MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol(
const MachineOperand &MO) const {
const char *Name = MO.getSymbolName();
MCSymbolWasm *WasmSym =
cast<MCSymbolWasm>(Printer.GetExternalSymbolSymbol(Name));
const WebAssemblySubtarget &Subtarget = Printer.getSubtarget();
// Except for the two exceptions (__stack_pointer and __cpp_exception), all
// other external 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) {
WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
WasmSym->setGlobalType(wasm::WasmGlobalType{
uint8_t(Subtarget.hasAddr64() ? wasm::WASM_TYPE_I64
: wasm::WASM_TYPE_I32),
true});
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;
}
MCSymbol *
WebAssemblyMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const {
const GlobalValue *Global = MO.getGlobal();
MCSymbolWasm *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;
}
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();
MCSymbolWasm *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_WebAssembly_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:
assert(MO.getTargetFlags() == WebAssemblyII::MO_NO_FLAG &&
"WebAssembly does not use target flags on GlobalAddresses");
MCOp = LowerSymbolOperand(GetGlobalAddressSymbol(MO), MO.getOffset(),
MO.getGlobal()->getValueType()->isFunctionTy(),
false, false);
break;
case MachineOperand::MO_ExternalSymbol:
// The target flag indicates whether this is a symbol for a
// variable or a function.
assert((MO.getTargetFlags() & ~WebAssemblyII::MO_SYMBOL_MASK) == 0 &&
"WebAssembly uses only symbol flags on ExternalSymbols");
MCOp = LowerSymbolOperand(
GetExternalSymbolSymbol(MO), /*Offset=*/0,
(MO.getTargetFlags() & WebAssemblyII::MO_SYMBOL_FUNCTION) != 0,
(MO.getTargetFlags() & WebAssemblyII::MO_SYMBOL_GLOBAL) != 0,
(MO.getTargetFlags() & WebAssemblyII::MO_SYMBOL_EVENT) != 0);
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.getMCSymbol(), /*Offset=*/0, false, false,
false);
break;
}
OutMI.addOperand(MCOp);
}
if (!WasmKeepRegisters)
removeRegisterOperands(MI, OutMI);
}
