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Diffstat (limited to 'lib/hipe/llvm/hipe_llvm_main.erl')
| -rw-r--r-- | lib/hipe/llvm/hipe_llvm_main.erl | 525 |
1 files changed, 525 insertions, 0 deletions
diff --git a/lib/hipe/llvm/hipe_llvm_main.erl b/lib/hipe/llvm/hipe_llvm_main.erl new file mode 100644 index 0000000000..476d6fb49c --- /dev/null +++ b/lib/hipe/llvm/hipe_llvm_main.erl @@ -0,0 +1,525 @@ +%% -*- 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, 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, Options) -> + Source = Dir ++ Filename ++ ".bc", + OptLevel = trans_optlev_flag(llc, Options), + Align = find_stack_alignment(), + LlcFlags = [OptLevel, "-code-model=medium", "-stack-alignment=" ++ Align + , "-tailcallopt", "-filetype=asm"], %%FIXME + 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", + Command = Compiler ++ " -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. + +%% @doc Join options. +fix_opts(Opts) -> + string: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. + +%%------------------------------------------------------------------------------ +%% 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, {ModName,_,_}) when Name =/= "" -> + case dict:fetch(Name, RelocsDict) of + {call, {bif, BifName, _}} -> {?CALL_LOCAL, Offset, BifName}; + %% MFA calls to functions in the same module are of type 3, while all + %% other MFA calls are of type 2. + %% XXX: Does this code break hot code loading (by transforming external + %% calls into local calls?) + {call, {ModName,_F,_A}=CallMFA} -> {?CALL_LOCAL, Offset, CallMFA}; + {call, 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, 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). |