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
getRegType(unsigned RegNo) const57 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
regToString(const MachineOperand & MO)69 std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
70 Register RegNo = MO.getReg();
71 assert(Register::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
getTargetStreamer()79 WebAssemblyTargetStreamer *WebAssemblyAsmPrinter::getTargetStreamer() {
80 MCTargetStreamer *TS = OutStreamer->getTargetStreamer();
81 return static_cast<WebAssemblyTargetStreamer *>(TS);
82 }
83
84 //===----------------------------------------------------------------------===//
85 // WebAssemblyAsmPrinter Implementation.
86 //===----------------------------------------------------------------------===//
87
EmitEndOfAsmFile(Module & M)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 if (F.isIntrinsic())
100 continue;
101
102 // Emit function type info for all undefined functions
103 if (F.isDeclarationForLinker()) {
104 SmallVector<MVT, 4> Results;
105 SmallVector<MVT, 4> Params;
106 computeSignatureVTs(F.getFunctionType(), F, TM, Params, Results);
107 auto *Sym = cast<MCSymbolWasm>(getSymbol(&F));
108 Sym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
109 if (!Sym->getSignature()) {
110 auto Signature = signatureFromMVTs(Results, Params);
111 Sym->setSignature(Signature.get());
112 addSignature(std::move(Signature));
113 }
114 // FIXME: this was originally intended for post-linking and was only used
115 // for imports that were only called indirectly (i.e. s2wasm could not
116 // infer the type from a call). With object files it applies to all
117 // imports. so fix the names and the tests, or rethink how import
118 // delcarations work in asm files.
119 getTargetStreamer()->emitFunctionType(Sym);
120
121 if (TM.getTargetTriple().isOSBinFormatWasm() &&
122 F.hasFnAttribute("wasm-import-module")) {
123 StringRef Name =
124 F.getFnAttribute("wasm-import-module").getValueAsString();
125 Sym->setImportModule(Name);
126 getTargetStreamer()->emitImportModule(Sym, Name);
127 }
128 if (TM.getTargetTriple().isOSBinFormatWasm() &&
129 F.hasFnAttribute("wasm-import-name")) {
130 StringRef Name =
131 F.getFnAttribute("wasm-import-name").getValueAsString();
132 Sym->setImportName(Name);
133 getTargetStreamer()->emitImportName(Sym, Name);
134 }
135 }
136
137 if (F.hasFnAttribute("wasm-export-name")) {
138 auto *Sym = cast<MCSymbolWasm>(getSymbol(&F));
139 StringRef Name = F.getFnAttribute("wasm-export-name").getValueAsString();
140 Sym->setExportName(Name);
141 getTargetStreamer()->emitExportName(Sym, Name);
142 }
143 }
144
145 for (const auto &G : M.globals()) {
146 if (!G.hasInitializer() && G.hasExternalLinkage()) {
147 if (G.getValueType()->isSized()) {
148 uint16_t Size = M.getDataLayout().getTypeAllocSize(G.getValueType());
149 OutStreamer->emitELFSize(getSymbol(&G),
150 MCConstantExpr::create(Size, OutContext));
151 }
152 }
153 }
154
155 if (const NamedMDNode *Named = M.getNamedMetadata("wasm.custom_sections")) {
156 for (const Metadata *MD : Named->operands()) {
157 const auto *Tuple = dyn_cast<MDTuple>(MD);
158 if (!Tuple || Tuple->getNumOperands() != 2)
159 continue;
160 const MDString *Name = dyn_cast<MDString>(Tuple->getOperand(0));
161 const MDString *Contents = dyn_cast<MDString>(Tuple->getOperand(1));
162 if (!Name || !Contents)
163 continue;
164
165 OutStreamer->PushSection();
