diff options
| -rw-r--r-- | lib/compiler/src/sys_core_fold.erl | 144 | ||||
| -rw-r--r-- | lib/compiler/test/core_fold_SUITE.erl | 31 | ||||
| -rw-r--r-- | lib/compiler/test/test_lib.erl | 4 |
3 files changed, 129 insertions, 50 deletions
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl index 72509947d6..c29b5cde41 100644 --- a/lib/compiler/src/sys_core_fold.erl +++ b/lib/compiler/src/sys_core_fold.erl @@ -2025,12 +2025,31 @@ case_opt_args([], Cs, _Sub, _LitExpr, Acc) -> %% Try to expand one argument to several arguments (if tuple/list) %% or to remove a literal argument. %% -case_opt_arg(E0, Sub, Cs0, LitExpr) -> - E = maybe_replace_var(E0, Sub), - case cerl:is_data(E) of +case_opt_arg(E0, Sub, Cs, LitExpr) -> + case cerl:is_c_var(E0) of + false -> + case_opt_arg_1(E0, Cs, LitExpr); + true -> + case case_will_var_match(Cs) of + true -> + %% All clauses will match a variable in the + %% current position. Don't expand this variable + %% (that can only make the code worse). + {error,Cs}; + false -> + %% If possible, expand this variable to a previously + %% matched term. + E = case_expand_var(E0, Sub), + case_opt_arg_1(E, Cs, LitExpr) + end + end. + +case_opt_arg_1(E0, Cs0, LitExpr) -> + case cerl:is_data(E0) of false -> {error,Cs0}; true -> + E = case_opt_compiler_generated(E0), Cs = case_opt_nomatch(E, Cs0, LitExpr), case cerl:data_type(E) of {atomic,_} -> @@ -2040,18 +2059,42 @@ case_opt_arg(E0, Sub, Cs0, LitExpr) -> end end. -%% maybe_replace_var(Expr0, Sub) -> Expr +%% case_will_var_match([Clause]) -> true | false. +%% Return if all clauses will match a variable in the +%% current position. +%% +case_will_var_match(Cs) -> + all(fun({[P|_],_,_,_}) -> + case cerl_clauses:match(P, any) of + {true,_} -> true; + _ -> false + end + end, Cs). + + +%% case_opt_compiler_generated(Core) -> Core' +%% Mark Core expressions as compiler generated to ensure that +%% no warnings are generated if they turn out to be unused. +%% To pretty-printed Core Erlang easier to read, don't mark +%% constructs that can't cause warnings to be emitted. +%% +case_opt_compiler_generated(Core) -> + F = fun(C) -> + case cerl:type(C) of + alias -> C; + var -> C; + _ -> cerl:set_ann(C, [compiler_generated]) + end + end, + cerl_trees:map(F, Core). + + +%% case_expand_var(Expr0, Sub) -> Expr %% If Expr0 is a variable that has been previously matched and %% is known to be a tuple, return the tuple instead. Otherwise %% return Expr0 unchanged. %% -maybe_replace_var(E, Sub) -> - case cerl:is_c_var(E) of - false -> E; - true -> maybe_replace_var_1(E, Sub) - end. - -maybe_replace_var_1(E, #sub{t=Tdb}) -> +case_expand_var(E, #sub{t=Tdb}) -> case orddict:find(cerl:var_name(E), Tdb) of {ok,T0} -> case cerl:is_c_tuple(T0) of @@ -2068,9 +2111,8 @@ maybe_replace_var_1(E, #sub{t=Tdb}) -> %% operator will fail when used in map %% construction (only the '=>' operator is allowed %% when constructing a map from scratch). - ToData = fun coerce_to_data/1, try - cerl_trees:map(ToData, T0) + cerl_trees:map(fun coerce_to_data/1, T0) catch