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 "WebAssemblyISelLowering.h" 21 #include "WebAssemblyMachineFunctionInfo.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 33 using namespace llvm; 34 35 // This disables the removal of registers when lowering into MC, as required 36 // by some current tests. 37 cl::opt<bool> 38 WasmKeepRegisters("wasm-keep-registers", cl::Hidden, 39 cl::desc("WebAssembly: output stack registers in" 40 " instruction output for test purposes only."), 41 cl::init(false)); 42 43 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI); 44 45 MCSymbol * 46 WebAssemblyMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const { 47 const GlobalValue *Global = MO.getGlobal(); 48 if (!isa<Function>(Global)) { 49 auto *WasmSym = cast<MCSymbolWasm>(Printer.getSymbol(Global)); 50 // If the symbol doesn't have an explicit WasmSymbolType yet and the 51 // GlobalValue is actually a WebAssembly global, then ensure the symbol is a 52 // WASM_SYMBOL_TYPE_GLOBAL. 53 if (WebAssembly::isWasmVarAddressSpace(Global->getAddressSpace()) && 54 !WasmSym->getType()) { 55 const MachineFunction &MF = *MO.getParent()->getParent()->getParent(); 56 const TargetMachine &TM = MF.getTarget(); 57 const Function &CurrentFunc = MF.getFunction(); 58 Type *GlobalVT = Global->getValueType(); 59 SmallVector<MVT, 1> VTs; 60 computeLegalValueVTs(CurrentFunc, TM, GlobalVT, VTs); 61 62 // Tables are represented as Arrays in LLVM IR therefore 63 // they reach this point as aggregate Array types with an element type 64 // that is a reference type. 65 wasm::ValType Type; 66 bool IsTable = false; 67 if (GlobalVT->isArrayTy() && 68 WebAssembly::isRefType(GlobalVT->getArrayElementType())) { 69 MVT VT; 70 IsTable = true; 71 switch (GlobalVT->getArrayElementType()->getPointerAddressSpace()) { 72 case WebAssembly::WasmAddressSpace::WASM_ADDRESS_SPACE_FUNCREF: 73 VT = MVT::funcref; 74 break; 75 case WebAssembly::WasmAddressSpace::WASM_ADDRESS_SPACE_EXTERNREF: 76 VT = MVT::externref; 77 break; 78 default: 79 report_fatal_error("unhandled address space type"); 80 } 81 Type = WebAssembly::toValType(VT); 82 } else if (VTs.size() == 1) { 83 Type = WebAssembly::toValType(VTs[0]); 84 } else 85 report_fatal_error("Aggregate globals not yet implemented"); 86 87 if (IsTable) { 88 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_TABLE); 89 WasmSym->setTableType(Type); 90 } else { 91 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL); 92 WasmSym->setGlobalType( 93 wasm::WasmGlobalType{uint8_t(Type), /*Mutable=*/true}); 94 } 95 } 96 return WasmSym; 97 } 98 99 const auto *FuncTy = cast<FunctionType>(Global->getValueType()); 100 const MachineFunction &MF = *MO.getParent()->getParent()->getParent(); 101 const TargetMachine &TM = MF.getTarget(); 102 const Function &CurrentFunc = MF.getFunction(); 103 104 SmallVector<MVT, 1> ResultMVTs; 105 SmallVector<MVT, 4> ParamMVTs; 106 const auto *const F = dyn_cast<Function>(Global); 107 computeSignatureVTs(FuncTy, F, CurrentFunc, TM, ParamMVTs, ResultMVTs); 108 auto Signature = signatureFromMVTs(ResultMVTs, ParamMVTs); 109 110 bool InvokeDetected = false; 111 auto *WasmSym = Printer.getMCSymbolForFunction( 112 F, WebAssembly::WasmEnableEmEH || WebAssembly::WasmEnableEmSjLj, 113 Signature.get(), InvokeDetected); 114 WasmSym->setSignature(Signature.get()); 115 Printer.addSignature(std::move(Signature)); 116 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 117 return WasmSym; 118 } 119 120 MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol( 121 const MachineOperand &MO) const { 122 return Printer.getOrCreateWasmSymbol(MO.getSymbolName()); 123 } 124 125 MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO, 126 MCSymbol *Sym) const { 127 MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None; 128 unsigned TargetFlags = MO.getTargetFlags(); 129 130 switch (TargetFlags) { 131 case WebAssemblyII::MO_NO_FLAG: 132 break; 133 case WebAssemblyII::MO_GOT_TLS: 134 Kind = MCSymbolRefExpr::VK_WASM_GOT_TLS; 135 break; 136 case WebAssemblyII::MO_GOT: 137 Kind = MCSymbolRefExpr::VK_GOT; 