198 computeLegalValueVTs(TLI, Ctx&: GV->getParent()->getContext(),
199 DL: GV->getDataLayout(), Ty: GlobalVT, ValueVTs&: VTs);
200 }
201 WebAssembly::wasmSymbolSetType(Sym, GlobalVT, VTs);
202 }
203
204 emitVisibility(Sym, Visibility: GV->getVisibility(), IsDefinition: !GV->isDeclaration());
205 emitSymbolType(Sym);
206 if (GV->hasInitializer()) {
207 assert(getSymbolPreferLocal(*GV) == Sym);
208 emitLinkage(GV, GVSym: Sym);
209 OutStreamer->emitLabel(Symbol: Sym);
210 // TODO: Actually emit the initializer value. Otherwise the global has the
211 // default value for its type (0, ref.null, etc).
212 OutStreamer->addBlankLine();
213 }
214}
215
216MCSymbol *WebAssemblyAsmPrinter::getOrCreateWasmSymbol(StringRef Name) {
217 auto *WasmSym = cast<MCSymbolWasm>(Val: GetExternalSymbolSymbol(Sym: Name));
218
219 // May be called multiple times, so early out.
220 if (WasmSym->getType())
221 return WasmSym;
222
223 const WebAssemblySubtarget &Subtarget = getSubtarget();
224
225 // Except for certain known symbols, all symbols used by CodeGen are
226 // functions. It's OK to hardcode knowledge of specific symbols here; this
227 // method is precisely there for fetching the signatures of known
228 // Clang-provided symbols.
229 if (Name == "__stack_pointer" || Name == "__tls_base" ||
230 Name == "__memory_base" || Name == "__table_base" ||
231 Name == "__tls_size" || Name == "__tls_align") {
232 bool Mutable =
233 Name == "__stack_pointer" || Name == "__tls_base";
234 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
235 WasmSym->setGlobalType(wasm::WasmGlobalType{
236 .Type: uint8_t(Subtarget.hasAddr64() ? wasm::WASM_TYPE_I64
237 : wasm::WASM_TYPE_I32),
238 .Mutable: Mutable});
239 return WasmSym;
240 }
241
242 if (Name.starts_with(Prefix: "GCC_except_table")) {
243 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_DATA);
244 return WasmSym;
245 }
246
247 SmallVector<wasm::ValType, 4> Returns;
248 SmallVector<wasm::ValType, 4> Params;
249 if (Name == "__cpp_exception" || Name == "__c_longjmp") {
250 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_TAG);
251 // In static linking we define tag symbols in WasmException::endModule().
252 // But we may have multiple objects to be linked together, each of which
253 // defines the tag symbols. To resolve them, we declare them as weak. In
254 // dynamic linking we make tag symbols undefined in the backend, define it
255 // in JS, and feed them to each importing module.
256 if (!isPositionIndependent())
257 WasmSym->setWeak(true);
258 WasmSym->setExternal(true);
259
260 // Currently both C++ exceptions and C longjmps have a single pointer type
261 // param. For C++ exceptions it is a pointer to an exception object, and for
262 // C longjmps it is pointer to a struct that contains a setjmp buffer and a
263 // longjmp return value. We may consider using multiple value parameters for
264 // longjmps later when multivalue support is ready.
265 wasm::ValType AddrType =
266 Subtarget.hasAddr64() ? wasm::ValType::I64 : wasm::ValType::I32;
267 Params.push_back(Elt: AddrType);
268 } else { // Function symbols
269 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
270 WebAssembly::getLibcallSignature(Subtarget, Name, Rets&: Returns, Params);
271 }
272 auto Signature = OutContext.createWasmSignature();
273 Signature->Returns = std::move(Returns);
274 Signature->Params = std::move(Params);
275 WasmSym->setSignature(Signature);
276
277 return WasmSym;
278}
279
280void WebAssemblyAsmPrinter::emitSymbolType(const MCSymbolWasm *Sym) {
281 std::optional<wasm::WasmSymbolType> WasmTy = Sym->getType();
282 if (!WasmTy)
283 return;
284
285 switch (*WasmTy) {
286 case wasm::WASM_SYMBOL_TYPE_GLOBAL:
287 getTargetStreamer()->emitGlobalType(Sym);
288 break;
289 case wasm::WASM_SYMBOL_TYPE_TAG:
290 getTargetStreamer()->emitTagType(Sym);
291 break;
292 case wasm::WASM_SYMBOL_TYPE_TABLE:
293 getTargetStreamer()->emitTableType(Sym);
294 break;
295 default:
296 break; // We only handle globals, tags and tables here
297 }
298}
299
300void WebAssemblyAsmPrinter::emitDecls(const Module &M) {
301 if (signaturesEmitted)
302 return;
303 signaturesEmitted = true;
304
305 // Normally symbols for globals get discovered as the MI gets lowered,
306 // but we need to know about them ahead of time. This will however,
307 // only find symbols that have been used. Unused symbols from globals will
308 // not be found here.
