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Diffstat (limited to 'lib/compiler/src/beam_ssa_opt.erl')
| -rw-r--r-- | lib/compiler/src/beam_ssa_opt.erl | 1652 |
1 files changed, 1652 insertions, 0 deletions
diff --git a/lib/compiler/src/beam_ssa_opt.erl b/lib/compiler/src/beam_ssa_opt.erl new file mode 100644 index 0000000000..83ee918b25 --- /dev/null +++ b/lib/compiler/src/beam_ssa_opt.erl @@ -0,0 +1,1652 @@ +%% +%% %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% +%% + +-module(beam_ssa_opt). +-export([module/2]). + +-include("beam_ssa.hrl"). +-import(lists, [all/2,append/1,foldl/3,keyfind/3,member/2,reverse/1,reverse/2, + splitwith/2,takewhile/2,unzip/1]). + +-spec module(beam_ssa:b_module(), [compile:option()]) -> + {'ok',beam_ssa:b_module()}. + +module(#b_module{body=Fs0}=Module, Opts) -> + Ps = passes(Opts), + Fs = functions(Fs0, Ps), + {ok,Module#b_module{body=Fs}}. + +functions([F|Fs], Ps) -> + [function(F, Ps)|functions(Fs, Ps)]; +functions([], _Ps) -> []. + +-type b_blk() :: beam_ssa:b_blk(). +-type b_var() :: beam_ssa:b_var(). +-type label() :: beam_ssa:label(). + +-record(st, {ssa :: beam_ssa:block_map() | [{label(),b_blk()}], + args :: [b_var()], + cnt :: label()}). +-define(PASS(N), {N,fun N/1}). + +passes(Opts0) -> + Ps = [?PASS(ssa_opt_split_blocks), + ?PASS(ssa_opt_coalesce_phis), + ?PASS(ssa_opt_element), + ?PASS(ssa_opt_linearize), + ?PASS(ssa_opt_record), + + %% Run ssa_opt_cse twice, because it will help ssa_opt_dead, + %% and ssa_opt_dead will help ssa_opt_cse. Run ssa_opt_live + %% twice, because it will help ssa_opt_dead and ssa_opt_dead + %% will help ssa_opt_live. + ?PASS(ssa_opt_cse), + ?PASS(ssa_opt_type), + ?PASS(ssa_opt_live), + ?PASS(ssa_opt_dead), + ?PASS(ssa_opt_cse), %Second time. + ?PASS(ssa_opt_float), + ?PASS(ssa_opt_live), %Second time. + + ?PASS(ssa_opt_bsm), + ?PASS(ssa_opt_bsm_shortcut), + ?PASS(ssa_opt_misc), + ?PASS(ssa_opt_tuple_size), + ?PASS(ssa_opt_sw), + ?PASS(ssa_opt_blockify), + ?PASS(ssa_opt_sink), + ?PASS(ssa_opt_merge_blocks)], + Negations = [{list_to_atom("no_"++atom_to_list(N)),N} || + {N,_} <- Ps], + Opts = proplists:substitute_negations(Negations, Opts0), + [case proplists:get_value(Name, Opts, true) of + true -> + P; + false -> + {NoName,Name} = keyfind(Name, 2, Negations), + {NoName,fun(S) -> S end} + end || {Name,_}=P <- Ps]. + +function(#b_function{anno=Anno,bs=Blocks0,args=Args,cnt=Count0}=F, Ps) -> + try + St = #st{ssa=Blocks0,args=Args,cnt=Count0}, + #st{ssa=Blocks,cnt=Count} = compile:run_sub_passes(Ps, St), + F#b_function{bs=Blocks,cnt=Count} + catch + Class:Error:Stack -> + #{func_info:={_,Name,Arity}} = Anno, + io:fwrite("Function: ~w/~w\n", [Name,Arity]), + erlang:raise(Class, Error, Stack) + end. + +%%% +%%% Trivial sub passes. +%%% + +ssa_opt_dead(#st{ssa=Linear}=St) -> + St#st{ssa=beam_ssa_dead:opt(Linear)}. + +ssa_opt_linearize(#st{ssa=Blocks}=St) -> + St#st{ssa=beam_ssa:linearize(Blocks)}. + +ssa_opt_type(#st{ssa=Linear,args=Args}=St) -> + St#st{ssa=beam_ssa_type:opt(Linear, Args)}. + +ssa_opt_blockify(#st{ssa=Linear}=St) -> + St#st{ssa=maps:from_list(Linear)}. + +%%% +%%% Split blocks before certain instructions to enable more optimizations. +%%% +%%% Splitting before element/2 enables the optimization that swaps +%%% element/2 instructions. +%%% +%%% Splitting before call and make_fun instructions gives more opportunities +%%% for sinking get_tuple_element instructions. +%%% + +ssa_opt_split_blocks(#st{ssa=Blocks0,cnt=Count0}=St) -> + P = fun(#b_set{op={bif,element}}) -> true; + (#b_set{op=call}) -> true; + (#b_set{op=make_fun}) -> true; + (_) -> false + end, + {Blocks,Count} = beam_ssa:split_blocks(P, Blocks0, Count0), + St#st{ssa=Blocks,cnt=Count}. + +%%% +%%% Coalesce phi nodes. +%%% +%%% Nested cases can led to code such as this: +%%% +%%% 10: +%%% _1 = phi {literal value1, label 8}, {Var, label 9} +%%% br 11 +%%% +%%% 11: +%%% _2 = phi {_1, label 10}, {literal false, label 3} +%%% +%%% The phi nodes can be coalesced like this: +%%% +%%% 11: +%%% _2 = phi {literal value1, label 8}, {Var, label 9}, {literal false, label 3} +%%% +%%% Coalescing can help other optimizations, and can in some cases reduce register +%%% shuffling (if the phi variables for two phi nodes happens to be allocated to +%%% different registers). +%%% + +ssa_opt_coalesce_phis(#st{ssa=Blocks0}=St) -> + Ls = beam_ssa:rpo(Blocks0), + Blocks = c_phis_1(Ls, Blocks0), + St#st{ssa=Blocks}. + +c_phis_1([L|Ls], Blocks0) -> + case maps:get(L, Blocks0) of + #b_blk{is=[#b_set{op=phi}|_]}=Blk -> + Blocks = c_phis_2(L, Blk, Blocks0), + c_phis_1(Ls, Blocks); + #b_blk{} -> + c_phis_1(Ls, Blocks0) + end; +c_phis_1([], Blocks) -> Blocks. + +c_phis_2(L, #b_blk{is=Is0}=Blk0, Blocks0) -> + case c_phis_args(Is0, Blocks0) of + none -> + Blocks0; + {_,_,Preds}=Info -> + Is = c_rewrite_phis(Is0, Info), + Blk = Blk0#b_blk{is=Is}, + Blocks = Blocks0#{L:=Blk}, + c_fix_branches(Preds, L, Blocks) + end. + +c_phis_args([#b_set{op=phi,args=Args0}|Is], Blocks) -> + case c_phis_args_1(Args0, Blocks) of + none -> + c_phis_args(Is, Blocks); + Res -> + Res + end; +c_phis_args(_, _Blocks) -> none. + +c_phis_args_1([{Var,Pred}|As], Blocks) -> + case c_get_pred_vars(Var, Pred, Blocks) of + none -> + c_phis_args_1(As, Blocks); + Result -> + Result + end; +c_phis_args_1([], _Blocks) -> none. + +c_get_pred_vars(Var, Pred, Blocks) -> + case maps:get(Pred, Blocks) of + #b_blk{is=[#b_set{op=phi,dst=Var,args=Args}]} -> + {Var,Pred,Args}; + #b_blk{} -> + none + end. + +c_rewrite_phis([#b_set{op=phi,args=Args0}=I|Is], Info) -> + Args = c_rewrite_phi(Args0, Info), + [I#b_set{args=Args}|c_rewrite_phis(Is, Info)]; +c_rewrite_phis(Is, _Info) -> Is. + +c_rewrite_phi([{Var,Pred}|As], {Var,Pred,Values}) -> + Values ++ As; +c_rewrite_phi([{Value,Pred}|As], {_,Pred,Values}) -> + [{Value,P} || {_,P} <- Values] ++ As; +c_rewrite_phi([A|As], Info) -> + [A|c_rewrite_phi(As, Info)]; +c_rewrite_phi([], _Info) -> []. + +c_fix_branches([{_,Pred}|As], L, Blocks0) -> + #b_blk{last=Last0} = Blk0 = maps:get(Pred, Blocks0), + #b_br{bool=#b_literal{val=true}} = Last0, %Assertion. + Last = Last0#b_br{bool=#b_literal{val=true},succ=L,fail=L}, + Blk = Blk0#b_blk{last=Last}, + Blocks = Blocks0#{Pred:=Blk}, + c_fix_branches(As, L, Blocks); +c_fix_branches([], _, Blocks) -> Blocks. + +%%% +%%% Order element/2 calls. +%%% +%%% Order an unbroken chain of element/2 calls for the same tuple +%%% with the same failure label so that the highest element is +%%% retrieved first. That will allow the other element/2 calls to +%%% be replaced with get_tuple_element/3 instructions. +%%% + +ssa_opt_element(#st{ssa=Blocks}=St) -> + %% Collect the information about element instructions in this + %% function. + GetEls = collect_element_calls(beam_ssa:linearize(Blocks)), + + %% Collect the element instructions into chains. The + %% element calls in each chain are ordered in reverse + %% execution order. + Chains = collect_chains(GetEls, []), + + %% For each chain, swap the first element call with the + %% element call with the highest index. + St#st{ssa=swap_element_calls(Chains, Blocks)}. + +collect_element_calls([{L,#b_blk{is=Is0,last=Last}}|Bs]) -> + case {Is0,Last} of + {[#b_set{op={bif,element},dst=Element, + args=[#b_literal{val=N},#b_var{}=Tuple]}, + #b_set{op=succeeded,dst=Bool,args=[Element]}], + #b_br{bool=Bool,succ=Succ,fail=Fail}} -> + Info = {L,Succ,{Tuple,Fail},N}, + [Info|collect_element_calls(Bs)]; + {_,_} -> + collect_element_calls(Bs) + end; +collect_element_calls([]) -> []. + +collect_chains([{This,_,V,_}=El|Els], [{_,This,V,_}|_]=Chain) -> + %% Add to the previous chain. + collect_chains(Els, [El|Chain]); +collect_chains([El|Els], [_,_|_]=Chain) -> + %% Save the previous chain and start a new chain. + [Chain|collect_chains(Els, [El])]; +collect_chains([El|Els], _Chain) -> + %% The previous chain is too short; discard it and start a new. + collect_chains(Els, [El]); +collect_chains([], [_,_|_]=Chain) -> + %% Save the last chain. + [Chain]; +collect_chains([], _) -> []. + +swap_element_calls([[{L,_,_,N}|_]=Chain|Chains], Blocks0) -> + Blocks = swap_element_calls_1(Chain, {N,L}, Blocks0), + swap_element_calls(Chains, Blocks); +swap_element_calls([], Blocks) -> Blocks. + +swap_element_calls_1([{L1,_,_,N1}], {N2,L2}, Blocks) when N2 > N1 -> + %% We have reached the end of the chain, and the first + %% element instrution to be executed. Its index is lower + %% than the maximum index found while traversing the chain, + %% so we will need to swap the instructions. + #{L1:=Blk1,L2:=Blk2} = Blocks, + [#b_set{dst=Dst1}=GetEl1,Succ1] = Blk1#b_blk.is, + [#b_set{dst=Dst2}=GetEl2,Succ2] = Blk2#b_blk.is, + Is1 = [GetEl2,Succ1#b_set{args=[Dst2]}], + Is2 = [GetEl1,Succ2#b_set{args=[Dst1]}], + Blocks#{L1:=Blk1#b_blk{is=Is1},L2:=Blk2#b_blk{is=Is2}}; +swap_element_calls_1([{L,_,_,N1}|Els], {N2,_}, Blocks) when N1 > N2 -> + swap_element_calls_1(Els, {N2,L}, Blocks); +swap_element_calls_1([_|Els], Highest, Blocks) -> + swap_element_calls_1(Els, Highest, Blocks); +swap_element_calls_1([], _, Blocks) -> + %% Nothing to do. The element call with highest index + %% is already the first one to be executed. + Blocks. + +%%% +%%% Record optimization. +%%% +%%% Replace tuple matching with an is_tagged_tuple instruction +%%% when applicable. +%%% + +ssa_opt_record(#st{ssa=Linear}=St) -> + Blocks = maps:from_list(Linear), + St#st{ssa=record_opt(Linear, Blocks)}. + +record_opt([{L,#b_blk{is=Is0,last=Last}=Blk0}|Bs], Blocks) -> + Is = record_opt_is(Is0, Last, Blocks), + Blk = Blk0#b_blk{is=Is}, + [{L,Blk}|record_opt(Bs, Blocks)]; +record_opt([], _Blocks) -> []. + +record_opt_is([#b_set{op={bif,is_tuple},dst=#b_var{name=Bool}, + args=[Tuple]}=Set], + Last, Blocks) -> + case is_tagged_tuple(Tuple, Bool, Last, Blocks) of + {yes,Size,Tag} -> + Args = [Tuple,Size,Tag], + [Set#b_set{op=is_tagged_tuple,args=Args}]; + no -> + [Set] + end; +record_opt_is([I|Is], Last, Blocks) -> + [I|record_opt_is(Is, Last, Blocks)]; +record_opt_is([], _Last, _Blocks) -> []. + +is_tagged_tuple(#b_var{name=Tuple}, Bool, + #b_br{bool=#b_var{name=Bool},succ=Succ,fail=Fail}, + Blocks) -> + SuccBlk = maps:get(Succ, Blocks), + is_tagged_tuple_1(SuccBlk, Tuple, Fail, Blocks); +is_tagged_tuple(_, _, _, _) -> no. + +is_tagged_tuple_1(#b_blk{is=Is,last=Last}, Tuple, Fail, Blocks) -> + case Is of + [#b_set{op={bif,tuple_size},dst=#b_var{name=ArityVar}, + args=[#b_var{name=Tuple}]}, + #b_set{op={bif,'=:='}, + dst=#b_var{name=Bool}, + args=[#b_var{name=ArityVar}, + #b_literal{val=ArityVal}=Arity]}] + when is_integer(ArityVal) -> + case Last of + #b_br{bool=#b_var{name=Bool},succ=Succ,fail=Fail} -> + SuccBlk = maps:get(Succ, Blocks), + case is_tagged_tuple_2(SuccBlk, Tuple, Fail) of + no -> + no; + {yes,Tag} -> + {yes,Arity,Tag} + end; + _ -> + no + end; + _ -> + no + end. + +is_tagged_tuple_2(#b_blk{is=Is, + last=#b_br{bool=#b_var{name=Bool},fail=Fail}}, + Tuple, Fail) -> + is_tagged_tuple_3(Is, Bool, Tuple); +is_tagged_tuple_2(#b_blk{}, _, _) -> no. + +is_tagged_tuple_3([#b_set{op=get_tuple_element, + dst=#b_var{name=TagVar}, + args=[#b_var{name=Tuple},#b_literal{val=0}]}|Is], + Bool, Tuple) -> + is_tagged_tuple_4(Is, Bool, TagVar); +is_tagged_tuple_3([_|Is], Bool, Tuple) -> + is_tagged_tuple_3(Is, Bool, Tuple); +is_tagged_tuple_3([], _, _) -> no. + +is_tagged_tuple_4([#b_set{op={bif,'=:='},dst=#b_var{name=Bool}, + args=[#b_var{name=TagVar}, + #b_literal{val=TagVal}=Tag]}], + Bool, TagVar) when is_atom(TagVal) -> + {yes,Tag}; +is_tagged_tuple_4([_|Is], Bool, TagVar) -> + is_tagged_tuple_4(Is, Bool, TagVar); +is_tagged_tuple_4([], _, _) -> no. + +%%% +%%% Common subexpression elimination (CSE). +%%% +%%% Eliminate repeated evaluation of identical expressions. To avoid +%%% increasing the size of the stack frame, we don't eliminate +%%% subexpressions across instructions that clobber the X registers. +%%% + +ssa_opt_cse(#st{ssa=Linear}=St) -> + M = #{0=>#{}}, + St#st{ssa=cse(Linear, #{}, M)}. + +cse([{L,#b_blk{is=Is0,last=Last0}=Blk}|Bs], Sub0, M0) -> + Es0 = maps:get(L, M0), + {Is1,Es,Sub} = cse_is(Is0, Es0, Sub0, []), + Last = sub(Last0, Sub), + M = cse_successors(Is1, Blk, Es, M0), + Is = reverse(Is1), + [{L,Blk#b_blk{is=Is,last=Last}}|cse(Bs, Sub, M)]; +cse([], _, _) -> []. + +cse_successors([#b_set{op=succeeded,args=[Src]},Bif|_], Blk, EsSucc, M0) -> + case