%% -*- erlang-indent-level: 2 -*-
-module(hipe_llvm_main).
-export([rtl_to_native/4]).
-include("../../kernel/src/hipe_ext_format.hrl").
-include("hipe_llvm_arch.hrl").
-include("elf_format.hrl").
%% @doc Translation of RTL to a loadable object. This function takes the RTL
%% code and calls hipe_rtl_to_llvm:translate/2 to translate the RTL code to
%% LLVM code. After this, LLVM asm is printed to a file and the LLVM tool
%% chain is invoked in order to produce an object file.
rtl_to_native(MFA, RTL, Roots, Options) ->
%% Compile to LLVM and get Instruction List (along with infos)
{LLVMCode, RelocsDict0, ConstTab0} =
hipe_rtl_to_llvm:translate(RTL, Roots),
%% Fix function name to an acceptable LLVM identifier (needed for closures)
{_Module, Fun, Arity} = hipe_rtl_to_llvm:fix_mfa_name(MFA),
%% Write LLVM Assembly to intermediate file (on disk)
{ok, Dir, ObjectFile} =
compile_with_llvm(Fun, Arity, LLVMCode, Options, false),
%%
%% Extract information from object file
%%
ObjBin = open_object_file(ObjectFile),
Obj = elf_format:read(ObjBin),
%% Get labels info (for switches and jump tables)
Labels = elf_format:extract_rela(Obj, ?RODATA),
Tables = get_tables(Obj),
%% Associate Labels with Switches and Closures with stack args
{SwitchInfos, ExposedClosures} = correlate_labels(Tables, Labels),
%% SwitchInfos: [{"table_50", [Labels]}]
%% ExposedClosures: [{"table_closures", [Labels]}]
%% Labelmap contains the offsets of the labels in the code that are
%% used for switch's jump tables
LabelMap = create_labelmap(MFA, SwitchInfos, RelocsDict0),
{RelocsDict, ConstTab} = extract_constants(RelocsDict0, ConstTab0, Obj),
%% Get relocation info
TextRelocs = elf_format:extract_rela(Obj, ?TEXT),
%% AccRefs contains the offsets of all references to relocatable symbols in
%% the code:
AccRefs = fix_relocations(TextRelocs, RelocsDict, MFA),
%% Get stack descriptors
SDescs = get_sdescs(Obj),
%% FixedSDescs are the stack descriptors after correcting calls that have
%% arguments in the stack
FixedSDescs =
fix_stack_descriptors(RelocsDict, AccRefs, SDescs, ExposedClosures),
Refs = AccRefs ++ FixedSDescs,
%% Get binary code from object file
BinCode = elf_format:extract_text(Obj),
%% Remove temp files (if needed)
ok = remove_temp_folder(Dir, Options),
%% Return the code together with information that will be used in the
%% hipe_llvm_merge module to produce the final binary that will be loaded
%% by the hipe unified loader.
{MFA, BinCode, byte_size(BinCode), ConstTab, Refs, LabelMap}.
%%------------------------------------------------------------------------------
%% LLVM tool chain
%%------------------------------------------------------------------------------
%% @doc Compile function FunName/Arity to LLVM. Return Dir (in order to remove
%% it if we do not want to store temporary files) and ObjectFile name that
%% is created by the LLVM tools.
compile_with_llvm(FunName, Arity, LLVMCode, Options, UseBuffer) ->
Filename = atom_to_list(FunName) ++ "_" ++ integer_to_list(Arity),
%% Save temp files in a unique folder
Dir = unique_folder(FunName, Arity, Options),
ok = file:make_dir(Dir),
%% Print LLVM assembly to file
OpenOpts = [append, raw] ++
case UseBuffer of
%% true -> [delayed_write]; % Use delayed_write!
false -> []
end,
{ok, File_llvm} = file:open(Dir ++ Filename ++ ".ll", OpenOpts),
Ver = hipe:get_llvm_version(), %% Should probably cache this
hipe_llvm:pp_ins_list(File_llvm, Ver, LLVMCode),
%% delayed_write can cause file:close not to do a close, hence the two calls
ok = file:close(File_llvm),
__ = file:close(File_llvm),
%% Invoke LLVM compiler tools to produce an object file
llvm_opt(Dir, Filename, Options),
llvm_llc(Dir, Filename, Ver, Options),
compile(Dir, Filename, "gcc"), %%FIXME: use llc -filetype=obj and skip this!
