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Diffstat (limited to 'lib/dialyzer/test/options1_SUITE_data/src/compiler/beam_jump.erl')
| -rw-r--r-- | lib/dialyzer/test/options1_SUITE_data/src/compiler/beam_jump.erl | 477 |
1 files changed, 477 insertions, 0 deletions
diff --git a/lib/dialyzer/test/options1_SUITE_data/src/compiler/beam_jump.erl b/lib/dialyzer/test/options1_SUITE_data/src/compiler/beam_jump.erl new file mode 100644 index 0000000000..b3c234c7bb --- /dev/null +++ b/lib/dialyzer/test/options1_SUITE_data/src/compiler/beam_jump.erl @@ -0,0 +1,477 @@ +%% ``The contents of this file are subject to the Erlang Public License, +%% Version 1.1, (the "License"); you may not use this file except in +%% compliance with the License. You should have received a copy of the +%% Erlang Public License along with this software. If not, it can be +%% retrieved via the world wide web at http://www.erlang.org/. +%% +%% Software distributed under the License is distributed on an "AS IS" +%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See +%% the License for the specific language governing rights and limitations +%% under the License. +%% +%% The Initial Developer of the Original Code is Ericsson Utvecklings AB. +%% Portions created by Ericsson are Copyright 1999, Ericsson Utvecklings +%% AB. All Rights Reserved.'' +%% +%% $Id: beam_jump.erl,v 1.1 2008/12/17 09:53:41 mikpe Exp $ +%% +%%% Purpose : Optimise jumps and remove unreachable code. + +-module(beam_jump). + +-export([module/2,module_labels/1, + is_unreachable_after/1,remove_unused_labels/1]). + +%%% The following optimisations are done: +%%% +%%% (1) This code with two identical instruction sequences +%%% +%%% L1: <Instruction sequence> +%%% L2: +%%% . . . +%%% L3: <Instruction sequence> +%%% L4: +%%% +%%% can be replaced with +%%% +%%% L1: jump L3 +%%% L2: +%%% . . . +%%% L3: <Instruction sequence> +%%% L4 +%%% +%%% Note: The instruction sequence must end with an instruction +%%% such as a jump that never transfers control to the instruction +%%% following it. +%%% +%%% (2) case_end, if_end, and badmatch, and function calls that cause an +%%% exit (such as calls to exit/1) are moved to the end of the function. +%%% The purpose is to allow further optimizations at the place from +%%% which the code was moved. +%%% +%%% (3) Any unreachable code is removed. Unreachable code is code after +%%% jump, call_last and other instructions which never transfer control +%%% to the following instruction. Code is unreachable up to the next +%%% *referenced* label. Note that the optimisations below might +%%% generate more possibilities for removing unreachable code. +%%% +%%% (4) This code: +%%% L1: jump L2 +%%% . . . +%%% L2: ... +%%% +%%% will be changed to +%%% +%%% jump L2 +%%% . . . +%%% L1: +%%% L2: ... +%%% +%%% If the jump is unreachable, it will be removed according to (1). +%%% +%%% (5) In +%%% +%%% jump L1 +%%% L1: +%%% +%%% the jump will be removed. +%%% +%%% (6) If test instructions are used to skip a single jump instruction, +%%% the test is inverted and the jump is eliminated (provided that +%%% the test can be inverted). Example: +%%% +%%% is_eq