cse_suitable(Bif) of + true -> + %% The previous instruction only has a valid value at the success branch. + %% We must remove the substitution for Src from the failure branch. + #b_blk{last=#b_br{succ=Succ,fail=Fail}} = Blk, + M = cse_successors_1([Succ], EsSucc, M0), + EsFail = maps:filter(fun(_, Val) -> Val =/= Src end, EsSucc), + cse_successors_1([Fail], EsFail, M); + false -> + %% There can't be any replacement for Src in EsSucc. No need for + %% any special handling. + cse_successors_1(beam_ssa:successors(Blk), EsSucc, M0) + end; +cse_successors(_Is, Blk, Es, M) -> + cse_successors_1(beam_ssa:successors(Blk), Es, M). + +cse_successors_1([L|Ls], Es0, M) -> + case M of + #{L:=Es1} when map_size(Es1) =:= 0 -> + %% The map is already empty. No need to do anything + %% since the intersection will be empty. + cse_successors_1(Ls, Es0, M); + #{L:=Es1} -> + %% Calculate the intersection of the two maps. + %% Both keys and values must match. + Es = maps:filter(fun(Key, Value) -> + case Es1 of + #{Key:=Value} -> true; + #{} -> false + end + end, Es0), + cse_successors_1(Ls, Es0, M#{L:=Es}); + #{} -> + cse_successors_1(Ls, Es0, M#{L=>Es0}) + end; +cse_successors_1([], _, M) -> M. + +cse_is([#b_set{op=succeeded,dst=Bool,args=[Src]}=I0|Is], Es, Sub0, Acc) -> + I = sub(I0, Sub0), + case I of + #b_set{args=[Src]} -> + cse_is(Is, Es, Sub0, [I|Acc]); + #b_set{} -> + %% The previous instruction has been eliminated. Eliminate the + %% 'succeeded' instruction too. + Sub = Sub0#{Bool=>#b_literal{val=true}}, + cse_is(Is, Es, Sub, Acc) + end; +cse_is([#b_set{dst=Dst}=I0|Is], Es0, Sub0, Acc) -> + I = sub(I0, Sub0), + case beam_ssa:clobbers_xregs(I) of + true -> + %% Retaining the expressions map across calls and other + %% clobbering instructions would work, but it would cause + %% the common subexpressions to be saved to Y registers, + %% which would probably increase the size of the stack + %% frame. + cse_is(Is, #{}, Sub0, [I|Acc]); + false -> + case cse_expr(I) of + none -> + %% Not suitable for CSE. + cse_is(Is, Es0, Sub0, [I|Acc]); + {ok,ExprKey} -> + case Es0 of + #{ExprKey:=Src} -> + Sub = Sub0#{Dst=>Src}, + cse_is(Is, Es0, Sub, Acc); + #{} -> + Es = Es0#{ExprKey=>Dst}, + cse_is(Is, Es, Sub0, [I|Acc]) + end + end + end; +cse_is([], Es, Sub, Acc) -> + {Acc,Es,Sub}. + +cse_expr(#b_set{op=Op,args=Args}=I) -> + case cse_suitable(I) of + true -> {ok,{Op,Args}}; + false -> none + end. + +cse_suitable(#b_set{op=get_hd}) -> true; +cse_suitable(#b_set{op=get_tl}) -> true; +cse_suitable(#b_set{op=put_list}) -> true; +cse_suitable(#b_set{op=put_tuple}) -> true; +cse_suitable(#b_set{op={bif,tuple_size}}) -> + %% Doing CSE for tuple_size/1 can prevent the + %% creation of test_arity and select_tuple_arity + %% instructions. That could decrease performance + %% and beam_validator could fail to understand + %% that tuple operations that follow are safe. + false; +cse_suitable(#b_set{anno=Anno,op={bif,Name},args=Args}) -> + %% Doing CSE for floating point operators is unsafe. + %% Doing CSE for comparison operators would prevent + %% creation of 'test' instructions. + Arity = length(Args), + not (is_map_key(float_op, Anno) orelse + erl_internal:new_type_test(Name, Arity) orelse + erl_internal:comp_op(Name, Arity) orelse + erl_internal:bool_op(Name, Arity)); +cse_suitable(#b_set{}) -> false. + +%%% +%%% Using floating point instructions. +%%% +%%% Use the special floating points version of arithmetic +%%% instructions, if the operands are known to be floats or the result +%%% of the operation will be a float. +%%% +%%% The float instructions were never used in guards before, so we +%%% will take special care to keep not using them in guards. Using +%%% them in guards would require a new version of the 'fconv' +%%% instruction that would take a failure label. Since it is unlikely +%%% that using float instructions in guards would be benefical, why +%%% bother implementing a new instruction? Also, implementing float +%%% instructions in guards in HiPE could turn out to be a lot of work. +%%% + +-record(fs, + {s=undefined :: 'undefined' | 'cleared', + regs=#{} :: #{beam_ssa:b_var():=beam_ssa:b_var()}, + fail=none :: 'none' | beam_ssa:label(), + non_guards :: gb_sets:set(beam_ssa:label()), + bs :: beam_ssa:block_map() + }). + +ssa_opt_float(#st{ssa=Linear0,cnt=Count0}=St) -> + NonGuards0 = float_non_guards(Linear0), + NonGuards = gb_sets:from_list(NonGuards0), + Blocks = maps:from_list(Linear0), + Fs = #fs{non_guards=NonGuards,bs=Blocks}, + {Linear,Count} = float_opt(Linear0, Count0, Fs), + St#st{ssa=Linear,cnt=Count}. + +float_non_guards([{L,#b_blk{is=Is}}|Bs]) -> + case Is of + [#b_set{op=landingpad}|_] -> + [L|float_non_guards(Bs)]; + _ -> + float_non_guards(Bs) + end; +float_non_guards([]) -> [?BADARG_BLOCK]. + +float_opt([{L,#b_blk{last=#b_br{fail=F}}=Blk}|Bs0], + Count0, #fs{non_guards=NonGuards}=Fs) -> + case gb_sets:is_member(F, NonGuards) of + true -> + %% This block is not inside a guard. + %% We can do the optimization. + float_opt_1(L, Blk, Bs0, Count0, Fs); + false -> + %% This block is inside a guard. Don't do + %% any floating point optimizations. + {Bs,Count} = float_opt(Bs0, Count0, Fs), + {[{L,Blk}|Bs],Count} + end; +float_opt([{L,Blk}|Bs], Count, Fs) -> + float_opt_1(L, Blk, Bs, Count, Fs); +float_opt([], Count, _Fs) -> + {[],Count}. + +float_opt_1(L, #b_blk{is=Is0}=Blk0, Bs0, Count0, Fs0) -> + case float_opt_is(Is0, Fs0, Count0, []) of + {Is1,Fs1,Count1} -> + Fs2 = float_fail_label(Blk0, Fs1), + Fail = Fs2#fs.fail, + {Flush,Blk,Fs,Count2} = float_maybe_flush(Blk0, Fs2, Count1), + Split = float_split_conv(Is1, Blk), + {Blks0,Count3} = float_number(Split, L, Count2), + {Blks,Count4} = float_conv(Blks0, Fail, Count3), + {Bs,Count} = float_opt(Bs0, Count4, Fs), + {Blks++Flush++Bs,Count}; + none -> + {Bs,Count} = float_opt(Bs0, Count0, Fs0), + {[{L,Blk0}|Bs],Count} + end. + +%% Split {float,convert} instructions into individual blocks. +float_split_conv(Is0, Blk) -> + Br = #b_br{bool=#b_literal{val=true},succ=0,fail=0}, + case splitwith(fun(#b_set{op=Op}) -> + Op =/= {float,convert} + end, Is0) of + {Is,[]} -> + [Blk#b_blk{is=Is}]; + {[_|_]=Is1,[#b_set{op={float,convert}}=Conv|Is2]} -> + [#b_blk{is=Is1,last=Br}, + #b_blk{is=[Conv],last=Br}|float_split_conv(Is2, Blk)]; + {[],[#b_set{op={float,convert}}=Conv|Is1]} -> + [#b_blk{is=[Conv],last=Br}|float_split_conv(Is1, Blk)] + end. + +%% Number the blocks that were split. +float_number([B|Bs0], FirstL, Count0) -> + {Bs,Count} = float_number(Bs0, Count0), + {[{FirstL,B}|Bs],Count}. + +float_number([B|Bs0], Count0) -> + {Bs,Count} = float_number(Bs0, Count0+1), + {[{Count0,B}|Bs],Count}; +float_number([], Count) -> + {[],Count}. + +%% Insert 'succeeded' instructions after each {float,convert} +%% instruction. +float_conv([{L,#b_blk{is=Is0}=Blk0}|Bs0], Fail, Count0) -> + case Is0 of + [#b_set{op={float,convert}}=Conv] -> + {Bool0,Count1} = new_reg('@ssa_bool', Count0), + Bool = #b_var{name=Bool0}, + Succeeded = #b_set{op=succeeded,dst=Bool, + args=[Conv#b_set.dst]}, + Is = [Conv,Succeeded], + [{NextL,_}|_] = Bs0, + Br = #b_br{bool=Bool,succ=NextL,fail=Fail}, + Blk = Blk0#b_blk{is=Is,last=Br}, + {Bs,Count} = float_conv(Bs0, Fail, Count1), + {[{L,Blk}|Bs],Count}; + [_|_] -> + case Bs0 of + [{NextL,_}|_] -> + Br = #b_br{bool=#b_literal{val=true}, + succ=NextL,fail=NextL}, + Blk = Blk0#b_blk{last=Br}, + {Bs,Count} = float_conv(Bs0, Fail, Count0), + {[{L,Blk}|Bs],Count}; + [] -> + {[{L,Blk0}],Count0} + end + end. + +float_maybe_flush(Blk0, #fs{s=cleared,fail=Fail,bs=Blocks}=Fs0, Count0) -> + #b_blk{last=#b_br{bool=#b_var{},succ=Succ}=Br} = Blk0, + #b_blk{is=Is} = maps:get(Succ, Blocks), + case Is of + [#b_set{anno=#{float_op:=_}}|_] -> + %% The next operation is also a floating point operation. + %% No flush needed. + {[],Blk0,Fs0,Count0}; + _ -> + %% Flush needed. + {Bool0,Count1} = new_reg('@ssa_bool', Count0), + Bool = #b_var{name=Bool0}, + + %% Allocate block numbers. + CheckL = Count1, %For checkerror. + FlushL = Count1 + 1, %For flushing of float regs. + Count = Count1 + 2, + Blk = Blk0#b_blk{last=Br#b_br{succ=CheckL}}, + + %% Build the block with the checkerror instruction. + CheckIs = [#b_set{op={float,checkerror},dst=Bool}], + CheckBr = #b_br{bool=Bool,succ=FlushL,fail=Fail}, + CheckBlk = #b_blk{is=CheckIs,last=CheckBr}, + + %% Build the block that flushes all registers. + FlushIs = float_flush_regs(Fs0), + FlushBr = #b_br{bool=#b_literal{val=true},succ=Succ,fail=Succ}, + FlushBlk = #b_blk{is=FlushIs,last=FlushBr}, + + %% Update state and blocks. + Fs = Fs0#fs{s=undefined,regs=#{},fail=none}, + FlushBs = [{CheckL,CheckBlk},{FlushL,FlushBlk}], + {FlushBs,Blk,Fs,Count} + end; +float_maybe_flush(Blk, Fs, Count) -> + {[],Blk,Fs,Count}. + +float_opt_is([#b_set{op=succeeded,args=[Src]}=I0], + #fs{regs=Rs}=Fs, Count, Acc) -> + case Rs of + #{Src:=Fr} -> + I = I0#b_set{args=[Fr]}, + {reverse(Acc, [I]),Fs,Count}; + #{} -> + {reverse(Acc, [I0]),Fs,Count} + end; +float_opt_is([#b_set{anno=Anno0}=I0|Is0], Fs0, Count0, Acc) -> + case Anno0 of + #{float_op:=FTypes} -> + Anno = maps:remove(float_op, Anno0), + I1 = I0#b_set{anno=Anno}, + {Is,Fs,Count} = float_make_op(I1, FTypes, Fs0, Count0), + float_opt_is(Is0, Fs, Count, reverse(Is, Acc)); + #{} -> + float_opt_is(Is0, Fs0#fs{regs=#{}}, Count0, [I0|Acc]) + end; +float_opt_is([], Fs, _Count, _Acc) -> + #fs{s=undefined} = Fs, %Assertion. + none. + +float_make_op(#b_set{op={bif,Op},dst=Dst,args=As0}=I0, + Ts, #fs{s=S,regs=Rs0}=Fs, Count0) -> + {As1,Rs1,Count1} = float_load(As0, Ts, Rs0, Count0, []), + {As,Is0} = unzip(As1), + {Fr,Count2} = new_reg('@fr', Count1), + FrDst = #b_var{name=Fr}, + I = I0#b_set{op={float,Op},dst=FrDst,args=As}, + Rs = Rs1#{Dst=>FrDst}, + Is = append(Is0) ++ [I], + case S of + undefined -> + {Ignore,Count} = new_reg('@ssa_ignore', Count2), + C = #b_set{op={float,clearerror},dst=#b_var{name=Ignore}}, + {[C|Is],Fs#fs{s=cleared,regs=Rs},Count}; + cleared -> + {Is,Fs#fs{regs=Rs},Count2} + end. + +float_load([A|As], [T|Ts], Rs0, Count0, Acc) -> + {Load,Rs,Count} = float_reg_arg(A, T, Rs0, Count0), + float_load(As, Ts, Rs, Count, [Load|Acc]); +float_load([], [], Rs, Count, Acc) -> + {reverse(Acc),Rs,Count}. + +float_reg_arg(A, T, Rs, Count0) -> + case Rs of + #{A:=Fr} -> + {{Fr,[]},Rs,Count0}; + #{} -> + {Fr,Count} = new_float_copy_reg(Count0), + Dst = #b_var{name=Fr}, + I = float_load_reg(T, A, Dst), + {{Dst,[I]},Rs#{A=>Dst},Count} + end. + +float_load_reg(convert, #b_var{}=Src, Dst) -> + #b_set{op={float,convert},dst=Dst,args=[Src]}; +float_load_reg(convert, #b_literal{val=Val}=Src, Dst) -> + try float(Val) of + F -> + #b_set{op={float,put},dst=Dst,args=[#b_literal{val=F}]} + catch + error:_ -> + %% Let the exception happen at runtime. + #b_set{op={float,convert},dst=Dst,args=[Src]} + end; +float_load_reg(float, Src, Dst) -> + #b_set{op={float,put},dst=Dst,args=[Src]}. + +new_float_copy_reg(Count) -> + new_reg('@fr_copy', Count). + +new_reg(Base, Count) -> + Fr = {Base,Count}, + {Fr,Count+1}. + +float_fail_label(#b_blk{last=Last}, Fs) -> + case Last of + #b_br{bool=#b_var{},fail=Fail} -> + Fs#fs{fail=Fail}; + _ -> + Fs + end. + +float_flush_regs(#fs{regs=Rs}) -> + maps:fold(fun(_, #b_var{name={'@fr_copy',_}}, Acc) -> + Acc; + (Dst, Fr, Acc) -> + [#b_set{op={float,get},dst=Dst,args=[Fr]}|Acc] + end, [], Rs). + +%%% +%%% Live optimization. +%%% +%%% Optimize instructions whose values are not used. They could be +%%% removed if they have no side effects, or in a few cases replaced +%%% with a cheaper instructions +%%% + +ssa_opt_live(#st{ssa=Linear}=St) -> + St#st{ssa=live_opt(reverse(Linear), #{}, [])}. + +live_opt([{L,Blk0}|Bs], LiveMap0, Acc) -> + Successors = beam_ssa:successors(Blk0), + Live0 = live_opt_succ(Successors, L, LiveMap0), + {Blk,Live} = live_opt_blk(Blk0, Live0), + LiveMap = live_opt_phis(Blk#b_blk.is, L, Live, LiveMap0), + live_opt(Bs, LiveMap, [{L,Blk}|Acc]); +live_opt([], _, Acc) -> Acc. + +live_opt_succ([S|Ss], L, LiveMap) -> + Live0 = live_opt_succ(Ss, L, LiveMap), + Key = {S,L}, + case LiveMap of + #{Key:=Live} -> + gb_sets:union(Live, Live0); + #{S:=Live} -> + gb_sets:union(Live, Live0); + #{} -> + Live0 + end; +live_opt_succ([], _, _) -> + gb_sets:empty(). + +live_opt_phis(Is, L, Live0, LiveMap0) -> + LiveMap = LiveMap0#{L=>Live0}, + Phis = takewhile(fun(#b_set{op=Op}) -> Op =:= phi end, Is), + case Phis of + [] -> + LiveMap; + [_|_] -> + PhiArgs = append([Args || #b_set{args=Args} <- Phis]), + case [{P,V} || {#b_var{name=V},P} <- PhiArgs] of + [_|_]=PhiVars -> + PhiLive0 = rel2fam(PhiVars), + PhiLive = [{{L,P},gb_sets:union(gb_sets:from_list(Vs), Live0)} || + {P,Vs} <- PhiLive0], + maps:merge(LiveMap, maps:from_list(PhiLive)); + [] -> + %% There were only literals in the phi node(s). + LiveMap + end + end. + +live_opt_blk(#b_blk{is=Is0,last=Last}=Blk, Live0) -> + Live1 = gb_sets:union(Live0, gb_sets:from_ordset(beam_ssa:used(Last))), + {Is,Live} = live_opt_is(reverse(Is0), Live1, []), + {Blk#b_blk{is=Is},Live}. + +live_opt_is([#b_set{op=phi,dst=#b_var{name=Dst}}=I|Is], Live, Acc) -> + case gb_sets:is_member(Dst, Live) of + true -> + live_opt_is(Is, Live, [I|Acc]); + false -> + live_opt_is(Is, Live, Acc) + end; +live_opt_is([#b_set{op=succeeded,dst=#b_var{name=SuccDst}=SuccDstVar, + args=[#b_var{name=Dst}]}=SuccI, + #b_set{dst=#b_var{name=Dst}}=I|Is], Live0, Acc) -> + case gb_sets:is_member(Dst, Live0) of + true -> + case gb_sets:is_member(SuccDst, Live0) of + true -> + Live1 = gb_sets:add(Dst, Live0), + Live = gb_sets:delete_any(SuccDst, Live1), + live_opt_is([I|Is], Live, [SuccI|Acc]); + false -> + live_opt_is([I|Is], Live0, Acc) + end; + false -> + case live_opt_unused(I) of + {replace,NewI0} -> + NewI = NewI0#b_set{dst=SuccDstVar}, + live_opt_is([NewI|Is], Live0, Acc); + keep -> + case gb_sets:is_member(SuccDst, Live0) of + true -> + Live1 = gb_sets:add(Dst, Live0), + Live = gb_sets:delete_any(SuccDst, Live1), + live_opt_is([I|Is], Live, [SuccI|Acc]); + false -> + live_opt_is([I|Is], Live0, Acc) + end + end + end; +live_opt_is([#b_set{dst=#b_var{name=Dst}}=I|Is], Live0, Acc) -> + case gb_sets:is_member(Dst, Live0) of + true -> + Live1 = gb_sets:union(Live0, gb_sets:from_ordset(beam_ssa:used(I))), + Live = gb_sets:delete_any(Dst, Live1), + live_opt_is(Is, Live, [I|Acc]); + false -> + case beam_ssa:no_side_effect(I) of + true -> + live_opt_is(Is, Live0, Acc); + false -> + Live = gb_sets:union(Live0, gb_sets:from_ordset(beam_ssa:used(I))), + live_opt_is(Is, Live, [I|Acc]) + end + end; +live_opt_is([], Live, Acc) -> + {Acc,Live}. + +live_opt_unused(#b_set{op=get_map_element}=Set) -> + {replace,Set#b_set{op=has_map_field}}; +live_opt_unused(_) -> keep. + +%%% +%%% Optimize binary matching instructions. +%%% + +ssa_opt_bsm(#st{ssa=Linear}=St) -> + Extracted0 = bsm_extracted(Linear), + Extracted = cerl_sets:from_list(Extracted0), + St#st{ssa=bsm_skip(Linear, Extracted)}. + +bsm_skip([{L,#b_blk{is=Is0}=Blk}|Bs], Extracted) -> + Is = bsm_skip_is(Is0, Extracted), + [{L,Blk#b_blk{is=Is}}|bsm_skip(Bs, Extracted)]; +bsm_skip([], _) -> []. + +bsm_skip_is([I0|Is], Extracted) -> + case I0 of + #b_set{op=bs_match,args=[#b_literal{val=string}|_]} -> + [I0|bsm_skip_is(Is, Extracted)]; + #b_set{op=bs_match,dst=Ctx,args=[Type,PrevCtx|Args0]} -> + I = case cerl_sets:is_element(Ctx, Extracted) of + true -> + I0; + false -> + %% The value is never extracted. + Args = [#b_literal{val=skip},PrevCtx,Type|Args0], + I0#b_set{args=Args} + end, + [I|Is]; + #b_set{} -> + [I0|bsm_skip_is(Is, Extracted)] + end; +bsm_skip_is([], _) -> []. + +bsm_extracted([{_,#b_blk{is=Is}}|Bs]) -> + case Is of + [#b_set{op=bs_extract,args=[Ctx]}|_] -> + [Ctx|bsm_extracted(Bs)]; + _ -> + bsm_extracted(Bs) + end; +bsm_extracted([]) -> []. + +%%% +%%% Short-cutting binary matching instructions. +%%% + +ssa_opt_bsm_shortcut(#st{ssa=Linear}=St) -> + Positions = bsm_positions(Linear, #{}), + case map_size(Positions) of + 0 -> + %% No binary matching instructions. + St; + _ -> + St#st{ssa=bsm_shortcut(Linear, Positions)} + end. + +bsm_positions([{L,#b_blk{is=Is,last=Last}}|Bs], PosMap0) -> + PosMap = bsm_positions_is(Is, PosMap0), + case {Is,Last} of + {[#b_set{op=bs_test_tail,dst=Bool,args=[Ctx,#b_literal{val=Bits0}]}], + #b_br{bool=Bool,fail=Fail}} -> + Bits = Bits0 + maps:get(Ctx, PosMap0), + bsm_positions(Bs, PosMap#{L=>{Bits,Fail}}); + {_,_} -> + bsm_positions(Bs, PosMap) + end; +bsm_positions([], PosMap) -> PosMap. + +bsm_positions_is([#b_set{op=bs_start_match,dst=New}|Is], PosMap0) -> + PosMap = PosMap0#{New=>0}, + bsm_positions_is(Is, PosMap); +bsm_positions_is([#b_set{op=bs_match,dst=New,args=Args}|Is], PosMap0) -> + [_,Old|_] = Args, + #{Old:=Bits0} = PosMap0, + Bits = bsm_update_bits(Args, Bits0), + PosMap = PosMap0#{New=>Bits}, + bsm_positions_is(Is, PosMap); +bsm_positions_is([_|Is], PosMap) -> + bsm_positions_is(Is, PosMap); +bsm_positions_is([], PosMap) -> PosMap. + +bsm_update_bits([#b_literal{val=string},_,#b_literal{val=String}], Bits) -> + Bits + bit_size(String); +bsm_update_bits([#b_literal{val=utf8}|_], Bits) -> + Bits + 8; +bsm_update_bits([#b_literal{val=utf16}|_], Bits) -> + Bits + 16; +bsm_update_bits([#b_literal{val=utf32}|_], Bits) -> + Bits + 32; +bsm_update_bits([_,_,_,#b_literal{val=Sz},#b_literal{val=U}], Bits) + when is_integer(Sz) -> + Bits + Sz*U; +bsm_update_bits(_, Bits) -> Bits. + +bsm_shortcut([{L,#b_blk{is=Is,last=Last0}=Blk}|Bs], PosMap) -> + case {Is,Last0} of + {[#b_set{op=bs_match,dst=New,args=[_,Old|_]}, + #b_set{op=succeeded,dst=Bool,args=[New]}], + #b_br{bool=Bool,fail=Fail}} -> + case PosMap of + #{Old:=Bits,Fail:={TailBits,NextFail}} when Bits > TailBits -> + Last = Last0#b_br{fail=NextFail}, + [{L,Blk#b_blk{last=Last}}|bsm_shortcut(Bs, PosMap)]; + #{} -> + [{L,Blk}|bsm_shortcut(Bs, PosMap)] + end; + {_,_} -> + [{L,Blk}|bsm_shortcut(Bs, PosMap)] + end; +bsm_shortcut([], _PosMap) -> []. + +%%% +%%% Miscellanous optimizations in execution order. +%%% + +ssa_opt_misc(#st{ssa=Linear}=St) -> + St#st{ssa=misc_opt(Linear, #{})}. + +misc_opt([{L,#b_blk{is=Is0,last=Last0}=Blk0}|Bs], Sub0) -> + {Is,Sub} = misc_opt_is(Is0, Sub0, []), + Last = sub(Last0, Sub), + Blk = Blk0#b_blk{is=Is,last=Last}, + [{L,Blk}|misc_opt(Bs, Sub)]; +misc_opt([], _) -> []. + +misc_opt_is([#b_set{op=phi}=I0|Is], Sub0, Acc) -> + #b_set{dst=Dst,args=Args} = I = sub(I0, Sub0), + case all_same(Args) of + true -> + %% Eliminate the phi node if there is just one source + %% value or if the values are identical. + [{Val,_}|_] = Args, + Sub = Sub0#{Dst=>Val}, + misc_opt_is(Is, Sub, Acc); + false -> + misc_opt_is(Is, Sub0, [I|Acc]) + end; +misc_opt_is([#b_set{op={bif,'and'}}=I0], Sub, Acc) -> + #b_set{dst=Dst,args=Args} = I = sub(I0, Sub), + case eval_and(Args) of + error -> + misc_opt_is([], Sub, [I|Acc]); + Val -> + misc_opt_is([], Sub#{Dst=>Val}, Acc) + end; +misc_opt_is([#b_set{op={bif,'or'}}=I0], Sub, Acc) -> + #b_set{dst=Dst,args=Args} = I = sub(I0, Sub), + case eval_or(Args) of + error -> + misc_opt_is([], Sub, [I|Acc]); + Val -> + misc_opt_is([], Sub#{Dst=>Val}, Acc) + end; +misc_opt_is([#b_set{}=I0|Is], Sub, Acc) -> + #b_set{op=Op,dst=Dst,args=Args} = I = sub(I0, Sub), + case make_literal(Op, Args) of + #b_literal{}=Literal -> + misc_opt_is(Is, Sub#{Dst=>Literal}, Acc); + error -> + misc_opt_is(Is, Sub, [I|Acc]) + end; +misc_opt_is([], Sub, Acc) -> + {reverse(Acc),Sub}. + +all_same([{H,_}|T]) -> + all(fun({E,_}) -> E =:= H end, T). + +make_literal(put_tuple, Args) -> + case make_literal_list(Args, []) of + error -> + error; + List -> + #b_literal{val=list_to_tuple(List)} + end; +make_literal(put_list, [#b_literal{val=H},#b_literal{val=T}]) -> + #b_literal{val=[H|T]}; +make_literal(_, _) -> error. + +make_literal_list([#b_literal{val=H}|T], Acc) -> + make_literal_list(T, [H|Acc]); +make_literal_list([_|_], _) -> + error; +make_literal_list([], Acc) -> + reverse(Acc). + +eval_and(Args) -> + case Args of + [_,#b_literal{val=false}=Res] -> Res; + [Res,#b_literal{val=true}] -> Res; + [_,_] -> error + end. + +eval_or(Args) -> + case Args of + [Res,#b_literal{val=false}] -> Res; + [_,#b_literal{val=true}=Res] -> Res; + [_,_] -> error + end. + +%%% +%%% Optimize expressions such as "tuple_size(Var) =:= 2". +%%% +%%% Consider this code: +%%% +%%% 0: +%%% . +%%% . +%%% . +%%% Size = bif:tuple_size Var +%%% BoolVar1 = succeeded Size +%%% br BoolVar1, label 4, label 3 +%%% +%%% 4: +%%% BoolVar2 = bif:'=:=' Size, literal 2 +%%% br BoolVar2, label 6, label 3 +%%% +%%% 6: ... %% OK +%%% +%%% 3: ... %% Not a tuple of size 2 +%%% +%%% The BEAM code will look this: +%%% +%%% {bif,tuple_size,{f,3},[{x,0}],{x,0}}. +%%% {test,is_eq_exact,{f,3},[{x,0},{integer,2}]}. +%%% +%%% Better BEAM code will be produced if we transform the +%%% code like this: +%%% +%%% 0: +%%% . +%%% . +%%% . +%%% br label 10 +%%% +%%% 10: +%%% NewBoolVar = bif:is_tuple Var +%%% br NewBoolVar, label 11, label 3 +%%% +%%% 11: +%%% Size = bif:tuple_size Var +%%% br label 4 +%%% +%%% 4: +%%% BoolVar2 = bif:'=:=' Size, literal 2 +%%% br BoolVar2, label 6, label 3 +%%% +%%% (The key part of the transformation is the removal of +%%% the 'succeeded' instruction to signal to the code generator +%%% that the call to tuple_size/1 can't fail.) +%%% +%%% The BEAM code will look like: +%%% +%%% {test,is_tuple,{f,3},[{x,0}]}. +%%% {test_arity,{f,3},[{x,0},2]}. +%%% +%%% Those two instructions will be combined into a single +%%% is_tuple_of_arity instruction by the loader. +%%% + +ssa_opt_tuple_size(#st{ssa=Linear0,cnt=Count0}=St) -> + {Linear,Count} = opt_tup_size(Linear0, Count0, []), + St#st{ssa=Linear,cnt=Count}. + +opt_tup_size([{L,#b_blk{is=Is,last=Last}=Blk}|Bs], Count0, Acc0) -> + case {Is,Last} of + {[#b_set{op={bif,'=:='},dst=Bool,args=[#b_var{}=Tup,#b_literal{val=Arity}]}], + #b_br{bool=Bool}} when is_integer(Arity), Arity >= 0 -> + {Acc,Count} = opt_tup_size_1(Tup, L, Count0, Acc0), + opt_tup_size(Bs, Count, [{L,Blk}|Acc]); + {_,_} -> + opt_tup_size(Bs, Count0, [{L,Blk}|Acc0]) + end; +opt_tup_size([], Count, Acc) -> + {reverse(Acc),Count}. + +opt_tup_size_1(Size, EqL, Count0, [{L,Blk0}|Acc]) -> + case Blk0 of + #b_blk{is=Is0,last=#b_br{bool=Bool,succ=EqL,fail=Fail}} -> + case opt_tup_size_is(Is0, Bool, Size, []) of + none -> + {[{L,Blk0}|Acc],Count0}; + {PreIs,TupleSizeIs,Tuple} -> + opt_tup_size_2(PreIs, TupleSizeIs, L, EqL, + Tuple, Fail, Count0, Acc) + end; + #b_blk{} -> + {[{L,Blk0}|Acc],Count0} + end; +opt_tup_size_1(_, _, Count, Acc) -> + {Acc,Count}. + +opt_tup_size_2(PreIs, TupleSizeIs, PreL, EqL, Tuple, Fail, Count0, Acc) -> + IsTupleL = Count0, + TupleSizeL = Count0 + 1, + Bool = #b_var{name={'@ssa_bool',Count0+2}}, + Count = Count0 + 3, + + True = #b_literal{val=true}, + PreBr = #b_br{bool=True,succ=IsTupleL,fail=IsTupleL}, + PreBlk = #b_blk{is=PreIs,last=PreBr}, + + IsTupleIs = [#b_set{op={bif,is_tuple},dst=Bool,args=[Tuple]}], + IsTupleBr = #b_br{bool=Bool,succ=TupleSizeL,fail=Fail}, + IsTupleBlk = #b_blk{is=IsTupleIs,last=IsTupleBr}, + + TupleSizeBr = #b_br{bool=True,succ=EqL,fail=EqL}, + TupleSizeBlk = #b_blk{is=TupleSizeIs,last=TupleSizeBr}, + {[{TupleSizeL,TupleSizeBlk}, + {IsTupleL,IsTupleBlk}, + {PreL,PreBlk}|Acc],Count}. + +opt_tup_size_is([#b_set{op={bif,tuple_size},dst=Size,args=[Tuple]}=I, + #b_set{op=succeeded,dst=Bool,args=[Size]}], + Bool, Size, Acc) -> + {reverse(Acc),[I],Tuple}; +opt_tup_size_is([I|Is], Bool, Size, Acc) -> + opt_tup_size_is(Is, Bool, Size, [I|Acc]); +opt_tup_size_is([], _, _, _Acc) -> none. + +%%% +%%% Optimize #b_switch{} instructions. +%%% +%%% If the argument for a #b_switch{} comes from a phi node with all +%%% literals, any values in the switch list which are not in the phi +%%% node can be removed. +%%% +%%% If the values in the phi node and switch list are the same, +%%% the failure label can't be reached and be eliminated. +%%% +%%% A #b_switch{} with only one value can be rewritten to +%%% a #b_br{}. A switch that only verifies that the argument +%%% is 'true' or 'false' can be rewritten to a is_boolean test. +%%% + +ssa_opt_sw(#st{ssa=Linear0,cnt=Count0}=St) -> + {Linear,Count} = opt_sw(Linear0, #{}, Count0, []), + St#st{ssa=Linear,cnt=Count}. + +opt_sw([{L,#b_blk{is=Is,last=#b_switch{}=Last0}=Blk0}|Bs], Phis0, Count0, Acc) -> + Phis = opt_sw_phis(Is, Phis0), + case opt_sw_last(Last0, Phis) of + #b_switch{arg=Arg,fail=Fail,list=[{Lit,Lbl}]} -> + %% Rewrite a single value switch to a br. + Bool = #b_var{name={'@ssa_bool',Count0}}, + Count = Count0 + 1, + IsEq = #b_set{op={bif,'=:='},dst=Bool,args=[Arg,Lit]}, + Br = #b_br{bool=Bool,succ=Lbl,fail=Fail}, + Blk = Blk0#b_blk{is=Is++[IsEq],last=Br}, + opt_sw(Bs, Phis, Count, [{L,Blk}|Acc]); + #b_switch{arg=Arg,fail=Fail, + list=[{#b_literal{val=B1},Lbl},{#b_literal{val=B2},Lbl}]} + when