| // WebAssemblyMCInstLower.cpp - Convert WebAssembly MachineInstr to an MCInst // |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| /// |
| /// \file |
| /// This file contains code to lower WebAssembly MachineInstrs to their |
| /// corresponding MCInst records. |
| /// |
| //===----------------------------------------------------------------------===// |
| |
| #include "WebAssemblyMCInstLower.h" |
| #include "WebAssemblyAsmPrinter.h" |
| #include "WebAssemblyMachineFunctionInfo.h" |
| #include "WebAssemblyRuntimeLibcallSignatures.h" |
| #include "WebAssemblyUtilities.h" |
| #include "llvm/CodeGen/AsmPrinter.h" |
| #include "llvm/CodeGen/MachineFunction.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/MC/MCAsmInfo.h" |
| #include "llvm/MC/MCContext.h" |
| #include "llvm/MC/MCExpr.h" |
| #include "llvm/MC/MCInst.h" |
| #include "llvm/MC/MCSymbolWasm.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/raw_ostream.h" |
| using namespace llvm; |
| |
| // Defines llvm::WebAssembly::getStackOpcode to convert register instructions to |
| // stack instructions |
| #define GET_INSTRMAP_INFO 1 |
| #include "WebAssemblyGenInstrInfo.inc" |
| |
| // This disables the removal of registers when lowering into MC, as required |
| // by some current tests. |
| cl::opt<bool> |
| WasmKeepRegisters("wasm-keep-registers", cl::Hidden, |
| cl::desc("WebAssembly: output stack registers in" |
| " instruction output for test purposes only."), |
| cl::init(false)); |
| |
| static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI); |
| |
| MCSymbol * |
| WebAssemblyMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const { |
| const GlobalValue *Global = MO.getGlobal(); |
| auto *WasmSym = cast<MCSymbolWasm>(Printer.getSymbol(Global)); |
| |
| if (const auto *FuncTy = dyn_cast<FunctionType>(Global->getValueType())) { |
| const MachineFunction &MF = *MO.getParent()->getParent()->getParent(); |
| const TargetMachine &TM = MF.getTarget(); |
| const Function &CurrentFunc = MF.getFunction(); |
| |
| SmallVector<MVT, 1> ResultMVTs; |
| SmallVector<MVT, 4> ParamMVTs; |
| computeSignatureVTs(FuncTy, CurrentFunc, TM, ParamMVTs, ResultMVTs); |
| |
| auto Signature = signatureFromMVTs(ResultMVTs, ParamMVTs); |
| WasmSym->setSignature(Signature.get()); |
| Printer.addSignature(std::move(Signature)); |
| WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); |
| } |
| |
| return WasmSym; |
| } |
| |
| MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol( |
| const MachineOperand &MO) const { |
| const char *Name = MO.getSymbolName(); |
| auto *WasmSym = cast<MCSymbolWasm>(Printer.GetExternalSymbolSymbol(Name)); |
| const WebAssemblySubtarget &Subtarget = Printer.getSubtarget(); |
| |
| // Except for certain known symbols, all symbols used by CodeGen are |
| // functions. It's OK to hardcode knowledge of specific symbols here; this |
| // method is precisely there for fetching the signatures of known |
| // Clang-provided symbols. |
| if (strcmp(Name, "__stack_pointer") == 0 || |
| strcmp(Name, "__memory_base") == 0 || strcmp(Name, "__table_base") == 0) { |
| bool Mutable = strcmp(Name, "__stack_pointer") == 0; |
| WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL); |
| WasmSym->setGlobalType(wasm::WasmGlobalType{ |
| uint8_t(Subtarget.hasAddr64() ? wasm::WASM_TYPE_I64 |
| : wasm::WASM_TYPE_I32), |
| Mutable}); |
| return WasmSym; |
| } |
| |
| SmallVector<wasm::ValType, 4> Returns; |
| SmallVector<wasm::ValType, 4> Params; |
| if (strcmp(Name, "__cpp_exception") == 0) { |
| WasmSym->setType(wasm::WASM_SYMBOL_TYPE_EVENT); |
| // We can't confirm its signature index for now because there can be |
| // imported exceptions. Set it to be 0 for now. |
| WasmSym->setEventType( |
| {wasm::WASM_EVENT_ATTRIBUTE_EXCEPTION, /* SigIndex */ 0}); |
| // We may have multiple C++ compilation units to be linked together, each of |
| // which defines the exception symbol. To resolve them, we declare them as |
