From 09112806c15a81be86730503af36e304ac11d1ed Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Wed, 7 Jun 2017 14:27:15 +0200 Subject: Fix unsafe bit syntax matching optimization As part of sys_core_fold, variables involved in bit syntax matching would be annotated when it would be safe for a later pass to do the delayed sub-binary creation optimization. An implicit assumption regarding the annotation was that the code must not be further optimized. That assumption was broken in 05130e48555891, which introduced a fixpoint iteration (applying the optimizations until there were no more changes). That means that a variable could be annotated as safe for reusing the match context in one iteration, but a later iteration could rewrite the code in a way that would make the optimization unsafe. One way to fix this would be to clear all reuse_for_context annotations before each iteration. But that would be wasteful. Instead I chose to fix the problem by moving out the annotation code to a separate pass (sys_core_bsm) that is run later after all major optimizations of Core Erlang has been done. --- lib/compiler/src/sys_core_fold.erl | 297 +------------------------------------ 1 file changed, 6 insertions(+), 291 deletions(-) (limited to 'lib/compiler/src/sys_core_fold.erl') diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl index 3673a339f6..cbf6e256f7 100644 --- a/lib/compiler/src/sys_core_fold.erl +++ b/lib/compiler/src/sys_core_fold.erl @@ -71,7 +71,7 @@ -export([module/2,format_error/1]). -import(lists, [map/2,foldl/3,foldr/3,mapfoldl/3,all/2,any/2, - reverse/1,reverse/2,member/2,nth/2,flatten/1, + reverse/1,reverse/2,member/2,flatten/1, unzip/1,keyfind/3]). -import(cerl, [ann_c_cons/3,ann_c_map/3,ann_c_tuple/2]). @@ -107,7 +107,6 @@ {'ok', cerl:c_module(), [_]}. module(#c_module{defs=Ds0}=Mod, Opts) -> - put(bin_opt_info, member(bin_opt_info, Opts)), put(no_inline_list_funcs, not member(inline_list_funcs, Opts)), case get(new_var_num) of undefined -> put(new_var_num, 0); @@ -116,7 +115,6 @@ module(#c_module{defs=Ds0}=Mod, Opts) -> init_warnings(), Ds1 = [function_1(D) || D <- Ds0], erase(no_inline_list_funcs), - erase(bin_opt_info), {ok,Mod#c_module{defs=Ds1},get_warnings()}. function_1({#c_var{name={F,Arity}}=Name,B0}) -> @@ -383,10 +381,8 @@ expr(#c_case{}=Case0, Ctxt, Sub) -> warn_no_clause_match(Case1, Case), Expr = eval_case(Case, Sub), case move_case_into_arg(Case, Sub) of - impossible -> - bsm_an(Expr); - Other -> - Other + impossible -> Expr; + Other -> Other end; Other -> expr(Other, Ctxt, Sub) @@ -2943,15 +2939,8 @@ update_types(Expr, Pat, #sub{t=Tdb0}=Sub) -> Tdb = update_types_1(Expr, Pat, Tdb0), Sub#sub{t=Tdb}. -update_types_1(#c_var{name=V,anno=Anno}, Pat, Types) -> - case member(reuse_for_context, Anno) of - true -> - %% If a variable has been marked for reuse of binary context, - %% optimizations based on type information are unsafe. - kill_types(V, Types); - false -> - update_types_2(V, Pat, Types) - end; +update_types_1(#c_var{name=V}, Pat, Types) -> + update_types_2(V, Pat, Types); update_types_1(_, _, Types) -> Types. update_types_2(V, [#c_tuple{}=P], Types) -> @@ -2994,253 +2983,6 @@ copy_type(_, _, Tdb) -> Tdb. void() -> #c_literal{val=ok}. -%%% -%%% Annotate bit syntax matching to faciliate optimization in further passes. -%%% - -bsm_an(#c_case{arg=#c_var{}=V}=Case) -> - bsm_an_1([V], Case); -bsm_an(#c_case{arg=#c_values{es=Es}}=Case) -> - bsm_an_1(Es, Case); -bsm_an(Other) -> Other. - -bsm_an_1(Vs, #c_case{clauses=Cs}=Case) -> - case bsm_leftmost(Cs) of - none -> Case; - Pos -> bsm_an_2(Vs, Cs, Case, Pos) - end. - -bsm_an_2(Vs, Cs, Case, Pos) -> - case bsm_nonempty(Cs, Pos) of - true -> bsm_an_3(Vs, Cs, Case, Pos); - false -> Case - end. - -bsm_an_3(Vs, Cs, Case, Pos) -> - try - bsm_ensure_no_partition(Cs, Pos), - bsm_do_an(Vs, Pos, Cs, Case) - catch - throw:{problem,Where,What} -> - add_bin_opt_info(Where, What), - Case - end. - -bsm_do_an(Vs0, Pos, Cs0, Case) -> - case nth(Pos, Vs0) of - #c_var{name=Vname}=V0 -> - Cs = bsm_do_an_var(Vname, Pos, Cs0, []), - V = bsm_annotate_for_reuse(V0), - Bef = lists:sublist(Vs0, Pos-1), - Aft = lists:nthtail(Pos, Vs0), - case Bef ++ [V|Aft] of - [_] -> - Case#c_case{arg=V,clauses=Cs}; - Vs -> - Case#c_case{arg=#c_values{es=Vs},clauses=Cs} - end; - _ -> - Case - end. - -bsm_do_an_var(V, S, [#c_clause{pats=Ps,guard=G,body=B0}=C0|Cs], Acc) -> - case nth(S, Ps) of - #c_var{name=VarName} -> - case core_lib:is_var_used(V, G) of - true -> bsm_problem(C0, orig_bin_var_used_in_guard); - false -> ok - end, - case core_lib:is_var_used(VarName, G) of - true -> bsm_problem(C0, bin_var_used_in_guard); - false -> ok - end, - B1 = bsm_maybe_ctx_to_binary(VarName, B0), - B = bsm_maybe_ctx_to_binary(V, B1), - C = C0#c_clause{body=B}, - bsm_do_an_var(V, S, Cs, [C|Acc]); - #c_alias{}=P -> - case bsm_could_match_binary(P) of - false -> - bsm_do_an_var(V, S, Cs, [C0|Acc]); - true -> - bsm_problem(C0, bin_opt_alias) - end; - P -> - case bsm_could_match_binary(P) andalso bsm_is_var_used(V, G, B0) of - false -> - bsm_do_an_var(V, S, Cs, [C0|Acc]); - true -> - bsm_problem(C0, bin_var_used) - end - end; -bsm_do_an_var(_, _, [], Acc) -> reverse(Acc). - -bsm_annotate_for_reuse(#c_var{anno=Anno}=Var) -> - case member(reuse_for_context, Anno) of - false -> Var#c_var{anno=[reuse_for_context|Anno]}; - true -> Var - end. - -bsm_is_var_used(V, G, B) -> - core_lib:is_var_used(V, G) orelse core_lib:is_var_used(V, B). - -bsm_maybe_ctx_to_binary(V, B) -> - case core_lib:is_var_used(V, B) andalso not previous_ctx_to_binary(V, B) of - false -> - B; - true -> - #c_seq{arg=#c_primop{name=#c_literal{val=bs_context_to_binary}, - args=[#c_var{name=V}]}, - body=B} - end. - -previous_ctx_to_binary(V, Core) -> - case Core of - #c_seq{arg=#c_primop{name=#c_literal{val=bs_context_to_binary}, - args=[#c_var{name=V}]}} -> - true; - _ -> - false - end. - -%% bsm_leftmost(Cs) -> none | ArgumentNumber -%% Find the leftmost argument that does binary matching. Return -%% the number of the argument (1-N). - -bsm_leftmost(Cs) -> - bsm_leftmost_1(Cs, none). - -bsm_leftmost_1([#c_clause{pats=Ps}|Cs], Pos) -> - bsm_leftmost_2(Ps, Cs, 1, Pos); -bsm_leftmost_1([], Pos) -> Pos. - -bsm_leftmost_2(_, Cs, Pos, Pos) -> - bsm_leftmost_1(Cs, Pos); -bsm_leftmost_2([#c_binary{}|_], Cs, N, _) -> - bsm_leftmost_1(Cs, N); -bsm_leftmost_2([_|Ps], Cs, N, Pos) -> - bsm_leftmost_2(Ps, Cs, N+1, Pos); -bsm_leftmost_2([], Cs, _, Pos) -> - bsm_leftmost_1(Cs, Pos). - -%% bsm_nonempty(Cs, Pos) -> true|false -%% Check if at least one of the clauses matches a non-empty -%% binary in the given argument position. -%% -bsm_nonempty([#c_clause{pats=Ps}|Cs], Pos) -> - case nth(Pos, Ps) of - #c_binary{segments=[_|_]} -> - true; - _ -> - bsm_nonempty(Cs, Pos) - end; -bsm_nonempty([], _ ) -> false. - -%% bsm_ensure_no_partition(Cs, Pos) -> ok (exception if problem) -%% We must make sure that matching is not partitioned between -%% variables like this: -%% foo(<<...>>) -> ... -%% foo() when ... -> ... -%% foo() -> -%% If there is such partition, we are not allowed to reuse the binary variable -%% for the match context. -%% -%% Also, arguments to the left of the argument that is matched -%% against a binary, are only allowed to be simple variables, not -%% used in guards. The reason is that we must know that the binary is -%% only matched in one place (i.e. there must be only one bs_start_match2 -%% instruction emitted). - -bsm_ensure_no_partition(Cs, Pos) -> - bsm_ensure_no_partition_1(Cs, Pos, before). - -%% Loop through each clause. -bsm_ensure_no_partition_1([#c_clause{pats=Ps,guard=G}|Cs], Pos, State0) -> - State = bsm_ensure_no_partition_2(Ps, Pos, G, simple_vars, State0), - case State of - 'after' -> - bsm_ensure_no_partition_after(Cs, Pos); - _ -> - ok - end, - bsm_ensure_no_partition_1(Cs, Pos, State); -bsm_ensure_no_partition_1([], _, _) -> ok. - -%% Loop through each pattern for this clause. -bsm_ensure_no_partition_2([#c_binary{}=Where|_], 1, _, Vstate, State) -> - case State of - before when Vstate =:= simple_vars -> within; - before -> bsm_problem(Where, Vstate); - within when Vstate =:= simple_vars -> within; - within -> bsm_problem(Where, Vstate) - end; -bsm_ensure_no_partition_2([#c_alias{}=Alias|_], 1, N, Vstate, State) -> - %% Retrieve the real pattern that the alias refers to and check that. - P = bsm_real_pattern(Alias), - bsm_ensure_no_partition_2([P], 1, N, Vstate, State); -bsm_ensure_no_partition_2([_|_], 1, _, _Vstate, before=State) -> - %% No binary matching yet - therefore no partition. - State; -bsm_ensure_no_partition_2([P|_], 1, _, Vstate, State) -> - case bsm_could_match_binary(P) of - false -> - %% If clauses can be freely arranged (Vstate =:= simple_vars), - %% a clause that cannot match a binary will not partition the clause. - %% Example: - %% - %% a(Var, <<>>) -> ... - %% a(Var, []) -> ... - %% a(Var, <>) -> ... - %% - %% But if the clauses can't be freely rearranged, as in - %% - %% b(Var, <>) -> ... - %% b(1, 2) -> ... - %% - %% we do have a problem. - %% - case Vstate of - simple_vars -> State; - _ -> bsm_problem(P, Vstate) - end; - true -> - %% The pattern P *may* match a binary, so we must update the state. - %% (P must be a variable.) - case State of - within -> 'after'; - 'after' -> 'after' - end - end; -bsm_ensure_no_partition_2([#c_var{name=V}|Ps], N, G, Vstate, S) -> - case core_lib:is_var_used(V, G) of - false -> - bsm_ensure_no_partition_2(Ps, N-1, G, Vstate, S); - true -> - bsm_ensure_no_partition_2(Ps, N-1, G, bin_left_var_used_in_guard, S) - end; -bsm_ensure_no_partition_2([_|Ps], N, G, _, S) -> - bsm_ensure_no_partition_2(Ps, N-1, G, bin_argument_order, S). - -bsm_ensure_no_partition_after([#c_clause{pats=Ps}=C|Cs], Pos) -> - case nth(Pos, Ps) of - #c_var{} -> - bsm_ensure_no_partition_after(Cs, Pos); - _ -> - bsm_problem(C, bin_partition) - end; -bsm_ensure_no_partition_after([], _) -> ok. - -bsm_could_match_binary(#c_alias{pat=P}) -> bsm_could_match_binary(P); -bsm_could_match_binary(#c_cons{}) -> false; -bsm_could_match_binary(#c_tuple{}) -> false; -bsm_could_match_binary(#c_literal{val=Lit}) -> is_bitstring(Lit); -bsm_could_match_binary(_) -> true. - -bsm_real_pattern(#c_alias{pat=P}) -> bsm_real_pattern(P); -bsm_real_pattern(P) -> P. - -bsm_problem(Where, What) -> - throw({problem,Where,What}). %%% %%% Handling of warnings. @@ -3249,12 +2991,6 @@ bsm_problem(Where, What) -> init_warnings() -> put({?MODULE,warnings}, []). -add_bin_opt_info(Core, Term) -> - case get(bin_opt_info) of - true -> add_warning(Core, Term); - false -> ok - end. - add_warning(Core, Term) -> case should_suppress_warning(Core) of true -> @@ -3376,28 +3112,7 @@ format_error(result_ignored) -> format_error(invalid_call) -> "invalid function call"; format_error(useless_building) -> - "a term is constructed, but never used"; -format_error(bin_opt_alias) -> - "INFO: the '=' operator will prevent delayed sub binary optimization"; -format_error(bin_partition) -> - "INFO: matching non-variables after a previous clause matching a variable " - "will prevent delayed sub binary optimization"; -format_error(bin_left_var_used_in_guard) -> - "INFO: a variable to the left of the binary pattern is used in a guard; " - "will prevent delayed sub binary optimization"; -format_error(bin_argument_order) -> - "INFO: matching anything else but a plain variable to the left of " - "binary pattern will prevent delayed sub binary optimization; " - "SUGGEST changing argument order"; -format_error(bin_var_used) -> - "INFO: using a matched out sub binary will prevent " - "delayed sub binary optimization"; -format_error(orig_bin_var_used_in_guard) -> - "INFO: using the original binary variable in a guard will prevent " - "delayed sub binary optimization"; -format_error(bin_var_used_in_guard) -> - "INFO: using a matched out sub binary in a guard will prevent " - "delayed sub binary optimization". + "a term is constructed, but never used". -ifdef(DEBUG). %% In order for simplify_let/2 to work correctly, the list of -- cgit v1.2.3