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 extern cl::opt<bool> WasmEnableEmEH; 44 extern cl::opt<bool> WasmEnableEmSjLj; 45 46 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI); 47 48 MCSymbol * 49 WebAssemblyMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const { 50 const GlobalValue *Global = MO.getGlobal(); 51 if (!isa<Function>(Global)) { 52 auto *WasmSym = cast<MCSymbolWasm>(Printer.getSymbol(Global)); 53 // If the symbol doesn't have an explicit WasmSymbolType yet and the 54 // GlobalValue is actually a WebAssembly global, then ensure the symbol is a 55 // WASM_SYMBOL_TYPE_GLOBAL. 56 if (WebAssembly::isWasmVarAddressSpace(Global->getAddressSpace()) && 57 !WasmSym->getType()) { 58 const MachineFunction &MF = *MO.getParent()->getParent()->getParent(); 59 const TargetMachine &TM = MF.getTarget(); 60 const Function &CurrentFunc = MF.getFunction(); 61 Type *GlobalVT = Global->getValueType(); 62 SmallVector<MVT, 1> VTs; 63 computeLegalValueVTs(CurrentFunc, TM, GlobalVT, VTs); 64 65 // Tables are represented as Arrays in LLVM IR therefore 66 // they reach this point as aggregate Array types with an element type 67 // that is a reference type. 68 wasm::ValType Type; 69 if (GlobalVT->isArrayTy() && 70 WebAssembly::isRefType(GlobalVT->getArrayElementType())) { 71 MVT VT; 72 switch (GlobalVT->getArrayElementType()->getPointerAddressSpace()) { 73 case WebAssembly::WasmAddressSpace::WASM_ADDRESS_SPACE_FUNCREF: 74 VT = MVT::funcref; 75 break; 76 case WebAssembly::WasmAddressSpace::WASM_ADDRESS_SPACE_EXTERNREF: 77 VT = MVT::externref; 78 break; 79 default: 80 report_fatal_error("unhandled address space type"); 81 } 82 Type = WebAssembly::toValType(VT); 83 } else if (VTs.size() == 1) { 84 Type = WebAssembly::toValType(VTs[0]); 85 } else 86 report_fatal_error("Aggregate globals not yet implemented"); 87 88 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL); 89 WasmSym->setGlobalType( 90 wasm::WasmGlobalType{uint8_t(Type), /*Mutable=*/true}); 91 } 92 return WasmSym; 93 } 94 95 const auto *FuncTy = cast<FunctionType>(Global->getValueType()); 96 const MachineFunction &MF = *MO.getParent()->getParent()->getParent(); 97 const TargetMachine &TM = MF.getTarget(); 98 const Function &CurrentFunc = MF.getFunction(); 99 100 SmallVector<MVT, 1> ResultMVTs; 101 SmallVector<MVT, 4> ParamMVTs; 102 const auto *const F = dyn_cast<Function>(Global); 103 computeSignatureVTs(FuncTy, F, CurrentFunc, TM, ParamMVTs, ResultMVTs); 104 auto Signature = signatureFromMVTs(ResultMVTs, ParamMVTs); 105 106 bool InvokeDetected = false; 107 auto *WasmSym = Printer.getMCSymbolForFunction( 108 F, WasmEnableEmEH || WasmEnableEmSjLj, Signature.get(), InvokeDetected); 109 WasmSym->setSignature(Signature.get()); 110 Printer.addSignature(std::move(Signature)); 111 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 112 return WasmSym; 113 } 114 115 MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol( 116 const MachineOperand &MO) const { 117 return Printer.getOrCreateWasmSymbol(MO.getSymbolName()); 118 } 119 120 MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO, 121 MCSymbol *Sym) const { 122 MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None; 123 unsigned TargetFlags = MO.getTargetFlags(); 124 125 switch (TargetFlags) { 126 case WebAssemblyII::MO_NO_FLAG: 127 break; 128 case WebAssemblyII::MO_GOT_TLS: 129 Kind = MCSymbolRefExpr::VK_WASM_GOT_TLS; 130 break; 131 case WebAssemblyII::MO_GOT: 132 Kind = MCSymbolRefExpr::VK_GOT; 133 break; 134 case WebAssemblyII::MO_MEMORY_BASE_REL: 135 Kind = MCSymbolRefExpr::VK_WASM_MBREL; 136 break; 137 case WebAssemblyII::MO_TLS_BASE_REL: 138 Kind = MCSymbolRefExpr::VK_WASM_TLSREL; 139 break; 140 case WebAssemblyII::MO_TABLE_BASE_REL: 141 Kind = MCSymbolRefExpr::VK_WASM_TBREL; 142 break; 143 default: 144 llvm_unreachable("Unknown target flag on GV operand"); 145 } 146 147 const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Kind, Ctx); 148 149 if (MO.getOffset() != 0) { 150 const auto *WasmSym = cast<MCSymbolWasm>(Sym); 151 if (TargetFlags == WebAssemblyII::MO_GOT) 152 report_fatal_error("GOT symbol references do not support offsets"); 153 if (WasmSym->isFunction()) 154 report_fatal_error("Function addresses with offsets not supported"); 155 if (WasmSym->isGlobal()) 156 report_fatal_error("Global indexes with offsets not supported"); 157 if (WasmSym->isTag()) 158 report_fatal_error("Tag indexes with offsets not supported"); 159 if (WasmSym->isTable()) 160 report_fatal_error("Table indexes with offsets not supported"); 161 162 Expr = MCBinaryExpr::createAdd( 163 Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx); 164 } 165 166 return MCOperand::createExpr(Expr); 