{ok, Dir, Dir ++ Filename ++ ".o"}.
%% @doc Invoke opt tool to optimize the bitcode (_name.ll -> _name.bc).
llvm_opt(Dir, Filename, Options) ->
Source = Dir ++ Filename ++ ".ll",
Dest = Dir ++ Filename ++ ".bc",
OptLevel = trans_optlev_flag(opt, Options),
OptFlags = [OptLevel, "-mem2reg", "-strip"],
Command = "opt " ++ fix_opts(OptFlags) ++ " " ++ Source ++ " -o " ++ Dest,
%% io:format("OPT: ~s~n", [Command]),
case os:cmd(Command) of
"" -> ok;
Error -> exit({?MODULE, opt, Error})
end.
%% @doc Invoke llc tool to compile the bitcode to object file
%% (_name.bc -> _name.o).
llvm_llc(Dir, Filename, Ver, Options) ->
Source = Dir ++ Filename ++ ".bc",
OptLevel = trans_optlev_flag(llc, Options),
VerFlags = llc_ver_flags(Ver),
Align = find_stack_alignment(),
Target = llc_target_opt(),
LlcFlags = [OptLevel, "-code-model=medium", "-stack-alignment=" ++ Align
, "-tailcallopt", "-filetype=asm" %FIXME
, Target
| VerFlags],
Command = "llc " ++ fix_opts(LlcFlags) ++ " " ++ Source,
%% io:format("LLC: ~s~n", [Command]),
case os:cmd(Command) of
"" -> ok;
Error -> exit({?MODULE, llc, Error})
end.
%% @doc Invoke the compiler tool ("gcc", "llvmc", etc.) to generate an object
%% file from native assembly.
compile(Dir, Fun_Name, Compiler) ->
Source = Dir ++ Fun_Name ++ ".s",
Dest = Dir ++ Fun_Name ++ ".o",
Target = compiler_target_opt(),
Command = Compiler ++ " " ++ Target ++ " -c " ++ Source ++ " -o " ++ Dest,
%% io:format("~s: ~s~n", [Compiler, Command]),
case os:cmd(Command) of
"" -> ok;
Error -> exit({?MODULE, cc, Error})
end.
find_stack_alignment() ->
case get(hipe_target_arch) of
x86 -> "4";
amd64 -> "8";
_ -> exit({?MODULE, find_stack_alignment, "Unimplemented architecture"})
end.
llc_target_opt() ->
case get(hipe_target_arch) of
x86 -> "-march=x86";
amd64 -> "-march=x86-64"
end.
compiler_target_opt() ->
case get(hipe_target_arch) of
x86 -> "-m32";
amd64 -> "-m64"
end.
%% @doc Join options.
fix_opts(Opts) ->
lists:flatten(lists:join(" ", Opts)).
%% @doc Translate optimization-level flag (default is "O2").
trans_optlev_flag(Tool, Options) ->
Flag = case Tool of
opt -> llvm_opt;
llc -> llvm_llc
end,
case proplists:get_value(Flag, Options) of
o0 -> ""; % "-O0" does not exist in opt tool
o1 -> "-O1";
o2 -> "-O2";
o3 -> "-O3";
undefined -> "-O2"
end.
llc_ver_flags(Ver = {_, _}) when Ver >= {3,9} ->
%% Works around a bug in the x86-call-frame-opt pass (as of LLVM 3.9) that
%% break the garbage collection stack descriptors.
["-no-x86-call-frame-opt"];
llc_ver_flags({_, _}) -> [].
%%------------------------------------------------------------------------------
%% Functions to manage Relocations
%%------------------------------------------------------------------------------
%% @doc Get switch table and closure table.
-spec get_tables(elf_format:elf()) -> [elf_sym()].
get_tables(Elf) ->
%% Search Symbol Table for entries where name is prefixed with "table_":
[S || S=#elf_sym{name="table_" ++ _} <- elf_format:elf_symbols(Elf)].
