Fix crash in beam_ssa_type

To improve compilation times, beam_ssa_type keeps track of variables
that are only used once and don't keep types for those variables. As
currently implemented, it turns to be unsafe. Change it to only keep
track of variables that are only used in the terminator of the block
they are defined in.

https://bugs.erlang.org/browse/ERL-840

1 files changed, 16 insertions, 0 deletions

diff --git a/lib/compiler/test/beam_type_SUITE.erl b/lib/compiler/test/beam_type_SUITE.erl
index 6efa98de44..a7ffc3f60a 100644
--- a/lib/compiler/test/beam_type_SUITE.erl
+++ b/lib/compiler/test/beam_type_SUITE.erl
@@ -222,6 +222,9 @@ coverage(Config) ->
 booleans(_Config) ->
     {'EXIT',{{case_clause,_},_}} = (catch do_booleans_1(42)),
 
+    ok = do_booleans_2(42, 41),
+    error = do_booleans_2(42, 42),
+
     AnyAtom = id(atom),
     true = is_atom(AnyAtom),
     false = is_boolean(AnyAtom),
@@ -250,6 +253,19 @@ do_booleans_1(B) ->
 	no -> no
     end.
 
+do_booleans_2(A, B) ->
+    Not = not do_booleans_cmp(A, B),
+    case Not of
+        true ->
+            case Not of
+                true -> error;
+                false -> ok
+            end;
+        false -> ok
+    end.
+
+do_booleans_cmp(A, B) -> A > B.
+
 setelement(_Config) ->
     T0 = id({a,42}),
     {a,_} = T0,