1 // WebAssemblyMCInstLower.cpp - Convert WebAssembly MachineInstr to an MCInst // 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 code to lower WebAssembly MachineInstrs to their 11 /// corresponding MCInst records. 12 /// 13 //===----------------------------------------------------------------------===// 14 15 #include "WebAssemblyMCInstLower.h" 16 #include "TargetInfo/WebAssemblyTargetInfo.h" 17 #include "Utils/WebAssemblyTypeUtilities.h" 18 #include "Utils/WebAssemblyUtilities.h" 19 #include "WebAssemblyAsmPrinter.h" 20 #include "WebAssemblyMachineFunctionInfo.h" 21 #include "WebAssemblyRuntimeLibcallSignatures.h" 22 #include "llvm/CodeGen/AsmPrinter.h" 23 #include "llvm/CodeGen/MachineFunction.h" 24 #include "llvm/IR/Constants.h" 25 #include "llvm/MC/MCAsmInfo.h" 26 #include "llvm/MC/MCContext.h" 27 #include "llvm/MC/MCExpr.h" 28 #include "llvm/MC/MCInst.h" 29 #include "llvm/MC/MCSymbolWasm.h" 30 #include "llvm/Support/ErrorHandling.h" 31 #include "llvm/Support/raw_ostream.h" 32 using namespace llvm; 33 34 // This disables the removal of registers when lowering into MC, as required 35 // by some current tests. 36 cl::opt<bool> 37 WasmKeepRegisters("wasm-keep-registers", cl::Hidden, 38 cl::desc("WebAssembly: output stack registers in" 39 " instruction output for test purposes only."), 40 cl::init(false)); 41 42 extern cl::opt<bool> EnableEmException; 43 extern cl::opt<bool> EnableEmSjLj; 44 45 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI); 46 47 MCSymbol * 48 WebAssemblyMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const { 49 const GlobalValue *Global = MO.getGlobal(); 50 if (!isa<Function>(Global)) { 51 auto *WasmSym = cast<MCSymbolWasm>(Printer.getSymbol(Global)); 52 // If the symbol doesn't have an explicit WasmSymbolType yet and the 53 // GlobalValue is actually a WebAssembly global, then ensure the symbol is a 54 // WASM_SYMBOL_TYPE_GLOBAL. 55 if (WebAssembly::isWasmVarAddressSpace(Global->getAddressSpace()) && 56 !WasmSym->getType()) { 57 const MachineFunction &MF = *MO.getParent()->getParent()->getParent(); 58 const TargetMachine &TM = MF.getTarget(); 59 const Function &CurrentFunc = MF.getFunction(); 60 SmallVector<MVT, 1> VTs; 61 computeLegalValueVTs(CurrentFunc, TM, Global->getValueType(), VTs); 62 if (VTs.size() != 1) 63 report_fatal_error("Aggregate globals not yet implemented"); 64 65 bool Mutable = true; 66 wasm::ValType Type = WebAssembly::toValType(VTs[0]); 67 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL); 68 WasmSym->setGlobalType(wasm::WasmGlobalType{uint8_t(Type), Mutable}); 69 } 70 return WasmSym; 71 } 72 73 const auto *FuncTy = cast<FunctionType>(Global->getValueType()); 74 const MachineFunction &MF = *MO.getParent()->getParent()->getParent(); 75 const TargetMachine &TM = MF.getTarget(); 76 const Function &CurrentFunc = MF.getFunction(); 77 78 SmallVector<MVT, 1> ResultMVTs; 79 SmallVector<MVT, 4> ParamMVTs; 80 const auto *const F = dyn_cast<Function>(Global); 81 computeSignatureVTs(FuncTy, F, CurrentFunc, TM, ParamMVTs, ResultMVTs); 82 auto Signature = signatureFromMVTs(ResultMVTs, ParamMVTs); 83 84 bool InvokeDetected = false; 85 auto *WasmSym = Printer.getMCSymbolForFunction( 86 F, EnableEmException || EnableEmSjLj, Signature.get(), InvokeDetected); 87 WasmSym->setSignature(Signature.get()); 88 Printer.addSignature(std::move(Signature)); 89 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 90 return WasmSym; 91 } 92 93 MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol( 94 const MachineOperand &MO) const { 95 const char *Name = MO.getSymbolName(); 96 auto *WasmSym = cast<MCSymbolWasm>(Printer.GetExternalSymbolSymbol(Name)); 97 const WebAssemblySubtarget &Subtarget = Printer.getSubtarget(); 98 99 // Except for certain known symbols, all symbols used by CodeGen are 100 // functions. It's OK to hardcode knowledge of specific symbols here; this 101 // method is precisely there for fetching the signatures of known 102 // Clang-provided symbols. 