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Diffstat (limited to 'lib/compiler/src/beam_dead.erl')
| -rw-r--r-- | lib/compiler/src/beam_dead.erl | 971 |
1 files changed, 0 insertions, 971 deletions
diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl deleted file mode 100644 index efad082152..0000000000 --- a/lib/compiler/src/beam_dead.erl +++ /dev/null @@ -1,971 +0,0 @@ -%% -%% %CopyrightBegin% -%% -%% Copyright Ericsson AB 2002-2018. All Rights Reserved. -%% -%% Licensed under the Apache License, Version 2.0 (the "License"); -%% you may not use this file except in compliance with the License. -%% You may obtain a copy of the License at -%% -%% http://www.apache.org/licenses/LICENSE-2.0 -%% -%% Unless required by applicable law or agreed to in writing, software -%% distributed under the License is distributed on an "AS IS" BASIS, -%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -%% See the License for the specific language governing permissions and -%% limitations under the License. -%% -%% %CopyrightEnd% -%% - --module(beam_dead). - --export([module/2]). - -%%% Dead code is code that is executed but has no effect. This -%%% optimization pass either removes dead code or jumps around it, -%%% potentially making it unreachable and a target for the -%%% the beam_jump pass. - --import(lists, [mapfoldl/3,reverse/1]). - - --spec module(beam_utils:module_code(), [compile:option()]) -> - {'ok',beam_utils:module_code()}. - -module({Mod,Exp,Attr,Fs0,_}, _Opts) -> - {Fs1,Lc1} = beam_clean:clean_labels(Fs0), - {Fs,Lc} = mapfoldl(fun function/2, Lc1, Fs1), - %%{Fs,Lc} = {Fs1,Lc1}, - {ok,{Mod,Exp,Attr,Fs,Lc}}. - -function({function,Name,Arity,CLabel,Is0}, Lc0) -> - try - Is1 = beam_jump:remove_unused_labels(Is0), - - %% Initialize label information with the code - %% for the func_info label. Without it, a register - %% may seem to be live when it is not. - [{label,L}|FiIs] = Is1, - D0 = beam_utils:empty_label_index(), - D = beam_utils:index_label(L, FiIs, D0), - - %% Optimize away dead code. - {Is2,Lc} = forward(Is1, Lc0), - Is3 = backward(Is2, D), - Is = move_move_into_block(Is3, []), - {{function,Name,Arity,CLabel,Is},Lc} - catch - Class:Error:Stack -> - io:fwrite("Function: ~w/~w\n", [Name,Arity]), - erlang:raise(Class, Error, Stack) - end. - -%% 'move' instructions outside of blocks may thwart the jump optimizer. -%% Move them back into the block. - -move_move_into_block([{block,Bl0},{move,S,D}|Is], Acc) -> - Bl = Bl0 ++ [{set,[D],[S],move}], - move_move_into_block([{block,Bl}|Is], Acc); -move_move_into_block([{move,S,D}|Is], Acc) -> - Bl = [{set,[D],[S],move}], - move_move_into_block([{block,Bl}|Is], Acc); -move_move_into_block([I|Is], Acc) -> - move_move_into_block(Is, [I|Acc]); -move_move_into_block([], Acc) -> reverse(Acc). - -%%% -%%% 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: -%%% -%%% test is_eq_exact SomeLabel Src Dst -%%% move Src Dst -%%% -%%% or in: -%%% -%%% test is_nil SomeLabel Dst -%%% move nil Dst -%%% -%%% or in: -%%% -%%% select_val Register FailLabel [... Literal => L1...] -%%% . -%%% . -%%% . -%%% L1: move Literal Register -%%% -%%% Also add extra labels to help the second backward pass. -%%% - -forward(Is, Lc) -> - forward(Is, #{}, Lc, []). - -forward([{move,_,_}=Move|[{label,L}|_]=Is], D, Lc, Acc) -> - %% move/2 followed by jump/1 is optimized by backward/3. - forward([Move,{jump,{f,L}}|Is], D, Lc, Acc); -forward([{bif,_,_,_,_}=Bif|[{label,L}|_]=Is], D, Lc, Acc) -> - %% bif/4 followed by jump/1 is optimized by backward/3. - forward([Bif,{jump,{f,L}}|Is], D, Lc, Acc); -forward([{block,[]}|Is], D, Lc, Acc) -> - %% Empty blocks can prevent optimizations. - forward(Is, D, Lc, Acc); -forward([{select,select_val,Reg,_,List}=I|Is], D0, Lc, Acc) -> - D = update_value_dict(List, Reg, D0), - forward(Is, D, Lc, [I|Acc]); -forward([{label,Lbl}=LblI,{block,[{set,[Dst],[Lit],move}|BlkIs]}=Blk|Is], D, Lc, Acc) -> - %% Assumption: The target labels in a select_val/3 instruction - %% cannot be reached in any other way than through the select_val/3 - %% instruction (i.e. there can be no fallthrough to such label and - %% it cannot be referenced by, for example, a jump/1 instruction). - Key = {Lbl,Dst}, - Block = case D of - #{Key := Lit} -> {block,BlkIs}; %Safe to remove move instruction. - _ -> Blk %Must keep move instruction. - end, - forward([Block|Is], D, Lc, [LblI|Acc]); -forward([{label,Lbl}=LblI|[{move,Lit,Dst}|Is1]=Is0], D, Lc, Acc) -> - %% Assumption: The target labels in a select_val/3 instruction - %% cannot be reached in any other way than through the select_val/3 - %% instruction (i.e. there can be no fallthrough to such label and - %% it cannot be referenced by, for example, a jump/1 instruction). - Is = case maps:find({Lbl,Dst}, D) of - {ok,Lit} -> Is1; %Safe to remove move instruction. - _ -> Is0 %Keep move instruction. - end, - forward(Is, D, Lc, [LblI|Acc]); -forward([{test,is_eq_exact,_,[Same,Same]}|Is], D, Lc, Acc) -> - forward(Is, D, Lc, Acc); -forward([{test,is_eq_exact,_,[Dst,Src]}=I, - {block,[{set,[Dst],[Src],move}|Bl]}|Is], D, Lc, Acc) -> - forward([I,{block,Bl}|Is], D, Lc, Acc); -forward([{test,is_nil,_,[Dst]}=I, - {block,[{set,[Dst],[nil],move}|Bl]}|Is], D, Lc, Acc) -> - forward([I,{block,Bl}|Is], D, Lc, Acc); -forward([{test,is_eq_exact,_,[Dst,Src]}=I,{move,Src,Dst}|Is], D, Lc, Acc) -> - forward([I|Is], D, Lc, Acc); -forward([{test,is_nil,_,[Dst]}=I,{move,nil,Dst}|Is], D, Lc, Acc) -> - forward([I|Is], D, Lc, Acc); -forward([{test,_,_,_}=I|Is]=Is0, D, Lc, Acc) -> - %% Help the second, backward pass to by inserting labels after - %% relational operators so that they can be skipped if they are - %% known to be true. - case useful_to_insert_label(Is0) of - false -> forward(Is, D, Lc, [I|Acc]); - true -> forward(Is, D, Lc+1, [{label,Lc},I|Acc]) - end; -forward([I|Is], D, Lc, Acc) -> - forward(Is, D, Lc, [I|Acc]); -forward([], _, Lc, Acc) -> {Acc,Lc}. - -update_value_dict([Lit,{f,Lbl}|T], Reg, D0) -> - Key = {Lbl,Reg}, - D = case D0 of - #{Key := inconsistent} -> D0; - #{Key := _} -> D0#{Key := inconsistent}; - _ -> D0#{Key => Lit} - end, - update_value_dict(T, Reg, D); -update_value_dict([], _, D) -> D. - -useful_to_insert_label([_,{label,_}|_]) -> - false; -useful_to_insert_label([{test,Op,_,_}|_]) -> - case Op of - is_lt -> true; - is_ge -> true; - is_eq_exact -> true; - is_ne_exact -> true; - _ -> false - end. - -%%% -%%% Scan instructions in reverse execution order and try to -%%% shortcut branch instructions. -%%% -%%% For example, in this code: -%%% -%%% move Literal Register -%%% jump L1 -%%% . -%%% . -%%% . -%%% L1: test is_{integer,atom} FailLabel Register -%%% select_val {x,0} FailLabel [... Literal => L2...] -%%% . -%%% . -%%% . -%%% L2: ... -%%% -%%% the 'selectval' instruction will always transfer control to L2, -%%% so we can just as well jump to L2 directly by rewriting the -%%% first part of the sequence like this: -%%% -%%% move Literal Register -%%% jump L2 -%%% -%%% If register Register is killed at label L2, we can remove the -%%% 'move' instruction, leaving just the 'jump' instruction: -%%% -%%% jump L2 -%%% -%%% These transformations may leave parts of the code unreachable. -%%% The beam_jump pass will remove the unreachable code. - -backward(Is, D) -> - backward(Is, D, []). - -backward([{test,is_eq_exact,Fail,[Dst,{integer,Arity}]}=I| - [{bif,tuple_size,Fail,[Reg],Dst}|Is]=Is0], D, Acc) -> - %% Provided that Dst is killed following this sequence, - %% we can rewrite the instructions like this: - %% - %% bif tuple_size Fail Reg Dst ==> is_tuple Fail Reg - %% is_eq_exact Fail Dst Integer test_arity Fail Reg Integer - %% - %% (still two instructions, but they they will be combined to - %% one by the loader). - case beam_utils:is_killed(Dst, Acc, D) andalso (Arity bsr 