L1 {x,1} {x,2} +%%% jump L2 +%%% L1: +%%% +%%% will be changed to +%%% +%%% is_ne L2 {x,1} {x,2} +%%% +%%% (The label L1 will be retained if there were previous references to it.) +%%% +%%% (7) Some redundant uses of is_boolean/1 is optimized away. +%%% +%%% Terminology note: The optimisation done here is called unreachable-code +%%% elimination, NOT dead-code elimination. Dead code elimination +%%% means the removal of instructions that are executed, but have no visible +%%% effect on the program state. +%%% + +-import(lists, [reverse/1,reverse/2,map/2,mapfoldl/3,foldl/3, + last/1,foreach/2,member/2]). + +module({Mod,Exp,Attr,Fs0,Lc}, _Opt) -> + Fs = map(fun function/1, Fs0), + {ok,{Mod,Exp,Attr,Fs,Lc}}. + +module_labels({Mod,Exp,Attr,Fs,Lc}) -> + {Mod,Exp,Attr,map(fun function_labels/1, Fs),Lc}. + +function_labels({function,Name,Arity,CLabel,Asm0}) -> + Asm = remove_unused_labels(Asm0), + {function,Name,Arity,CLabel,Asm}. + +function({function,Name,Arity,CLabel,Asm0}) -> + Asm1 = share(Asm0), + Asm2 = bopt(Asm1), + Asm3 = move(Asm2), + Asm4 = opt(Asm3, CLabel), + Asm = remove_unused_labels(Asm4), + {function,Name,Arity,CLabel,Asm}. + +%%% +%%% (1) We try to share the code for identical code segments by replacing all +%%% occurrences except the last with jumps to the last occurrence. +%%% + +share(Is) -> + share_1(reverse(Is), gb_trees:empty(), [], []). + +share_1([{label,_}=Lbl|Is], Dict, [], Acc) -> + share_1(Is, Dict, [], [Lbl|Acc]); +share_1([{label,L}=Lbl|Is], Dict0, Seq, Acc) -> + case is_unreachable_after(last(Seq)) of + false -> + share_1(Is, Dict0, [], [Lbl|Seq ++ Acc]); + true -> + case gb_trees:lookup(Seq, Dict0) of + none -> + Dict = gb_trees:insert(Seq, L, Dict0), + share_1(Is, Dict, [], [Lbl|Seq ++ Acc]); + {value,Label} -> + share_1(Is, Dict0, [], [Lbl,{jump,{f,Label}}|Acc]) + end + end; +share_1([{func_info,_,_,_}=I|Is], _, [], Acc) -> + Is++[I|Acc]; +share_1([I|Is], Dict, Seq, Acc) -> + case is_unreachable_after(I) of + false -> + share_1(Is, Dict, [I|Seq], Acc); + true -> + share_1(Is, Dict, [I], Acc) + end. + +%%% +%%% (2) Move short code sequences ending in an instruction that causes an exit +%%% to the end of the function. +%%% + +move(Is) -> + move_1(Is, [], []). + +move_1([I|Is], End, Acc) -> + case is_exit_instruction(I) of + false -> move_1(Is, End, [I|Acc]); + true -> move_2(I, Is, End, Acc) + end; +move_1([], End, Acc) -> + reverse(Acc, reverse(End)). + +move_2(Exit, Is, End, [{block,_},{label,_},{func_info,_,_,_}|_]=Acc) -> + move_1(Is, End, [Exit|Acc]); +move_2(Exit, Is, End, [{kill,_Y}|Acc]) -> + move_2(Exit, Is, End, Acc); +move_2(Exit, Is, End, [{block,_}=Blk,{label,_}=Lbl,Dead|More]=Acc) -> + case is_unreachable_after(Dead) of + false -> + move_1(Is, End, [Exit|Acc]); + true -> + move_1([Dead|Is], [Exit,Blk,Lbl|End], More) + end; +move_2(Exit, Is, End, [{label,_}=Lbl,Dead|More]=Acc) -> + case is_unreachable_after(Dead) of + false -> + move_1(Is, End, [Exit|Acc]); + true -> + move_1([Dead|Is], [Exit,Lbl|End], More) + end; +move_2(Exit, Is, End, Acc) -> + move_1(Is, End, [Exit|Acc]). + +%%% +%%% (7) Remove redundant is_boolean