103 if (strcmp(Name, "__stack_pointer") == 0 || strcmp(Name, "__tls_base") == 0 || 104 strcmp(Name, "__memory_base") == 0 || strcmp(Name, "__table_base") == 0 || 105 strcmp(Name, "__tls_size") == 0 || strcmp(Name, "__tls_align") == 0) { 106 bool Mutable = 107 strcmp(Name, "__stack_pointer") == 0 || strcmp(Name, "__tls_base") == 0; 108 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL); 109 WasmSym->setGlobalType(wasm::WasmGlobalType{ 110 uint8_t(Subtarget.hasAddr64() ? wasm::WASM_TYPE_I64 111 : wasm::WASM_TYPE_I32), 112 Mutable}); 113 return WasmSym; 114 } 115 116 SmallVector<wasm::ValType, 4> Returns; 117 SmallVector<wasm::ValType, 4> Params; 118 if (strcmp(Name, "__cpp_exception") == 0) { 119 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_TAG); 120 // We can't confirm its signature index for now because there can be 121 // imported exceptions. Set it to be 0 for now. 122 WasmSym->setTagType({wasm::WASM_TAG_ATTRIBUTE_EXCEPTION, /* SigIndex */ 0}); 123 // We may have multiple C++ compilation units to be linked together, each of 124 // which defines the exception symbol. To resolve them, we declare them as 125 // weak. 126 WasmSym->setWeak(true); 127 WasmSym->setExternal(true); 128 129 // All C++ exceptions are assumed to have a single i32 (for wasm32) or i64 130 // (for wasm64) param type and void return type. The reaon is, all C++ 131 // exception values are pointers, and to share the type section with 132 // functions, exceptions are assumed to have void return type. 133 Params.push_back(Subtarget.hasAddr64() ? wasm::ValType::I64 134 : wasm::ValType::I32); 135 } else { // Function symbols 136 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 137 getLibcallSignature(Subtarget, Name, Returns, Params); 138 } 139 auto Signature = 140 std::make_unique<wasm::WasmSignature>(std::move(Returns), std::move(Params)); 141 WasmSym->setSignature(Signature.get()); 142 Printer.addSignature(std::move(Signature)); 143 144 return WasmSym; 145 } 146 147 MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO, 148 MCSymbol *Sym) const { 149 MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None; 150 unsigned TargetFlags = MO.getTargetFlags(); 151 152 switch (TargetFlags) { 153 case WebAssemblyII::MO_NO_FLAG: 154 break; 155 case WebAssemblyII::MO_GOT: 156 Kind = MCSymbolRefExpr::VK_GOT; 157 break; 158 case WebAssemblyII::MO_MEMORY_BASE_REL: 159 Kind = MCSymbolRefExpr::VK_WASM_MBREL; 160 break; 161 case WebAssemblyII::MO_TLS_BASE_REL: 162 Kind = MCSymbolRefExpr::VK_WASM_TLSREL; 163 break; 164 case WebAssemblyII::MO_TABLE_BASE_REL: 165 Kind = MCSymbolRefExpr::VK_WASM_TBREL; 166 break; 167 default: 168 llvm_unreachable("Unknown target flag on GV operand"); 169 } 170 171 const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Kind, Ctx); 172 173 if (MO.getOffset() != 0) { 174 const auto *WasmSym = cast<MCSymbolWasm>(Sym); 175 if (TargetFlags == WebAssemblyII::MO_GOT) 176 report_fatal_error("GOT symbol references do not support offsets"); 177 if (WasmSym->isFunction()) 178 report_fatal_error("Function addresses with offsets not supported"); 179 if (WasmSym->isGlobal()) 180 report_fatal_error("Global indexes with offsets not supported"); 181 if (WasmSym->isTag()) 182 report_fatal_error("Tag indexes with offsets not supported"); 183 if (WasmSym->isTable()) 184 report_fatal_error("Table indexes with offsets not supported"); 185 186 Expr = MCBinaryExpr::createAdd( 187 Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx); 