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/WebAssemblyMCAsmInfo.h" 17 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h" 18 #include "TargetInfo/WebAssemblyTargetInfo.h" 19 #include "Utils/WebAssemblyTypeUtilities.h" 20 #include "WebAssemblyAsmPrinter.h" 21 #include "WebAssemblyMachineFunctionInfo.h" 22 #include "WebAssemblyUtilities.h" 23 #include "llvm/CodeGen/AsmPrinter.h" 24 #include "llvm/CodeGen/MachineFunction.h" 25 #include "llvm/IR/Constants.h" 26 #include "llvm/MC/MCAsmInfo.h" 27 #include "llvm/MC/MCContext.h" 28 #include "llvm/MC/MCExpr.h" 29 #include "llvm/MC/MCInst.h" 30 #include "llvm/MC/MCSymbolWasm.h" 31 #include "llvm/Support/ErrorHandling.h" 32 #include "llvm/Support/raw_ostream.h" 33 34 using namespace llvm; 35 36 // This disables the removal of registers when lowering into MC, as required 37 // by some current tests. 38 static cl::opt<bool> 39 WasmKeepRegisters("wasm-keep-registers", cl::Hidden, 40 cl::desc("WebAssembly: output stack registers in" 41 " instruction output for test purposes only."), 42 cl::init(false)); 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 Type *GlobalVT = Global->getValueType(); 60 SmallVector<MVT, 1> VTs; 61 computeLegalValueVTs(CurrentFunc, TM, GlobalVT, VTs); 62 63 WebAssembly::wasmSymbolSetType(WasmSym, GlobalVT, VTs); 64 } 65 return WasmSym; 66 } 67 68 const auto *FuncTy = cast<FunctionType>(Global->getValueType()); 69 const MachineFunction &MF = *MO.getParent()->getParent()->getParent(); 70 const TargetMachine &TM = MF.getTarget(); 71 const Function &CurrentFunc = MF.getFunction(); 72 73 SmallVector<MVT, 1> ResultMVTs; 74 SmallVector<MVT, 4> ParamMVTs; 75 const auto *const F = dyn_cast<Function>(Global); 76 computeSignatureVTs(FuncTy, F, CurrentFunc, TM, ParamMVTs, ResultMVTs); 77 auto Signature = signatureFromMVTs(Ctx, ResultMVTs, ParamMVTs); 78 79 bool InvokeDetected = false; 80 auto *WasmSym = Printer.getMCSymbolForFunction(F, Signature, InvokeDetected); 81 WasmSym->setSignature(Signature); 82 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 83 return WasmSym; 84 } 85 86 MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol( 87 const MachineOperand &MO) const { 88 return Printer.getOrCreateWasmSymbol(MO.getSymbolName()); 89 } 90 91 MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO, 92 MCSymbol *Sym) const { 93 auto Spec = WebAssembly::S_None; 94 unsigned TargetFlags = MO.getTargetFlags(); 95 96 switch (TargetFlags) { 97 case WebAssemblyII::MO_NO_FLAG: 98 break; 99 case WebAssemblyII::MO_GOT_TLS: 100 Spec = WebAssembly::S_GOT_TLS; 101 break; 102 case WebAssemblyII::MO_GOT: 103 Spec = WebAssembly::S_GOT; 104 break; 105 case WebAssemblyII::MO_MEMORY_BASE_REL: 106 Spec = WebAssembly::S_MBREL; 107 break; 108 case WebAssemblyII::MO_TLS_BASE_REL: 109 Spec = WebAssembly::S_TLSREL; 110 break; 111 case WebAssemblyII::MO_TABLE_BASE_REL: 112 Spec = WebAssembly::S_TBREL; 113 break; 114 default: 115 llvm_unreachable("Unknown target flag on GV operand"); 116 } 117 118 const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Spec, Ctx); 119 120 if (MO.getOffset() != 0) { 121 const auto *WasmSym = cast<MCSymbolWasm>(Sym); 122 if (TargetFlags == WebAssemblyII::MO_GOT) 123 report_fatal_error("GOT symbol references do not support offsets"); 124 if (WasmSym->isFunction()) 125 report_fatal_error("Function addresses with offsets not supported"); 126 if (WasmSym->isGlobal()) 127 report_fatal_error("Global indexes with offsets not supported"); 128 if (WasmSym->isTag()) 129 report_fatal_error("Tag indexes with offsets not supported"); 130 if (WasmSym->isTable()) 131 report_fatal_error("Table indexes with offsets not supported"); 132 133 Expr = MCBinaryExpr::createAdd( 