32) =:= 0 of - false -> - %% Not safe because the register Dst is not killed - %% (probably cannot not happen in practice) or the arity - %% does not fit in 32 bits (the loader will fail to load - %% the module). We must move the first instruction to the - %% accumulator to avoid an infinite loop. - backward(Is0, D, [I|Acc]); - true -> - %% Safe. - backward([{test,test_arity,Fail,[Reg,Arity]}, - {test,is_tuple,Fail,[Reg]}|Is], D, Acc) - end; -backward([{label,Lbl}=L|Is], D, Acc) -> - backward(Is, beam_utils:index_label(Lbl, Acc, D), [L|Acc]); -backward([{select,select_val,Reg,{f,Fail0},List0}|Is], D, Acc) -> - List1 = shortcut_select_list(List0, Reg, D, []), - Fail1 = shortcut_label(Fail0, D), - Fail = shortcut_bs_test(Fail1, Is, D), - List = prune_redundant(List1, Fail), - case List of - [] -> - Jump = {jump,{f,Fail}}, - backward([Jump|Is], D, Acc); - [V,F] -> - Test = {test,is_eq_exact,{f,Fail},[Reg,V]}, - Jump = {jump,F}, - backward([Jump,Test|Is], D, Acc); - [{atom,B1},F,{atom,B2},F] when B1 =:= not B2 -> - Test = {test,is_boolean,{f,Fail},[Reg]}, - Jump = {jump,F}, - backward([Jump,Test|Is], D, Acc); - [_|_] -> - Sel = {select,select_val,Reg,{f,Fail},List}, - backward(Is, D, [Sel|Acc]) - end; -backward([{jump,{f,To0}},{move,Src,Reg}=Move|Is], D, Acc) -> - To = shortcut_select_label(To0, Reg, Src, D), - Jump = {jump,{f,To}}, - case is_killed_at(Reg, To, D) of - false -> backward([Move|Is], D, [Jump|Acc]); - true -> backward([Jump|Is], D, Acc) - end; -backward([{jump,{f,To}}=J|[{bif,Op,{f,BifFail},Ops,Reg}|Is]=Is0], D, Acc) -> - try replace_comp_op(To, Reg, Op, Ops, D) of - {Test,Jump} -> - backward([Jump,Test|Is], D, Acc) - catch - throw:not_possible -> - case To =:= BifFail of - true -> - %% The bif instruction is redundant. See the comment - %% in the next clause for why there is no need to - %% test for liveness of Reg at label To. - backward([J|Is], D, Acc); - false -> - backward(Is0, D, [J|Acc]) - end - end; -backward([{jump,{f,To}}=J|[{gc_bif,_,{f,To},_,_,_Dst}|Is]], D, Acc) -> - %% The gc_bif instruction is redundant, since either the gc_bif - %% instruction itself or the jump instruction will transfer control - %% to label To. Note that a gc_bif instruction does not assign its - %% destination register if the failure branch is taken; therefore, - %% the code at label To is not allowed to assume that the destination - %% register is initialized, and it is therefore no need to test - %% for liveness of the destination register at label To. - backward([J|Is], D, Acc); -backward([{test,bs_start_match2,F,Live,[Src,_]=Args,Ctxt}|Is], D, Acc0) -> - {f,To0} = F, - case test_bs_literal(F, Ctxt, D, Acc0) of - {none,Acc} -> - %% Ctxt killed immediately after bs_start_match2. - To = shortcut_bs_context_to_binary(To0, Src, D), - I = {test,is_bitstr,{f,To},[Src]}, - backward(Is, D, [I|Acc]); - {Literal,Acc} -> - %% Ctxt killed after matching a literal. - To = shortcut_bs_context_to_binary(To0, Src, D), - Eq = {test,is_eq_exact,{f,To},[Src,{literal,Literal}]}, - backward(Is, D, [Eq|Acc]); - not_killed -> - %% Ctxt not killed. Not much to do. - To = shortcut_bs_start_match(To0, Src, D), - I = {test,bs_start_match2,{f,To},Live,Args,Ctxt}, - backward(Is, D, [I|Acc0]) - end; -backward([{test,Op,{f,To0},Ops0}|Is], D, Acc) -> - To1 = shortcut_bs_test(To0, Is, D), - To2 = shortcut_label(To1, D), - To3 = shortcut_rel_op(To2, Op, Ops0, D), - - %% Try to shortcut a repeated test: - %% - %% test Op {f,Fail1} Operands test Op {f,Fail2} Operands - %% . . . ==> ... - %% Fail1: test Op {f,Fail2} Operands Fail1: test Op {f,Fail2} Operands - %% - To = case beam_utils:code_at(To3, D) of - [{test,Op,{f,To4},Ops}|_] -> - case equal_ops(Ops0, Ops) of - true -> To4; - false -> To3 - end; - _Code -> - To3 - end, - I = case Op of - is_eq_exact -> combine_eqs(To, Ops0, D, Acc); - _ -> {test,Op,{f,To},Ops0} - end, - case {I,Acc} of - {{test,is_atom,Fail,Ops0},[{test,is_boolean,Fail,Ops0}|_]} -> - %% An is_atom test before an is_boolean test (with the - %% same failure label) is redundant. - backward(Is, D, Acc); - {{test,is_atom,Fail,[R]}, - [{test,is_eq_exact,Fail,[R,{atom,_}]}|_]} -> - %% An is_atom test before a comparison with an atom (with - %% the same failure label) is redundant. - backward(Is, D, Acc); - {{test,is_integer,Fail,[R]}, - [{test,is_eq_exact,Fail,[R,{integer,_}]}|_]} -> - %% An is_integer test before a comparison with an integer - %% (with the same failure label) is redundant. - backward(Is, D, Acc); - {{test,_,_,_},_} -> - %% Still a test instruction. Done. - backward(Is, D, [I|Acc]); - {_,_} -> - %% Rewritten to a select_val. Rescan. - backward([I|Is], D, Acc) - end; -backward([{test,Op,{f,To0},Live,Ops0,Dst}|Is], D, Acc) -> - To1 = shortcut_bs_test(To0, Is, D), - To2 = shortcut_label(To1, D), - %% Try to shortcut a repeated test: - %% - %% test Op {f,Fail1} _ Ops _ test Op {f,Fail2} _ Ops _ - %% . . . ==> ... - %% Fail1: test Op {f,Fail2} _ Ops _ Fail1: test Op {f,Fail2} _ Ops _ - %% - To = case beam_utils:code_at(To2, D) of - [{test,Op,{f,To3},_,Ops,_}|_] -> - case equal_ops(Ops0, Ops) of - true -> To3; - false -> To2 - end; - _Code -> - To2 - end, - I = {test,Op,{f,To},Live,Ops0,Dst}, - backward(Is, D, [I|Acc]); -backward([{kill,_}=I|Is], D, [{line,_},Exit|_]=Acc) -> - case beam_jump:is_exit_instruction(Exit) of - false -> backward(Is, D, [I|Acc]); - true -> backward(Is, D, Acc) - end; -backward([{bif,'or',{f,To0},[Dst,{atom,false}],Dst}=I|Is], D, - [{test,is_eq_exact,{f,To},[Dst,{atom,true}]}|_]=Acc) -> - case shortcut_label(To0, D) of - To -> - backward(Is, D, Acc); - _ -> - backward(Is, D, [I|Acc]) - end; -backward([{bif,map_get,{f,FF},[Key,Map],_}=I0, - {test,has_map_fields,{f,FT}=F,[Map|Keys0]}=I1|Is], D, Acc) when FF =/= 0 -> - case shortcut_label(FF, D) of - FT -> - case lists:delete(Key, Keys0) of - [] -> - backward([I0|Is], D, Acc); - Keys -> - Test = {test,has_map_fields,F,[Map|Keys]}, - backward([Test|Is], D, [I0|Acc]) - end; - _ -> - backward([I1|Is], D, [I0|Acc]) - end; -backward([{bif,map_get,{f,FF},[_,Map],_}=I0, - {test,is_map,{f,FT},[Map]}=I1|Is], D, Acc) when FF =/= 0 -> - case shortcut_label(FF, D) of - FT -> backward([I0|Is], D, Acc); - _ -> backward([I1|Is], D, [I0|Acc]) - end; -backward([I|Is], D, Acc) -> - backward(Is, D, [I|Acc]); -backward([], _D, Acc) -> Acc. - -equal_ops([{field_flags,FlA0}|T0], [{field_flags,FlB0}|T1]) -> - FlA = lists:keydelete(anno, 1, FlA0), - FlB = lists:keydelete(anno, 1, FlB0), - FlA =:= FlB andalso equal_ops(T0, T1); -equal_ops([Op|T0], [Op|T1]) -> - equal_ops(T0, T1); -equal_ops([], []) -> true; -equal_ops(_, _) -> false. - -shortcut_select_list([Lit,{f,To0}|T], Reg, D, Acc) -> - To = shortcut_select_label(To0, Reg, Lit, D), - shortcut_select_list(T, Reg, D, [{f,To},Lit|Acc]); -shortcut_select_list([], _, _, Acc) -> reverse(Acc). - -shortcut_label(0, _) -> - 0; -shortcut_label(To0, D) -> - case beam_utils:code_at(To0, D) of - [{jump,{f,To}}|_] -> shortcut_label(To, D); - _ -> To0 - end. - -shortcut_select_label(To, Reg, Lit, D) -> - shortcut_rel_op(To, is_ne_exact, [Reg,Lit], D). - -prune_redundant([_,{f,Fail}|T], Fail) -> - prune_redundant(T, Fail); -prune_redundant([V,F|T], Fail) -> - [V,F|prune_redundant(T, Fail)]; -prune_redundant([], _) -> []. - -%% Replace a comparison operator with a test instruction and a jump. -%% For example, if we have this code: -%% -%% bif '=:=' Fail Src1 Src2 {x,0} -%% jump L1 -%% . -%% . -%% . -%% L1: select_val {x,0} FailLabel [... true => L2..., ...false => L3...] -%% -%% the first two instructions can be replaced with -%% -%% test is_eq_exact L3 Src1 Src2 -%% jump L2 -%% -%% provided that {x,0} is killed at both L2 and L3. - -replace_comp_op(To, Reg, Op, Ops, D) -> - False = comp_op_find_shortcut(To, Reg, {atom,false}, D), - True = comp_op_find_shortcut(To, Reg, {atom,true}, D), - {bif_to_test(Op, Ops, False),{jump,{f,True}}}. - -comp_op_find_shortcut(To0, Reg, Val, D) -> - case shortcut_select_label(To0, Reg, Val, D) of - To0 -> - not_possible(); - To -> - case is_killed_at(Reg, To, D) of - false -> not_possible(); - true -> To - end - end. - -bif_to_test(Name, Args, Fail) -> - try - beam_utils:bif_to_test(Name, Args, {f,Fail}) - catch - error:_ -> not_possible() - end. - -not_possible() -> throw(not_possible). - -%% combine_eqs(To, Operands, Acc) -> Instruction. -%% Combine two is_eq_exact instructions or (an is_eq_exact -%% instruction and a select_val instruction) to a select_val -%% instruction if possible. -%% -%% Example: -%% -%% is_eq_exact F1 Reg Lit1 select_val Reg F2 [ Lit1 L1 -%% L1: . Lit2 L2 ] -%% . -%% . ==> -%% . -%% F1: is_eq_exact F2 Reg Lit2 F1: is_eq_exact F2 Reg Lit2 -%% L2: .... L2: -%% -combine_eqs(To, [Reg,{Type,_}=Lit1]=Ops, D, Acc) - when Type =:= atom; Type =:= integer -> - Next = case Acc of - [{label,Lbl}|_] -> Lbl; - [{jump,{f,Lbl}}|_] -> Lbl - end, - case beam_utils:code_at(To, D) of - [{test,is_eq_exact,{f,F2},[Reg,{Type,_}=Lit2]}, - {label,L2}|_] when Lit1 =/= Lit2 -> - {select,select_val,Reg,{f,F2},[Lit1,{f,Next},Lit2,{f,L2}]}; - [{test,is_eq_exact,{f,F2},[Reg,{Type,_}=Lit2]}, - {jump,{f,L2}}|_] when Lit1 =/= Lit2 -> - {select,select_val,Reg,{f,F2},[Lit1,{f,Next},Lit2,{f,L2}]}; - [{select,select_val,Reg,{f,F2},[{Type,_}|_]=List0}|_] -> - List = remove_from_list(Lit1, List0), - {select,select_val,Reg,{f,F2},[Lit1,{f,Next}|List]}; - _Is -> - {test,is_eq_exact,{f,To},Ops} - end; -combine_eqs(To, Ops, _D, _Acc) -> - {test,is_eq_exact,{f,To},Ops}. - -remove_from_list(Lit, [Lit,{f,_}|T]) -> - T; -remove_from_list(Lit, [Val,{f,_}=Fail|T]) -> - [Val,Fail|remove_from_list(Lit, T)]; -remove_from_list(_, []) -> []. - - -test_bs_literal(F, Ctxt, D, - [{test,bs_match_string,F,[Ctxt,Bs]}, - {test,bs_test_tail2,F,[Ctxt,0]}|Acc]) -> - test_bs_literal_1(Ctxt, Acc, D, Bs); -test_bs_literal(F, Ctxt, D, [{test,bs_test_tail2,F,[Ctxt,0]}|Acc]) -> - test_bs_literal_1(Ctxt, Acc, D, <<>>); -test_bs_literal(_, Ctxt, D, Acc) -> - test_bs_literal_1(Ctxt, Acc, D, none). - -test_bs_literal_1(Ctxt, Is, D, Literal) -> - case beam_utils:is_killed(Ctxt, Is, D) of - true -> {Literal,Is}; - false -> not_killed - end. - -%% shortcut_bs_test(TargetLabel, ReversedInstructions, D) -> TargetLabel' -%% Try to shortcut the failure label for bit syntax matching. - -shortcut_bs_test(To, Is, D) -> - shortcut_bs_test_1(beam_utils:code_at(To, D), Is, To, D). - -shortcut_bs_test_1([{bs_restore2,Reg,SavePoint}, - {label,_}, - {test,bs_test_tail2,{f,To},[_,TailBits]}|_], - PrevIs, To0, D) -> - case count_bits_matched(PrevIs, {Reg,SavePoint}, 0) of - Bits when Bits > TailBits -> - %% This instruction will fail. We know because a restore has been - %% done from the previous point SavePoint in the binary, and we - %% also know that the binary contains at least Bits bits from - %% SavePoint. - %% - %% Since we will skip a bs_restore2 if we shortcut to label To, - %% we must now make sure that code at To does not depend on - %% the position in the context in any way. - case shortcut_bs_pos_used(To, Reg, D) of - false -> To; - true -> To0 - end; - _Bits -> - To0 - end; -shortcut_bs_test_1([_|_], _, To, _) -> To. - -%% counts_bits_matched(ReversedInstructions, SavePoint, Bits) -> Bits' -%% Given a reversed instruction stream, determine the minimum number -%% of bits that will be matched by bit syntax instructions up to the -%% given save point. - -count_bits_matched([{test,bs_get_utf8,{f,_},_,_,_}|Is], SavePoint, Bits) -> - count_bits_matched(Is, SavePoint, Bits+8); -count_bits_matched([{test,bs_get_utf16,{f,_},_,_,_}|Is], SavePoint, Bits) -> - count_bits_matched(Is, SavePoint, Bits+16); -count_bits_matched([{test,bs_get_utf32,{f,_},_,_,_}|Is], SavePoint, Bits) -> - count_bits_matched(Is, SavePoint, Bits+32); -count_bits_matched([{test,_,_,_,[_,Sz,U,{field_flags,_}],_}|Is], SavePoint, Bits) -> - case