%% @doc This function associates symbols who point to some table of labels with
%% the corresponding offsets of the labels in the code. These tables can
%% either be jump tables for switches or a table which contains the labels
%% of blocks that contain closure calls with more than ?NR_ARG_REGS.
correlate_labels([], _L) -> {[], []};
correlate_labels(Tables, Labels) ->
%% Assumes that the relocations are sorted
RelocTree = gb_trees:from_orddict(
[{Rel#elf_rel.offset, Rel#elf_rel.addend} || Rel <- Labels]),
%% Lookup all relocations pertaining to each symbol
NamesValues = [{Name, lookup_range(Value, Value+Size, RelocTree)}
|| #elf_sym{name=Name, value=Value, size=Size} <- Tables],
case lists:keytake("table_closures", 1, NamesValues) of
false -> %% No closures in the code, no closure table
{NamesValues, []};
{value, ClosureTableNV, SwitchesNV} ->
{SwitchesNV, ClosureTableNV}
end.
%% Fetches all values with a key in [Low, Hi)
-spec lookup_range(_::K, _::K, gb_trees:tree(K,V)) -> [_::V].
lookup_range(Low, Hi, Tree) ->
lookup_range_1(Hi, gb_trees:iterator_from(Low, Tree)).
lookup_range_1(Hi, Iter0) ->
case gb_trees:next(Iter0) of
{Key, Value, Iter} when Key < Hi -> [Value | lookup_range_1(Hi, Iter)];
_ -> []
end.
%% @doc Create a gb_tree which contains information about the labels that used
%% for switch's jump tables. The keys of the gb_tree are of the form
%% {MFA, Label} and the values are the actual Offsets.
create_labelmap(MFA, SwitchInfos, RelocsDict) ->
create_labelmap(MFA, SwitchInfos, RelocsDict, gb_trees:empty()).
create_labelmap(_, [], _, LabelMap) -> LabelMap;
create_labelmap(MFA, [{Name, Offsets} | Rest], RelocsDict, LabelMap) ->
case dict:fetch(Name, RelocsDict) of
{switch, {_TableType, LabelList, _NrLabels, _SortOrder}, _JTabLab} ->
KVDict = lists:ukeysort(1, lists:zip(LabelList, Offsets)),
NewLabelMap = insert_to_labelmap(KVDict, LabelMap),
create_labelmap(MFA, Rest, RelocsDict, NewLabelMap);
_ ->
exit({?MODULE, create_labelmap, "Not a jump table!"})
end.
%% @doc Insert a list of [{Key,Value}] to a LabelMap (gb_tree).
insert_to_labelmap([], LabelMap) -> LabelMap;
insert_to_labelmap([{Key, Value}|Rest], LabelMap) ->
case gb_trees:lookup(Key, LabelMap) of
none ->
insert_to_labelmap(Rest, gb_trees:insert(Key, Value, LabelMap));
{value, Value} -> %% Exists with the *exact* same Value.
insert_to_labelmap(Rest, LabelMap)
end.
%% Find any LLVM-generated constants and add them to the constant table
extract_constants(RelocsDict0, ConstTab0, Obj) ->
TextRelocs = elf_format:extract_rela(Obj, ?TEXT),
AnonConstSections =
lists:usort([{Sec, Offset}
|| #elf_rel{symbol=#elf_sym{type=section, section=Sec},
addend=Offset} <- TextRelocs]),
lists:foldl(
fun({#elf_shdr{name=Name, type=progbits, addralign=Align, entsize=EntSize,
size=Size} = Section, Offset}, {RelocsDict1, ConstTab1})
when EntSize > 0, 0 =:= Size rem EntSize, 0 =:= Offset rem EntSize ->
SectionBin = elf_format:section_contents(Section, Obj),
Constant = binary:part(SectionBin, Offset, EntSize),
{ConstTab, ConstLbl} =
hipe_consttab:insert_binary_const(ConstTab1, Align, Constant),
{dict:store({anon, Name, Offset}, {constant, ConstLbl}, RelocsDict1),
ConstTab}
end, {RelocsDict0, ConstTab0}, AnonConstSections).
%% @doc Correlate object file relocation symbols with info from translation to
%% llvm code.
fix_relocations(Relocs, RelocsDict, MFA) ->
lists:map(fun(Reloc) -> fix_reloc(Reloc, RelocsDict, MFA) end, Relocs).
%% Relocation types and expected addends for x86 and amd64
-define(PCREL_T, 'pc32').
-define(PCREL_A, -4). %% Hard-coded in hipe_x86.c and hipe_amd64.c
-ifdef(BIT32).
-define(ABS_T, '32').
-define(ABS_A, _). %% We support any addend
-else.
-define(ABS_T, '64').