309 MachineModuleInfoWasm &MMIW = MMI->getObjFileInfo<MachineModuleInfoWasm>();
310 for (StringRef Name : MMIW.MachineSymbolsUsed) {
311 auto *WasmSym = cast<MCSymbolWasm>(Val: getOrCreateWasmSymbol(Name));
312 if (WasmSym->isFunction()) {
313 // TODO(wvo): is there any case where this overlaps with the call to
314 // emitFunctionType in the loop below?
315 getTargetStreamer()->emitFunctionType(Sym: WasmSym);
316 }
317 }
318
319 for (auto &It : OutContext.getSymbols()) {
320 // Emit .globaltype, .tagtype, or .tabletype declarations for extern
321 // declarations, i.e. those that have only been declared (but not defined)
322 // in the current module
323 auto Sym = cast_or_null<MCSymbolWasm>(Val: It.getValue().Symbol);
324 if (Sym && !Sym->isDefined())
325 emitSymbolType(Sym);
326 }
327
328 DenseSet<MCSymbol *> InvokeSymbols;
329 for (const auto &F : M) {
330 if (F.isIntrinsic())
331 continue;
332
333 // Emit function type info for all functions. This will emit duplicate
334 // information for defined functions (which already have function type
335 // info emitted alongside their definition), but this is necessary in
336 // order to enable the single-pass WebAssemblyAsmTypeCheck to succeed.
337 SmallVector<MVT, 4> Results;
338 SmallVector<MVT, 4> Params;
339 computeSignatureVTs(Ty: F.getFunctionType(), TargetFunc: &F, ContextFunc: F, TM, Params, Results);
340 // At this point these MCSymbols may or may not have been created already
341 // and thus also contain a signature, but we need to get the signature
342 // anyway here in case it is an invoke that has not yet been created. We
343 // will discard it later if it turns out not to be necessary.
344 auto Signature = signatureFromMVTs(Ctx&: OutContext, Results, Params);
345 bool InvokeDetected = false;
346 auto *Sym = getMCSymbolForFunction(
347 F: &F, EnableEmEH: WebAssembly::WasmEnableEmEH || WebAssembly::WasmEnableEmSjLj,
348 Sig: Signature, InvokeDetected);
349
350 // Multiple functions can be mapped to the same invoke symbol. For
351 // example, two IR functions '__invoke_void_i8*' and '__invoke_void_i32'
352 // are both mapped to '__invoke_vi'. We keep them in a set once we emit an
353 // Emscripten EH symbol so we don't emit the same symbol twice.
354 if (InvokeDetected && !InvokeSymbols.insert(V: Sym).second)
355 continue;
356
357 Sym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
358 if (!Sym->getSignature()) {
359 Sym->setSignature(Signature);
360 }
361
362 getTargetStreamer()->emitFunctionType(Sym);
363
364 if (F.hasFnAttribute(Kind: "wasm-import-module")) {
365 StringRef Name =
366 F.getFnAttribute(Kind: "wasm-import-module").getValueAsString();
367 Sym->setImportModule(OutContext.allocateString(s: Name));
368 getTargetStreamer()->emitImportModule(Sym, ImportModule: Name);
369 }
370 if (F.hasFnAttribute(Kind: "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(Kind: "wasm-import-name").getValueAsString();
377 Sym->setImportName(OutContext.allocateString(s: Name));
378 getTargetStreamer()->emitImportName(Sym, ImportName: Name);
379 }
380
381 if (F.hasFnAttribute(Kind: "wasm-export-name")) {
382 auto *Sym = cast<MCSymbolWasm>(Val: getSymbol(GV: &F));
383 StringRef Name = F.getFnAttribute(Kind: "wasm-export-name").getValueAsString();
384 Sym->setExportName(OutContext.allocateString(s: Name));
385 getTargetStreamer()->emitExportName(Sym, ExportName: Name);
386 }
387 }
388}
389
390void 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(Ctx&: OutContext, Subtarget);
406 OutStreamer->emitSymbolAttribute(Symbol: FunctionTable, Attribute: MCSA_NoDeadStrip);
407 break;
408 }
409 }
410
411 for (const auto &G : M.globals()) {
412 if (!G.hasInitializer() && G.hasExternalLinkage() &&
413 !WebAssembly::isWasmVarAddressSpace(AS: G.getAddressSpace()) &&
414 G.getValueType()->isSized()) {
415 uint16_t Size = M.getDataLayout().getTypeAllocSize(Ty: G.getValueType());
416 OutStreamer->emitELFSize(Symbol: getSymbol(GV: &G),
417 Value: MCConstantExpr::create(Value: Size, Ctx&: OutContext));
418 }
419 }
420
421 if (const NamedMDNode *Named = M.getNamedMetadata(Name: "wasm.custom_sections")) {