throw:impossible -> %% Something unsuitable was found (map or @@ -2124,8 +2166,9 @@ case_opt_nomatch(_, [], _) -> []. %% will match, and we can remove the corresponding pattern from %% each clause. %% -%% The only complication is if the literal is a binary. Binary -%% pattern matching is tricky, so we will give up in that case. +%% The only complication is if the literal is a binary or map. +%% In general, it is difficult to know whether a binary or +%% map pattern will match, so we give up in that case. case_opt_lit(Lit, Cs0) -> try case_opt_lit_1(Lit, Cs0) of @@ -2152,6 +2195,10 @@ case_opt_lit_1(E, [{[P|Ps],C,PsAcc,Bs0}|Cs]) -> case_opt_lit_1(_, []) -> []. %% case_opt_data(Expr, Clauses0, LitExpr) -> {ok,Exprs,Clauses} +%% The case expression is a non-atomic data constructor (cons +%% or tuple). We can know at compile time whether each clause +%% will match, and we can delay the building of the data to +%% the clauses where it is actually needed. case_opt_data(E, Cs0) -> Es = cerl:data_es(E), @@ -2161,45 +2208,48 @@ case_opt_data(E, Cs0) -> {ok,Es,Cs} catch throw:impossible -> + %% The pattern contained a binary or map. {error,Cs0} end. -case_opt_data_1([{[P|Ps0],C,PsAcc,Bs0}|Cs], Es, TypeSig) -> - {ok,Ps1,Bs1} = case_data_pat(P, TypeSig), - [{Ps1++Ps0,C,PsAcc,Bs1++Bs0}| - case_opt_data_1(Cs, Es, TypeSig)]; +case_opt_data_1([{[P0|Ps0],C,PsAcc,Bs0}|Cs], Es, TypeSig) -> + P = case_opt_compiler_generated(P0), + BindTo = #c_var{name=dummy}, + {Ps1,[{BindTo,_}|Bs1]} = case_data_pat_alias(P, BindTo, TypeSig, []), + [{Ps1++Ps0,C,PsAcc,Bs1++Bs0}|case_opt_data_1(Cs, Es, TypeSig)]; case_opt_data_1([], _, _) -> []. -%% case_data_pat(Pattern, Type, Arity) -> {ok,[Pattern],[{AliasVar,Pat}]} | error. - -case_data_pat(P, TypeSig) -> - case cerl:is_data(P) of - false -> - case_data_pat_var(P, TypeSig); - true -> - {ok,cerl:data_es(P),[]} - end. - -%% case_data_pat_var(Pattern, {DataType,ArityType}) -> -%% {ok,[Pattern],[{AliasVar,Pat}]} - -case_data_pat_var(P, {Type,Arity}=TypeSig) -> - %% If the entire case statement is evaluated in an effect - %% context (e.g. "case {A,B} of ... end, ok"), there will - %% be a warning that a term is constructed but never used. - %% To avoid that warning, we must annotate the data - %% constructor as compiler generated. - Ann = [compiler_generated|cerl:get_ann(P)], +case_data_pat_alias(P, BindTo0, TypeSig, Bs0) -> case cerl:type(P) of - var -> - Vars = make_vars(cerl:get_ann(P), Arity), - {ok,Vars,[{P,cerl:ann_make_data(Ann, Type, Vars)}]}; alias -> - V = cerl:alias_var(P), - Apat = cerl:alias_pat(P), - {ok,Ps,Bs} = case_data_pat(Apat, TypeSig), - {ok,Ps,[{V,cerl:ann_make_data(Ann, Type, - pat_to_expr_list(Ps))}|Bs]} + %% Recursively handle the pattern and bind to + %% the alias variable. + BindTo = cerl:alias_var(P), + Apat0 = cerl:alias_pat(P), + Ann = [compiler_generated], + Apat = cerl:set_ann(Apat0, Ann), + {Ps,Bs} = case_data_pat_alias(Apat, BindTo, TypeSig, Bs0), + {Ps,[{BindTo0,BindTo}|Bs]}; + var -> + %% Here we will need to actually build the data and bind + %% it to the