134 Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx); 135 } 136 137 return MCOperand::createExpr(Expr); 138 } 139 140 MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand( 141 SmallVectorImpl<wasm::ValType> &&Returns, 142 SmallVectorImpl<wasm::ValType> &&Params) const { 143 auto Signature = Ctx.createWasmSignature(); 144 Signature->Returns = std::move(Returns); 145 Signature->Params = std::move(Params); 146 MCSymbol *Sym = Printer.createTempSymbol("typeindex"); 147 auto *WasmSym = cast<MCSymbolWasm>(Sym); 148 WasmSym->setSignature(Signature); 149 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); 150 const MCExpr *Expr = 151 MCSymbolRefExpr::create(WasmSym, WebAssembly::S_TYPEINDEX, Ctx); 152 return MCOperand::createExpr(Expr); 153 } 154 155 static void getFunctionReturns(const MachineInstr *MI, 156 SmallVectorImpl<wasm::ValType> &Returns) { 157 const Function &F = MI->getMF()->getFunction(); 158 const TargetMachine &TM = MI->getMF()->getTarget(); 159 Type *RetTy = F.getReturnType(); 160 SmallVector<MVT, 4> CallerRetTys; 161 computeLegalValueVTs(F, TM, RetTy, CallerRetTys); 162 valTypesFromMVTs(CallerRetTys, Returns); 163 } 164 165 void WebAssemblyMCInstLower::lower(const MachineInstr *MI, 166 MCInst &OutMI) const { 167 OutMI.setOpcode(MI->getOpcode()); 168 169 const MCInstrDesc &Desc = MI->getDesc(); 170 unsigned NumVariadicDefs = MI->getNumExplicitDefs() - Desc.getNumDefs(); 171 const MachineFunction *MF = MI->getMF(); 172 const auto &TLI = 173 *MF->getSubtarget<WebAssemblySubtarget>().getTargetLowering(); 174 wasm::ValType PtrTy = TLI.getPointerTy(MF->getDataLayout()) == MVT::i32 175 ? wasm::ValType::I32 176 : wasm::ValType::I64; 177 178 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) { 179 const MachineOperand &MO = MI->getOperand(I); 180 181 MCOperand MCOp; 182 switch (MO.getType()) { 183 default: 184 MI->print(errs()); 185 llvm_unreachable("unknown operand type"); 186 case MachineOperand::MO_MachineBasicBlock: 187 MI->print(errs()); 188 llvm_unreachable("MachineBasicBlock operand should have been rewritten"); 189 case MachineOperand::MO_Register: { 190 // Ignore all implicit register operands. 191 if (MO.isImplicit()) 192 continue; 193 const WebAssemblyFunctionInfo &MFI = 194 *MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>(); 195 unsigned WAReg = MFI.getWAReg(MO.getReg()); 196 MCOp = MCOperand::createReg(WAReg); 197 break; 198 } 199 case MachineOperand::MO_Immediate: { 200 unsigned DescIndex = I - NumVariadicDefs; 201 if (DescIndex < Desc.NumOperands) { 202 const MCOperandInfo &Info = Desc.operands()[DescIndex]; 203 if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) { 204 SmallVector<wasm::ValType, 4> Returns; 205 SmallVector<wasm::ValType, 4> Params; 206 207 const MachineRegisterInfo &MRI = 208 MI->getParent()->getParent()->getRegInfo(); 209 for (const MachineOperand &MO : MI->defs()) 210 Returns.push_back(WebAssembly::regClassToValType( 211 MRI.getRegClass(MO.getReg())->getID())); 212 for (const MachineOperand &MO : MI->explicit_uses()) 213 if (MO.isReg()) 214 Params.push_back(WebAssembly::regClassToValType( 215 MRI.getRegClass(MO.getReg())->getID())); 216 217 // call_indirect instructions have a callee operand at the end which 218 // doesn't count as a param. 