diff options
Diffstat (limited to 'lib/compiler/src/beam_jump.erl')
| -rw-r--r-- | lib/compiler/src/beam_jump.erl | 414 |
1 files changed, 267 insertions, 147 deletions
diff --git a/lib/compiler/src/beam_jump.erl b/lib/compiler/src/beam_jump.erl index 22974da398..8b0e3e32f8 100644 --- a/lib/compiler/src/beam_jump.erl +++ b/lib/compiler/src/beam_jump.erl @@ -22,7 +22,7 @@ -module(beam_jump). -export([module/2, - is_unreachable_after/1,is_exit_instruction/1, + is_exit_instruction/1, remove_unused_labels/1]). %%% The following optimisations are done: @@ -101,6 +101,10 @@ %%% always keep the label. (beam_clean will remove any unused %%% labels.) %%% +%%% (7) Replace a jump to a return instruction with a return instruction. +%%% Similarly, replace a jump to deallocate + return with those +%%% instructions. +%%% %%% Note: This modules depends on (almost) all branches and jumps only %%% going forward, so that we can remove instructions (including definition %%% of labels) after any label that has not been referenced by the code @@ -128,27 +132,127 @@ %%% on the program state. %%% --import(lists, [dropwhile/2,reverse/1,reverse/2,foldl/3]). +-import(lists, [foldl/3,mapfoldl/3,reverse/1,reverse/2]). -type instruction() :: beam_utils:instruction(). -spec module(beam_utils:module_code(), [compile:option()]) -> {'ok',beam_utils:module_code()}. -module({Mod,Exp,Attr,Fs0,Lc}, _Opt) -> - Fs = [function(F) || F <- Fs0], +module({Mod,Exp,Attr,Fs0,Lc0}, _Opt) -> + {Fs,Lc} = mapfoldl(fun function/2, Lc0, Fs0), {ok,{Mod,Exp,Attr,Fs,Lc}}. %% function(Function) -> Function' %% Optimize jumps and branches. %% %% NOTE: This function assumes that there are no labels inside blocks. -function({function,Name,Arity,CLabel,Asm0}) -> - Asm1 = share(Asm0), - Asm2 = move(Asm1), - Asm3 = opt(Asm2, CLabel), - Asm = remove_unused_labels(Asm3), - {function,Name,Arity,CLabel,Asm}. +function({function,Name,Arity,CLabel,Asm0}, Lc0) -> + try + Asm1 = eliminate_moves(Asm0), + {Asm2,Lc} = insert_labels(Asm1, Lc0, []), + Asm3 = share(Asm2), + Asm4 = move(Asm3), + Asm5 = opt(Asm4, CLabel), + Asm6 = unshare(Asm5), + Asm = remove_unused_labels(Asm6), + {{function,Name,Arity,CLabel,Asm},Lc} + catch + Class:Error:Stack -> + io:fwrite("Function: ~w/~w\n", [Name,Arity]), + erlang:raise(Class, Error, Stack) + end. + +%%% +%%% Scan instructions in execution order and remove redundant 'move' +%%% instructions. 'move' instructions are redundant if we know that +%%% the register already contains the value being assigned, as in the +%%% following code: +%%% +%%% select_val Register FailLabel [... Literal => L1...] +%%% . +%%% . +%%% . +%%% L1: move Literal Register +%%% + +eliminate_moves(Is) -> + eliminate_moves(Is, #{}, []). + +eliminate_moves([{select,select_val,Reg,_,List}=I|Is], D0, Acc) -> + D = update_value_dict(List, Reg, D0), + eliminate_moves(Is, D, [I|Acc]); +eliminate_moves([{label,Lbl},{block,[{set,[Dst],[Lit],move}|BlkIs]}=Blk0|Is], + D, Acc0) -> + Acc = [{label,Lbl}|Acc0], + case already_has_value(Lit, Lbl, Dst, D) andalso + no_fallthrough(Acc0) of + true -> + %% Remove redundant 'move' instruction. + Blk = {block,BlkIs}, + eliminate_moves([Blk|Is], D, Acc); + false -> + %% Keep 'move' instruction. + eliminate_moves([Blk0|Is], D, Acc) + end; +eliminate_moves([{block,[]}|Is], D, Acc) -> + %% Empty blocks can prevent further jump optimizations. + eliminate_moves(Is, D, Acc); +eliminate_moves([I|Is], D0, Acc) -> + D = update_unsafe_labels(I, D0), + eliminate_moves(Is, D, [I|Acc]); +eliminate_moves([], _, Acc) -> reverse(Acc). + +no_fallthrough([I|_]) -> + is_unreachable_after(I). + +already_has_value(Lit, Lbl, Reg, D) -> + case D of + #{Lbl:={Reg,Lit}} -> + true; + #{} -> + false + end. + +update_value_dict([Lit,{f,Lbl}|T], Reg, D0) -> + D = case D0 of + #{Lbl:=unsafe} -> D0; + #{Lbl:={Reg,Lit}} -> D0; + #{Lbl:=_} -> D0#{Lbl:=unsafe}; + #{} -> D0#{Lbl=>{Reg,Lit}} + end, + update_value_dict(T, Reg, D); +update_value_dict([], _, D) -> D. + +update_unsafe_labels(I, D) -> + Ls = instr_labels(I), + update_unsafe_labels_1(Ls, D). + +update_unsafe_labels_1([L|Ls], D) -> + update_unsafe_labels_1(Ls, D#{L=>unsafe}); +update_unsafe_labels_1([], D) -> D. + +%%% +%%% It seems to be useful to insert extra labels after certain +%%% test instructions. This used to be done by beam_dead. +%%% + +insert_labels([{test,Op,_,_}=I|Is], Lc, Acc) -> + Useful = case Op of + is_lt -> true; + is_ge -> true; + is_eq_exact -> true; + is_ne_exact -> true; + _ -> false + end, + case Useful of + false -> insert_labels(Is, Lc, [I|Acc]); + true -> insert_labels(Is, Lc+1, [{label,Lc},I|Acc]) + end; +insert_labels([I|Is], Lc, Acc) -> + insert_labels(Is, Lc, [I|Acc]); +insert_labels([], Lc, Acc) -> + {reverse(Acc),Lc}. %%% %%% (1) We try to share the code for identical code segments by replacing all @@ -156,41 +260,51 @@ function({function,Name,Arity,CLabel,Asm0}) -> %%% share(Is0) -> - %% We will get more sharing if we never fall through to a label. - Is = eliminate_fallthroughs(Is0, []), - share_1(Is, #{}, [], []). + Is1 = eliminate_fallthroughs(Is0, []), + Is2 = find_fixpoint(fun(Is) -> + share_1(Is, #{}, #{}, [], []) + end, Is1), + reverse(Is2). -share_1([{label,L}=Lbl|Is], Dict0, [_|_]=Seq, Acc) -> +share_1([{label,L}=Lbl|Is], Dict0, Lbls0, [_|_]=Seq, Acc) -> case maps:find(Seq, Dict0) of - error -> - Dict = maps:put(Seq, L, Dict0), - share_1(Is, Dict, [], [Lbl|Seq ++ Acc]); - {ok,Label} -> - share_1(Is, Dict0, [], [Lbl,{jump,{f,Label}}|Acc]) + error -> + Dict = maps:put(Seq, L, Dict0), + share_1(Is, Dict, Lbls0, [], [[Lbl|Seq]|Acc]); + {ok,Label} -> + Lbls = maps:put(L, Label, Lbls0), + share_1(Is, Dict0, Lbls, [], [[Lbl,{jump,{f,Label}}]|Acc]) end; -share_1([{func_info,_,_,_}=I|Is], _, [], Acc) -> - reverse(Is, [I|Acc]); -share_1([{'catch',_,_}=I|Is], Dict0, Seq, Acc) -> - Dict = clean_non_sharable(Dict0), - share_1(Is, Dict, [I|Seq], Acc); -share_1([{'try',_,_}=I|Is], Dict0, Seq, Acc) -> - Dict = clean_non_sharable(Dict0), - share_1(Is, Dict, [I|Seq], Acc); -share_1([{try_case,_}=I|Is], Dict0, Seq, Acc) -> - Dict = clean_non_sharable(Dict0), - share_1(Is, Dict, [I|Seq], Acc); -share_1([{catch_end,_}=I|Is], Dict0, Seq, Acc) -> - Dict = clean_non_sharable(Dict0), - share_1(Is, Dict, [I|Seq], Acc); -share_1([I|Is], Dict, Seq, Acc) -> +share_1([{func_info,_,_,_}|_]=Is0, _, Lbls, [], Acc0) when Lbls =/= #{} -> + lists:foldl(fun(Is, Acc) -> + beam_utils:replace_labels(Is, Acc, Lbls, fun(Old) -> Old end) + end, Is0, Acc0); +share_1([{func_info,_,_,_}|_]=Is, _, Lbls, [], Acc) when Lbls =:= #{} -> + lists:foldl(fun