tests. +%%% + +bopt(Is) -> + bopt_1(Is, []). + +bopt_1([{test,is_boolean,_,_}=I|Is], Acc0) -> + case opt_is_bool(I, Acc0) of + no -> bopt_1(Is, [I|Acc0]); + yes -> bopt_1(Is, Acc0); + {yes,Acc} -> bopt_1(Is, Acc) + end; +bopt_1([I|Is], Acc) -> bopt_1(Is, [I|Acc]); +bopt_1([], Acc) -> reverse(Acc). + +opt_is_bool({test,is_boolean,{f,Lbl},[Reg]}, Acc) -> + opt_is_bool_1(Acc, Reg, Lbl). + +opt_is_bool_1([{test,is_eq_exact,{f,Lbl},[Reg,{atom,true}]}|_], Reg, Lbl) -> + %% Instruction not needed in this context. + yes; +opt_is_bool_1([{test,is_ne_exact,{f,Lbl},[Reg,{atom,true}]}|Acc], Reg, Lbl) -> + %% Rewrite to shorter test. + {yes,[{test,is_eq_exact,{f,Lbl},[Reg,{atom,false}]}|Acc]}; +opt_is_bool_1([{test,_,{f,Lbl},_}=Test|Acc0], Reg, Lbl) -> + case opt_is_bool_1(Acc0, Reg, Lbl) of + {yes,Acc} -> {yes,[Test|Acc]}; + Other -> Other + end; +opt_is_bool_1(_, _, _) -> no. + +%%% +%%% (3) (4) (5) (6) Jump and unreachable code optimizations. +%%% + +-record(st, {fc, %Label for function class errors. + entry, %Entry label (must not be moved). + mlbl, %Moved labels. + labels %Set of referenced labels. + }). + +opt([{label,Fc}|_]=Is, CLabel) -> + Lbls = initial_labels(Is), + St = #st{fc=Fc,entry=CLabel,mlbl=dict:new(),labels=Lbls}, + opt(Is, [], St). + +opt([{test,Test0,{f,Lnum}=Lbl,Ops}=I|Is0], Acc, St) -> + case Is0 of + [{jump,To}|[{label,Lnum}|Is2]=Is1] -> + case invert_test(Test0) of + not_possible -> + opt(Is0, [I|Acc], label_used(Lbl, St)); + Test -> + Is = case is_label_used(Lnum, St) of + true -> Is1; + false -> Is2 + end, + opt([{test,Test,To,Ops}|Is], Acc, label_used(To, St)) + end; + _Other -> + opt(Is0, [I|Acc], label_used(Lbl, St)) + end; +opt([{select_val,_R,Fail,{list,Vls}}=I|Is], Acc, St) -> + skip_unreachable(Is, [I|Acc], label_used([Fail|Vls], St)); +opt([{select_tuple_arity,_R,Fail,{list,Vls}}=I|Is], Acc, St) -> + skip_unreachable(Is, [I|Acc], label_used([Fail|Vls], St)); +opt([{'try',_R,Lbl}=I|Is], Acc, St) -> + opt(Is, [I|Acc], label_used(Lbl, St)); +opt([{'catch',_R,Lbl}=I|Is], Acc, St) -> + opt(Is, [I|Acc], label_used(Lbl, St)); +opt([{label,L}=I|Is], Acc, #st{entry=L}=St) -> + %% NEVER move the entry label. + opt(Is, [I|Acc], St); +opt([{label,L1},{jump,{f,L2}}=I|Is], [Prev|Acc], St0) -> + St = St0#st{mlbl=dict:append(L2, L1, St0#st.mlbl)}, + opt([Prev,I|Is], Acc, label_used({f,L2}, St)); +opt([{label,Lbl}=I|Is], Acc, #st{mlbl=Mlbl}=St0) -> + case dict:find(Lbl, Mlbl) of + {ok,Lbls} -> + %% Essential to remove the list of labels from the dictionary, + %% since we will rescan the inserted labels. We MUST rescan. + St = St0#st{mlbl=dict:erase(Lbl, Mlbl)}, + insert_labels([Lbl|Lbls], Is, Acc, St); + error -> opt(Is, [I|Acc], St0) + end; +opt([{jump,{f,Lbl}},{label,Lbl}=I|Is], Acc, St) -> + opt([I|Is], Acc, St); +opt([{jump,Lbl}=I|Is], Acc, St) -> + skip_unreachable(Is, [I|Acc], label_used(Lbl, St)); +opt([{loop_rec,Lbl,_R}=I|Is], Acc, St) -> + opt(Is, [I|Acc], label_used(Lbl, St)); +opt([{bif,_Name,Lbl,_As,_R}=I|Is], Acc, St) -> + opt(Is, [I|Acc], label_used(Lbl, St)); +opt([{bs_put_integer,Lbl,_Bits,_Unit,_Fl,_Val}=I|Is], Acc, St) -> + opt(Is, [I|Acc], label_used(Lbl, St)); +opt([{bs_put_binary,Lbl,_Bits,_Unit,_Fl,_Val}=I|Is], Acc, St) -> + opt(Is, [I|Acc], label_used(Lbl, St)); +opt([{bs_put_float,Lbl,_Bits,_Unit,_Fl,_Val}=I|Is], Acc, St) -> + opt(Is, [I|Acc], label_used(Lbl, St)); +opt([{bs_final,Lbl,_R}=I|Is], Acc, St) -> + opt(Is, [I|Acc], label_used(Lbl, St)); +opt([{bs_init2,Lbl,_,_,_,_,_}=I|Is], Acc, St) -> + opt(Is, [I|Acc], label_used(Lbl, St)); +opt([{bs_add,Lbl,_,_}=I|Is], Acc, St) -> + opt(Is, [I|Acc], label_used(Lbl, St)); +opt([{bs_bits_to_bytes,Lbl,_,_}=I|Is], Acc, St) -> + opt(Is, [I|Acc], label_used(Lbl, St)); +opt([I|Is], Acc, St) -> + case is_unreachable_after(I) of + true -> skip_unreachable(Is, [I|Acc], St); + false -> opt(Is, [I|Acc], St) + end; +opt([], Acc, #st{fc=Fc,mlbl=Mlbl}) -> + Code = reverse(Acc), + case dict:find(Fc, Mlbl) of + {ok,Lbls} -> insert_fc_labels(Lbls, Mlbl, Code); + error -> Code + end. + +insert_fc_labels([L|Ls], Mlbl, Acc0) -> + Acc = [{label,L}|Acc0], + case dict:find(L, Mlbl) of + error -> + insert_fc_labels(Ls, Mlbl, Acc); + {ok,Lbls} -> + insert_fc_labels(Lbls++Ls, Mlbl, Acc) + end; +insert_fc_labels([], _, Acc) -> Acc. + +%% invert_test(Test0) -> not_possible | Test + +invert_test(is_ge) -> is_lt; +invert_test(is_lt) -> is_ge; +invert_test(is_eq) -> is_ne; +invert_test(is_ne) -> is_eq; +invert_test(is_eq_exact) -> is_ne_exact; +invert_test(is_ne_exact) -> is_eq_exact; +invert_test(_) -> not_possible. + +insert_labels([L|Ls], Is, [{jump,{f,L}}|Acc], St) -> + insert_labels(Ls, [{label,L}|Is], Acc, St); +insert_labels([L|Ls], Is, Acc, St) -> + insert_labels(Ls, [{label,L}|Is], Acc, St); +insert_labels([], Is, Acc, St) -> + opt(Is, Acc, St). + +%% Skip unreachable code up to the next referenced label. + +skip_unreachable([{label,L}|Is], [{jump,{f,L}}|Acc], St) -> + opt([{label,L}|Is], Acc, St); +skip_unreachable([{label,L}|Is], Acc, St) -> + case is_label_used(L, St) of + true -> opt([{label,L}|Is], Acc, St); + false -> skip_unreachable(Is, Acc, St) + end; +skip_unreachable([_|Is], Acc, St) -> + skip_unreachable(Is, Acc, St); +skip_unreachable([], Acc, St) -> + opt([], Acc, St). + +%% Add one or more label to the set of used labels. + +label_used({f,0}, St) -> St; +label_used({f,L}, St) -> St#st{labels=gb_sets:add(L, St#st.labels)}; +label_used([H|T], St0) -> label_used(T, label_used(H, St0)); +label_used([], St) -> St; +label_used(_Other, St) -> St. + +%% Test if label is used. + +is_label_used(L, St) -> + gb_sets:is_member(L, St#st.labels). + +%% is_unreachable_after(Instruction) -> true|false +%% Test whether the code after Instruction is unreachable. + +is_unreachable_after({func_info,_M,_F,_A}) -> true; +is_unreachable_after(return) -> true; +is_unreachable_after({call_ext_last,_Ar,_ExtFunc,_D}) -> true; +is_unreachable_after({call_ext_only,_Ar,_ExtFunc}) -> true; +is_unreachable_after({call_last,_Ar,_Lbl,_D}) -> true; +is_unreachable_after({call_only,_Ar,_Lbl}) -> true; +is_unreachable_after({apply_last,_Ar,_N}) -> true; +is_unreachable_after({jump,_Lbl}) -> true; +is_unreachable_after({select_val,_R,_Lbl,_Cases}) -> true; +is_unreachable_after({select_tuple_arity,_R,_Lbl,_Cases}) -> true; +is_unreachable_after({loop_rec_end,_}) -> true; +is_unreachable_after({wait,_}) -> true; +is_unreachable_after(I) -> is_exit_instruction(I). + +%% is_exit_instruction(Instruction) -> true|false +%% Test whether the instruction Instruction always +%% causes an exit/failure. + +is_exit_instruction({call_ext,_,{extfunc,M,F,A}}) -> + is_exit_instruction_1(M, F, A); +is_exit_instruction({call_ext_last,_,{extfunc,M,F,A},_}) -> + is_exit_instruction_1(M, F, A); +is_exit_instruction({call_ext_only,_,{extfunc,M,F,A}}) -> + is_exit_instruction_1(M, F, A); +is_exit_instruction(if_end) -> true; +is_exit_instruction({case_end,_}) -> true; +is_exit_instruction({try_case_end,_}) -> true; +is_exit_instruction({badmatch,_}) -> true; +is_exit_instruction(_) -> false. + +is_exit_instruction_1(erlang, exit, 1) -> true; +is_exit_instruction_1(erlang, throw, 1) -> true; +is_exit_instruction_1(erlang, error, 1) -> true; +is_exit_instruction_1(erlang, error, 2) -> true; +is_exit_instruction_1(erlang, fault, 1) -> true; +is_exit_instruction_1(erlang, fault, 2) -> true; +is_exit_instruction_1(_, _, _) -> false. + +%% remove_unused_labels(Instructions0) -> Instructions +%% Remove all unused labels. + +remove_unused_labels(Is) -> + Used0 = initial_labels(Is), + Used = foldl(fun ulbl/2, Used0, Is), + rem_unused(Is, Used, []). + +rem_unused([{label,Lbl}=I|Is], Used, Acc) -> + case gb_sets:is_member(Lbl, Used) of + false -> rem_unused(Is, Used, Acc); + true -> rem_unused(Is, Used, [I|Acc]) + end; +rem_unused([I|Is], Used, Acc) -> + rem_unused(Is, Used, [I|Acc]); +rem_unused([], _, Acc) -> reverse(Acc). + +initial_labels(Is) -> + initial_labels(Is, []). + +initial_labels([{label,Lbl}|Is], Acc) -> + initial_labels(Is, [Lbl|Acc]); +initial_labels([{func_info,_,_,_},{label,Lbl}|_], Acc) -> + gb_sets:from_list([Lbl|Acc]). + +ulbl({test,_,Fail,_}, Used) -> + mark_used(Fail, Used); +ulbl({select_val,_,Fail,{list,Vls}}, Used) -> + mark_used_list(Vls, mark_used(Fail, Used)); +ulbl({select_tuple_arity,_,Fail,{list,Vls}}, Used) -> + mark_used_list(Vls, mark_used(Fail, Used)); +ulbl({'try',_,Lbl}, Used) -> + mark_used(Lbl, Used); +ulbl({'catch',_,Lbl}, Used) -> + mark_used(Lbl, Used); +ulbl({jump,Lbl}, Used) -> + mark_used(Lbl, Used); +ulbl({loop_rec,Lbl,_}, Used) -> + mark_used(Lbl, Used); +ulbl({loop_rec_end,Lbl}, Used) -> + mark_used(Lbl, Used); +ulbl({wait,Lbl}, Used) -> + mark_used(Lbl, Used); +ulbl({wait_timeout,Lbl,_To}, Used) -> + mark_used(Lbl, Used); +ulbl({bif,_Name,Lbl,_As,_R}, Used) -> + mark_used(Lbl, Used); +ulbl({bs_init2,Lbl,_,_,_,_,_}, Used) -> + mark_used(Lbl, Used); +ulbl({bs_put_integer,Lbl,_Bits,_Unit,_Fl,_Val}, Used) -> + mark_used(Lbl, Used); +ulbl({bs_put_float,Lbl,_Bits,_Unit,_Fl,_Val}, Used) -> + mark_used(Lbl, Used); +ulbl({bs_put_binary,Lbl,_Bits,_Unit,_Fl,_Val}, Used) -> + mark_used(Lbl, Used); +ulbl({bs_final,Lbl,_}, Used) -> + mark_used(Lbl, Used); +ulbl({bs_add,Lbl,_,_}, Used) -> + mark_used(Lbl, Used); +ulbl({bs_bits_to_bytes,Lbl,_,_}, Used) -> + mark_used(Lbl, Used); +ulbl(_, Used) -> Used. + +mark_used({f,0}, Used) -> Used; +mark_used({f,L}, Used) -> gb_sets:add(L, Used); +mark_used(_, Used) -> Used. + +mark_used_list([H|T], Used) -> + mark_used_list(T, mark_used(H, Used)); +mark_used_list([], Used) -> Used. |