422 for (const Metadata *MD : Named->operands()) {
423 const auto *Tuple = dyn_cast<MDTuple>(Val: MD);
424 if (!Tuple || Tuple->getNumOperands() != 2)
425 continue;
426 const MDString *Name = dyn_cast<MDString>(Val: Tuple->getOperand(I: 0));
427 const MDString *Contents = dyn_cast<MDString>(Val: Tuple->getOperand(I: 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(Section: SectionName, K: SectionKind::getMetadata());
435 OutStreamer->switchSection(Section: MySection);
436 OutStreamer->emitBytes(Data: Contents->getString());
437 OutStreamer->popSection();
438 }
439 }
440
441 EmitProducerInfo(M);
442 EmitTargetFeatures(M);
443 EmitFunctionAttributes(M);
444}
445
446void WebAssemblyAsmPrinter::EmitProducerInfo(Module &M) {
447 llvm::SmallVector<std::pair<std::string, std::string>, 4> Languages;
448 if (const NamedMDNode *Debug = M.getNamedMetadata(Name: "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>(Val: Debug->getOperand(i: I));
452 StringRef Language = dwarf::LanguageString(Language: CU->getSourceLanguage());
453 Language.consume_front(Prefix: "DW_LANG_");
454 if (SeenLanguages.insert(V: Language).second)
455 Languages.emplace_back(Args: Language.str(), Args: "");
456 }
457 }
458
459 llvm::SmallVector<std::pair<std::string, std::string>, 4> Tools;
460 if (const NamedMDNode *Ident = M.getNamedMetadata(Name: "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>(Val: Ident->getOperand(i: I)->getOperand(I: 0));
464 std::pair<StringRef, StringRef> Field = S->getString().split(Separator: "version");
465 StringRef Name = Field.first.trim();
466 StringRef Version = Field.second.trim();
467 if (SeenTools.insert(V: Name).second)
468 Tools.emplace_back(Args: Name.str(), Args: Version.str());
469 }
470 }
471
472 int FieldCount = int(!Languages.empty()) + int(!Tools.empty());
473 if (FieldCount != 0) {
474 MCSectionWasm *Producers = OutContext.getWasmSection(
475 Section: ".custom_section.producers", K: SectionKind::getMetadata());
476 OutStreamer->pushSection();
477 OutStreamer->switchSection(Section: Producers);
478 OutStreamer->emitULEB128IntValue(Value: FieldCount);
479 for (auto &Producers : {std::make_pair(x: "language", y: &Languages),
480 std::make_pair(x: "processed-by", y: &Tools)}) {
481 if (Producers.second->empty())
482 continue;
483 OutStreamer->emitULEB128IntValue(Value: strlen(s: Producers.first));
484 OutStreamer->emitBytes(Data: Producers.first);
485 OutStreamer->emitULEB128IntValue(Value: Producers.second->size());
486 for (auto &Producer : *Producers.second) {
487 OutStreamer->emitULEB128IntValue(Value: Producer.first.size());
488 OutStreamer->emitBytes(Data: Producer.first);
489 OutStreamer->emitULEB128IntValue(Value: Producer.second.size());
490 OutStreamer->emitBytes(Data: Producer.second);
491 }
492 }
493 OutStreamer->popSection();
494 }
495}
496
497void 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(Key: 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>(Val: Policy))
516 if (auto *I = cast<ConstantInt>(Val: 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(Elt: 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(Elt: {.Prefix: wasm::WASM_FEATURE_PREFIX_USED, .Name: "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 Section: ".custom_section.target_features", K: SectionKind::getMetadata());
549 OutStreamer->pushSection();
550 OutStreamer->switchSection(Section: FeaturesSection);
551
552 OutStreamer->emitULEB128IntValue(Value: EmittedFeatures.size());
553 for (auto &F : EmittedFeatures) {
554 OutStreamer->emitIntValue(Value: F.Prefix, Size: 1);
555 OutStreamer->emitULEB128IntValue(Value: F.Name.size());
556 OutStreamer->emitBytes(Data: F.Name);
557 }
558
559 OutStreamer->popSection();
560}
561
562void WebAssemblyAsmPrinter::EmitFunctionAttributes(Module &M) {
563 auto V = M.getNamedGlobal(Name: "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>(Val: V->getOperand(i_nocapture: 0));
570 for (Value *Op : CA->operands()) {
571 auto *CS = cast<ConstantStruct>(Val: Op);
572 // The first field is a pointer to the annotated variable.