lists:reverse/2, Is, Acc); +share_1([{'catch',_,_}=I|Is], Dict0, Lbls0, Seq, Acc) -> + {Dict,Lbls} = clean_non_sharable(Dict0, Lbls0), + share_1(Is, Dict, Lbls, [I|Seq], Acc); +share_1([{'try',_,_}=I|Is], Dict0, Lbls0, Seq, Acc) -> + {Dict,Lbls} = clean_non_sharable(Dict0, Lbls0), + share_1(Is, Dict, Lbls, [I|Seq], Acc); +share_1([{try_case,_}=I|Is], Dict0, Lbls0, Seq, Acc) -> + {Dict,Lbls} = clean_non_sharable(Dict0, Lbls0), + share_1(Is, Dict, Lbls, [I|Seq], Acc); +share_1([{catch_end,_}=I|Is], Dict0, Lbls0, Seq, Acc) -> + {Dict,Lbls} = clean_non_sharable(Dict0, Lbls0), + share_1(Is, Dict, Lbls, [I|Seq], Acc); +share_1([{jump,{f,To}}=I,{label,L}=Lbl|Is], Dict0, Lbls0, _Seq, Acc) -> + Lbls = maps:put(L, To, Lbls0), + share_1(Is, Dict0, Lbls, [], [[Lbl,I]|Acc]); +share_1([I|Is], Dict, Lbls, Seq, Acc) -> case is_unreachable_after(I) of false -> - share_1(Is, Dict, [I|Seq], Acc); + share_1(Is, Dict, Lbls, [I|Seq], Acc); true -> - share_1(Is, Dict, [I], Acc) + share_1(Is, Dict, Lbls, [I], Acc) end. -clean_non_sharable(Dict) -> +clean_non_sharable(Dict0, Lbls0) -> %% We are passing in or out of a 'catch' or 'try' block. Remove %% sequences that should not be shared over the boundaries of the %% block. Since the end of the sequence must match, the only @@ -198,7 +312,17 @@ clean_non_sharable(Dict) -> %% the 'catch'/'try' block is a sequence that ends with an %% instruction that causes an exception. Any sequence that causes %% an exception must contain a line/1 instruction. - maps:filter(fun(K, _V) -> sharable_with_try(K) end, Dict). + Dict1 = maps:to_list(Dict0), + Lbls1 = maps:to_list(Lbls0), + {Dict2,Lbls2} = foldl(fun({K, V}, {Dict,Lbls}) -> + case sharable_with_try(K) of + true -> + {[{K,V}|Dict],lists:keydelete(V, 2, Lbls)}; + false -> + {Dict,Lbls} + end + end, {[],Lbls1}, Dict1), + {maps:from_list(Dict2),maps:from_list(Lbls2)}. sharable_with_try([{line,_}|_]) -> %% This sequence may cause an exception and may potentially @@ -251,8 +375,6 @@ extract_seq([{line,_}=Line|Is], Acc) -> extract_seq(Is, [Line|Acc]); extract_seq([{block,_}=Bl|Is], Acc) -> extract_seq_1(Is, [Bl|Acc]); -extract_seq([{bs_context_to_binary,_}=I|Is], Acc) -> - extract_seq_1(Is, [I|Acc]); extract_seq([{label,_}|_]=Is, Acc) -> extract_seq_1(Is, Acc); extract_seq(_, _) -> no. @@ -276,14 +398,13 @@ extract_seq_1(_, _) -> no. { entry :: beam_asm:label(), %Entry label (must not be moved). replace :: #{beam_asm:label() := beam_asm:label()}, %Labels to replace. - labels :: cerl_sets:set(), %Set of referenced labels. - index :: beam_utils:code_index() | {lazy,[beam_utils:instruction()]} %Index built lazily only if needed + labels :: cerl_sets:set() %Set of referenced labels. }). opt(Is0, CLabel) -> find_fixpoint(fun(Is) -> Lbls = initial_labels(Is), - St = #st{entry=CLabel,replace=#{},labels=Lbls,index={lazy,Is}}, + St = #st{entry=CLabel,replace=#{},labels=Lbls}, opt(Is, [], St) end, Is0). @@ -293,7 +414,7 @@ find_fixpoint(OptFun, Is0) -> Is -> find_fixpoint(OptFun, Is) end. -opt([{test,_,{f,L}=Lbl,_}=I|[{jump,{f,L}}|_]=Is], Acc0, St0) -> +opt([{test,_,{f,L}=Lbl,_}=I|[{jump,{f,L}}|_]=Is], Acc, St) -> %% We have %% Test Label Ops %% jump Label @@ -302,23 +423,10 @@ opt([{test,_,{f,L}=Lbl,_}=I|[{jump,{f,L}}|_]=Is], Acc0, St0) -> case beam_utils:is_pure_test(I) of false -> %% Test is not pure; we must keep it. - opt(Is, [I|Acc0], label_used(Lbl, St0)); + opt(Is, [I|Acc], label_used(Lbl, St)); true -> %% The test is pure and its failure label is the same %% as in the jump that follows -- thus it is not needed. - %% Check if any of the previous instructions could also be