138 break; 139 case WebAssemblyII::MO_MEMORY_BASE_REL: 140 Kind = MCSymbolRefExpr::VK_WASM_MBREL; 141 break; 142 case WebAssemblyII::MO_TLS_BASE_REL: 143 Kind = MCSymbolRefExpr::VK_WASM_TLSREL; 144 break; 145 case WebAssemblyII::MO_TABLE_BASE_REL: 146 Kind = MCSymbolRefExpr::VK_WASM_TBREL; 147 break; 148 default: 149 llvm_unreachable("Unknown target flag on GV operand"); 150 } 151 152 const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Kind, Ctx); 153 154 if (MO.getOffset() != 0) { 155 const auto *WasmSym = cast<MCSymbolWasm>(Sym); 156 if (TargetFlags == WebAssemblyII::MO_GOT) 157 report_fatal_error("GOT symbol references do not support offsets"); 158 if (WasmSym->isFunction()) 159 report_fatal_error("Function addresses with offsets not supported"); 160 if (WasmSym->isGlobal()) 161 report_fatal_error("Global indexes with offsets not supported"); 162 if (WasmSym->isTag()) 163 report_fatal_error("Tag indexes with offsets not supported"); 164 if (WasmSym->isTable()) 165 report_fatal_error("Table indexes with offsets not supported"); 166 167 Expr = MCBinaryExpr::createAdd( 168 Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx); 169 } 170 171 return MCOperand::createExpr(Expr); 172 } 173 174 MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand( 175 SmallVector<wasm::ValType, 1> &&Returns, 176 SmallVector<wasm::ValType, 4> &&Params) const { 177 auto Signature = std::make_unique<wasm::WasmSignature>(std::move(Returns), 178 std::move(Params)); 179 MCSymbol *Sym = Printer.createTempSymbol("typeindex"); 180 auto *WasmSym = cast<MCSymbolWasm>(Sym); 181 WasmSym->setSignature(Signature.get()); 182 Printer.addSignature(std::move(Signature)); 183 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 184 const MCExpr *Expr = 185 MCSymbolRefExpr::create(WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx); 186 return MCOperand::createExpr(Expr); 187 } 188 189 // Return the WebAssembly type associated with the given register class. 190 static wasm::ValType getType(const TargetRegisterClass *RC) { 191 if (RC == &WebAssembly::I32RegClass) 192 return wasm::ValType::I32; 193 if (RC == &WebAssembly::I64RegClass) 194 return wasm::ValType::I64; 195 if (RC == &WebAssembly::F32RegClass) 196 return wasm::ValType::F32; 197 if (RC == &WebAssembly::F64RegClass) 198 return wasm::ValType::F64; 199 if (RC == &WebAssembly::V128RegClass) 200 return wasm::ValType::V128; 201 if (RC == &WebAssembly::EXTERNREFRegClass) 202 return wasm::ValType::EXTERNREF; 203 if (RC == &WebAssembly::FUNCREFRegClass) 204 return wasm::ValType::FUNCREF; 205 llvm_unreachable("Unexpected register class"); 206 } 207 208 static void getFunctionReturns(const MachineInstr *MI, 209 SmallVectorImpl<wasm::ValType> &Returns) { 210 const Function &F = MI->getMF()->getFunction(); 211 const TargetMachine &TM = MI->getMF()->getTarget(); 212 Type *RetTy = F.getReturnType(); 213 SmallVector<MVT, 4> CallerRetTys; 214 computeLegalValueVTs(F, TM, RetTy, CallerRetTys); 215 valTypesFromMVTs(CallerRetTys, Returns); 216 } 217 218 void WebAssemblyMCInstLower::lower(const MachineInstr *MI, 219 MCInst &OutMI) const { 220 OutMI.setOpcode(MI->getOpcode()); 221 222 const MCInstrDesc &Desc = MI->getDesc(); 223 unsigned NumVariadicDefs = MI->getNumExplicitDefs() - Desc.getNumDefs(); 224 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) { 225 const MachineOperand &MO = MI->getOperand(I); 226 227 MCOperand MCOp; 228 switch (MO.getType()) { 229 default: 230 MI->print(errs()); 231 llvm_unreachable("unknown operand type"); 232 case MachineOperand::MO_MachineBasicBlock: 233 MI->print(errs()); 234 llvm_unreachable("MachineBasicBlock operand should have been rewritten"); 235 case MachineOperand::MO_Register: { 236 // Ignore all implicit register operands. 