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Diffstat (limited to 'lib/compiler/src/beam_ssa_funs.erl')
| -rw-r--r-- | lib/compiler/src/beam_ssa_funs.erl | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/lib/compiler/src/beam_ssa_funs.erl b/lib/compiler/src/beam_ssa_funs.erl new file mode 100644 index 0000000000..e77c00fa89 --- /dev/null +++ b/lib/compiler/src/beam_ssa_funs.erl @@ -0,0 +1,149 @@ +%% +%% %CopyrightBegin% +%% +%% Copyright Ericsson AB 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% +%% + +%%% +%%% If a fun is defined locally and only used for calls, it can be replaced +%%% with direct calls to the relevant function. This greatly speeds up "named +%%% functions" (which rely on make_fun to recreate themselves) and macros that +%%% wrap their body in a fun. +%%% + +-module(beam_ssa_funs). + +-export([module/2]). + +-include("beam_ssa.hrl"). + +-import(lists, [foldl/3]). + +-spec module(Module, Options) -> Result when + Module :: beam_ssa:b_module(), + Options :: [compile:option()], + Result :: {ok, beam_ssa:b_module()}. + +module(#b_module{body=Fs0}=Module, _Opts) -> + Trampolines = foldl(fun find_trampolines/2, #{}, Fs0), + Fs = [lfo(F, Trampolines) || F <- Fs0], + {ok, Module#b_module{body=Fs}}. + +%% If a function does absolutely nothing beyond calling another function with +%% the same arguments in the same order, we can shave off a call by short- +%% circuiting it. +find_trampolines(#b_function{args=Args,bs=Blocks}=F, Trampolines) -> + case map_get(0, Blocks) of + #b_blk{is=[#b_set{op=call, + args=[#b_local{}=Actual | Args], + dst=Dst}], + last=#b_ret{arg=Dst}} -> + {_, Name, Arity} = beam_ssa:get_anno(func_info, F), + Trampoline = #b_local{name=#b_literal{val=Name},arity=Arity}, + Trampolines#{Trampoline => Actual}; + _ -> + Trampolines + end. + +lfo(#b_function{bs=Blocks0}=F, Trampolines) -> + Linear0 = beam_ssa:linearize(Blocks0), + Linear = lfo_optimize(Linear0, lfo_analyze(Linear0, #{}), Trampolines), + F#b_function{bs=maps:from_list(Linear)}. + +%% Gather a map of the locally defined funs that are only used for calls. +lfo_analyze([{_L,#b_blk{is=Is,last=Last}}|Bs], LFuns0) -> + LFuns = lfo_analyze_last(Last, lfo_analyze_is(Is, LFuns0)), + lfo_analyze(Bs, LFuns); +lfo_analyze([], LFuns) -> + LFuns. + +lfo_analyze_is([#b_set{op=make_fun, + dst=Dst, + args=[#b_local{} | FreeVars]}=Def | Is], + LFuns0) -> + LFuns = maps:put(Dst, Def, maps:without(FreeVars, LFuns0)), + lfo_analyze_is(Is, LFuns); +lfo_analyze_is([#b_set{op=call, + args=[Fun | CallArgs]} | Is], + LFuns) when is_map_key(Fun, LFuns) -> + #b_set{args=[#b_local{arity=Arity} | FreeVars]} = map_get(Fun, LFuns), + case length(CallArgs) + length(FreeVars) of + Arity -> + lfo_analyze_is(Is, maps:without(CallArgs, LFuns)); + _ -> + %% This will `badarity` at runtime, and it's easier to disable the + %% optimization than to simulate it. + lfo_analyze_is(Is, maps:without([Fun | CallArgs], LFuns)) + end; +lfo_analyze_is([#b_set{args=Args} | Is], LFuns) when map_size(LFuns) =/= 0 -> + %% We disqualify funs that are used outside calls because this forces them + %% to be created anyway, and the slight performance gain from direct calls + %% is not enough to offset the potential increase in stack frame size (the + %% free variables need to be kept alive until the call). + %% + %% This is also a kludge to make HiPE work, as the latter will generate + %% code with the assumption that the functions referenced in a make_fun + %% will only be used by funs, which will not be the case if we mix it with + %% direct calls. See cerl_cconv.erl for details. + %% + %% Future optimizations like delaying fun creation until use may require us + %% to copy affected functions so that HiPE gets its own to play with (until + %% HiPE is fixed anyway). + lfo_analyze_is(Is, maps:without(Args, LFuns)); +lfo_analyze_is([_ | Is], LFuns) -> + lfo_analyze_is(Is, LFuns); +lfo_analyze_is([], LFuns) -> + LFuns. + +lfo_analyze_last(#b_switch{arg=Arg}, LFuns) -> + maps:remove(Arg, LFuns); +lfo_analyze_last(#b_ret{arg=Arg}, LFuns) -> + maps:remove(Arg, LFuns); +lfo_analyze_last(_, LFuns) -> + LFuns. + +%% Replace all calls of suitable funs with a direct call to their +%% implementation. Liveness optimization will get rid of the make_fun +%% instruction. +lfo_optimize(Linear, LFuns, _Trampolines) when map_size(LFuns) =:= 0 -> + Linear; +lfo_optimize(Linear, LFuns, Trampolines) -> + lfo_optimize_1(Linear, LFuns, Trampolines). + +lfo_optimize_1([{L,#b_blk{is=Is0}=Blk}|Bs], LFuns, Trampolines) -> + Is = lfo_optimize_is(Is0, LFuns, Trampolines), + [{L,Blk#b_blk{is=Is}} | lfo_optimize_1(Bs, LFuns, Trampolines)]; +lfo_optimize_1([], _LFuns, _Trampolines) -> + []. + +lfo_optimize_is([#b_set{op=call, + args=[Fun | CallArgs]}=Call0 | Is], + LFuns, Trampolines) when is_map_key(Fun, LFuns) -> + #b_set{args=[Local | FreeVars]} = map_get(Fun, LFuns), + Args = [lfo_short_circuit(Local, Trampolines) | CallArgs ++ FreeVars], + Call = beam_ssa:add_anno(local_fun_opt, Fun, Call0#b_set{args=Args}), + [Call | lfo_optimize_is(Is, LFuns, Trampolines)]; +lfo_optimize_is([I | Is], LFuns, Trampolines) -> + [I | lfo_optimize_is(Is, LFuns, Trampolines)]; +lfo_optimize_is([], _LFuns, _Trampolines) -> + []. + +lfo_short_circuit(Call, Trampolines) -> + case maps:find(Call, Trampolines) of + {ok, Other} -> lfo_short_circuit(Other, Trampolines); + error -> Call + end. |