-define(ABS_A, 0).
-endif.
fix_reloc(#elf_rel{symbol=#elf_sym{name=Name, section=undefined, type=notype},
offset=Offset, type=?PCREL_T, addend=?PCREL_A},
RelocsDict, {_,_,_}) when Name =/= "" ->
case dict:fetch(Name, RelocsDict) of
{call, _, {bif, BifName, _}} -> {?CALL_LOCAL, Offset, BifName};
{call, not_remote, CallMFA} -> {?CALL_LOCAL, Offset, CallMFA};
{call, remote, CallMFA} -> {?CALL_REMOTE, Offset, CallMFA}
end;
fix_reloc(#elf_rel{symbol=#elf_sym{name=Name, section=undefined, type=notype},
offset=Offset, type=?ABS_T, addend=?ABS_A},
RelocsDict, _) when Name =/= "" ->
case dict:fetch(Name, RelocsDict) of
{atom, AtomName} -> {?LOAD_ATOM, Offset, AtomName};
{constant, Label} -> {?LOAD_ADDRESS, Offset, {constant, Label}};
{closure, _}=Closure -> {?LOAD_ADDRESS, Offset, Closure}
end;
fix_reloc(#elf_rel{symbol=#elf_sym{name=Name, section=#elf_shdr{name=?TEXT},
type=func},
offset=Offset, type=?PCREL_T, addend=?PCREL_A},
RelocsDict, MFA) when Name =/= "" ->
case dict:fetch(Name, RelocsDict) of
{call, not_remote, MFA} -> {?CALL_LOCAL, Offset, MFA}
end;
fix_reloc(#elf_rel{symbol=#elf_sym{name=Name, section=#elf_shdr{name=?RODATA},
type=object},
offset=Offset, type=?ABS_T, addend=?ABS_A},
RelocsDict, _) when Name =/= "" ->
case dict:fetch(Name, RelocsDict) of
{switch, _, JTabLab} -> %% Treat switch exactly as constant
{?LOAD_ADDRESS, Offset, {constant, JTabLab}}
end;
fix_reloc(#elf_rel{symbol=#elf_sym{type=section, section=#elf_shdr{name=Name}},
offset=Offset, type=?ABS_T, addend=Addend}, RelocsDict, _) ->
case dict:fetch({anon, Name, Addend}, RelocsDict) of
{constant, Label} -> {?LOAD_ADDRESS, Offset, {constant, Label}}
end.
%%------------------------------------------------------------------------------
%% Functions to manage Stack Descriptors
%%------------------------------------------------------------------------------
%% @doc This function takes an ELF Object File binary and returns a proper sdesc
%% list for Erlang/OTP System's loader. The return value should be of the
%% form:
%% {
%% 4, Safepoint Address,
%% {ExnLabel OR [], FrameSize, StackArity, {Liveroot stack frame indexes}},
%% }
get_sdescs(Elf) ->
case elf_format:extract_note(Elf, ?NOTE_ERLGC_NAME) of
<<>> -> % Object file has no ".note.gc" section!
[];
NoteGC_bin ->
%% Get safe point addresses (stored in ".rela.note.gc" section):
RelaNoteGC = elf_format:extract_rela(Elf, ?NOTE(?NOTE_ERLGC_NAME)),
SPCount = length(RelaNoteGC),
T = SPCount * ?SP_ADDR_SIZE,
%% Pattern match fields of ".note.gc":
<<SPCount:(?bits(?SP_COUNT_SIZE))/integer-little, % Sanity check!
_SPAddrs:T/binary, % NOTE: In 64bit they are relocs!
StkFrameSize:(?bits(?SP_STKFRAME_SIZE))/integer-little,
StkArity:(?bits(?SP_STKARITY_SIZE))/integer-little,
_LiveRootCount:(?bits(?SP_LIVEROOTCNT_SIZE))/integer-little, % Skip
Roots/binary>> = NoteGC_bin,
LiveRoots = get_liveroots(Roots, []),
%% Extract the safe point offsets:
SPOffs = [A || #elf_rel{addend=A} <- RelaNoteGC],
%% Extract Exception Handler labels:
ExnHandlers = elf_format:get_exn_handlers(Elf),
%% Combine ExnHandlers and Safe point addresses (return addresses):
ExnAndSPOffs = combine_ras_and_exns(ExnHandlers, SPOffs, []),
create_sdesc_list(ExnAndSPOffs, StkFrameSize, StkArity, LiveRoots, [])
end.