573 Value *AnnotatedVar = CS->getOperand(i_nocapture: 0)->stripPointerCasts();
574 // Only annotated functions are supported for now.
575 if (!isa<Function>(Val: AnnotatedVar))
576 continue;
577 auto *F = cast<Function>(Val: AnnotatedVar);
578
579 // The second field is a pointer to a global annotation string.
580 auto *GV = cast<GlobalVariable>(Val: CS->getOperand(i_nocapture: 1)->stripPointerCasts());
581 StringRef AnnotationString;
582 getConstantStringInfo(V: GV, Str&: AnnotationString);
583 auto *Sym = cast<MCSymbolWasm>(Val: getSymbol(GV: F));
584 CustomSections[AnnotationString].push_back(Elt: 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 Section: ".custom_section.llvm.func_attr.annotate." + Name, K: SectionKind::getMetadata());
591 OutStreamer->pushSection();
592 OutStreamer->switchSection(Section: CustomSection);
593
594 for (auto &Sym : Symbols) {
595 OutStreamer->emitValue(
596 Value: MCSymbolRefExpr::create(Symbol: Sym, Kind: MCSymbolRefExpr::VK_WASM_FUNCINDEX,
597 Ctx&: OutContext),
598 Size: 4);
599 }
600 OutStreamer->popSection();
601 }
602}
603
604void WebAssemblyAsmPrinter::emitConstantPool() {
605 emitDecls(M: *MMI->getModule());
606 assert(MF->getConstantPool()->getConstants().empty() &&
607 "WebAssembly disables constant pools");
608}
609
610void WebAssemblyAsmPrinter::emitJumpTableInfo() {
611 // Nothing to do; jump tables are incorporated into the instruction stream.
612}
613
614void WebAssemblyAsmPrinter::emitFunctionBodyStart() {
615 const Function &F = MF->getFunction();
616 SmallVector<MVT, 1> ResultVTs;
617 SmallVector<MVT, 4> ParamVTs;
618 computeSignatureVTs(Ty: F.getFunctionType(), TargetFunc: &F, ContextFunc: F, TM, Params&: ParamVTs, Results&: ResultVTs);
619
620 auto Signature = signatureFromMVTs(Ctx&: OutContext, Results: ResultVTs, Params: ParamVTs);
621 auto *WasmSym = cast<MCSymbolWasm>(Val: CurrentFnSym);
622 WasmSym->setSignature(Signature);
623 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
624
625 getTargetStreamer()->emitFunctionType(Sym: WasmSym);
626
627 // Emit the function index.
