File 2166-dialyzer-Improve-handling-of-complex-guards.patch of Package erlang
From fd9b5ae4193fbab66093c88728c0dbeaa3b57312 Mon Sep 17 00:00:00 2001
From: Hans Bolinder <hasse@erlang.org>
Date: Mon, 27 Aug 2018 13:14:29 +0200
Subject: [PATCH] dialyzer: Improve handling of complex guards
See also https://bugs.erlang.org/browse/ERL-680.
The right associative short circuit expressions 'andalso' and 'orelse'
are expanded by the Compiler (see v3_core) into 'case' expressions. If
parentheses are used to enforce left associativeness, variables are
introduced, and the time needed by Dialyzer increases exponentially.
Rather than trying to fix Dialyzer itself, v3_core now rewrites
repeated use of 'andalso' ('orelse') into right associative
expressions before creating the 'case' expressions.
---
lib/compiler/src/v3_core.erl | 19 ++++-
.../test/small_SUITE_data/results/left_assoc | 2 +
.../test/small_SUITE_data/src/left_assoc.erl | 96 ++++++++++++++++++++++
3 files changed, 115 insertions(+), 2 deletions(-)
create mode 100644 lib/dialyzer/test/small_SUITE_data/results/left_assoc
create mode 100644 lib/dialyzer/test/small_SUITE_data/src/left_assoc.erl
diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index 3b746ab5bf..c9517c3e51 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -328,14 +328,16 @@ gexpr({protect,Line,Arg}, Bools0, St0) ->
Anno = lineno_anno(Line, St),
{#iprotect{anno=#a{anno=Anno},body=Eps++[E]},[],Bools0,St}
end;
-gexpr({op,L,'andalso',E1,E2}, Bools, St0) ->
+gexpr({op,_,'andalso',_,_}=E0, Bools, St0) ->
+ {op,L,'andalso',E1,E2} = right_assoc(E0, 'andalso', St0),
Anno = lineno_anno(L, St0),
{#c_var{name=V0},St} = new_var(Anno, St0),
V = {var,L,V0},
False = {atom,L,false},
E = make_bool_switch_guard(L, E1, V, E2, False),
gexpr(E, Bools, St);
-gexpr({op,L,'orelse',E1,E2}, Bools, St0) ->
+gexpr({op,_,'orelse',_,_}=E0, Bools, St0) ->
+ {op,L,'orelse',E1,E2} = right_assoc(E0, 'orelse', St0),
Anno = lineno_anno(L, St0),
{#c_var{name=V0},St} = new_var(Anno, St0),
V = {var,L,V0},
@@ -2054,6 +2056,19 @@ fail_clause(Pats, Anno, Arg) ->
body=[#iprimop{anno=#a{anno=Anno},name=#c_literal{val=match_fail},
args=[Arg]}]}.
+%% Optimization for Dialyzer.
+right_assoc(E, Op, St) ->
+ case member(dialyzer, St#core.opts) of
+ true ->
+ right_assoc2(E, Op);
+ false ->
+ E
+ end.
+
+right_assoc2({op,L1,Op,{op,L2,Op,E1,E2},E3}, Op) ->
+ right_assoc2({op,L2,Op,E1,{op,L1,Op,E2,E3}}, Op);
+right_assoc2(E, _Op) -> E.
+
annotate_tuple(A, Es, St) ->
case member(dialyzer, St#core.opts) of
true ->
diff --git a/lib/dialyzer/test/small_SUITE_data/results/left_assoc b/lib/dialyzer/test/small_SUITE_data/results/left_assoc
new file mode 100644
index 0000000000..58cdad29de
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/results/left_assoc
@@ -0,0 +1,2 @@
+
+left_assoc.erl:93: The variable __@2 can never match since previous clauses completely covered the type binary()
diff --git a/lib/dialyzer/test/small_SUITE_data/src/left_assoc.erl b/lib/dialyzer/test/small_SUITE_data/src/left_assoc.erl
new file mode 100644
index 0000000000..0250e4ab49
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/left_assoc.erl
@@ -0,0 +1,96 @@
+-module(left_assoc).
+
+%% As pointed out in ERL-680, analyzing guards with short circuit
+%% operators becomes very slow as the number of left associations
+%% grows.
+
+-spec from_iso8601('Elixir.String':t(), 'Elixir.Calendar':calendar()) ->
+ {ok, t()} | {error, atom()}.
+
+-export_type([t/0]).
+
+-type t() ::
+ #{'__struct__' := 'Elixir.Date',
+ calendar := 'Elixir.Calendar':calendar(),
+ day := 'Elixir.Calendar':day(),
+ month := 'Elixir.Calendar':month(),
+ year := 'Elixir.Calendar':year()}.
+
+-export([from_iso8601/1,
+ from_iso8601/2]).
+
+from_iso8601(__@1) ->
+ from_iso8601(__@1, 'Elixir.Calendar.ISO').
+
+from_iso8601(<<45/integer,_rest@1/binary>>, _calendar@1) ->
+ case raw_from_iso8601(_rest@1, _calendar@1) of
+ {ok,#{year := _year@1} = _date@1} ->
+ {ok,_date@1#{year := - _year@1}};
+ __@1 ->
+ __@1
+ end;
+from_iso8601(<<_rest@1/binary>>, _calendar@1) ->
+ raw_from_iso8601(_rest@1, _calendar@1).
+
+raw_from_iso8601(_string@1, _calendar@1) ->
+ case _string@1 of
+ <<_y1@1/integer,
+ _y2@1/integer,
+ _y3@1/integer,
+ _y4@1/integer,
+ 45/integer,
+ _m1@1/integer,
+ _m2@1/integer,
+ 45/integer,
+ _d1@1/integer,
+ _d2@1/integer>>
+ when
+ ((((((((((((((_y1@1 >= 48
+ andalso
+ _y1@1 =< 57)
+ andalso
+ _y2@1 >= 48)
+ andalso
+ _y2@1 =< 57)
+ andalso
+ _y3@1 >= 48)
+ andalso
+ _y3@1 =< 57)
+ andalso
+ _y4@1 >= 48)
+ andalso
+ _y4@1 =< 57)
+ andalso
+ _m1@1 >= 48)
+ andalso
+ _m1@1 =< 57)
+ andalso
+ _m2@1 >= 48)
+ andalso
+ _m2@1 =< 57)
+ andalso
+ _d1@1 >= 48)
+ andalso
+ _d1@1 =< 57)
+ andalso
+ _d2@1 >= 48)
+ andalso
+ _d2@1 =< 57 ->
+ {ok,
+ #{year => (_y1@1 - 48) * 1000 + (_y2@1 - 48) * 100
+ +
+ (_y3@1 - 48) * 10
+ +
+ (_y4@1 - 48),
+ month => (_m1@1 - 48) * 10 + (_m2@1 - 48),
+ day => (_d1@1 - 48) * 10 + (_d2@1 - 48),
+ calendar => _calendar@1,
+ '__struct__' => 'Elixir.Date'}};
+ __@1 ->
+ case __@1 of
+ _ ->
+ {error,invalid_format};
+ __@2 ->
+ error({with_clause,__@2})
+ end
+ end.
--
2.16.4