Sz of - {integer,N} -> count_bits_matched(Is, SavePoint, Bits+N*U); - _ -> count_bits_matched(Is, SavePoint, Bits) - end; -count_bits_matched([{test,bs_match_string,_,[_,Bs]}|Is], SavePoint, Bits) -> - count_bits_matched(Is, SavePoint, Bits+bit_size(Bs)); -count_bits_matched([{test,_,_,_}|Is], SavePoint, Bits) -> - count_bits_matched(Is, SavePoint, Bits); -count_bits_matched([{bs_save2,Reg,SavePoint}|_], {Reg,SavePoint}, Bits) -> - %% The save point we are looking for - we are done. - Bits; -count_bits_matched([_|_], _, Bits) -> Bits. - -shortcut_bs_pos_used(To, Reg, D) -> - shortcut_bs_pos_used_1(beam_utils:code_at(To, D), Reg, D). - -shortcut_bs_pos_used_1([{bs_context_to_binary,Reg}|_], Reg, _) -> - false; -shortcut_bs_pos_used_1(Is, Reg, D) -> - not beam_utils:is_killed(Reg, Is, D). - -%% shortcut_bs_start_match(TargetLabel, Reg) -> TargetLabel -%% A failing bs_start_match2 instruction means that the source (Reg) -%% cannot be a binary. That means that it is safe to skip -%% bs_context_to_binary instructions operating on Reg, and -%% bs_start_match2 instructions operating on Reg. - -shortcut_bs_start_match(To, Reg, D) -> - shortcut_bs_start_match_1(beam_utils:code_at(To, D), Reg, To, D). - -shortcut_bs_start_match_1([{bs_context_to_binary,Reg}|Is], Reg, To, D) -> - shortcut_bs_start_match_1(Is, Reg, To, D); -shortcut_bs_start_match_1([{jump,{f,To}}|_], Reg, _, D) -> - Code = beam_utils:code_at(To, D), - shortcut_bs_start_match_1(Code, Reg, To, D); -shortcut_bs_start_match_1([{test,bs_start_match2,{f,To},_,[Reg|_],_}|_], - Reg, _, D) -> - Code = beam_utils:code_at(To, D), - shortcut_bs_start_match_1(Code, Reg, To, D); -shortcut_bs_start_match_1(_, _, To, _) -> - To. - -%% shortcut_bs_context_to_binary(TargetLabel, Reg) -> TargetLabel -%% If a bs_start_match2 instruction has been eliminated, the -%% bs_context_to_binary instruction can be eliminated too. - -shortcut_bs_context_to_binary(To, Reg, D) -> - shortcut_bs_ctb_1(beam_utils:code_at(To, D), Reg, To, D). - -shortcut_bs_ctb_1([{bs_context_to_binary,Reg}|Is], Reg, To, D) -> - shortcut_bs_ctb_1(Is, Reg, To, D); -shortcut_bs_ctb_1([{jump,{f,To}}|_], Reg, _, D) -> - Code = beam_utils:code_at(To, D), - shortcut_bs_ctb_1(Code, Reg, To, D); -shortcut_bs_ctb_1(_, _, To, _) -> - To. - -%% shortcut_rel_op(FailLabel, Operator, [Operand], D) -> FailLabel' -%% Try to shortcut the given test instruction. Example: -%% -%% is_ge L1 {x,0} 48 -%% . -%% . -%% . -%% L1: is_ge L2 {x,0} 65 -%% -%% The first test instruction can be rewritten to "is_ge L2 {x,0} 48" -%% since the instruction at L1 will also fail. -%% -%% If there are instructions between L1 and the other test instruction -%% it may still be possible to do the shortcut. For example: -%% -%% L1: is_eq_exact L3 {x,0} 92 -%% is_ge L2 {x,0} 65 -%% -%% Since the first test instruction failed, we know that {x,0} must -%% be less than 48; therefore, we know that {x,0} cannot be equal to -%% 92 and the jump to L3 cannot happen. - -shortcut_rel_op(To, Op, Ops, D) -> - case normalize_op({test,Op,{f,To},Ops}) of - {{NormOp,A,B},_} -> - Normalized = {negate_op(NormOp),A,B}, - shortcut_rel_op_fp(To, Normalized, D); - {_,_} -> - To; - error -> - To - end. - -shortcut_rel_op_fp(To0, Normalized, D) -> - Code = beam_utils:code_at(To0, D), - case shortcut_any_label(Code, Normalized) of - error -> - To0; - To -> - shortcut_rel_op_fp(To, Normalized, D) - end. - -%% shortcut_any_label([Instruction], PrevCondition) -> FailLabel | error -%% Using PrevCondition (a previous condition known to be true), -%% try to shortcut to another failure label. - -shortcut_any_label([{jump,{f,Lbl}}|_], _Prev) -> - Lbl; -shortcut_any_label([{label,Lbl}|_], _Prev) -> - Lbl; -shortcut_any_label([{select,select_val,R,{f,Fail},L}|_], Prev) -> - shortcut_selectval(L, R, Fail, Prev); -shortcut_any_label([I|Is], Prev) -> - case