188 } 189 190 return MCOperand::createExpr(Expr); 191 } 192 193 MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand( 194 SmallVector<wasm::ValType, 1> &&Returns, 195 SmallVector<wasm::ValType, 4> &&Params) const { 196 auto Signature = std::make_unique<wasm::WasmSignature>(std::move(Returns), 197 std::move(Params)); 198 MCSymbol *Sym = Printer.createTempSymbol("typeindex"); 199 auto *WasmSym = cast<MCSymbolWasm>(Sym); 200 WasmSym->setSignature(Signature.get()); 201 Printer.addSignature(std::move(Signature)); 202 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 203 const MCExpr *Expr = 204 MCSymbolRefExpr::create(WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx); 205 return MCOperand::createExpr(Expr); 206 } 207 208 // Return the WebAssembly type associated with the given register class. 209 static wasm::ValType getType(const TargetRegisterClass *RC) { 210 if (RC == &WebAssembly::I32RegClass) 211 return wasm::ValType::I32; 212 if (RC == &WebAssembly::I64RegClass) 213 return wasm::ValType::I64; 214 if (RC == &WebAssembly::F32RegClass) 215 return wasm::ValType::F32; 216 if (RC == &WebAssembly::F64RegClass) 217 return wasm::ValType::F64; 218 if (RC == &WebAssembly::V128RegClass) 219 return wasm::ValType::V128; 220 llvm_unreachable("Unexpected register class"); 221 } 222 223 static void getFunctionReturns(const MachineInstr *MI, 224 SmallVectorImpl<wasm::ValType> &Returns) { 225 const Function &F = MI->getMF()->getFunction(); 226 const TargetMachine &TM = MI->getMF()->getTarget(); 227 Type *RetTy = F.getReturnType(); 228 SmallVector<MVT, 4> CallerRetTys; 229 computeLegalValueVTs(F, TM, RetTy, CallerRetTys); 230 valTypesFromMVTs(CallerRetTys, Returns); 231 } 232 233 void WebAssemblyMCInstLower::lower(const MachineInstr *MI, 234 MCInst &OutMI) const { 235 OutMI.setOpcode(MI->getOpcode()); 236 237 const MCInstrDesc &Desc = MI->getDesc(); 238 unsigned NumVariadicDefs = MI->getNumExplicitDefs() - Desc.getNumDefs(); 239 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) { 240 const MachineOperand &MO = MI->getOperand(I); 241 242 MCOperand MCOp; 243 switch (MO.getType()) { 244 default: 245 MI->print(errs()); 246 llvm_unreachable("unknown operand type"); 247 case MachineOperand::MO_MachineBasicBlock: 248 MI->print(errs()); 249 llvm_unreachable("MachineBasicBlock operand should have been rewritten"); 250 case MachineOperand::MO_Register: { 251 // Ignore all implicit register operands. 252 if (MO.isImplicit()) 253 continue; 254 const WebAssemblyFunctionInfo &MFI = 255 *MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>(); 256 unsigned WAReg = MFI.getWAReg(MO.getReg()); 257 MCOp = MCOperand::createReg(WAReg); 258 break; 259 } 260 case MachineOperand::MO_Immediate: { 261 unsigned DescIndex = I - NumVariadicDefs; 262 if (DescIndex < Desc.NumOperands) { 263 const MCOperandInfo &Info = Desc.OpInfo[DescIndex]; 264 if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) { 265 SmallVector<wasm::ValType, 4> Returns; 266 SmallVector<wasm::ValType, 4> Params; 267 268 const MachineRegisterInfo &MRI = 269 MI->getParent()->getParent()->getRegInfo(); 270 for (const MachineOperand &MO : MI->defs()) 271 Returns.push_back(getType(MRI.getRegClass(MO.getReg()))); 272 for (const MachineOperand &MO : MI->explicit_uses()) 273 if (MO.isReg()) 274 Params.push_back(getType(MRI.getRegClass(MO.getReg()))); 275 276 // call_indirect instructions have a callee operand at the end which 277 // doesn't count as a param. 