219 if (WebAssembly::isCallIndirect(MI->getOpcode())) 220 Params.pop_back(); 221 222 // return_call_indirect instructions have the return type of the 223 // caller 224 if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT) 225 getFunctionReturns(MI, Returns); 226 227 MCOp = lowerTypeIndexOperand(std::move(Returns), std::move(Params)); 228 break; 229 } 230 if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) { 231 auto BT = static_cast<WebAssembly::BlockType>(MO.getImm()); 232 assert(BT != WebAssembly::BlockType::Invalid); 233 if (BT == WebAssembly::BlockType::Multivalue) { 234 SmallVector<wasm::ValType, 2> Returns; 235 // Multivalue blocks are emitted in two cases: 236 // 1. When the blocks will never be exited and are at the ends of 237 // functions (see 238 // WebAssemblyCFGStackify::fixEndsAtEndOfFunction). In this case 239 // the exact multivalue signature can always be inferred from the 240 // return type of the parent function. 241 // 2. (catch_ref ...) clause in try_table instruction. Currently all 242 // tags we support (cpp_exception and c_longjmp) throws a single 243 // pointer, so the multivalue signature for this case will be 244 // (ptr, exnref). Having MO_CATCH_BLOCK_SIG target flags means 245 // this is a destination of a catch_ref. 246 if (MO.getTargetFlags() == WebAssemblyII::MO_CATCH_BLOCK_SIG) { 247 Returns = {PtrTy, wasm::ValType::EXNREF}; 248 } else 249 getFunctionReturns(MI, Returns); 250 MCOp = lowerTypeIndexOperand(std::move(Returns), 251 SmallVector<wasm::ValType, 4>()); 252 break; 253 } 254 } 255 } 256 MCOp = MCOperand::createImm(MO.getImm()); 257 break; 258 } 259 case MachineOperand::MO_FPImmediate: { 260 const ConstantFP *Imm = MO.getFPImm(); 261 const uint64_t BitPattern = 262 Imm->getValueAPF().bitcastToAPInt().getZExtValue(); 263 if (Imm->getType()->isFloatTy()) 264 MCOp = MCOperand::createSFPImm(static_cast<uint32_t>(BitPattern)); 265 else if (Imm->getType()->isDoubleTy()) 266 MCOp = MCOperand::createDFPImm(BitPattern); 267 else 268 llvm_unreachable("unknown floating point immediate type"); 269 break; 270 } 271 case MachineOperand::MO_GlobalAddress: 272 MCOp = lowerSymbolOperand(MO, GetGlobalAddressSymbol(MO)); 273 break; 274 case MachineOperand::MO_ExternalSymbol: 275 MCOp = lowerSymbolOperand(MO, GetExternalSymbolSymbol(MO)); 276 break; 277 case MachineOperand::MO_MCSymbol: 278 assert(MO.getTargetFlags() == 0 && 279 "WebAssembly does not use target flags on MCSymbol"); 280 MCOp = lowerSymbolOperand(MO, MO.getMCSymbol()); 281 break; 282 } 283 284 OutMI.addOperand(MCOp); 285 } 286 287 if (!WasmKeepRegisters) 288 removeRegisterOperands(MI, OutMI); 289 else if (Desc.variadicOpsAreDefs()) 290 OutMI.insert(OutMI.begin(), MCOperand::createImm(MI->getNumExplicitDefs())); 291 } 292 293 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) { 294 // Remove all uses of stackified registers to bring the instruction format 295 // into its final stack form used thruout MC, and transition opcodes to 296 // their _S variant. 297 // We do this separate from the above code that still may need these 298 // registers for e.g. call_indirect signatures. 299 // See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for 300 // details. 301 // TODO: the code above creates new registers which are then removed here. 302 // That code could be slightly simplified by not doing that, though maybe 303 // it is simpler conceptually to keep the code above in "register mode" 304 // until this transition point. 305 // FIXME: we are not processing inline assembly, which contains register 306 // operands, because it is used by later target generic code. 307 if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm()) 308 return; 309 310 // Transform to _S instruction. 311 auto RegOpcode = OutMI.getOpcode(); 312 auto StackOpcode = WebAssembly::getStackOpcode(RegOpcode); 313 assert(StackOpcode != -1 && "Failed to stackify instruction"); 314 OutMI.setOpcode(StackOpcode); 315 316 // Remove register operands. 317 for (auto I = OutMI.getNumOperands(); I; --I) { 318 auto &MO = OutMI.getOperand(I - 1); 319 if (MO.isReg()) { 320 OutMI.erase(&MO); 321 } 322 } 323 } 324