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Diffstat (limited to 'lib/compiler/src/beam_bs.erl')
| -rw-r--r-- | lib/compiler/src/beam_bs.erl | 278 |
1 files changed, 278 insertions, 0 deletions
diff --git a/lib/compiler/src/beam_bs.erl b/lib/compiler/src/beam_bs.erl new file mode 100644 index 0000000000..2aed98d4e7 --- /dev/null +++ b/lib/compiler/src/beam_bs.erl @@ -0,0 +1,278 @@ +%% +%% %CopyrightBegin% +%% +%% Copyright Ericsson AB 1999-2016. 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% +%% +%% Purpose : Partitions assembly instructions into basic blocks and +%% optimizes them. + +-module(beam_bs). + +-export([module/2]). +-import(lists, [mapfoldl/3,reverse/1]). + +module({Mod,Exp,Attr,Fs0,Lc0}, _Opt) -> + {Fs,Lc} = mapfoldl(fun function/2, Lc0, Fs0), + {ok,{Mod,Exp,Attr,Fs,Lc}}. + +function({function,Name,Arity,CLabel,Is0}, Lc0) -> + try + Is1 = bs_put_opt(Is0), + {Is,Lc} = bsm_opt(Is1, Lc0), + {{function,Name,Arity,CLabel,Is},Lc} + catch + Class:Error -> + Stack = erlang:get_stacktrace(), + io:fwrite("Function: ~w/~w\n", [Name,Arity]), + erlang:raise(Class, Error, Stack) + end. + +%%% +%%% Evaluation of constant bit fields. +%%% + +bs_put_opt([{bs_put,_,_,_}=I|Is0]) -> + {BsPuts0,Is} = collect_bs_puts(Is0, [I]), + BsPuts = opt_bs_puts(BsPuts0), + BsPuts ++ bs_put_opt(Is); +bs_put_opt([I|Is]) -> + [I|bs_put_opt(Is)]; +bs_put_opt([]) -> []. + +collect_bs_puts([{bs_put,_,_,_}=I|Is], Acc) -> + collect_bs_puts(Is, [I|Acc]); +collect_bs_puts([_|_]=Is, Acc) -> + {reverse(Acc),Is}. + +opt_bs_puts(Is) -> + opt_bs_1(Is, []). + +opt_bs_1([{bs_put,Fail, + {bs_put_float,1,Flags0},[{integer,Sz},Src]}=I0|Is], Acc) -> + try eval_put_float(Src, Sz, Flags0) of + <<Int:Sz>> -> + Flags = force_big(Flags0), + I = {bs_put,Fail,{bs_put_integer,1,Flags}, + [{integer,Sz},{integer,Int}]}, + opt_bs_1([I|Is], Acc) + catch + error:_ -> + opt_bs_1(Is, [I0|Acc]) + end; +opt_bs_1([{bs_put,_,{bs_put_integer,1,_},[{integer,8},{integer,_}]}|_]=IsAll, + Acc0) -> + {Is,Acc} = bs_collect_string(IsAll, Acc0), + opt_bs_1(Is, Acc); +opt_bs_1([{bs_put,Fail,{bs_put_integer,1,F},[{integer,Sz},{integer,N}]}=I|Is0], + Acc) when Sz > 8 -> + case field_endian(F) of + big -> + %% We can do this optimization for any field size without + %% risk for code explosion. + case bs_split_int(N, Sz, Fail, Is0) of + no_split -> opt_bs_1(Is0, [I|Acc]); + Is -> opt_bs_1(Is, Acc) + end; + little when Sz < 128 -> + %% We only try to optimize relatively small fields, to + %% avoid an explosion in code size. + <<Int:Sz>> = <<N:Sz/little>>, + Flags = force_big(F), + Is = [{bs_put,Fail,{bs_put_integer,1,Flags}, + [{integer,Sz},{integer,Int}]}|Is0], + opt_bs_1(Is, Acc); + _ -> %native or too wide little field + opt_bs_1(Is0, [I|Acc]) + end; +opt_bs_1([{bs_put,Fail,{Op,U,F},[{integer,Sz},Src]}|Is], Acc) when U > 1 -> + opt_bs_1([{bs_put,Fail,{Op,1,F},[{integer,U*Sz},Src]}|Is], Acc); +opt_bs_1([I|Is], Acc) -> + opt_bs_1(Is, [I|Acc]); +opt_bs_1([], Acc) -> reverse(Acc). + +eval_put_float(Src, Sz, Flags) when