278 if (WebAssembly::isCallIndirect(MI->getOpcode())) 279 Params.pop_back(); 280 281 // return_call_indirect instructions have the return type of the 282 // caller 283 if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT) 284 getFunctionReturns(MI, Returns); 285 286 MCOp = lowerTypeIndexOperand(std::move(Returns), std::move(Params)); 287 break; 288 } else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) { 289 auto BT = static_cast<WebAssembly::BlockType>(MO.getImm()); 290 assert(BT != WebAssembly::BlockType::Invalid); 291 if (BT == WebAssembly::BlockType::Multivalue) { 292 SmallVector<wasm::ValType, 1> Returns; 293 getFunctionReturns(MI, Returns); 294 MCOp = lowerTypeIndexOperand(std::move(Returns), 295 SmallVector<wasm::ValType, 4>()); 296 break; 297 } 298 } else if (Info.OperandType == WebAssembly::OPERAND_HEAPTYPE) { 299 assert(static_cast<WebAssembly::HeapType>(MO.getImm()) != 300 WebAssembly::HeapType::Invalid); 301 // With typed function references, this will need a case for type 302 // index operands. Otherwise, fall through. 303 } 304 } 305 MCOp = MCOperand::createImm(MO.getImm()); 306 break; 307 } 308 case MachineOperand::MO_FPImmediate: { 309 const ConstantFP *Imm = MO.getFPImm(); 310 const uint64_t BitPattern = 311 Imm->getValueAPF().bitcastToAPInt().getZExtValue(); 312 if (Imm->getType()->isFloatTy()) 313 MCOp = MCOperand::createSFPImm(static_cast<uint32_t>(BitPattern)); 314 else if (Imm->getType()->isDoubleTy()) 315 MCOp = MCOperand::createDFPImm(BitPattern); 316 else 317 llvm_unreachable("unknown floating point immediate type"); 318 break; 319 } 320 case MachineOperand::MO_GlobalAddress: 321 MCOp = lowerSymbolOperand(MO, GetGlobalAddressSymbol(MO)); 322 break; 323 case MachineOperand::MO_ExternalSymbol: 324 // The target flag indicates whether this is a symbol for a 325 // variable or a function. 326 assert(MO.getTargetFlags() == 0 && 327 "WebAssembly uses only symbol flags on ExternalSymbols"); 328 MCOp = lowerSymbolOperand(MO, GetExternalSymbolSymbol(MO)); 329 break; 330 case MachineOperand::MO_MCSymbol: 331 // This is currently used only for LSDA symbols (GCC_except_table), 332 // because global addresses or other external symbols are handled above. 333 assert(MO.getTargetFlags() == 0 && 334 "WebAssembly does not use target flags on MCSymbol"); 335 MCOp = lowerSymbolOperand(MO, MO.getMCSymbol()); 336 break; 337 } 338 339 OutMI.addOperand(MCOp); 340 } 341 342 if (!WasmKeepRegisters) 343 removeRegisterOperands(MI, OutMI); 344 else if (Desc.variadicOpsAreDefs()) 345 OutMI.insert(OutMI.begin(), MCOperand::createImm(MI->getNumExplicitDefs())); 346 } 347 348 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) { 349 // Remove all uses of stackified registers to bring the instruction format 350 // into its final stack form used thruout MC, and transition opcodes to 351 // their _S variant. 352 // We do this separate from the above code that still may need these 353 // registers for e.g. call_indirect signatures. 354 // See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for 355 // details. 356 // TODO: the code above creates new registers which are then removed here. 357 // That code could be slightly simplified by not doing that, though maybe 358 // it is simpler conceptually to keep the code above in "register mode" 359 // until this transition point. 360 // FIXME: we are not processing inline assembly, which contains register 361 // operands, because it is used by later target generic code. 362 if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm()) 363 return; 364 365 // Transform to _S instruction. 366 auto RegOpcode = OutMI.getOpcode(); 367 auto StackOpcode = WebAssembly::getStackOpcode(RegOpcode); 368 assert(StackOpcode != -1 && "Failed to stackify instruction"); 369 OutMI.setOpcode(StackOpcode); 370 371 // Remove register operands. 372 for (auto I = OutMI.getNumOperands(); I; --I) { 373 auto &MO = OutMI.getOperand(I - 1); 374 if (MO.isReg()) { 375 OutMI.erase(&MO); 376 } 377 } 378 } 379