variable. + {Type,Arity} = TypeSig, + Vars = make_vars([], Arity), + Ann = [compiler_generated], + Data = cerl:ann_make_data(Ann, Type, Vars), + Bs = [{BindTo0,P},{P,Data}|Bs0], + {Vars,Bs}; + _ -> + %% Since case_opt_nomatch/3 has removed all clauses that + %% cannot match, we KNOW that this clause must match and + %% that the pattern must be a data constructor. + %% Here we must build the data and bind it to the variable. + {Type,_} = TypeSig, + DataEs = cerl:data_es(P), + Vars = pat_to_expr_list(DataEs), + Ann = [compiler_generated], + Data = cerl:ann_make_data(Ann, Type, Vars), + {DataEs,[{BindTo0,Data}]} end. %% pat_to_expr(Pattern) -> Expression. diff --git a/lib/compiler/test/core_fold_SUITE.erl b/lib/compiler/test/core_fold_SUITE.erl index bca8afb1b0..b45874433c 100644 --- a/lib/compiler/test/core_fold_SUITE.erl +++ b/lib/compiler/test/core_fold_SUITE.erl @@ -23,7 +23,8 @@ t_element/1,setelement/1,t_length/1,append/1,t_apply/1,bifs/1, eq/1,nested_call_in_case/1,guard_try_catch/1,coverage/1, unused_multiple_values_error/1,unused_multiple_values/1, - multiple_aliases/1,redundant_boolean_clauses/1,mixed_matching_clauses/1]). + multiple_aliases/1,redundant_boolean_clauses/1, + mixed_matching_clauses/1,unnecessary_building/1]). -export([foo/0,foo/1,foo/2,foo/3]). @@ -40,7 +41,8 @@ groups() -> [t_element,setelement,t_length,append,t_apply,bifs, eq,nested_call_in_case,guard_try_catch,coverage, unused_multiple_values_error,unused_multiple_values, - multiple_aliases,redundant_boolean_clauses,mixed_matching_clauses]}]. + multiple_aliases,redundant_boolean_clauses, + mixed_matching_clauses,unnecessary_building]}]. init_per_suite(Config) -> @@ -403,4 +405,29 @@ mixed_matching_clauses(Config) when is_list(Config) -> end, ok. +unnecessary_building(Config) when is_list(Config) -> + Term1 = do_unnecessary_building_1(test_lib:id(a)), + [{a,a},{a,a}] = Term1, + 7 = erts_debug:size(Term1), + + %% The Input term should not be rebuilt (thus, it should + %% only be counted once in the size of the combined term). + Input = test_lib:id({a,b,c}), + Term2 = test_lib:id(do_unnecessary_building_2(Input)), + {b,[{a,b,c},none],x} = Term2, + 4+4+4+2 = erts_debug:size([Term2|Input]), + + ok. + +do_unnecessary_building_1(S) -> + %% The tuple must only be built once. + F0 = F1 = {S,S}, + [F0,F1]. + +do_unnecessary_building_2({a,_,_}=T) -> + %% The T term should not be rebuilt. + {b, + [_,_] = [T,none], + x}. + id(I) -> I. diff --git a/lib/compiler/test/test_lib.erl b/lib/compiler/test/test_lib.erl index e06e42276a..e8f469c5b4 100644 --- a/lib/compiler/test/test_lib.erl +++ b/lib/compiler/test/test_lib.erl @@ -20,9 +20,11 @@ -include("test_server.hrl"). -compile({no_auto_import,[binary_part/2]}). --export([recompile/1,parallel/0,uniq/0,opt_opts/1,get_data_dir/1, +-export([id/1,recompile/1,parallel/0,uniq/0,opt_opts/1,get_data_dir/1, smoke_disasm/1,p_run/2,binary_part/2]). +id(I) -> I. + recompile(Mod) when is_atom(Mod) -> case whereis(cover_server) of undefined -> ok; 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