eliminated. - {Acc,St} = opt_useless_loads(Acc0, L, St0), - opt(Is, Acc, St) - end; -opt([{test,_,{f,L}=Lbl,_}=I|[{label,L}|_]=Is], Acc0, St0) -> - %% Similar to the above, except we have a fall-through rather than jump - %% Test Label Ops - %% label Label - case beam_utils:is_pure_test(I) of - false -> - opt(Is, [I|Acc0], label_used(Lbl, St0)); - true -> - {Acc,St} = opt_useless_loads(Acc0, L, St0), opt(Is, Acc, St) end; opt([{test,Test0,{f,L}=Lbl,Ops}=I|[{jump,To}|Is]=Is0], Acc, St) -> @@ -385,51 +493,6 @@ normalize_replace([{From,To0}|Rest], Replace, Acc) -> normalize_replace([], _Replace, Acc) -> maps:from_list(Acc). -%% After eliminating a test, it might happen, that a register was only used -%% in this test. Let's check if that was the case and if it was so, we can -%% eliminate the load into the register completely. -opt_useless_loads([{block,_}|_]=Is, L, #st{index={lazy,FIs}}=St) -> - opt_useless_loads(Is, L, St#st{index=beam_utils:index_labels(FIs)}); -opt_useless_loads([{block,Block0}|Is], L, #st{index=Index}=St) -> - case opt_useless_block_loads(Block0, L, Index) of - [] -> - opt_useless_loads(Is, L, St); - [_|_]=Block -> - {[{block,Block}|Is],St} - end; -%% After eliminating the test and useless blocks, it might happen, -%% that the previous test could also be eliminated. -%% It might be that the label was already marked as used, even if ultimately, -%% it never will be - we can't do much about it at that point, though -opt_useless_loads([{test,_,{f,L},_}=I|Is], L, St) -> - case beam_utils:is_pure_test(I) of - false -> - {[I|Is],St}; - true -> - opt_useless_loads(Is, L, St) - end; -opt_useless_loads(Is, _L, St) -> - {Is,St}. - -opt_useless_block_loads([{set,[Dst],_,_}=I|Is0], L, Index) -> - BlockJump = [{block,Is0},{jump,{f,L}}], - case beam_utils:is_killed(Dst, BlockJump, Index) of - true -> - %% The register is killed and not used, we can remove the load. - %% Remove any `put` instructions in case we just - %% removed a `put_tuple` instruction. - Is = dropwhile(fun({set,_,_,put}) -> true; - (_) -> false - end, Is0), - opt_useless_block_loads(Is, L, Index); - false -> - [I|opt_useless_block_loads(Is0, L, Index)] - end; -opt_useless_block_loads([I|Is], L, Index) -> - [I|opt_useless_block_loads(Is, L, Index)]; -opt_useless_block_loads([], _L, _Index) -> - []. - collect_labels(Is, Label, #st{entry=Entry,replace=Replace} = St) -> collect_labels_1(Is, Label, Entry, Replace, St). @@ -556,52 +619,109 @@ drop_upto_label([{label,_}|_]=Is) -> Is; drop_upto_label([_|Is]) -> drop_upto_label(Is); drop_upto_label([]) -> []. -%% ulbl(Instruction, UsedGbSet) -> UsedGbSet' -%% Update the gb_set UsedGbSet with any function-local labels +%% unshare([Instruction]) -> [Instruction]. +%% Replace a jump to a return sequence (a `return` instruction +%% optionally preced by a `deallocate` instruction) with the return +%% sequence. This always saves execution time and may also save code +%% space (depending on the architecture). Eliminating `jump` +%% instructions also gives beam_trim more opportunities to trim the +%% stack. + +unshare(Is) -> + Short = unshare_collect_short(Is, #{}), + unshare_short(Is, Short). + +unshare_collect_short([{label,L},return|Is], Map) -> + unshare_collect_short(Is, Map#{L=>[return]}); +unshare_collect_short([{label,L},{deallocate,_}=D,return|Is], Map) -> + %% `deallocate` and `return` are combined into one instruction by + %% the