Function lookup_or_create_malloc_fn 

pub fn lookup_or_create_malloc_fn(
    ctx: &mut Context,
    symbol_table_collection: &mut SymbolTableCollection,
    symbol_table_op: Box<dyn SymbolTableInterface>,
) -> Result<FuncOp>

Get a declaration to the malloc function, inserting it if it doesn’t already exist in the symbol table.