From cabdef3b97c077119fe6f43538dbdd5cffe9dd91 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Mon, 20 May 2019 11:54:22 +0200
Subject: Fix non-terminating compilation

The compiler would not terminate while compiling the following code:

    foo(<<N:32>>, Tuple, NewValue) ->
        _ = element(N, Tuple),
        setelement(N, Tuple, NewValue).

The type analysis pass would attempt to construct a huge list when
attempting analyse the type of `Tuple` after the call to
`setelement/3`.

https://bugs.erlang.org/browse/ERL-948
---
 lib/compiler/src/beam_ssa_type.erl    | 16 +++++++++++-----
 lib/compiler/test/beam_type_SUITE.erl | 14 ++++++++++++++
 2 files changed, 25 insertions(+), 5 deletions(-)

(limited to 'lib')

diff --git a/lib/compiler/src/beam_ssa_type.erl b/lib/compiler/src/beam_ssa_type.erl
index 06b42f1928..2ea7e89dfa 100644
--- a/lib/compiler/src/beam_ssa_type.erl
+++ b/lib/compiler/src/beam_ssa_type.erl
@@ -24,7 +24,7 @@
 -include("beam_ssa_opt.hrl").
 -import(lists, [all/2,any/2,droplast/1,foldl/3,last/1,member/2,
                 keyfind/3,partition/2,reverse/1,reverse/2,
-                seq/2,sort/1,split/2]).
+                sort/1,split/2]).
 
 -define(UNICODE_INT, #t_integer{elements={0,16#10FFFF}}).
 
@@ -874,11 +874,11 @@ type(call, [#b_remote{mod=#b_literal{val=Mod},
                         true ->
                             none
                     end;
-                {#t_integer{elements={Min,Max}},
+                {#t_integer{elements={Min,_}}=IntType,
                  #t_tuple{elements=Es0,size=Size}=T} ->
-                    %% We know this will land between Min and Max, so kill the
-                    %% types for those indexes.
-                    Es = maps:without(seq(Min, Max), Es0),
+                    %% Remove type information for all indices that
+                    %% falls into the range of the integer.
+                    Es = remove_element_info(IntType, Es0),
                     case T#t_tuple.exact of
                         false ->
                             T#t_tuple{elements=Es,size=max(Min, Size)};
@@ -1649,6 +1649,12 @@ get_literal_from_type(nil) ->
     #b_literal{val=[]};
 get_literal_from_type(_) -> none.
 
+remove_element_info(#t_integer{elements={Min,Max}}, Es) ->
+    foldl(fun(El, Acc) when Min =< El, El =< Max ->
+                  maps:remove(El, Acc);
+             (_El, Acc) -> Acc
+          end, Es, maps:keys(Es)).
+
 t_atom() ->
     #t_atom{elements=any}.
 
diff --git a/lib/compiler/test/beam_type_SUITE.erl b/lib/compiler/test/beam_type_SUITE.erl
index 882e281a44..0d1680fb15 100644
--- a/lib/compiler/test/beam_type_SUITE.erl
+++ b/lib/compiler/test/beam_type_SUITE.erl
@@ -271,8 +271,22 @@ setelement(_Config) ->
     T0 = id({a,42}),
     {a,_} = T0,
     {b,_} = setelement(1, T0, b),
+    {z,b} = do_setelement_1(<<(id(1)):32>>, {a,b}, z),
+    {new,two} = do_setelement_2(<<(id(1)):1>>, {one,two}, new),
     ok.
 
+do_setelement_1(<<N:32>>, Tuple, NewValue) ->
+    _ = element(N, Tuple),
+    %% While updating the type for Tuple, beam_ssa_type would do:
+    %%   maps:without(lists:seq(0, 4294967295), Elements)
+    setelement(N, Tuple, NewValue).
+
+do_setelement_2(<<N:1>>, Tuple, NewValue) ->
+    %% Cover the second clause in remove_element_info/2. The
+    %% type for the second element will be kept.
+    two = element(2, Tuple),
+    setelement(N, Tuple, NewValue).
+
 cons(_Config) ->
     [did] = cons(assigned, did),
 
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