Sz =< 256 -> + %%Only evaluate if Sz is reasonable. + Val = value(Src), + case field_endian(Flags) of + little -> <<Val:Sz/little-float-unit:1>>; + big -> <<Val:Sz/big-float-unit:1>> + %% native intentionally not handled here - we can't optimize + %% it. + end. + +value({integer,I}) -> I; +value({float,F}) -> F. + +bs_collect_string(Is, [{bs_put,_,{bs_put_string,Len,{string,Str}},[]}|Acc]) -> + bs_coll_str_1(Is, Len, reverse(Str), Acc); +bs_collect_string(Is, Acc) -> + bs_coll_str_1(Is, 0, [], Acc). + +bs_coll_str_1([{bs_put,_,{bs_put_integer,U,_},[{integer,Sz},{integer,V}]}|Is], + Len, StrAcc, IsAcc) when U*Sz =:= 8 -> + Byte = V band 16#FF, + bs_coll_str_1(Is, Len+1, [Byte|StrAcc], IsAcc); +bs_coll_str_1(Is, Len, StrAcc, IsAcc) -> + {Is,[{bs_put,{f,0},{bs_put_string,Len,{string,reverse(StrAcc)}},[]}|IsAcc]}. + +field_endian({field_flags,F}) -> field_endian_1(F). + +field_endian_1([big=E|_]) -> E; +field_endian_1([little=E|_]) -> E; +field_endian_1([native=E|_]) -> E; +field_endian_1([_|Fs]) -> field_endian_1(Fs). + +force_big({field_flags,F}) -> + {field_flags,force_big_1(F)}. + +force_big_1([big|_]=Fs) -> Fs; +force_big_1([little|Fs]) -> [big|Fs]; +force_big_1([F|Fs]) -> [F|force_big_1(Fs)]. + +bs_split_int(0, Sz, _, _) when Sz > 64 -> + %% We don't want to split in this case because the + %% string will consist of only zeroes. + no_split; +bs_split_int(-1, Sz, _, _) when Sz > 64 -> + %% We don't want to split in this case because the + %% string will consist of only 255 bytes. + no_split; +bs_split_int(N, Sz, Fail, Acc) -> + FirstByteSz = case Sz rem 8 of + 0 -> 8; + Rem -> Rem + end, + bs_split_int_1(N, FirstByteSz, Sz, Fail, Acc). + +bs_split_int_1(-1, _, Sz, Fail, Acc) when Sz > 64 -> + I = {bs_put,Fail,{bs_put_integer,1,{field_flags,[big]}}, + [{integer,Sz},{integer,-1}]}, + [I|Acc]; +bs_split_int_1(0, _, Sz, Fail, Acc) when Sz > 64 -> + I = {bs_put,Fail,{bs_put_integer,1,{field_flags,[big]}}, + [{integer,Sz},{integer,0}]}, + [I|Acc]; +bs_split_int_1(N, ByteSz, Sz, Fail, Acc) when Sz > 0 -> + Mask = (1 bsl ByteSz) - 1, + I = {bs_put,Fail,{bs_put_integer,1,{field_flags,[big]}}, + [{integer,ByteSz},{integer,N band Mask}]}, + bs_split_int_1(N bsr ByteSz, 8, Sz-ByteSz, Fail, [I|Acc]); +bs_split_int_1(_, _, _, _, Acc) -> Acc. + +%%% +%%% Optimization of bit syntax matching: get rid +%%% of redundant bs_restore2/2 instructions across select_val +%%% instructions, as well as a few other simple peep-hole +%%% optimizations. +%%% + +bsm_opt(Is0, Lc0) -> + {Is1,D0,Lc} = bsm_scan(Is0, [], Lc0, []), + Is2 = case D0 of + [] -> + %% No bit syntax matching in this function. + Is1; + [_|_] -> + %% Optimize the bit syntax matching. + D = gb_trees:from_orddict(orddict:from_list(D0)), + bsm_reroute(Is1, D, none, []) + end, + Is = beam_clean:bs_clean_saves(Is2), + {bsm_opt_2(Is, []),Lc}. + +bsm_scan([{label,L}=Lbl,{bs_restore2,_,Save}=R|Is], D0, Lc, Acc0) -> + D = [{{L,Save},Lc}|D0], + Acc = [{label,Lc},R,Lbl|Acc0], + bsm_scan(Is, D, Lc+1, Acc); +bsm_scan([I|Is], D, Lc, Acc) -> + bsm_scan(Is, D, Lc, [I|Acc]); +bsm_scan([], D, Lc, Acc) -> + {reverse(Acc),D,Lc}. + +bsm_reroute([{bs_save2,Reg,Save}=I|Is], D, _, Acc) -> + bsm_reroute(Is, D, {Reg,Save}, [I|Acc]); +bsm_reroute([{bs_restore2,Reg,Save}=I|Is], D, _, Acc) -> + bsm_reroute(Is, D, {Reg,Save}, [I|Acc]); +bsm_reroute([{label,_}=I|Is], D, S, Acc) -> + bsm_reroute(Is, D, S, [I|Acc]); +bsm_reroute([{select,select_val,Reg,F0,Lbls0}|Is], D, {_,Save}=S, Acc0) -> + [F|Lbls] = bsm_subst_labels([F0|Lbls0], Save, D), + Acc = [{select,select_val,Reg,F,Lbls}|Acc0], + bsm_reroute(Is, D, S, Acc); +bsm_reroute([{test,TestOp,F0,TestArgs}=I|Is], D, {_,Save}=S, Acc0) -> + F = bsm_subst_label(F0, Save, D), + Acc = [{test,TestOp,F,TestArgs}|Acc0], + case bsm_not_bs_test(I) of + true -> + %% The test instruction will not update the bit offset for + %% the binary being matched. Therefore the save position + %% can be kept. + bsm_reroute(Is, D, S, Acc); + false -> + %% The test instruction might update the bit offset. Kill + %% our remembered Save position. + bsm_reroute(Is, D, none, Acc) + end; +bsm_reroute([{test,TestOp,F0,Live,TestArgs,Dst}|Is], D, {_,Save}, Acc0) -> + F = bsm_subst_label(F0, Save, D), + Acc = [{test,TestOp,F,Live,TestArgs,Dst}|Acc0], + %% The test instruction will update the bit offset. Kill our + %% remembered Save position. + bsm_reroute(Is, D, none, Acc); +bsm_reroute([{block,[{set,[],[],{alloc,_,_}}]}=Bl, + {bs_context_to_binary,_}=I|Is], D, S, Acc) -> + %% To help further bit syntax optimizations. + bsm_reroute([I,Bl|Is], D, S, Acc); +bsm_reroute([I|Is], D, _, Acc) -> + bsm_reroute(Is, D, none, [I|Acc]); +bsm_reroute([], _, _, Acc) -> reverse(Acc). + +bsm_opt_2([{test,bs_test_tail2,F,[Ctx,Bits]}|Is], + [{test,bs_skip_bits2,F,[Ctx,{integer,I},Unit,_Flags]}|Acc]) -> + bsm_opt_2(Is, [{test,bs_test_tail2,F,[Ctx,Bits+I*Unit]}|Acc]); +bsm_opt_2([{test,bs_skip_bits2,F,[Ctx,{integer,I1},Unit1,_]}|Is], + [{test,bs_skip_bits2,F,[Ctx,{integer,I2},Unit2,Flags]}|Acc]) -> + bsm_opt_2(Is, [{test,bs_skip_bits2,F, + [Ctx,{integer,I1*Unit1+I2*Unit2},1,Flags]}|Acc]); +bsm_opt_2([I|Is], Acc) -> + bsm_opt_2(Is, [I|Acc]); +bsm_opt_2([], Acc) -> reverse(Acc). + +%% bsm_not_bs_test({test,Name,_,Operands}) -> true|false. +%% Test whether is the test is a "safe", i.e. does not move the +%% bit offset for a binary. +%% +%% 'true' means that the test is safe, 'false' that we don't know or +%% that the test moves the offset (e.g. bs_get_integer2). + +bsm_not_bs_test({test,bs_test_tail2,_,[_,_]}) -> true; +bsm_not_bs_test(Test) -> beam_utils:is_pure_test(Test). + +bsm_subst_labels(Fs, Save, D) -> + bsm_subst_labels_1(Fs, Save, D, []). + +bsm_subst_labels_1([F|Fs], Save, D, Acc) -> + bsm_subst_labels_1(Fs, Save, D, [bsm_subst_label(F, Save, D)|Acc]); +bsm_subst_labels_1([], _, _, Acc) -> + reverse(Acc). + +bsm_subst_label({f,Lbl0}=F, Save, D) -> + case gb_trees:lookup({Lbl0,Save}, D) of + {value,Lbl} -> {f,Lbl}; + none -> F + end; +bsm_subst_label(Other, _, _) -> Other. |