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authorBjörn Gustavsson <[email protected]>2016-09-19 12:46:03 +0200
committerBjörn Gustavsson <[email protected]>2016-09-26 16:20:40 +0200
commit05130e485558919344584f9bbfa057efdca94c3d (patch)
treec361c1c839b4b001ad814dca9e3a00124dc46933
parent7169258d1315b86622093e1f14faf2267c9c448e (diff)
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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.
-rw-r--r--lib/compiler/src/sys_core_fold.erl77
1 files 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 <Var> = Arg in <OtherVar> ==> 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 <Var> = 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 <Var> = 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.