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 WebAssembly::wasmSymbolSetType(WasmSym, GlobalVT, VTs); 63 } 64 return WasmSym; 65 } 66 67 const auto *FuncTy = cast<FunctionType>(Global->getValueType()); 68 const MachineFunction &MF = *MO.getParent()->getParent()->getParent(); 69 const TargetMachine &TM = MF.getTarget(); 70 const Function &CurrentFunc = MF.getFunction(); 71 72 SmallVector<MVT, 1> ResultMVTs; 73 SmallVector<MVT, 4> ParamMVTs; 74 const auto *const F = dyn_cast<Function>(Global); 75 computeSignatureVTs(FuncTy, F, CurrentFunc, TM, ParamMVTs, ResultMVTs); 76 auto Signature = signatureFromMVTs(ResultMVTs, ParamMVTs); 77 78 bool InvokeDetected = false; 79 auto *WasmSym = Printer.getMCSymbolForFunction( 80 F, WebAssembly::WasmEnableEmEH || WebAssembly::WasmEnableEmSjLj, 81 Signature.get(), InvokeDetected); 82 WasmSym->setSignature(Signature.get()); 83 Printer.addSignature(std::move(Signature)); 84 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 85 return WasmSym; 86 } 87 88 MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol( 89 const MachineOperand &MO) const { 90 return Printer.getOrCreateWasmSymbol(MO.getSymbolName()); 91 } 92 93 MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO, 94 MCSymbol *Sym) const { 95 MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None; 96 unsigned TargetFlags = MO.getTargetFlags(); 97 98 switch (TargetFlags) { 99 case WebAssemblyII::MO_NO_FLAG: 100 break; 101 case WebAssemblyII::MO_GOT_TLS: 102 Kind = MCSymbolRefExpr::VK_WASM_GOT_TLS; 103 break; 104 case WebAssemblyII::MO_GOT: 105 Kind = MCSymbolRefExpr::VK_GOT; 106 break; 107 case WebAssemblyII::MO_MEMORY_BASE_REL: 108 Kind = MCSymbolRefExpr::VK_WASM_MBREL; 109 break; 110 case WebAssemblyII::MO_TLS_BASE_REL: 111 Kind = MCSymbolRefExpr::VK_WASM_TLSREL; 112 break; 113 case WebAssemblyII::MO_TABLE_BASE_REL: 114 Kind = MCSymbolRefExpr::VK_WASM_TBREL; 115 break; 116 default: 117 llvm_unreachable("Unknown target flag on GV operand"); 118 } 119 120 const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Kind, Ctx); 121 122 if (MO.getOffset() != 0) { 123 const auto *WasmSym = cast<MCSymbolWasm>(Sym); 124 if (TargetFlags == WebAssemblyII::MO_GOT) 125 report_fatal_error("GOT symbol references do not support offsets"); 126 if (WasmSym->isFunction()) 127 report_fatal_error("Function addresses with offsets not supported"); 128 if (WasmSym->isGlobal()) 129 report_fatal_error("Global indexes with offsets not supported"); 130 if (WasmSym->isTag()) 131 report_fatal_error("Tag indexes with offsets not supported"); 132 if (WasmSym->isTable()) 133 report_fatal_error("Table indexes with offsets not supported"); 134 135 Expr = MCBinaryExpr::createAdd( 136 Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx); 137 } 138 139 return MCOperand::createExpr(Expr); 140 } 141 142 MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand( 143 SmallVector<wasm::ValType, 1> &&Returns, 144 SmallVector<wasm::ValType, 4> &&Params) const { 145 auto Signature = std::make_unique<wasm::WasmSignature>(std::move(Returns), 146 std::move(Params)); 147 MCSymbol *Sym = Printer.createTempSymbol("typeindex"); 148 auto *WasmSym = cast<MCSymbolWasm>(Sym); 149 WasmSym->setSignature(Signature.get()); 150 Printer.addSignature(std::move(Signature)); 151 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 152 const MCExpr *Expr = 153 MCSymbolRefExpr::create(WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx); 154 return MCOperand::createExpr(Expr); 155 } 156 157 static void getFunctionReturns(const MachineInstr *MI, 158 SmallVectorImpl<wasm::ValType> &Returns) { 159 const Function &F = MI->getMF()->getFunction(); 160 const TargetMachine &TM = MI->getMF()->getTarget(); 161 Type *RetTy = F.getReturnType(); 162 SmallVector<MVT, 4> CallerRetTys; 163 computeLegalValueVTs(F, TM, RetTy, CallerRetTys); 164 valTypesFromMVTs(CallerRetTys, Returns); 165 } 166 167 void WebAssemblyMCInstLower::lower(const MachineInstr *MI, 168 MCInst &OutMI) const { 169 OutMI.setOpcode(MI->getOpcode()); 170 171 const MCInstrDesc &Desc = MI->getDesc(); 172 unsigned NumVariadicDefs = MI->getNumExplicitDefs() - Desc.getNumDefs(); 173 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) { 174 const MachineOperand &MO = MI->getOperand(I); 175 176 MCOperand MCOp; 177 switch (MO.getType()) { 178 default: 179 MI->print(errs()); 180 llvm_unreachable("unknown operand type"); 181 case MachineOperand::MO_MachineBasicBlock: 182 MI->print(errs()); 183 llvm_unreachable("MachineBasicBlock operand should have been rewritten"); 184 case MachineOperand::MO_Register: { 185 // Ignore all implicit register operands. 