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 "MCTargetDesc/WebAssemblyMCTargetDesc.h" 17 #include "TargetInfo/WebAssemblyTargetInfo.h" 18 #include "Utils/WebAssemblyTypeUtilities.h" 19 #include "WebAssemblyAsmPrinter.h" 20 #include "WebAssemblyMachineFunctionInfo.h" 21 #include "WebAssemblyUtilities.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(Ctx, ResultMVTs, ParamMVTs); 77 78 bool InvokeDetected = false; 79 auto *WasmSym = Printer.getMCSymbolForFunction( 80 F, WebAssembly::WasmEnableEmEH || WebAssembly::WasmEnableEmSjLj, 81 Signature, InvokeDetected); 82 WasmSym->setSignature(Signature); 83 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 84 return WasmSym; 85 } 86 87 MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol( 88 const MachineOperand &MO) const { 89 return Printer.getOrCreateWasmSymbol(MO.getSymbolName()); 90 } 91 92 MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO, 93 MCSymbol *Sym) const { 94 MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None; 95 unsigned TargetFlags = MO.getTargetFlags(); 96 97 switch (TargetFlags) { 98 case WebAssemblyII::MO_NO_FLAG: 99 break; 100 case WebAssemblyII::MO_GOT_TLS: 101 Kind = MCSymbolRefExpr::VK_WASM_GOT_TLS; 102 break; 103 case WebAssemblyII::MO_GOT: 104 Kind = MCSymbolRefExpr::VK_GOT; 105 break; 106 case WebAssemblyII::MO_MEMORY_BASE_REL: 107 Kind = MCSymbolRefExpr::VK_WASM_MBREL; 108 break; 109 case WebAssemblyII::MO_TLS_BASE_REL: 110 Kind = MCSymbolRefExpr::VK_WASM_TLSREL; 111 break; 112 case WebAssemblyII::MO_TABLE_BASE_REL: 113 Kind = MCSymbolRefExpr::VK_WASM_TBREL; 114 break; 115 default: 116 llvm_unreachable("Unknown target flag on GV operand"); 117 } 118 119 const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Kind, Ctx); 120 121 if (MO.getOffset() != 0) { 122 const auto *WasmSym = cast<MCSymbolWasm>(Sym); 123 if (TargetFlags == WebAssemblyII::MO_GOT) 124 report_fatal_error("GOT symbol references do not support offsets"); 125 if (WasmSym->isFunction()) 126 report_fatal_error("Function addresses with offsets not supported"); 127 if (WasmSym->isGlobal()) 128 report_fatal_error("Global indexes with offsets not supported"); 129 if (WasmSym->isTag()) 130 report_fatal_error("Tag indexes with offsets not supported"); 131 if (WasmSym->isTable()) 132 report_fatal_error("Table indexes with offsets not supported"); 133 134 Expr = MCBinaryExpr::createAdd( 135 Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx); 136 } 137 138 return MCOperand::createExpr(Expr); 139 } 140 141 MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand( 142 SmallVectorImpl<wasm::ValType> &&Returns, 143 SmallVectorImpl<wasm::ValType> &&Params) const { 144 auto Signature = Ctx.createWasmSignature(); 145 Signature->Returns = std::move(Returns); 146 Signature->Params = std::move(Params); 147 MCSymbol *Sym = Printer.createTempSymbol("typeindex"); 148 auto *WasmSym = cast<MCSymbolWasm>(Sym); 149 WasmSym->setSignature(Signature); 150 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 151 const MCExpr *Expr = 152 MCSymbolRefExpr::create(WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx); 153 return MCOperand::createExpr(Expr); 154 } 155 156 static void getFunctionReturns(const MachineInstr *MI, 157 SmallVectorImpl<wasm::ValType> &Returns) { 158 const Function &F = MI->getMF()->getFunction(); 159 const TargetMachine &TM = MI->getMF()->getTarget(); 160 Type *RetTy = F.getReturnType(); 161 SmallVector<MVT, 4> CallerRetTys; 162 computeLegalValueVTs(F, TM, RetTy, CallerRetTys); 163 valTypesFromMVTs(CallerRetTys, Returns); 164 } 165 166 void WebAssemblyMCInstLower::lower(const MachineInstr *MI, 167 MCInst &OutMI) const { 168 OutMI.setOpcode(MI->getOpcode()); 169 170 const MCInstrDesc &Desc = MI->getDesc(); 171 unsigned NumVariadicDefs = MI->getNumExplicitDefs() - Desc.getNumDefs(); 172 const MachineFunction *MF = MI->getMF(); 173 const auto &TLI = 174 *MF->getSubtarget<WebAssemblySubtarget>().getTargetLowering(); 175 wasm::ValType PtrTy = TLI.getPointerTy(MF->getDataLayout()) == MVT::i32 176 ? wasm::ValType::I32 177 : wasm::ValType::I64; 178 179 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) { 180 const MachineOperand &MO = MI->getOperand(I); 181 182 MCOperand MCOp; 183 switch (MO.getType()) { 184 default: 185 MI->print(errs()); 186 llvm_unreachable("unknown operand type"); 187 case MachineOperand::MO_MachineBasicBlock: 188 MI->print(errs()); 189 llvm_unreachable("MachineBasicBlock operand should have been rewritten"); 190 case MachineOperand::MO_Register: { 191 // Ignore all implicit register operands. 