loader. + unshare_collect_short(Is, Map#{L=>[D,return]}); +unshare_collect_short([_|Is], Map) -> + unshare_collect_short(Is, Map); +unshare_collect_short([], Map) -> Map. + +unshare_short([{jump,{f,F}}=I|Is], Map) -> + case Map of + #{F:=Seq} -> + Seq ++ unshare_short(Is, Map); + #{} -> + [I|unshare_short(Is, Map)] + end; +unshare_short([I|Is], Map) -> + [I|unshare_short(Is, Map)]; +unshare_short([], _Map) -> []. + +%% ulbl(Instruction, UsedCerlSet) -> UsedCerlSet' +%% Update the cerl_set UsedCerlSet with any function-local labels %% (i.e. not with labels in call instructions) referenced by %% the instruction Instruction. %% %% NOTE: This function does NOT look for labels inside blocks. -ulbl({test,_,Fail,_}, Used) -> - mark_used(Fail, Used); -ulbl({test,_,Fail,_,_,_}, Used) -> - mark_used(Fail, Used); -ulbl({select,_,_,Fail,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({gc_bif,_Name,Lbl,_Live,_As,_R}, Used) -> - mark_used(Lbl, Used); -ulbl({bs_init,Lbl,_,_,_,_}, Used) -> - mark_used(Lbl, Used); -ulbl({bs_put,Lbl,_,_}, Used) -> - mark_used(Lbl, Used); -ulbl({put_map,Lbl,_Op,_Src,_Dst,_Live,_List}, Used) -> - mark_used(Lbl, Used); -ulbl({get_map_elements,Lbl,_Src,_List}, Used) -> - mark_used(Lbl, Used); -ulbl(_, Used) -> Used. - -mark_used({f,0}, Used) -> Used; -mark_used({f,L}, Used) -> cerl_sets:add_element(L, Used). - -mark_used_list([{f,L}|T], Used) -> - mark_used_list(T, cerl_sets:add_element(L, Used)); -mark_used_list([_|T], Used) -> - mark_used_list(T, Used); -mark_used_list([], Used) -> Used. +ulbl(I, Used) -> + case instr_labels(I) of + [] -> + Used; + [Lbl] -> + cerl_sets:add_element(Lbl, Used); + [_|_]=L -> + ulbl_list(L, Used) + end. + +ulbl_list([L|Ls], Used) -> + ulbl_list(Ls, cerl_sets:add_element(L, Used)); +ulbl_list([], Used) -> Used. + +-spec instr_labels(Instruction) -> Labels when + Instruction :: instruction(), + Labels :: [beam_asm:label()]. + +instr_labels({test,_,Fail,_}) -> + do_instr_labels(Fail); +instr_labels({test,_,Fail,_,_,_}) -> + do_instr_labels(Fail); +instr_labels({select,_,_,Fail,Vls}) -> + do_instr_labels_list(Vls, do_instr_labels(Fail)); +instr_labels({'try',_,Lbl}) -> + do_instr_labels(Lbl); +instr_labels({'catch',_,Lbl}) -> + do_instr_labels(Lbl); +instr_labels({jump,Lbl}) -> + do_instr_labels(Lbl); +instr_labels({loop_rec,Lbl,_}) -> + do_instr_labels(Lbl); +instr_labels({loop_rec_end,Lbl}) -> + do_instr_labels(Lbl); +instr_labels({wait,Lbl}) -> + do_instr_labels(Lbl); +instr_labels({wait_timeout,Lbl,_To}) -> + do_instr_labels(Lbl); +instr_labels({bif,_Name,Lbl,_As,_R}) -> + do_instr_labels(Lbl); +instr_labels({gc_bif,_Name,Lbl,_Live,_As,_R}) -> + do_instr_labels(Lbl); +instr_labels({bs_init,Lbl,_,_,_,_}) -> + do_instr_labels(Lbl); +instr_labels({bs_put,Lbl,_,_}) -> + do_instr_labels(Lbl); +instr_labels({put_map,Lbl,_Op,_Src,_Dst,_Live,_List}) -> + do_instr_labels(Lbl); +instr_labels({get_map_elements,Lbl,_Src,_List}) -> + do_instr_labels(Lbl); +instr_labels({recv_mark,Lbl}) -> + do_instr_labels(Lbl); +instr_labels({recv_set,Lbl}) -> + do_instr_labels(Lbl); +instr_labels({fcheckerror,Lbl}) -> + do_instr_labels(Lbl); +instr_labels(_) -> []. + +do_instr_labels({f,0}) -> []; +do_instr_labels({f,F}) -> [F]. + +do_instr_labels_list([{f,F}|T], Acc) -> + do_instr_labels_list(T, [F|Acc]); +do_instr_labels_list([_|T], Acc) -> + do_instr_labels_list(T, Acc); +do_instr_labels_list([], Acc) -> Acc. |