167 } 168 169 MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand( 170 SmallVector<wasm::ValType, 1> &&Returns, 171 SmallVector<wasm::ValType, 4> &&Params) const { 172 auto Signature = std::make_unique<wasm::WasmSignature>(std::move(Returns), 173 std::move(Params)); 174 MCSymbol *Sym = Printer.createTempSymbol("typeindex"); 175 auto *WasmSym = cast<MCSymbolWasm>(Sym); 176 WasmSym->setSignature(Signature.get()); 177 Printer.addSignature(std::move(Signature)); 178 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 179 const MCExpr *Expr = 180 MCSymbolRefExpr::create(WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx); 181 return MCOperand::createExpr(Expr); 182 } 183 184 // Return the WebAssembly type associated with the given register class. 185 static wasm::ValType getType(const TargetRegisterClass *RC) { 186 if (RC == &WebAssembly::I32RegClass) 187 return wasm::ValType::I32; 188 if (RC == &WebAssembly::I64RegClass) 189 return wasm::ValType::I64; 190 if (RC == &WebAssembly::F32RegClass) 191 return wasm::ValType::F32; 192 if (RC == &WebAssembly::F64RegClass) 193 return wasm::ValType::F64; 194 if (RC == &WebAssembly::V128RegClass) 195 return wasm::ValType::V128; 196 if (RC == &WebAssembly::EXTERNREFRegClass) 197 return wasm::ValType::EXTERNREF; 198 if (RC == &WebAssembly::FUNCREFRegClass) 199 return wasm::ValType::FUNCREF; 200 llvm_unreachable("Unexpected register class"); 201 } 202 203 static void getFunctionReturns(const MachineInstr *MI, 204 SmallVectorImpl<wasm::ValType> &Returns) { 205 const Function &F = MI->getMF()->getFunction(); 206 const TargetMachine &TM = MI->getMF()->getTarget(); 207 Type *RetTy = F.getReturnType(); 208 SmallVector<MVT, 4> CallerRetTys; 209 computeLegalValueVTs(F, TM, RetTy, CallerRetTys); 210 valTypesFromMVTs(CallerRetTys, Returns); 211 } 212 213 void WebAssemblyMCInstLower::lower(const MachineInstr *MI, 214 MCInst &OutMI) const { 215 OutMI.setOpcode(MI->getOpcode()); 216 217 const MCInstrDesc &Desc = MI->getDesc(); 218 unsigned NumVariadicDefs = MI->getNumExplicitDefs() - Desc.getNumDefs(); 219 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) { 220 const MachineOperand &MO = MI->getOperand(I); 221 222 MCOperand MCOp; 223 switch (MO.getType()) { 224 default: 225 MI->print(errs()); 226 llvm_unreachable("unknown operand type"); 227 case MachineOperand::MO_MachineBasicBlock: 228 MI->print(errs()); 229 llvm_unreachable("MachineBasicBlock operand should have been rewritten"); 230 case MachineOperand::MO_Register: { 231 // Ignore all implicit register operands. 232 if (MO.isImplicit()) 233 continue; 234 const WebAssemblyFunctionInfo &MFI = 235 *MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>(); 236 unsigned WAReg = MFI.getWAReg(MO.getReg()); 237 MCOp = MCOperand::createReg(WAReg); 238 break; 239 } 240 case MachineOperand::MO_Immediate: { 241 unsigned DescIndex = I - NumVariadicDefs; 242 if (DescIndex < Desc.NumOperands) { 243 const MCOperandInfo &Info = Desc.OpInfo[DescIndex]; 244 if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) { 245 SmallVector<wasm::ValType, 4> Returns; 246 SmallVector<wasm::ValType, 4> Params; 247 248 const MachineRegisterInfo &MRI = 249 MI->getParent()->getParent()->getRegInfo(); 250 for (const MachineOperand &MO : MI->defs()) 251 Returns.push_back(getType(MRI.getRegClass(MO.getReg()))); 252 for (const MachineOperand &MO : MI->explicit_uses()) 253 if (MO.isReg()) 254 Params.push_back(getType(MRI.getRegClass(MO.getReg()))); 255 256 // call_indirect instructions have a callee operand at the end which 257 // doesn't count as a param. 258 if (WebAssembly::isCallIndirect(MI->getOpcode())) 259 Params.pop_back(); 260 261 // return_call_indirect instructions have the return type of the 262 // caller 263 if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT) 264 getFunctionReturns(MI, Returns); 265 266 MCOp = lowerTypeIndexOperand(std::move(Returns), std::move(Params)); 267 break; 268 } else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) { 269 auto BT = static_cast<WebAssembly::BlockType>(MO.getImm()); 270 assert(BT != WebAssembly::BlockType::Invalid); 271 if (BT == WebAssembly::BlockType::Multivalue) { 272 SmallVector<wasm::ValType, 1> Returns; 273 getFunctionReturns(MI, Returns); 274 MCOp = lowerTypeIndexOperand(std::move(Returns), 275 SmallVector<wasm::ValType, 4>()); 276 break; 277 } 278 } else if (Info.OperandType == WebAssembly::OPERAND_HEAPTYPE) { 279 assert(static_cast<WebAssembly::HeapType>(MO.getImm()) != 280 WebAssembly::HeapType::Invalid); 281 // With typed function references, this will need a case for type 282 // index operands. Otherwise, fall through. 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