192 if (MO.isImplicit()) 193 continue; 194 const WebAssemblyFunctionInfo &MFI = 195 *MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>(); 196 unsigned WAReg = MFI.getWAReg(MO.getReg()); 197 MCOp = MCOperand::createReg(WAReg); 198 break; 199 } 200 case MachineOperand::MO_Immediate: { 201 unsigned DescIndex = I - NumVariadicDefs; 202 if (DescIndex < Desc.NumOperands) { 203 const MCOperandInfo &Info = Desc.operands()[DescIndex]; 204 if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) { 205 SmallVector<wasm::ValType, 4> Returns; 206 SmallVector<wasm::ValType, 4> Params; 207 208 const MachineRegisterInfo &MRI = 209 MI->getParent()->getParent()->getRegInfo(); 210 for (const MachineOperand &MO : MI->defs()) 211 Returns.push_back(WebAssembly::regClassToValType( 212 MRI.getRegClass(MO.getReg())->getID())); 213 for (const MachineOperand &MO : MI->explicit_uses()) 214 if (MO.isReg()) 215 Params.push_back(WebAssembly::regClassToValType( 216 MRI.getRegClass(MO.getReg())->getID())); 217 218 // call_indirect instructions have a callee operand at the end which 219 // doesn't count as a param. 220 if (WebAssembly::isCallIndirect(MI->getOpcode())) 221 Params.pop_back(); 222 223 // return_call_indirect instructions have the return type of the 224 // caller 225 if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT) 226 getFunctionReturns(MI, Returns); 227 228 MCOp = lowerTypeIndexOperand(std::move(Returns), std::move(Params)); 229 break; 230 } 231 if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) { 232 auto BT = static_cast<WebAssembly::BlockType>(MO.getImm()); 233 assert(BT != WebAssembly::BlockType::Invalid); 234 if (BT == WebAssembly::BlockType::Multivalue) { 235 SmallVector<wasm::ValType, 2> Returns; 236 // Multivalue blocks are emitted in two cases: 237 // 1. When the blocks will never be exited and are at the ends of 238 // functions (see 239 // WebAssemblyCFGStackify::fixEndsAtEndOfFunction). In this case 240 // the exact multivalue signature can always be inferred from the 241 // return type of the parent function. 242 // 2. (catch_ref ...) clause in try_table instruction. Currently all 243 // tags we support (cpp_exception and c_longjmp) throws a single 244 // pointer, so the multivalue signature for this case will be 245 // (ptr, exnref). Having MO_CATCH_BLOCK_SIG target flags means 246 // this is a destination of a catch_ref. 247 if (MO.getTargetFlags() == WebAssemblyII::MO_CATCH_BLOCK_SIG) { 248 Returns = {PtrTy, wasm::ValType::EXNREF}; 249 } else 250 getFunctionReturns(MI, Returns); 251 MCOp = lowerTypeIndexOperand(std::move(Returns), 252 SmallVector<wasm::ValType, 4>()); 253 break; 254 } 255 } 256 } 257 MCOp = MCOperand::createImm(MO.getImm()); 258 break; 259 } 260 case MachineOperand::MO_FPImmediate: { 261 const ConstantFP *Imm = MO.getFPImm(); 262 const uint64_t BitPattern = 263 Imm->getValueAPF().bitcastToAPInt().getZExtValue(); 264 if (Imm->getType()->isFloatTy()) 265 MCOp = MCOperand::createSFPImm(static_cast<uint32_t>(BitPattern)); 266 else if (Imm->getType()->isDoubleTy()) 267 MCOp = MCOperand::createDFPImm(BitPattern); 268 else 269 llvm_unreachable("unknown floating point immediate type"); 270 break; 271 } 272 case MachineOperand::MO_GlobalAddress: 273 MCOp = lowerSymbolOperand(MO, GetGlobalAddressSymbol(MO)); 274 break; 275 case MachineOperand::MO_ExternalSymbol: 276 MCOp = lowerSymbolOperand(MO, GetExternalSymbolSymbol(MO)); 277 break; 278 case MachineOperand::MO_MCSymbol: 279 assert(MO.getTargetFlags() == 0 && 280 "WebAssembly does not use target flags on MCSymbol"); 281 MCOp = lowerSymbolOperand(MO, MO.getMCSymbol()); 282 break; 283 } 284 285 OutMI.addOperand(MCOp); 286 } 287 288 if (!WasmKeepRegisters) 289 removeRegisterOperands(MI, OutMI); 290 else if (Desc.variadicOpsAreDefs()) 291 OutMI.insert(OutMI.begin(), MCOperand::createImm(MI->getNumExplicitDefs())); 292 } 293 294 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) { 295 // Remove all uses of stackified registers to bring the instruction format 296 // into its final stack form used thruout MC, and transition opcodes to 297 // their _S variant. 298 // We do this separate from the above code that still may need these 299 // registers for e.g. call_indirect signatures. 300 // See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for 301 // details. 302 // TODO: the code above creates new registers which are then removed here. 303 // That code could be slightly simplified by not doing that, though maybe 304 // it is simpler conceptually to keep the code above in "register mode" 305 // until this transition point. 306 // FIXME: we are not processing inline assembly, which contains register 307 // operands, because it is used by later target generic code. 308 if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm()) 309 return; 310 311 // Transform to _S instruction. 312 auto RegOpcode = OutMI.getOpcode(); 313 auto StackOpcode = WebAssembly::getStackOpcode(RegOpcode); 314 assert(StackOpcode != -1 && "Failed to stackify instruction"); 315 OutMI.setOpcode(StackOpcode); 316 317 // Remove register operands. 318 for (auto I = OutMI.getNumOperands(); I; --I) { 319 auto &MO = OutMI.getOperand(I - 1); 320 if (MO.isReg()) { 321 OutMI.erase(&MO); 322 } 323 } 324 } 325