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