Using libjava-core.mpl as an example, if I run it through irbuild to produce libjava-core.irb.mpl, the generated syncenter instruction has an extra second operand of constval 2. There are some 1000 of the following kind of diff between libjava-core.mpl and libjava-core.irb.mpl:

2813902c2762002

< syncenter (dread ref %Reg9_R43769)

---

> syncenter (dread ref %Reg9_R43769, constval i32 2)

My investigation showed that the extra operand was introduced when the .mpl was parsed by the MIR parser. The following code in mir_parser.cpp:MIRParser::ParseNaryStmt() is responsible:

```

if (op == OP_syncenter) {

if (lexer.GetTokenKind() == TK_coma) {

lexer.NextToken();

BaseNode *exprSync = nullptr;

if (!ParseExpression(exprSync)) {

Error("ParseStmtReturn failed");

return false;

}

stmtReturn->GetNopnd().push_back(exprSync);

} else {

MIRType *intType = GlobalTables::GetTypeTable().GetTypeFromTyIdx((TyIdx)PTY_i32);

// default 2 for __sync_enter_fast()

MIRIntConst *intConst = mod.GetMemPool()->New<MIRIntConst>(2, *intType);

ConstvalNode *exprConst = mod.GetMemPool()->New<ConstvalNode>();

exprConst->SetPrimType(PTY_i32);

exprConst->SetConstVal(intConst);

stmtReturn->GetNopnd().push_back(exprConst);

stmtReturn->SetNumOpnds(stmtReturn->GetNopndSize());

}

}

```

My question is: is the extra inserted operand really needed? If so, for what purpose, and would it be better to be generated by jbc2mpl