166 std::string SectionName = (".custom_section." + Name->getString()).str();
167 MCSectionWasm *MySection =
168 OutContext.getWasmSection(SectionName, SectionKind::getMetadata());
169 OutStreamer->SwitchSection(MySection);
170 OutStreamer->EmitBytes(Contents->getString());
171 OutStreamer->PopSection();
172 }
173 }
174
175 EmitProducerInfo(M);
176 EmitTargetFeatures(M);
177 }
178
EmitProducerInfo(Module & M)179 void WebAssemblyAsmPrinter::EmitProducerInfo(Module &M) {
180 llvm::SmallVector<std::pair<std::string, std::string>, 4> Languages;
181 if (const NamedMDNode *Debug = M.getNamedMetadata("llvm.dbg.cu")) {
182 llvm::SmallSet<StringRef, 4> SeenLanguages;
183 for (size_t I = 0, E = Debug->getNumOperands(); I < E; ++I) {
184 const auto *CU = cast<DICompileUnit>(Debug->getOperand(I));
185 StringRef Language = dwarf::LanguageString(CU->getSourceLanguage());
186 Language.consume_front("DW_LANG_");
187 if (SeenLanguages.insert(Language).second)
188 Languages.emplace_back(Language.str(), "");
189 }
190 }
191
192 llvm::SmallVector<std::pair<std::string, std::string>, 4> Tools;
193 if (const NamedMDNode *Ident = M.getNamedMetadata("llvm.ident")) {
194 llvm::SmallSet<StringRef, 4> SeenTools;
195 for (size_t I = 0, E = Ident->getNumOperands(); I < E; ++I) {
196 const auto *S = cast<MDString>(Ident->getOperand(I)->getOperand(0));
197 std::pair<StringRef, StringRef> Field = S->getString().split("version");
198 StringRef Name = Field.first.trim();
199 StringRef Version = Field.second.trim();
200 if (SeenTools.insert(Name).second)
201 Tools.emplace_back(Name.str(), Version.str());
202 }
203 }
204
205 int FieldCount = int(!Languages.empty()) + int(!Tools.empty());
206 if (FieldCount != 0) {
207 MCSectionWasm *Producers = OutContext.getWasmSection(
208 ".custom_section.producers", SectionKind::getMetadata());
209 OutStreamer->PushSection();
210 OutStreamer->SwitchSection(Producers);
211 OutStreamer->EmitULEB128IntValue(FieldCount);
212 for (auto &Producers : {std::make_pair("language", &Languages),
213 std::make_pair("processed-by", &Tools)}) {
214 if (Producers.second->empty())
215 continue;
216 OutStreamer->EmitULEB128IntValue(strlen(Producers.first));
217 OutStreamer->EmitBytes(Producers.first);
218 OutStreamer->EmitULEB128IntValue(Producers.second->size());
219 for (auto &Producer : *Producers.second) {
220 OutStreamer->EmitULEB128IntValue(Producer.first.size());
221 OutStreamer->EmitBytes(Producer.first);
222 OutStreamer->EmitULEB128IntValue(Producer.second.size());
223 OutStreamer->EmitBytes(Producer.second);
224 }
225 }
226 OutStreamer->PopSection();
227 }
228 }
229
EmitTargetFeatures(Module & M)230 void WebAssemblyAsmPrinter::EmitTargetFeatures(Module &M) {
231 struct FeatureEntry {
232 uint8_t Prefix;
233 StringRef Name;
234 };
235
236 // Read target features and linkage policies from module metadata
237 SmallVector<FeatureEntry, 4> EmittedFeatures;
238 for (const SubtargetFeatureKV &KV : WebAssemblyFeatureKV) {
239 std::string MDKey = (StringRef("wasm-feature-") + KV.Key).str();
240 Metadata *Policy = M.getModuleFlag(MDKey);
241 if (Policy == nullptr)
242 continue;
243
244 FeatureEntry Entry;
245 Entry.Prefix = 0;
246 Entry.Name = KV.Key;
247
248 if (auto *MD = cast<ConstantAsMetadata>(Policy))
249 if (auto *I = cast<ConstantInt>(MD->getValue()))
250 Entry.Prefix = I->getZExtValue();
251
252 // Silently ignore invalid metadata