237 if (MO.isImplicit()) 238 continue; 239 const WebAssemblyFunctionInfo &MFI = 240 *MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>(); 241 unsigned WAReg = MFI.getWAReg(MO.getReg()); 242 MCOp = MCOperand::createReg(WAReg); 243 break; 244 } 245 case MachineOperand::MO_Immediate: { 246 unsigned DescIndex = I - NumVariadicDefs; 247 if (DescIndex < Desc.NumOperands) { 248 const MCOperandInfo &Info = Desc.OpInfo[DescIndex]; 249 if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) { 250 SmallVector<wasm::ValType, 4> Returns; 251 SmallVector<wasm::ValType, 4> Params; 252 253 const MachineRegisterInfo &MRI = 254 MI->getParent()->getParent()->getRegInfo(); 255 for (const MachineOperand &MO : MI->defs()) 256 Returns.push_back(getType(MRI.getRegClass(MO.getReg()))); 257 for (const MachineOperand &MO : MI->explicit_uses()) 258 if (MO.isReg()) 259 Params.push_back(getType(MRI.getRegClass(MO.getReg()))); 260 261 // call_indirect instructions have a callee operand at the end which 262 // doesn't count as a param. 263 if (WebAssembly::isCallIndirect(MI->getOpcode())) 264 Params.pop_back(); 265 266 // return_call_indirect instructions have the return type of the 267 // caller 268 if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT) 269 getFunctionReturns(MI, Returns); 270 271 MCOp = lowerTypeIndexOperand(std::move(Returns), std::move(Params)); 272 break; 273 } else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) { 274 auto BT = static_cast<WebAssembly::BlockType>(MO.getImm()); 275 assert(BT != WebAssembly::BlockType::Invalid); 276 if (BT == WebAssembly::BlockType::Multivalue) { 277 SmallVector<wasm::ValType, 1> Returns; 278 getFunctionReturns(MI, Returns); 279 MCOp = lowerTypeIndexOperand(std::move(Returns), 280 SmallVector<wasm::ValType, 4>()); 281 break; 282 } 283 } 284 } 285 MCOp = MCOperand::createImm(MO.getImm()); 286 break; 287 } 288 case MachineOperand::MO_FPImmediate: { 289 const ConstantFP *Imm = MO.getFPImm(); 290 const uint64_t BitPattern = 291 Imm->getValueAPF().bitcastToAPInt().getZExtValue(); 292 if (Imm->getType()->isFloatTy()) 293 MCOp = MCOperand::createSFPImm(static_cast<uint32_t>(BitPattern)); 294 else if (Imm->getType()->isDoubleTy()) 295 MCOp = MCOperand::createDFPImm(BitPattern); 296 else 297 llvm_unreachable("unknown floating point immediate type"); 298 break; 299 } 300 case MachineOperand::MO_GlobalAddress: 301 MCOp = lowerSymbolOperand(MO, GetGlobalAddressSymbol(MO)); 302 break; 303 case MachineOperand::MO_ExternalSymbol: 304 MCOp = lowerSymbolOperand(MO, GetExternalSymbolSymbol(MO)); 305 break; 306 case MachineOperand::MO_MCSymbol: 307 assert(MO.getTargetFlags() == 0 && 308 "WebAssembly does not use target flags on MCSymbol"); 309 MCOp = lowerSymbolOperand(MO, MO.getMCSymbol()); 310 break; 311 } 312 313 OutMI.addOperand(MCOp); 314 } 315 316 if (!WasmKeepRegisters) 317 removeRegisterOperands(MI, OutMI); 318 else if (Desc.variadicOpsAreDefs()) 319 OutMI.insert(OutMI.begin(), MCOperand::createImm(MI->getNumExplicitDefs())); 320 } 321 322 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) { 323 // Remove all uses of stackified registers to bring the instruction format 324 // into its final stack form used thruout MC, and transition opcodes to 325 // their _S variant. 326 // We do this separate from the above code that still may need these 327 // registers for e.g. call_indirect signatures. 328 // See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for 329 // details. 330 // TODO: the code above creates new registers which are then removed here. 331 // That code could be slightly simplified by not doing that, though maybe 332 // it is simpler conceptually to keep the code above in "register mode" 333 // until this transition point. 334 // FIXME: we are not processing inline assembly, which contains register 335 // operands, because it is used by later target generic code. 336 if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm()) 337 return; 338 339 // Transform to _S instruction. 340 auto RegOpcode = OutMI.getOpcode(); 341 auto StackOpcode = WebAssembly::getStackOpcode(RegOpcode); 342 assert(StackOpcode != -1 && "Failed to stackify instruction"); 343 OutMI.setOpcode(StackOpcode); 344 345 // Remove register operands. 346 for (auto I = OutMI.getNumOperands(); I; --I) { 347 auto &MO = OutMI.getOperand(I - 1); 348 if (MO.isReg()) { 349 OutMI.erase(&MO); 350 } 351 } 352 } 353