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-rw-r--r--lib/compiler/src/sys_core_fold.erl94
1 files changed, 22 insertions, 72 deletions
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 5d7fd37270..50d28c0a5f 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -373,7 +373,7 @@ expr(#c_case{}=Case0, Ctxt, Sub) ->
%% (in addition to any warnings that may have been emitted
%% according to the rules above).
%%
- case opt_bool_case(Case0) of
+ case opt_bool_case(Case0, Sub) of
#c_case{arg=Arg0,clauses=Cs0}=Case1 ->
Arg1 = body(Arg0, value, Sub),
LitExpr = cerl:is_literal(Arg1),
@@ -1554,9 +1554,11 @@ will_match(E, [P]) ->
will_match_1({false,_}) -> maybe;
will_match_1({true,_}) -> yes.
-%% opt_bool_case(CoreExpr) - CoreExpr'.
-%% Do various optimizations to case statement that has a
-%% boolean case expression.
+%% opt_bool_case(CoreExpr, Sub) - CoreExpr'.
+%%
+%% In bodies, do various optimizations to case statements that have
+%% boolean case expressions. We don't do the optimizations in guards,
+%% because they would thwart the optimization in v3_kernel.
%%
%% We start with some simple optimizations and normalization
%% to facilitate later optimizations.
@@ -1565,7 +1567,7 @@ will_match_1({true,_}) -> yes.
%% (or fail), we can remove any clause that cannot
%% possibly match 'true' or 'false'. Also, any clause
%% following both 'true' and 'false' clause can
-%% be removed. If successful, we will end up this:
+%% be removed. If successful, we will end up like this:
%%
%% case BoolExpr of case BoolExpr of
%% true -> false ->
@@ -1576,8 +1578,11 @@ will_match_1({true,_}) -> yes.
%%
%% We give up if there are clauses with guards, or if there
%% is a variable clause that matches anything.
-%%
-opt_bool_case(#c_case{arg=Arg}=Case0) ->
+
+opt_bool_case(#c_case{}=Case, #sub{in_guard=true}) ->
+ %% v3_kernel does a better job without "help".
+ Case;
+opt_bool_case(#c_case{arg=Arg}=Case0, #sub{in_guard=false}) ->
case is_bool_expr(Arg) of
false ->
Case0;
@@ -1589,8 +1594,7 @@ opt_bool_case(#c_case{arg=Arg}=Case0) ->
impossible ->
Case0
end
- end;
-opt_bool_case(Core) -> Core.
+ end.
opt_bool_clauses(#c_case{clauses=Cs}=Case) ->
Case#c_case{clauses=opt_bool_clauses(Cs, false, false)}.
@@ -1606,16 +1610,14 @@ opt_bool_clauses(Cs, true, true) ->
[]
end;
opt_bool_clauses([#c_clause{pats=[#c_literal{val=Lit}],
- guard=#c_literal{val=true},
- body=B}=C0|Cs], SeenT, SeenF) ->
+ guard=#c_literal{val=true}}=C|Cs], SeenT, SeenF) ->
case is_boolean(Lit) of
false ->
%% Not a boolean - this clause can't match.
- add_warning(C0, nomatch_clause_type),
+ add_warning(C, nomatch_clause_type),
opt_bool_clauses(Cs, SeenT, SeenF);
true ->
%% This clause will match.
- C = C0#c_clause{body=opt_bool_case(B)},
case {Lit,SeenT,SeenF} of
{false,_,false} ->
[C|opt_bool_clauses(Cs, SeenT, true)];
@@ -2238,14 +2240,14 @@ inverse_rel_op(_) -> no.
%% opt_bool_case_in_let(LetExpr) -> Core
-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_bool_case_in_let(#c_let{vars=Vs,arg=Arg,body=B}=Let, Sub) ->
+ opt_bool_case_in_let_1(Vs, Arg, B, Let, Sub).
opt_bool_case_in_let_1([#c_var{name=V}], Arg,
- #c_case{arg=#c_var{name=V}}=Case0, Let) ->
+ #c_case{arg=#c_var{name=V}}=Case0, Let, Sub) ->
case is_simple_case_arg(Arg) of
true ->
- Case = opt_bool_case(Case0#c_case{arg=Arg}),
+ Case = opt_bool_case(Case0#c_case{arg=Arg}, Sub),
case core_lib:is_var_used(V, Case) of
false -> Case;
true -> Let
@@ -2253,7 +2255,7 @@ opt_bool_case_in_let_1([#c_var{name=V}], Arg,
false ->
Let
end;
-opt_bool_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
@@ -2386,9 +2388,7 @@ is_safe_bool_expr_list([], _, _) -> true.
%% as a let or a sequence, move the original let body into the complex
%% expression.
-simplify_let(#c_let{arg=Arg0}=Let0, Sub) ->
- Arg = opt_bool_case(Arg0),
- Let = Let0#c_let{arg=Arg},
+simplify_let(#c_let{arg=Arg}=Let, Sub) ->
move_let_into_expr(Let, Arg, Sub).
move_let_into_expr(#c_let{vars=InnerVs0,body=InnerBody0}=Inner,
@@ -2688,8 +2688,7 @@ opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, 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),
- opt_case_in_let_arg(Let2, Ctxt, Sub)
+ opt_bool_case_in_let(Let1, Sub)
end
end.
@@ -2817,48 +2816,6 @@ move_case_into_arg(#c_case{arg=#c_seq{arg=OuterArg,body=InnerArg}=Outer,
move_case_into_arg(_, _) ->
impossible.
-%% In guards only, rewrite a case in a let argument like
-%%
-%% let <Var> = case <> of
-%% <> when AnyGuard -> Literal1;
-%% <> when AnyGuard -> Literal2
-%% end
-%% in LetBody
-%%
-%% to
-%%
-%% case <> of
-%% <> when AnyGuard ->
-%% let <Var> = Literal1 in LetBody
-%% <> when 'true' ->
-%% let <Var> = Literal2 in LetBody
-%% end
-%%
-%% In the worst case, the size of the code could increase.
-%% In practice, though, substituting the literals into
-%% LetBody and doing constant folding will decrease the code
-%% size. (Doing this transformation outside of guards could
-%% lead to a substantational increase in code size.)
-%%
-opt_case_in_let_arg(#c_let{arg=#c_case{}=Case}=Let, Ctxt,
- #sub{in_guard=true}=Sub) ->
- opt_case_in_let_arg_1(Let, Case, Ctxt, Sub);
-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) ->
- 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}},
- Case0#c_case{clauses=[Ca,Cb]};
- _ ->
- Let
- end;
-opt_case_in_let_arg_1(Let, _, _, _) -> Let.
-
is_any_var_used([#c_var{name=V}|Vs], Expr) ->
case core_lib:is_var_used(V, Expr) of
false -> is_any_var_used(Vs, Expr);
@@ -3289,13 +3246,6 @@ bsm_problem(Where, What) ->
%%% Handling of warnings.
%%%
-mark_compiler_generated(Term) ->
- cerl_trees:map(fun mark_compiler_generated_1/1, Term).
-
-mark_compiler_generated_1(#c_call{anno=Anno}=Term) ->
- Term#c_call{anno=[compiler_generated|Anno--[compiler_generated]]};
-mark_compiler_generated_1(Term) -> Term.
-
init_warnings() ->
put({?MODULE,warnings}, []).
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-04 16:59:51 +0000