normalize_op(I) of - error -> - error; - {Normalized,Fail} -> - %% We have a relational operator. - case will_succeed(Prev, Normalized) of - no -> - %% This test instruction will always branch - %% to Fail. - Fail; - yes -> - %% This test instruction will never branch, - %% so we will look at the next instruction. - shortcut_any_label(Is, Prev); - maybe -> - %% May or may not branch. From now on, we can only - %% shortcut to the this specific failure label - %% Fail. - shortcut_specific_label(Is, Fail, Prev) - end - end. - -%% shortcut_specific_label([Instruction], FailLabel, PrevCondition) -> -%% FailLabel | error -%% We have previously encountered a test instruction that may or -%% may not branch to FailLabel. Therefore we are only allowed -%% to do the shortcut to the same fail label (FailLabel). - -shortcut_specific_label([{label,_}|Is], Fail, Prev) -> - shortcut_specific_label(Is, Fail, Prev); -shortcut_specific_label([{select,select_val,R,{f,F},L}|_], Fail, Prev) -> - case shortcut_selectval(L, R, F, Prev) of - Fail -> Fail; - _ -> error - end; -shortcut_specific_label([I|Is], Fail, Prev) -> - case normalize_op(I) of - error -> - error; - {Normalized,Fail} -> - case will_succeed(Prev, Normalized) of - no -> - %% Will branch to FailLabel. - Fail; - yes -> - %% Will definitely never branch. - shortcut_specific_label(Is, Fail, Prev); - maybe -> - %% May branch, but still OK since it will branch - %% to FailLabel. - shortcut_specific_label(Is, Fail, Prev) - end; - {Normalized,_} -> - %% This test instruction will branch to a different - %% fail label, if it branches at all. - case will_succeed(Prev, Normalized) of - yes -> - %% Still OK, since the branch will never be - %% taken. - shortcut_specific_label(Is, Fail, Prev); - no -> - %% Give up. The branch will definitely be taken - %% to a different fail label. - error; - maybe -> - %% Give up. If the branch is taken, it will be - %% to a different fail label. - error - end - end. - - -%% shortcut_selectval(List, Reg, Fail, PrevCond) -> FailLabel | error -%% Try to shortcut a selectval instruction. A selectval instruction -%% is equivalent to the following instruction sequence: -%% -%% is_ne_exact L1 Reg Value1 -%% . -%% . -%% . -%% is_ne_exact LN Reg ValueN -%% jump DefaultFailLabel -%% -shortcut_selectval([Val,{f,Lbl}|T], R, Fail, Prev) -> - case will_succeed(Prev, {'=/=',R,get_literal(Val)}) of - yes -> shortcut_selectval(T, R, Fail, Prev); - no -> Lbl; - maybe -> error - end; -shortcut_selectval([], _, Fail, _) -> Fail. - -%% will_succeed(PrevCondition, Condition) -> yes | no | maybe -%% PrevCondition is a condition known to be true. This function -%% will tell whether Condition will succeed. - -will_succeed({Op1,Reg,A}, {Op2,Reg,B}) -> - will_succeed_1(Op1, A, Op2, B); -will_succeed({'=:=',Reg,{literal,A}}, {TypeTest,Reg}) -> - case erlang:TypeTest(A) of - false -> no; - true -> yes - end; -will_succeed({_,_,_}, maybe) -> - maybe; -will_succeed({_,_,_}, Test) when is_tuple(Test) -> - maybe. - -will_succeed_1('=:=', A, '<', B) -> - if - B =< A -> no; - true -> yes - end; -will_succeed_1('=:=', A, '=<', B) -> - if - B < A -> no; - true -> yes - end; -will_succeed_1('=:=', A, '=:=', B) -> - if - A =:= B -> yes; - true -> no - end; -will_succeed_1('=:=', A, '=/=', B) -> - if - A =:= B -> no; - true -> yes - end; -will_succeed_1('=:=', A, '>=', B) -> - if - B > A -> no; - true -> yes - end; -will_succeed_1('=:=', A, '>', B) -> - if - B >= A -> no; - true -> yes - end; - -will_succeed_1('=/=', A, '=/=', B) when A =:= B -> yes; -will_succeed_1('=/=', A, '=:=', B) when A =:= B -> no; - -will_succeed_1('<', A, '=:=', B) when B >= A -> no; -will_succeed_1('<', A, '=/=', B) when B >= A -> yes; -will_succeed_1('<', A, '<', B) when B >= A -> yes; -will_succeed_1('<', A, '=<', B) when B > A -> yes; -will_succeed_1('<', A, '>=', B) when B > A -> no; -will_succeed_1('<', A, '>', B) when B >= A -> no; - -will_succeed_1('=<', A, '=:=', B) when B > A -> no; -will_succeed_1('=<', A, '=/=', B) when B > A -> yes; -will_succeed_1('=<', A, '<', B) when B > A -> yes; -will_succeed_1('=<', A, '=<', B) when B >= A -> yes; -will_succeed_1('=<', A, '>=', B) when B > A -> no; -will_succeed_1('=<', A, '>', B) when B >= A -> no; - -will_succeed_1('>=', A, '=:=', B) when B < A -> no; -will_succeed_1('>=', A, '=/=', B) when B < A -> yes; -will_succeed_1('>=', A, '<', B) when B =< A -> no; -will_succeed_1('>=', A, '=<', B) when B < A -> no; -will_succeed_1('>=', A, '>=', B) when B =< A -> yes; -will_succeed_1('>=', A, '>', B) when B < A -> yes; - -will_succeed_1('>', A, '=:=', B) when B =< A -> no; -will_succeed_1('>', A, '=/=', B) when B =< A -> yes; -will_succeed_1('>', A, '<', B) when B =< A -> no; -will_succeed_1('>', A, '=<', B) when B < A -> no; -will_succeed_1('>', A, '>=', B) when B =< A -> yes; -will_succeed_1('>', A, '>', B) when B < A -> yes; - -will_succeed_1(_, _, _, _) -> maybe. - -%% normalize_op(Instruction) -> {Normalized,FailLabel} | error -%% Normalized = {Operator,Register,Literal} | -%% {TypeTest,Register} | -%% maybe -%% Operation = '<' | '=<' | '=:=' | '=/=' | '>=' | '>' -%% TypeTest = is_atom | is_integer ... -%% Literal = {literal,Term} -%% -%% Normalize a relational operator to facilitate further -%% comparisons between operators. Always make the register -%% operand the first operand. Thus the following instruction: -%% -%% {test,is_ge,{f,99},{integer,13},{x,0}} -%% -%% will be normalized to: -%% -%% {'=<',{x,0},{literal,13}} -%% -%% NOTE: Bit syntax test instructions are scary. They may change the -%% state of match contexts and update registers, so we don't dare -%% mess with them. - -normalize_op({test,is_ge,{f,Fail},Ops}) -> - normalize_op_1('>=', Ops, Fail); -normalize_op({test,is_lt,{f,Fail},Ops}) -> - normalize_op_1('<', Ops, Fail); -normalize_op({test,is_eq_exact,{f,Fail},Ops}) -> - normalize_op_1('=:=', Ops, Fail); -normalize_op({test,is_ne_exact,{f,Fail},Ops}) -> - normalize_op_1('=/=', Ops, Fail); -normalize_op({test,is_nil,{f,Fail},[R]}) -> - normalize_op_1('=:=', [R,nil], Fail); -normalize_op({test,Op,{f,Fail},[R]}) -> - case erl_internal:new_type_test(Op, 1) of - true -> {{Op,R},Fail}; - false -> {maybe,Fail} - end; -normalize_op({test,_,{f,Fail},_}=I) -> - case beam_utils:is_pure_test(I) of - true -> {maybe,Fail}; - false -> error - end; -normalize_op(_) -> - error. - -normalize_op_1(Op, [Op1,Op2], Fail) -> - case {get_literal(Op1),get_literal(Op2)} of - {error,error} -> - %% Both operands are registers. - {maybe,Fail}; - {error,Lit} -> - {{Op,Op1,Lit},Fail}; - {Lit,error} -> - {{turn_op(Op),Op2,Lit},Fail}; - {_,_} -> - %% Both operands are literals. Can probably only - %% happen if the Core Erlang optimizations passes were - %% turned off, so don't bother trying to do something - %% smart here. - {maybe,Fail} - end. - -turn_op('<') -> '>'; -turn_op('>=') -> '=<'; -turn_op('=:='=Op) -> Op; -turn_op('=/='=Op) -> Op. - -negate_op('>=') -> '<'; -negate_op('<') -> '>='; -negate_op('=<') -> '>'; -negate_op('>') -> '=<'; -negate_op('=:=') -> '=/='; -negate_op('=/=') -> '=:='. - -get_literal({atom,Val}) -> - {literal,Val}; -get_literal({integer,Val}) -> - {literal,Val}; -get_literal({float,Val}) -> - {literal,Val}; -get_literal(nil) -> - {literal,[]}; -get_literal({literal,_}=Lit) -> - Lit; -get_literal({_,_}) -> error. - - -%%% -%%% Removing stores to Y registers is not always safe -%%% if there is an instruction that causes an exception -%%% within a catch. In practice, there are few or no -%%% opportunities for removing stores to Y registers anyway -%%% if sys_core_fold has been run. -%%% - -is_killed_at({x,_}=Reg, Lbl, D) -> - beam_utils:is_killed_at(Reg, Lbl, D); -is_killed_at({y,_}, _, _) -> - false. |