B1 =:= not B2 -> + %% Replace with is_boolean test. + Bool = #b_var{name={'@ssa_bool',Count0}}, + Count = Count0 + 1, + IsBool = #b_set{op={bif,is_boolean},dst=Bool,args=[Arg]}, + Br = #b_br{bool=Bool,succ=Lbl,fail=Fail}, + Blk = Blk0#b_blk{is=Is++[IsBool],last=Br}, + opt_sw(Bs, Phis, Count, [{L,Blk}|Acc]); + Last0 -> + opt_sw(Bs, Phis, Count0, [{L,Blk0}|Acc]); + Last -> + Blk = Blk0#b_blk{last=Last}, + opt_sw(Bs, Phis, Count0, [{L,Blk}|Acc]) + end; +opt_sw([{L,#b_blk{is=Is}=Blk}|Bs], Phis0, Count, Acc) -> + Phis = opt_sw_phis(Is, Phis0), + opt_sw(Bs, Phis, Count, [{L,Blk}|Acc]); +opt_sw([], _Phis, Count, Acc) -> + {reverse(Acc),Count}. + +opt_sw_phis([#b_set{op=phi,dst=Dst,args=Args}|Is], Phis) -> + case opt_sw_literals(Args, []) of + error -> + opt_sw_phis(Is, Phis); + Literals -> + opt_sw_phis(Is, Phis#{Dst=>Literals}) + end; +opt_sw_phis(_, Phis) -> Phis. + +opt_sw_last(#b_switch{arg=Arg,fail=Fail,list=List0}=Sw0, Phis) -> + case Phis of + #{Arg:=Values0} -> + Values = gb_sets:from_list(Values0), + + %% Prune the switch list to only contain the possible values. + List1 = [P || {Lit,_}=P <- List0, gb_sets:is_member(Lit, Values)], + + %% Now test whether the failure label can ever be reached. + Sw = case gb_sets:size(Values) =:= length(List1) of + true -> + %% The switch list has the same number of values as the phi node. + %% The values must be the same, because the values that were not + %% possible were pruned from the switch list. Therefore, the + %% failure label can't possibly be reached, and we can choose a + %% a new failure label by picking a value from the list. + case List1 of + [{#b_literal{},Lbl}|List] -> + Sw0#b_switch{fail=Lbl,list=List}; + [] -> + Sw0#b_switch{list=List1} + end; + false -> + %% There are some values in the phi node that are not in the + %% switch list; thus, the failure label can still be reached. + Sw0 + end, + beam_ssa:normalize(Sw); + #{} -> + %% Ensure that no label in the switch list is the same + %% as the failure label. + List = [{Val,Lbl} || {Val,Lbl} <- List0, Lbl =/= Fail], + Sw = Sw0#b_switch{list=List}, + beam_ssa:normalize(Sw) + end. + +opt_sw_literals([{#b_literal{}=Lit,_}|T], Acc) -> + opt_sw_literals(T, [Lit|Acc]); +opt_sw_literals([_|_], _Acc) -> + error; +opt_sw_literals([], Acc) -> Acc. + + +%%% +%%% Merge blocks. +%%% + +ssa_opt_merge_blocks(#st{ssa=Blocks}=St) -> + Preds = beam_ssa:predecessors(Blocks), + St#st{ssa=merge_blocks_1(beam_ssa:rpo(Blocks), Preds, Blocks)}. + +merge_blocks_1([L|Ls], Preds0, Blocks0) -> + case Preds0 of + #{L:=[P]} -> + #{P:=Blk0,L:=Blk1} = Blocks0, + case is_merge_allowed(L, Blk0, Blk1) of + true -> + #b_blk{is=Is0} = Blk0, + #b_blk{is=Is1} = Blk1, + Is = Is0 ++ Is1, + Blk = Blk1#b_blk{is=Is}, + Blocks1 = maps:remove(L, Blocks0), + Blocks2 = maps:put(P, Blk, Blocks1), + Successors = beam_ssa:successors(Blk), + Blocks = beam_ssa:update_phi_labels(Successors, L, P, Blocks2), + Preds = merge_update_preds(Successors, L, P, Preds0), + merge_blocks_1(Ls, Preds, Blocks); + false -> + merge_blocks_1(Ls, Preds0, Blocks0) + end; + #{} -> + merge_blocks_1(Ls, Preds0, Blocks0) + end; +merge_blocks_1([], _Preds, Blocks) -> Blocks. + +merge_update_preds([L|Ls], From, To, Preds0) -> + Ps = [rename_label(P, From, To) || P <- maps:get(L, Preds0)], + Preds = maps:put(L, Ps, Preds0), + merge_update_preds(Ls, From, To, Preds); +merge_update_preds([], _, _, Preds) -> Preds. + +rename_label(From, From, To) -> To; +rename_label(Lbl, _, _) -> Lbl. + +is_merge_allowed(_, _, #b_blk{is=[#b_set{op=peek_message}|_]}) -> + false; +is_merge_allowed(L, Blk0, #b_blk{}) -> + case beam_ssa:successors(Blk0) of + [L] -> true; + [_|_] -> false + end. + +%%% +%%% When a tuple is matched, the pattern matching compiler generates a +%%% get_tuple_element instruction for every tuple element that will +%%% ever be used in the rest of the function. That often forces the +%%% extracted tuple elements to be stored in Y registers until it's +%%% time to use them. It could also mean that there could be execution +%%% paths that will never use the extracted elements. +%%% +%%% This optimization will sink get_tuple_element instructions, that +%%% is, move them forward in the execution stream to the last possible +%%% block there they will still dominate all uses. That may reduce the +%%% size of stack frames, reduce register shuffling, and avoid +%%% extracting tuple elements on execution paths that never use the +%%% extracted values. +%%% + +ssa_opt_sink(#st{ssa=Blocks0}=St) -> + Linear = beam_ssa:linearize(Blocks0), + + %% Create a map with all variables that define get_tuple_element + %% instructions. The variable name map to the block it is defined in. + Defs = maps:from_list(def_blocks(Linear)), + + %% Now find all the blocks that use variables defined by get_tuple_element + %% instructions. + Used = used_blocks(Linear, Defs, []), + + %% Calculate dominators. + Dom0 = beam_ssa:dominators(Blocks0), + + %% It is not safe to move get_tuple_element instructions to blocks + %% that begin with certain instructions. It is also unsafe to move + %% the instructions into any part of a receive. To avoid such + %% unsafe moves, pretend that the unsuitable blocks are not + %% dominators. + Unsuitable = unsuitable(Linear, Blocks0), + Dom = case gb_sets:is_empty(Unsuitable) of + true -> + Dom0; + false -> + F = fun(_, DomBy) -> + [L || L <- DomBy, + not gb_sets:is_element(L, Unsuitable)] + end, + maps:map(F, Dom0) + end, + + %% Calculate new positions for get_tuple_element instructions. The new + %% position is a block that dominates all uses of the variable. + DefLoc = new_def_locations(Used, Defs, Dom), + + %% Now move all suitable get_tuple_element instructions to their + %% new blocks. + Blocks = foldl(fun({V,To}, A) -> + From = maps:get(V, Defs), + move_defs(V, From, To, A) + end, Blocks0, DefLoc), + St#st{ssa=Blocks}. + +def_blocks([{L,#b_blk{is=Is}}|Bs]) -> + def_blocks_is(Is, L, def_blocks(Bs)); +def_blocks([]) -> []. + +def_blocks_is([#b_set{op=get_tuple_element,dst=#b_var{name=Dst}}|Is], L, Acc) -> + def_blocks_is(Is, L, [{Dst,L}|Acc]); +def_blocks_is([_|Is], L, Acc) -> + def_blocks_is(Is, L, Acc); +def_blocks_is([], _, Acc) -> Acc. + +used_blocks([{L,Blk}|Bs], Def, Acc0) -> + Used = beam_ssa:used(Blk), + Acc = [{V,L} || V <- Used, maps:is_key(V, Def)] ++ Acc0, + used_blocks(Bs, Def, Acc); +used_blocks([], _Def, Acc) -> + rel2fam(Acc). + +%% unsuitable(Linear, Blocks) -> Unsuitable. +%% Return an ordset of block labels for the blocks that are not +%% suitable for sinking of get_tuple_element instructions. + +unsuitable(Linear, Blocks) -> + Predecessors = beam_ssa:predecessors(Blocks), + Unsuitable0 = unsuitable_1(Linear), + Unsuitable1 = unsuitable_recv(Linear, Blocks, Predecessors), + gb_sets:from_list(Unsuitable0 ++ Unsuitable1). + +unsuitable_1([{L,#b_blk{is=[#b_set{op=Op}|_]}}|Bs]) -> + Unsuitable = case Op of + bs_extract -> true; + bs_put -> true; + {float,_} -> true; + landingpad -> true; + peek_message -> true; + wait_timeout -> true; + _ -> false + end, + case Unsuitable of + true -> + [L|unsuitable_1(Bs)]; + false -> + unsuitable_1(Bs) + end; +unsuitable_1([{_,#b_blk{}}|Bs]) -> + unsuitable_1(Bs); +unsuitable_1([]) -> []. + +unsuitable_recv([{L,#b_blk{is=[#b_set{op=Op}|_]}}|Bs], Blocks, Predecessors) -> + Ls = case Op of + remove_message -> + unsuitable_loop(L, Blocks, Predecessors); + recv_next -> + unsuitable_loop(L, Blocks, Predecessors); + _ -> + [] + end, + Ls ++ unsuitable_recv(Bs, Blocks, Predecessors); +unsuitable_recv([_|Bs], Blocks, Predecessors) -> + unsuitable_recv(Bs, Blocks, Predecessors); +unsuitable_recv([], _, _) -> []. + +unsuitable_loop(L, Blocks, Predecessors) -> + unsuitable_loop(L, Blocks, Predecessors, []). + +unsuitable_loop(L, Blocks, Predecessors, Acc) -> + Ps = maps:get(L, Predecessors), + unsuitable_loop_1(Ps, Blocks, Predecessors, Acc). + +unsuitable_loop_1([P|Ps], Blocks, Predecessors, Acc0) -> + case maps:get(P, Blocks) of + #b_blk{is=[#b_set{op=peek_message}|_]} -> + unsuitable_loop_1(Ps, Blocks, Predecessors, Acc0); + #b_blk{} -> + case ordsets:is_element(P, Acc0) of + false -> + Acc1 = ordsets:add_element(P, Acc0), + Acc = unsuitable_loop(P, Blocks, Predecessors, Acc1), + unsuitable_loop_1(Ps, Blocks, Predecessors, Acc); + true -> + unsuitable_loop_1(Ps, Blocks, Predecessors, Acc0) + end + end; +unsuitable_loop_1([], _, _, Acc) -> Acc. + +%% new_def_locations([{Variable,[UsedInBlock]}|Vs], Defs, Dominators) -> +%% [{Variable,NewDefinitionBlock}] +%% Calculate new locations for get_tuple_element instructions. For each +%% variable, the new location is a block that dominates all uses of +%% variable and as near to the uses of as possible. If no such block +%% distinct from the block where the instruction currently is, the +%% variable will not be included in the result list. + +new_def_locations([{V,UsedIn}|Vs], Defs, Dom) -> + DefIn = maps:get(V, Defs), + case common_dom(UsedIn, DefIn, Dom) of + [] -> + new_def_locations(Vs, Defs, Dom); + [_|_]=BetterDef -> + L = most_dominated(BetterDef, Dom), + [{V,L}|new_def_locations(Vs, Defs, Dom)] + end; +new_def_locations([], _, _) -> []. + +common_dom([L|Ls], DefIn, Dom) -> + DomBy0 = maps:get(L, Dom), + DomBy = ordsets:subtract(DomBy0, maps:get(DefIn, Dom)), + common_dom_1(Ls, Dom, DomBy). + +common_dom_1(_, _, []) -> + []; +common_dom_1([L|Ls], Dom, [_|_]=DomBy0) -> + DomBy1 = maps:get(L, Dom), + DomBy = ordsets:intersection(DomBy0, DomBy1), + common_dom_1(Ls, Dom, DomBy); +common_dom_1([], _, DomBy) -> DomBy. + +most_dominated([L|Ls], Dom) -> + most_dominated(Ls, L, maps:get(L, Dom), Dom). + +most_dominated([L|Ls], L0, DomBy, Dom) -> + case member(L, DomBy) of + true -> + most_dominated(Ls, L0, DomBy, Dom); + false -> + most_dominated(Ls, L, maps:get(L, Dom), Dom) + end; +most_dominated([], L, _, _) -> L. + + +%% Move get_tuple_element instructions to their new locations. + +move_defs(V, From, To, Blocks) -> + #{From:=FromBlk0,To:=ToBlk0} = Blocks, + {Def,FromBlk} = remove_def(V, FromBlk0), + try insert_def(V, Def, ToBlk0) of + ToBlk -> + %%io:format("~p: ~p => ~p\n", [V,From,To]), + Blocks#{From:=FromBlk,To:=ToBlk} + catch + throw:not_possible -> + Blocks + end. + +remove_def(V, #b_blk{is=Is0}=Blk) -> + {Def,Is} = remove_def_is(Is0, V, []), + {Def,Blk#b_blk{is=Is}}. + +remove_def_is([#b_set{dst=#b_var{name=Dst}}=Def|Is], Dst, Acc) -> + {Def,reverse(Acc, Is)}; +remove_def_is([I|Is], Dst, Acc) -> + remove_def_is(Is, Dst, [I|Acc]). + +insert_def(V, Def, #b_blk{is=Is0}=Blk) -> + Is = insert_def_is(Is0, V, Def), + Blk#b_blk{is=Is}. + +insert_def_is([#b_set{op=phi}=I|Is], V, Def) -> + case member(V, beam_ssa:used(I)) of + true -> + throw(not_possible); + false -> + [I|insert_def_is(Is, V, Def)] + end; +insert_def_is([#b_set{op=Op}=I|Is]=Is0, V, Def) -> + Action0 = case Op of + call -> beyond; + 'catch_end' -> beyond; + set_tuple_element -> beyond; + timeout -> beyond; + _ -> here + end, + Action = case Is of + [#b_set{op=succeeded}|_] -> here; + _ -> Action0 + end, + case Action of + beyond -> + case member(V, beam_ssa:used(I)) of + true -> + %% The variable is used by this instruction. We must + %% place the definition before this instruction. + [Def|Is0]; + false -> + %% Place it beyond the current instruction. + [I|insert_def_is(Is, V, Def)] + end; + here -> + [Def|Is0] + end; +insert_def_is([], _V, Def) -> + [Def]. + + +%%% +%%% Common utilities. +%%% + +rel2fam(S0) -> + S1 = sofs:relation(S0), + S = sofs:rel2fam(S1), + sofs:to_external(S). + +sub(I, Sub) -> + beam_ssa:normalize(sub_1(I, Sub)). + +sub_1(#b_set{op=phi,args=Args}=I, Sub) -> + I#b_set{args=[{sub_arg(A, Sub),P} || {A,P} <- Args]}; +sub_1(#b_set{args=Args}=I, Sub) -> + I#b_set{args=[sub_arg(A, Sub) || A <- Args]}; +sub_1(#b_br{bool=#b_var{}=Old}=Br, Sub) -> + New = sub_arg(Old, Sub), + Br#b_br{bool=New}; +sub_1(#b_switch{arg=#b_var{}=Old}=Sw, Sub) -> + New = sub_arg(Old, Sub), + Sw#b_switch{arg=New}; +sub_1(#b_ret{arg=#b_var{}=Old}=Ret, Sub) -> + New = sub_arg(Old, Sub), + Ret#b_ret{arg=New}; +sub_1(Last, _) -> Last. + +sub_arg(#b_remote{mod=Mod,name=Name}=Rem, Sub) -> + Rem#b_remote{mod=sub_arg(Mod, Sub),name=sub_arg(Name, Sub)}; +sub_arg(Old, Sub) -> + case Sub of + #{Old:=New} -> New; + #{} -> Old + end. |