| // weak. |
| WasmSym->setWeak(true); |
| WasmSym->setExternal(true); |
| |
| // All C++ exceptions are assumed to have a single i32 (for wasm32) or i64 |
| // (for wasm64) param type and void return type. The reaon is, all C++ |
| // exception values are pointers, and to share the type section with |
| // functions, exceptions are assumed to have void return type. |
| Params.push_back(Subtarget.hasAddr64() ? wasm::ValType::I64 |
| : wasm::ValType::I32); |
| } else { // Function symbols |
| WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); |
| getLibcallSignature(Subtarget, Name, Returns, Params); |
| } |
| auto Signature = |
| make_unique<wasm::WasmSignature>(std::move(Returns), std::move(Params)); |
| WasmSym->setSignature(Signature.get()); |
| Printer.addSignature(std::move(Signature)); |
| |
| return WasmSym; |
| } |
| |
| MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO, |
| MCSymbol *Sym) const { |
| MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None; |
| unsigned TargetFlags = MO.getTargetFlags(); |
| |
| switch (TargetFlags) { |
| case WebAssemblyII::MO_NO_FLAG: |
| break; |
| case WebAssemblyII::MO_GOT: |
| Kind = MCSymbolRefExpr::VK_GOT; |
| break; |
| case WebAssemblyII::MO_MEMORY_BASE_REL: |
| Kind = MCSymbolRefExpr::VK_WASM_MBREL; |
| break; |
| case WebAssemblyII::MO_TABLE_BASE_REL: |
| Kind = MCSymbolRefExpr::VK_WASM_TBREL; |
| break; |
| default: |
| llvm_unreachable("Unknown target flag on GV operand"); |
| } |
| |
| const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Kind, Ctx); |
| |
| if (MO.getOffset() != 0) { |
| const auto *WasmSym = cast<MCSymbolWasm>(Sym); |
| if (TargetFlags == WebAssemblyII::MO_GOT) |
| report_fatal_error("GOT symbol references do not support offsets"); |
| if (WasmSym->isFunction()) |
| report_fatal_error("Function addresses with offsets not supported"); |
| if (WasmSym->isGlobal()) |
| report_fatal_error("Global indexes with offsets not supported"); |
| if (WasmSym->isEvent()) |
| report_fatal_error("Event indexes with offsets not supported"); |
| |
| Expr = MCBinaryExpr::createAdd( |
| Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx); |
| } |
| |
| return MCOperand::createExpr(Expr); |
| } |
| |
| // Return the WebAssembly type associated with the given register class. |
| static wasm::ValType getType(const TargetRegisterClass *RC) { |
| if (RC == &WebAssembly::I32RegClass) |
| return wasm::ValType::I32; |
| if (RC == &WebAssembly::I64RegClass) |
| return wasm::ValType::I64; |
| if (RC == &WebAssembly::F32RegClass) |
| return wasm::ValType::F32; |
| if (RC == &WebAssembly::F64RegClass) |
| return wasm::ValType::F64; |
| if (RC == &WebAssembly::V128RegClass) |
| return wasm::ValType::V128; |
| llvm_unreachable("Unexpected register class"); |
| } |
| |
| void WebAssemblyMCInstLower::lower(const MachineInstr *MI, |
| MCInst &OutMI) const { |
| OutMI.setOpcode(MI->getOpcode()); |
| |
| const MCInstrDesc &Desc = MI->getDesc(); |
| for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) { |
| const MachineOperand &MO = MI->getOperand(I); |
| |
| MCOperand MCOp; |
| switch (MO.getType()) { |
| default: |
| MI->print(errs()); |
| llvm_unreachable("unknown operand type"); |
| case MachineOperand::MO_MachineBasicBlock: |
| MI->print(errs()); |
| llvm_unreachable("MachineBasicBlock operand should have been rewritten"); |
| case MachineOperand::MO_Register: { |
| // Ignore all implicit register operands. |
| if (MO.isImplicit()) |
| continue; |
| const WebAssemblyFunctionInfo &MFI = |
| *MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>(); |
| unsigned WAReg = MFI.getWAReg(MO.getReg()); |
| MCOp = MCOperand::createReg(WAReg); |
| break; |
| } |
| case MachineOperand::MO_Immediate: |
| if (I < Desc.NumOperands) { |
| const MCOperandInfo &Info = Desc.OpInfo[I]; |
| if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) { |
| MCSymbol *Sym = Printer.createTempSymbol("typeindex"); |
| |