%% @doc Extracts a bunch of integers (live roots) from a binary. Returns a tuple
%% as need for stack descriptors.
get_liveroots(<<>>, Acc) ->
list_to_tuple(Acc);
get_liveroots(<<Root:?bits(?LR_STKINDEX_SIZE)/integer-little,
MoreRoots/binary>>, Acc) ->
get_liveroots(MoreRoots, [Root | Acc]).
combine_ras_and_exns(_, [], Acc) ->
lists:reverse(Acc);
combine_ras_and_exns(ExnHandlers, [RA | MoreRAs], Acc) ->
%% FIXME: do something better than O(n^2) by taking advantage of the property
%% ||ExnHandlers|| <= ||RAs||
Handler = find_exn_handler(RA, ExnHandlers),
combine_ras_and_exns(ExnHandlers, MoreRAs, [{Handler, RA} | Acc]).
find_exn_handler(_, []) ->
[];
find_exn_handler(RA, [{Start, End, Handler} | MoreExnHandlers]) ->
case (RA >= Start andalso RA =< End) of
true ->
Handler;
false ->
find_exn_handler(RA, MoreExnHandlers)
end.
create_sdesc_list([], _, _, _, Acc) ->
lists:reverse(Acc);
create_sdesc_list([{ExnLbl, SPOff} | MoreExnAndSPOffs],
StkFrameSize, StkArity, LiveRoots, Acc) ->
Hdlr = case ExnLbl of
0 -> [];
N -> N
end,
create_sdesc_list(MoreExnAndSPOffs, StkFrameSize, StkArity, LiveRoots,
[{?SDESC, SPOff, {Hdlr, StkFrameSize, StkArity, LiveRoots}}
| Acc]).
%% @doc This function is responsible for correcting the stack descriptors of
%% the calls that are found in the code and have more than NR_ARG_REGS
%% (thus, some of their arguments are passed to the stack). Because of the
%% Reserved Call Frame feature that the LLVM uses, the stack descriptors
%% are not correct since at the point of call the frame size is reduced
%% by the number of arguments that are passed on the stack. Also, the
%% offsets of the roots need to be re-adjusted.
fix_stack_descriptors(_, _, [], _) ->
[];
fix_stack_descriptors(RelocsDict, Relocs, SDescs, ExposedClosures) ->
%% NamedCalls are MFA and BIF calls that need fix
NamedCalls = calls_with_stack_args(RelocsDict),
NamedCallsOffs = calls_offsets_arity(Relocs, NamedCalls),
ExposedClosures1 =
case dict:is_key("table_closures", RelocsDict) of
true -> %% A Table with closures exists
{table_closures, ArityList} = dict:fetch("table_closures", RelocsDict),
case ExposedClosures of
{_, Offsets} ->
lists:zip(Offsets, ArityList);
_ ->
exit({?MODULE, fix_stack_descriptors,
{"Wrong exposed closures", ExposedClosures}})
end;
false ->
[]
end,
ClosuresOffs = closures_offsets_arity(ExposedClosures1, SDescs),
fix_sdescs(NamedCallsOffs ++ ClosuresOffs, SDescs).
%% @doc This function takes as argument the relocation dictionary as produced by
%% the translation of RTL code to LLVM and finds the names of the calls
%% (MFA and BIF calls) that have more than NR_ARG_REGS.
calls_with_stack_args(Dict) ->
calls_with_stack_args(dict:to_list(Dict), []).
calls_with_stack_args([], Calls) -> Calls;
calls_with_stack_args([ {_Name, {call, _, {M, F, A}}} | Rest], Calls)
when A > ?NR_ARG_REGS ->
Call =
case M of
bif -> {F,A};
_ -> {M,F,A}
end,
calls_with_stack_args(Rest, [Call|Calls]);
calls_with_stack_args([_|Rest], Calls) ->
calls_with_stack_args(Rest, Calls).