628 if (MDNode *Idx = F.getMetadata(Kind: "wasm.index")) {
629 assert(Idx->getNumOperands() == 1);
630
631 getTargetStreamer()->emitIndIdx(Value: AsmPrinter::lowerConstant(
632 CV: cast<ConstantAsMetadata>(Val: Idx->getOperand(I: 0))->getValue()));
633 }
634
635 SmallVector<wasm::ValType, 16> Locals;
636 valTypesFromMVTs(In: MFI->getLocals(), Out&: Locals);
637 getTargetStreamer()->emitLocal(Types: Locals);
638
639 AsmPrinter::emitFunctionBodyStart();
640}
641
642void WebAssemblyAsmPrinter::emitInstruction(const MachineInstr *MI) {
643 LLVM_DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
644 WebAssembly_MC::verifyInstructionPredicates(Opcode: MI->getOpcode(),
645 Features: Subtarget->getFeatureBits());
646
647 switch (MI->getOpcode()) {
648 case WebAssembly::ARGUMENT_i32:
649 case WebAssembly::ARGUMENT_i32_S:
650 case WebAssembly::ARGUMENT_i64:
651 case WebAssembly::ARGUMENT_i64_S:
652 case WebAssembly::ARGUMENT_f32:
653 case WebAssembly::ARGUMENT_f32_S:
654 case WebAssembly::ARGUMENT_f64:
655 case WebAssembly::ARGUMENT_f64_S:
656 case WebAssembly::ARGUMENT_v16i8:
657 case WebAssembly::ARGUMENT_v16i8_S:
658 case WebAssembly::ARGUMENT_v8i16:
659 case WebAssembly::ARGUMENT_v8i16_S:
660 case WebAssembly::ARGUMENT_v4i32:
661 case WebAssembly::ARGUMENT_v4i32_S:
662 case WebAssembly::ARGUMENT_v2i64:
663 case WebAssembly::ARGUMENT_v2i64_S:
664 case WebAssembly::ARGUMENT_v4f32:
665 case WebAssembly::ARGUMENT_v4f32_S:
666 case WebAssembly::ARGUMENT_v2f64:
667 case WebAssembly::ARGUMENT_v2f64_S:
668 case WebAssembly::ARGUMENT_v8f16:
669 case WebAssembly::ARGUMENT_v8f16_S:
670 // These represent values which are live into the function entry, so there's
671 // no instruction to emit.
672 break;
673 case WebAssembly::FALLTHROUGH_RETURN: {
674 // These instructions represent the implicit return at the end of a
675 // function body.
676 if (isVerbose()) {
677 OutStreamer->AddComment(T: "fallthrough-return");
678 OutStreamer->addBlankLine();
679 }
680 break;
681 }
682 case WebAssembly::COMPILER_FENCE:
683 // This is a compiler barrier that prevents instruction reordering during
684 // backend compilation, and should not be emitted.
685 break;
686 default: {
687 WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
688 MCInst TmpInst;
689 MCInstLowering.lower(MI, OutMI&: TmpInst);
690 EmitToStreamer(S&: *OutStreamer, Inst: TmpInst);
691 break;
692 }
693 }
694}
695
696bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
697 unsigned OpNo,
698 const char *ExtraCode,
699 raw_ostream &OS) {
700 // First try the generic code, which knows about modifiers like 'c' and 'n'.
701 if (!AsmPrinter::PrintAsmOperand(MI, OpNo, ExtraCode, OS))
702 return false;
703
704 if (!ExtraCode) {
705 const MachineOperand &MO = MI->getOperand(i: OpNo);
706 switch (MO.getType()) {
707 case MachineOperand::MO_Immediate:
708 OS << MO.getImm();
709 return false;
710 case MachineOperand::MO_Register:
711 // FIXME: only opcode that still contains registers, as required by
712 // MachineInstr::getDebugVariable().
713 assert(MI->getOpcode() == WebAssembly::INLINEASM);
714 OS << regToString(MO);
715 return false;
716 case MachineOperand::MO_GlobalAddress:
717 PrintSymbolOperand(MO, OS);
718 return false;
719 case MachineOperand::MO_ExternalSymbol:
720 GetExternalSymbolSymbol(Sym: MO.getSymbolName())->print(OS, MAI);
721 printOffset(Offset: MO.getOffset(), OS);
722 return false;
723 case MachineOperand::MO_MachineBasicBlock:
724 MO.getMBB()->getSymbol()->print(OS, MAI);
725 return false;
726 default:
727 break;
728 }
729 }
730
731 return true;
732}
733
734bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
735 unsigned OpNo,
736 const char *ExtraCode,
737 raw_ostream &OS) {
738 // The current approach to inline asm is that "r" constraints are expressed
739 // as local indices, rather than values on the operand stack. This simplifies
740 // using "r" as it eliminates the need to push and pop the values in a
741 // particular order, however it also makes it impossible to have an "m"
742 // constraint. So we don't support it.
743
744 return AsmPrinter::PrintAsmMemoryOperand(MI, OpNo, ExtraCode, OS);
745}
746
747// Force static initialization.
748extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyAsmPrinter() {
749 RegisterAsmPrinter<WebAssemblyAsmPrinter> X(getTheWebAssemblyTarget32());
750 RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(getTheWebAssemblyTarget64());
751}
752