| SmallVector<wasm::ValType, 4> Returns; |
| SmallVector<wasm::ValType, 4> Params; |
| |
| const MachineRegisterInfo &MRI = |
| MI->getParent()->getParent()->getRegInfo(); |
| for (const MachineOperand &MO : MI->defs()) |
| Returns.push_back(getType(MRI.getRegClass(MO.getReg()))); |
| for (const MachineOperand &MO : MI->explicit_uses()) |
| if (MO.isReg()) |
| Params.push_back(getType(MRI.getRegClass(MO.getReg()))); |
| |
| // call_indirect instructions have a callee operand at the end which |
| // doesn't count as a param. |
| if (WebAssembly::isCallIndirect(*MI)) |
| Params.pop_back(); |
| |
| auto *WasmSym = cast<MCSymbolWasm>(Sym); |
| auto Signature = make_unique<wasm::WasmSignature>(std::move(Returns), |
| std::move(Params)); |
| WasmSym->setSignature(Signature.get()); |
| Printer.addSignature(std::move(Signature)); |
| WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); |
| |
| const MCExpr *Expr = MCSymbolRefExpr::create( |
| WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx); |
| MCOp = MCOperand::createExpr(Expr); |
| break; |
| } |
| } |
| MCOp = MCOperand::createImm(MO.getImm()); |
| break; |
| case MachineOperand::MO_FPImmediate: { |
| // TODO: MC converts all floating point immediate operands to double. |
| // This is fine for numeric values, but may cause NaNs to change bits. |
| const ConstantFP *Imm = MO.getFPImm(); |
| if (Imm->getType()->isFloatTy()) |
| MCOp = MCOperand::createFPImm(Imm->getValueAPF().convertToFloat()); |
| else if (Imm->getType()->isDoubleTy()) |
| MCOp = MCOperand::createFPImm(Imm->getValueAPF().convertToDouble()); |
| else |
| llvm_unreachable("unknown floating point immediate type"); |
| break; |
| } |
| case MachineOperand::MO_GlobalAddress: |
| MCOp = lowerSymbolOperand(MO, GetGlobalAddressSymbol(MO)); |
| break; |
| case MachineOperand::MO_ExternalSymbol: |
| // The target flag indicates whether this is a symbol for a |
| // variable or a function. |
| assert(MO.getTargetFlags() == 0 && |
| "WebAssembly uses only symbol flags on ExternalSymbols"); |
| MCOp = lowerSymbolOperand(MO, GetExternalSymbolSymbol(MO)); |
| break; |
| case MachineOperand::MO_MCSymbol: |
| // This is currently used only for LSDA symbols (GCC_except_table), |
| // because global addresses or other external symbols are handled above. |
| assert(MO.getTargetFlags() == 0 && |
| "WebAssembly does not use target flags on MCSymbol"); |
| MCOp = lowerSymbolOperand(MO, MO.getMCSymbol()); |
| break; |
| } |
| |
| OutMI.addOperand(MCOp); |
| } |
| |
| if (!WasmKeepRegisters) |
| removeRegisterOperands(MI, OutMI); |
| } |
| |
| static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) { |
| // Remove all uses of stackified registers to bring the instruction format |
| // into its final stack form used thruout MC, and transition opcodes to |
| // their _S variant. |
| // We do this seperate from the above code that still may need these |
| // registers for e.g. call_indirect signatures. |
| // See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for |
| // details. |
| // TODO: the code above creates new registers which are then removed here. |
| // That code could be slightly simplified by not doing that, though maybe |
| // it is simpler conceptually to keep the code above in "register mode" |
| // until this transition point. |
| // FIXME: we are not processing inline assembly, which contains register |
| // operands, because it is used by later target generic code. |
| if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm()) |
| return; |
| |
| // Transform to _S instruction. |
| auto RegOpcode = OutMI.getOpcode(); |
| auto StackOpcode = WebAssembly::getStackOpcode(RegOpcode); |
| assert(StackOpcode != -1 && "Failed to stackify instruction"); |
| OutMI.setOpcode(StackOpcode); |
| |
| // Remove register operands. |
| for (auto I = OutMI.getNumOperands(); I; --I) { |
| auto &MO = OutMI.getOperand(I - 1); |
| if (MO.isReg()) { |
| OutMI.erase(&MO); |
| } |
| } |
| } |