253 if (Entry.Prefix != wasm::WASM_FEATURE_PREFIX_USED &&
254 Entry.Prefix != wasm::WASM_FEATURE_PREFIX_REQUIRED &&
255 Entry.Prefix != wasm::WASM_FEATURE_PREFIX_DISALLOWED)
256 continue;
257
258 EmittedFeatures.push_back(Entry);
259 }
260
261 if (EmittedFeatures.size() == 0)
262 return;
263
264 // Emit features and linkage policies into the "target_features" section
265 MCSectionWasm *FeaturesSection = OutContext.getWasmSection(
266 ".custom_section.target_features", SectionKind::getMetadata());
267 OutStreamer->PushSection();
268 OutStreamer->SwitchSection(FeaturesSection);
269
270 OutStreamer->EmitULEB128IntValue(EmittedFeatures.size());
271 for (auto &F : EmittedFeatures) {
272 OutStreamer->EmitIntValue(F.Prefix, 1);
273 OutStreamer->EmitULEB128IntValue(F.Name.size());
274 OutStreamer->EmitBytes(F.Name);
275 }
276
277 OutStreamer->PopSection();
278 }
279
EmitConstantPool()280 void WebAssemblyAsmPrinter::EmitConstantPool() {
281 assert(MF->getConstantPool()->getConstants().empty() &&
282 "WebAssembly disables constant pools");
283 }
284
EmitJumpTableInfo()285 void WebAssemblyAsmPrinter::EmitJumpTableInfo() {
286 // Nothing to do; jump tables are incorporated into the instruction stream.
287 }
288
EmitFunctionBodyStart()289 void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
290 const Function &F = MF->getFunction();
291 SmallVector<MVT, 1> ResultVTs;
292 SmallVector<MVT, 4> ParamVTs;
293 computeSignatureVTs(F.getFunctionType(), F, TM, ParamVTs, ResultVTs);
294 auto Signature = signatureFromMVTs(ResultVTs, ParamVTs);
295 auto *WasmSym = cast<MCSymbolWasm>(CurrentFnSym);
296 WasmSym->setSignature(Signature.get());
297 addSignature(std::move(Signature));
298 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
299
300 // FIXME: clean up how params and results are emitted (use signatures)
301 getTargetStreamer()->emitFunctionType(WasmSym);
302
303 // Emit the function index.
304 if (MDNode *Idx = F.getMetadata("wasm.index")) {
305 assert(Idx->getNumOperands() == 1);
306
307 getTargetStreamer()->emitIndIdx(AsmPrinter::lowerConstant(
308 cast<ConstantAsMetadata>(Idx->getOperand(0))->getValue()));
309 }
310
311 SmallVector<wasm::ValType, 16> Locals;
312 valTypesFromMVTs(MFI->getLocals(), Locals);
313 getTargetStreamer()->emitLocal(Locals);
314
315 AsmPrinter::EmitFunctionBodyStart();
316 }
317
EmitInstruction(const MachineInstr * MI)318 void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
319 LLVM_DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
320
321 switch (MI->getOpcode()) {
322 case WebAssembly::ARGUMENT_i32:
323 case WebAssembly::ARGUMENT_i32_S:
324 case WebAssembly::ARGUMENT_i64:
325 case WebAssembly::ARGUMENT_i64_S:
326 case WebAssembly::ARGUMENT_f32:
327 case WebAssembly::ARGUMENT_f32_S:
328 case WebAssembly::ARGUMENT_f64:
329 case WebAssembly::ARGUMENT_f64_S:
330 case WebAssembly::ARGUMENT_v16i8:
331 case WebAssembly::ARGUMENT_v16i8_S:
332 case WebAssembly::ARGUMENT_v8i16:
333 case WebAssembly::ARGUMENT_v8i16_S:
334 case WebAssembly::ARGUMENT_v4i32:
335 case WebAssembly::ARGUMENT_v4i32_S:
336 case WebAssembly::ARGUMENT_v2i64:
337 case WebAssembly::ARGUMENT_v2i64_S:
338 case WebAssembly::ARGUMENT_v4f32:
339 case WebAssembly::ARGUMENT_v4f32_S:
340 case WebAssembly::ARGUMENT_v2f64:
341 case WebAssembly::ARGUMENT_v2f64_S:
342 // These represent values which are live into the function entry, so there's
343 // no instruction to emit.