186 if (MO.isImplicit()) 187 continue; 188 const WebAssemblyFunctionInfo &MFI = 189 *MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>(); 190 unsigned WAReg = MFI.getWAReg(MO.getReg()); 191 MCOp = MCOperand::createReg(WAReg); 192 break; 193 } 194 case MachineOperand::MO_Immediate: { 195 unsigned DescIndex = I - NumVariadicDefs; 196 if (DescIndex < Desc.NumOperands) { 197 const MCOperandInfo &Info = Desc.operands()[DescIndex]; 198 if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) { 199 SmallVector<wasm::ValType, 4> Returns; 200 SmallVector<wasm::ValType, 4> Params; 201 202 const MachineRegisterInfo &MRI = 203 MI->getParent()->getParent()->getRegInfo(); 204 for (const MachineOperand &MO : MI->defs()) 205 Returns.push_back( 206 WebAssembly::regClassToValType(MRI.getRegClass(MO.getReg()))); 207 for (const MachineOperand &MO : MI->explicit_uses()) 208 if (MO.isReg()) 209 Params.push_back( 210 WebAssembly::regClassToValType(MRI.getRegClass(MO.getReg()))); 211 212 // call_indirect instructions have a callee operand at the end which 213 // doesn't count as a param. 214 if (WebAssembly::isCallIndirect(MI->getOpcode())) 215 Params.pop_back(); 216 217 // return_call_indirect instructions have the return type of the 218 // caller 219 if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT) 220 getFunctionReturns(MI, Returns); 221 222 MCOp = lowerTypeIndexOperand(std::move(Returns), std::move(Params)); 223 break; 224 } else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) { 225 auto BT = static_cast<WebAssembly::BlockType>(MO.getImm()); 226 assert(BT != WebAssembly::BlockType::Invalid); 227 if (BT == WebAssembly::BlockType::Multivalue) { 228 SmallVector<wasm::ValType, 1> Returns; 229 getFunctionReturns(MI, Returns); 230 MCOp = lowerTypeIndexOperand(std::move(Returns), 231 SmallVector<wasm::ValType, 4>()); 232 break; 233 } 234 } 235 } 236 MCOp = MCOperand::createImm(MO.getImm()); 237 break; 238 } 239 case MachineOperand::MO_FPImmediate: { 240 const ConstantFP *Imm = MO.getFPImm(); 241 const uint64_t BitPattern = 242 Imm->getValueAPF().bitcastToAPInt().getZExtValue(); 243 if (Imm->getType()->isFloatTy()) 244 MCOp = MCOperand::createSFPImm(static_cast<uint32_t>(BitPattern)); 245 else if (Imm->getType()->isDoubleTy()) 246 MCOp = MCOperand::createDFPImm(BitPattern); 247 else 248 llvm_unreachable("unknown floating point immediate type"); 249 break; 250 } 251 case MachineOperand::MO_GlobalAddress: 252 MCOp = lowerSymbolOperand(MO, GetGlobalAddressSymbol(MO)); 253 break; 254 case MachineOperand::MO_ExternalSymbol: 255 MCOp = lowerSymbolOperand(MO, GetExternalSymbolSymbol(MO)); 256 break; 257 case MachineOperand::MO_MCSymbol: 258 assert(MO.getTargetFlags() == 0 && 259 "WebAssembly does not use target flags on MCSymbol"); 260 MCOp = lowerSymbolOperand(MO, MO.getMCSymbol()); 261 break; 262 } 263 264 OutMI.addOperand(MCOp); 265 } 266 267 if (!WasmKeepRegisters) 268 removeRegisterOperands(MI, OutMI); 269 else if (Desc.variadicOpsAreDefs()) 270 OutMI.insert(OutMI.begin(), MCOperand::createImm(MI->getNumExplicitDefs())); 271 } 272 273 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) { 274 // Remove all uses of stackified registers to bring the instruction format 275 // into its final stack form used thruout MC, and transition opcodes to 276 // their _S variant. 277 // We do this separate from the above code that still may need these 278 // registers for e.g. call_indirect signatures. 279 // See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for 280 // details. 281 // TODO: the code above creates new registers which are then removed here. 282 // That code could be slightly simplified by not doing that, though maybe 283 // it is simpler conceptually to keep the code above in "register mode" 284 // until this transition point. 285 // FIXME: we are not processing inline assembly, which contains register 286 // operands, because it is used by later target generic code. 287 if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm()) 288 return; 289 290 // Transform to _S instruction. 291 auto RegOpcode = OutMI.getOpcode(); 292 auto StackOpcode = WebAssembly::getStackOpcode(RegOpcode); 293 assert(StackOpcode != -1 && "Failed to stackify instruction"); 294 OutMI.setOpcode(StackOpcode); 295 296 // Remove register operands. 297 for (auto I = OutMI.getNumOperands(); I; --I) { 298 auto &MO = OutMI.getOperand(I - 1); 299 if (MO.isReg()) { 300 OutMI.erase(&MO); 301 } 302 } 303 } 304