%% @doc This function extracts the stack arity and the offset in the code of
%% the named calls (MFAs, BIFs) that have stack arguments.
calls_offsets_arity(AccRefs, CallsWithStackArgs) ->
calls_offsets_arity(AccRefs, CallsWithStackArgs, []).
calls_offsets_arity([], _, Acc) -> Acc;
calls_offsets_arity([{Type, Offset, Term} | Rest], CallsWithStackArgs, Acc)
when Type =:= ?CALL_REMOTE orelse Type =:= ?CALL_LOCAL ->
case lists:member(Term, CallsWithStackArgs) of
true ->
Arity =
case Term of
{_M, _F, A} -> A;
{_F, A} -> A
end,
calls_offsets_arity(Rest, CallsWithStackArgs,
[{Offset + 4, Arity - ?NR_ARG_REGS} | Acc]);
false ->
calls_offsets_arity(Rest, CallsWithStackArgs, Acc)
end;
calls_offsets_arity([_|Rest], CallsWithStackArgs, Acc) ->
calls_offsets_arity(Rest, CallsWithStackArgs, Acc).
%% @doc This function extracts the stack arity and the offsets of closures that
%% have stack arity. The Closures argument represents the
%% hipe_bifs:llvm_exposure_closure/0 calls in the code. The actual closure
%% is the next call in the code, so the offset of the next call must be
%% calculated from the stack descriptors.
closures_offsets_arity([], _) ->
[];
closures_offsets_arity(ExposedClosures, SDescs) ->
Offsets = [Offset || {_, Offset, _} <- SDescs],
%% Offsets and closures must be sorted in order for find_offsets/3 to work
SortedOffsets = lists:sort(Offsets),
SortedExposedClosures = lists:keysort(1, ExposedClosures),
find_offsets(SortedExposedClosures, SortedOffsets, []).
find_offsets([], _, Acc) -> Acc;
find_offsets([{Off,Arity}|Rest], Offsets, Acc) ->
[I | RestOffsets] = lists:dropwhile(fun (Y) -> Y<Off end, Offsets),
find_offsets(Rest, RestOffsets, [{I, Arity}|Acc]).
%% The function below corrects the stack descriptors of calls with arguments
%% that are passed on the stack (more than NR_ARG_REGS) by subtracting the
%% number of stacked arguments from the frame size and from the offset of the
%% roots.
fix_sdescs([], SDescs) -> SDescs;
fix_sdescs([{Offset, Arity} | Rest], SDescs) ->
case lists:keyfind(Offset, 2, SDescs) of
false ->
fix_sdescs(Rest, SDescs);
{?SDESC, Offset, {ExnHandler, FrameSize, StkArity, Roots}} ->
FixedRoots = list_to_tuple([Ri - Arity || Ri <- tuple_to_list(Roots)]),
FixedSDesc =
{?SDESC, Offset, {ExnHandler, FrameSize - Arity, StkArity, FixedRoots}},
fix_sdescs(Rest, [FixedSDesc | lists:keydelete(Offset, 2, SDescs)])
end.
%%------------------------------------------------------------------------------
%% Miscellaneous functions
%%------------------------------------------------------------------------------
%% @doc A function that opens a file as binary. The function takes as argument
%% the name of the file and returns an Erlang binary.
-spec open_object_file(string()) -> binary().
open_object_file(ObjFile) ->
case file:read_file(ObjFile) of
{ok, Binary} ->
Binary;
{error, Reason} ->
exit({?MODULE, open_file, Reason})
end.
remove_temp_folder(Dir, Options) ->
case proplists:get_bool(llvm_save_temps, Options) of
true -> ok;
false -> spawn(fun () -> "" = os:cmd("rm -rf " ++ Dir) end), ok
end.
unique_id(FunName, Arity) ->
integer_to_list(erlang:phash2({FunName, Arity, erlang:unique_integer()})).
unique_folder(FunName, Arity, Options) ->
DirName = "llvm_" ++ unique_id(FunName, Arity) ++ "/",
Dir =
case proplists:get_bool(llvm_save_temps, Options) of
true -> %% Store folder in current directory
DirName;
false -> %% Temporarily store folder in tempfs (/dev/shm/)
"/dev/shm/" ++ DirName
end,
%% Make sure it does not exist
case dir_exists(Dir) of
true -> %% Dir already exists! Generate again.
unique_folder(FunName, Arity, Options);
false ->
Dir
end.
%% @doc Function that checks that a given Filename is an existing Directory
%% Name (from http://rosettacode.org/wiki/Ensure_that_a_file_exists#Erlang)
dir_exists(Filename) ->
{Flag, Info} = file:read_file_info(Filename),
(Flag =:= ok) andalso (element(3, Info) =:= directory).