344 break;
345 case WebAssembly::FALLTHROUGH_RETURN: {
346 // These instructions represent the implicit return at the end of a
347 // function body.
348 if (isVerbose()) {
349 OutStreamer->AddComment("fallthrough-return");
350 OutStreamer->AddBlankLine();
351 }
352 break;
353 }
354 case WebAssembly::COMPILER_FENCE:
355 // This is a compiler barrier that prevents instruction reordering during
356 // backend compilation, and should not be emitted.
357 break;
358 case WebAssembly::EXTRACT_EXCEPTION_I32:
359 case WebAssembly::EXTRACT_EXCEPTION_I32_S:
360 // These are pseudo instructions that simulates popping values from stack.
361 // We print these only when we have -wasm-keep-registers on for assembly
362 // readability.
363 if (!WasmKeepRegisters)
364 break;
365 LLVM_FALLTHROUGH;
366 default: {
367 WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
368 MCInst TmpInst;
369 MCInstLowering.lower(MI, TmpInst);
370 EmitToStreamer(*OutStreamer, TmpInst);
371 break;
372 }
373 }
374 }
375
PrintAsmOperand(const MachineInstr * MI,unsigned OpNo,const char * ExtraCode,raw_ostream & OS)376 bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
377 unsigned OpNo,
378 const char *ExtraCode,
379 raw_ostream &OS) {
380 // First try the generic code, which knows about modifiers like 'c' and 'n'.
381 if (!AsmPrinter::PrintAsmOperand(MI, OpNo, ExtraCode, OS))
382 return false;
383
384 if (!ExtraCode) {
385 const MachineOperand &MO = MI->getOperand(OpNo);
386 switch (MO.getType()) {
387 case MachineOperand::MO_Immediate:
388 OS << MO.getImm();
389 return false;
390 case MachineOperand::MO_Register:
391 // FIXME: only opcode that still contains registers, as required by
392 // MachineInstr::getDebugVariable().
393 assert(MI->getOpcode() == WebAssembly::INLINEASM);
394 OS << regToString(MO);
395 return false;
396 case MachineOperand::MO_GlobalAddress:
397 PrintSymbolOperand(MO, OS);
398 return false;
399 case MachineOperand::MO_ExternalSymbol:
400 GetExternalSymbolSymbol(MO.getSymbolName())->print(OS, MAI);
401 printOffset(MO.getOffset(), OS);
402 return false;
403 case MachineOperand::MO_MachineBasicBlock:
404 MO.getMBB()->getSymbol()->print(OS, MAI);
405 return false;
406 default:
407 break;
408 }
409 }
410
411 return true;
412 }
413
PrintAsmMemoryOperand(const MachineInstr * MI,unsigned OpNo,const char * ExtraCode,raw_ostream & OS)414 bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
415 unsigned OpNo,
416 const char *ExtraCode,
417 raw_ostream &OS) {
418 // The current approach to inline asm is that "r" constraints are expressed
419 // as local indices, rather than values on the operand stack. This simplifies
420 // using "r" as it eliminates the need to push and pop the values in a
421 // particular order, however it also makes it impossible to have an "m"
422 // constraint. So we don't support it.
423
424 return AsmPrinter::PrintAsmMemoryOperand(MI, OpNo, ExtraCode, OS);
425 }
426
427 // Force static initialization.
LLVMInitializeWebAssemblyAsmPrinter()428 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyAsmPrinter() {
429 RegisterAsmPrinter<WebAssemblyAsmPrinter> X(getTheWebAssemblyTarget32());
430 RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(getTheWebAssemblyTarget64());
431 }
432