From 05130e485558919344584f9bbfa057efdca94c3d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Mon, 19 Sep 2016 12:46:03 +0200 Subject: sys_core_fold: Run optimizations to a fixpoint Run the optimizations until a fixpoint is reached, or until the maximum iteration count is reached. The hope is that in the future we can many small optimizations instead of optimizations that try to do everything in one pass. This change allows us to remove the ad-hoc calls to expr/2 to run more optimizations on a piece of code. --- lib/compiler/src/sys_core_fold.erl | 77 ++++++++++++++++++++------------------ 1 file changed, 41 insertions(+), 36 deletions(-) diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl index b8df4e04f8..303ce52ee3 100644 --- a/lib/compiler/src/sys_core_fold.erl +++ b/lib/compiler/src/sys_core_fold.erl @@ -121,7 +121,10 @@ module(#c_module{defs=Ds0}=Mod, Opts) -> function_1({#c_var{name={F,Arity}}=Name,B0}) -> try - B = expr(B0, value, sub_new()), %This must be a fun! + B = find_fixpoint(fun(Core) -> + %% This must be a fun! + expr(Core, value, sub_new()) + end, B0, 20), {Name,B} catch Class:Error -> @@ -130,6 +133,14 @@ function_1({#c_var{name={F,Arity}}=Name,B0}) -> erlang:raise(Class, Error, Stack) end. +find_fixpoint(_OptFun, Core, 0) -> + Core; +find_fixpoint(OptFun, Core0, Max) -> + case OptFun(Core0) of + Core0 -> Core0; + Core -> find_fixpoint(OptFun, Core, Max-1) + end. + %% body(Expr, Sub) -> Expr. %% body(Expr, Context, Sub) -> Expr. %% No special handling of anything except values. @@ -240,7 +251,7 @@ expr(#c_cons{anno=Anno,hd=H0,tl=T0}=Cons, Ctxt, Sub) -> case Ctxt of effect -> add_warning(Cons, useless_building), - expr(make_effect_seq([H1,T1], Sub), Ctxt, Sub); + make_effect_seq([H1,T1], Sub); value -> ann_c_cons(Anno, H1, T1) end; @@ -249,7 +260,7 @@ expr(#c_tuple{anno=Anno,es=Es0}=Tuple, Ctxt, Sub) -> case Ctxt of effect -> add_warning(Tuple, useless_building), - expr(make_effect_seq(Es, Sub), Ctxt, Sub); + make_effect_seq(Es, Sub); value -> ann_c_tuple(Anno, Es) end; @@ -258,7 +269,7 @@ expr(#c_map{anno=Anno,arg=V0,es=Es0}=Map, Ctxt, Sub) -> case Ctxt of effect -> add_warning(Map, useless_building), - expr(make_effect_seq(Es, Sub), Ctxt, Sub); + make_effect_seq(Es, Sub); value -> V = expr(V0, Ctxt, Sub), ann_c_map(Anno,V,Es) @@ -311,7 +322,7 @@ expr(#c_let{}=Let0, Ctxt, Sub) -> Expr -> %% The let body was successfully moved into the let argument. %% Now recursively re-process the new expression. - expr(Expr, Ctxt, sub_new_preserve_types(Sub)) + Expr end; expr(#c_letrec{body=#c_var{}}=Letrec, effect, _Sub) -> %% This is named fun in an 'effect' context. Warn and ignore. @@ -365,7 +376,7 @@ expr(#c_case{}=Case0, Ctxt, Sub) -> impossible -> bsm_an(Expr); Other -> - expr(Other, Ctxt, sub_new_preserve_types(Sub)) + Other end; Other -> expr(Other, Ctxt, Sub) @@ -1398,9 +1409,6 @@ sub_new() -> #sub{v=orddict:new(),s=cerl_sets:new(),t=#{}}. sub_new(#sub{}=Sub) -> Sub#sub{v=orddict:new(),t=#{}}. -sub_new_preserve_types(#sub{}=Sub) -> - Sub#sub{v=orddict:new()}. - sub_get_var(#c_var{name=V}=Var, #sub{v=S}) -> case orddict:find(V, S) of {ok,Val} -> Val; @@ -2220,24 +2228,24 @@ inverse_rel_op('=<') -> '>'; inverse_rel_op(_) -> no. -%% opt_bool_case_in_let(LetExpr, Sub) -> Core +%% opt_bool_case_in_let(LetExpr) -> Core -opt_bool_case_in_let(#c_let{vars=Vs,arg=Arg,body=B}=Let, Sub) -> - opt_case_in_let_1(Vs, Arg, B, Let, Sub). +opt_bool_case_in_let(#c_let{vars=Vs,arg=Arg,body=B}=Let) -> + opt_bool_case_in_let_1(Vs, Arg, B, Let). -opt_case_in_let_1([#c_var{name=V}], Arg, - #c_case{arg=#c_var{name=V}}=Case0, Let, Sub) -> +opt_bool_case_in_let_1([#c_var{name=V}], Arg, + #c_case{arg=#c_var{name=V}}=Case0, Let) -> case is_simple_case_arg(Arg) of true -> Case = opt_bool_case(Case0#c_case{arg=Arg}), case core_lib:is_var_used(V, Case) of - false -> expr(Case, sub_new(Sub)); + false -> Case; true -> Let end; false -> Let end; -opt_case_in_let_1(_, _, _, Let, _) -> Let. +opt_bool_case_in_let_1(_, _, _, Let) -> Let. %% is_simple_case_arg(Expr) -> true|false %% Determine whether the Expr is simple enough to be worth @@ -2645,25 +2653,23 @@ opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, Sub) -> false -> %% let = Arg in ==> seq Arg OtherVar Arg = maybe_suppress_warnings(Arg1, Vs0, PrevBody), - expr(#c_seq{arg=Arg,body=Body}, Ctxt, - sub_new_preserve_types(Sub)) + #c_seq{arg=Arg,body=Body} end; {[],#c_values{es=[]},_} -> %% No variables left. Body; {Vs,Arg1,#c_literal{}} -> Arg = maybe_suppress_warnings(Arg1, Vs, PrevBody), - E = case Ctxt of - effect -> - %% Throw away the literal body. - Arg; - value -> - %% Since the variable is not used in the body, we - %% can rewrite the let to a sequence. - %% let = Arg in Literal ==> seq Arg Literal - #c_seq{arg=Arg,body=Body} - end, - expr(E, Ctxt, sub_new_preserve_types(Sub)); + case Ctxt of + effect -> + %% Throw away the literal body. + Arg; + value -> + %% Since the variable is not used in the body, we + %% can rewrite the let to a sequence. + %% let = Arg in Literal ==> seq Arg Literal + #c_seq{arg=Arg,body=Body} + end; {Vs,Arg1,Body} -> %% If none of the variables are used in the body, we can %% rewrite the let to a sequence: @@ -2672,11 +2678,10 @@ opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, Sub) -> case is_any_var_used(Vs, Body) of false -> Arg = maybe_suppress_warnings(Arg1, Vs, PrevBody), - expr(#c_seq{arg=Arg,body=Body}, Ctxt, - sub_new_preserve_types(Sub)); + #c_seq{arg=Arg,body=Body}; true -> Let1 = Let0#c_let{vars=Vs,arg=Arg1,body=Body}, - Let2 = opt_bool_case_in_let(Let1, Sub), + Let2 = opt_bool_case_in_let(Let1), opt_case_in_let_arg(Let2, Ctxt, Sub) end end. @@ -2834,16 +2839,16 @@ opt_case_in_let_arg(#c_let{arg=#c_case{}=Case}=Let, Ctxt, opt_case_in_let_arg(Let, _, _) -> Let. opt_case_in_let_arg_1(Let0, #c_case{arg=#c_values{es=[]}, - clauses=Cs}=Case0, Ctxt, Sub) -> + clauses=Cs}=Case0, _Ctxt, _Sub) -> Let = mark_compiler_generated(Let0), case Cs of [#c_clause{body=#c_literal{}=BodyA}=Ca0, #c_clause{body=#c_literal{}=BodyB}=Cb0] -> Ca = Ca0#c_clause{body=Let#c_let{arg=BodyA}}, Cb = Cb0#c_clause{body=Let#c_let{arg=BodyB}}, - Case = Case0#c_case{clauses=[Ca,Cb]}, - expr(Case, Ctxt, sub_new_preserve_types(Sub)); - _ -> Let + Case0#c_case{clauses=[Ca,Cb]}; + _ -> + Let end; opt_case_in_let_arg_1(Let, _, _, _) -> Let. -- cgit v1.2.3