From a034ff64abab5f5cbf5c6aa38762044c968fe377 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Sat, 25 May 2019 10:23:20 +0200 Subject: Fix unsafe optimizations where guard tests could be removed A repeated test could be optimized away. Example: bar(A) -> if is_bitstring(A) -> if is_binary(A) -> binary; true -> bitstring end; true -> other end. In the example, the `is_binary/1` test would be optimized away, basically turning the example into: bar(A) -> if is_bitstring(A) -> bitstring; true -> other end. Thanks user Marcus Kruse in the Elixir forum for noticing this bug. --- lib/compiler/test/guard_SUITE.erl | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) (limited to 'lib/compiler/test/guard_SUITE.erl') diff --git a/lib/compiler/test/guard_SUITE.erl b/lib/compiler/test/guard_SUITE.erl index ed0a56f064..cea7a374cd 100644 --- a/lib/compiler/test/guard_SUITE.erl +++ b/lib/compiler/test/guard_SUITE.erl @@ -35,7 +35,8 @@ basic_andalso_orelse/1,traverse_dcd/1, check_qlc_hrl/1,andalso_semi/1,t_tuple_size/1,binary_part/1, bad_constants/1,bad_guards/1, - guard_in_catch/1,beam_bool_SUITE/1]). + guard_in_catch/1,beam_bool_SUITE/1, + repeated_type_tests/1]). suite() -> [{ct_hooks,[ts_install_cth]}]. @@ -53,7 +54,8 @@ groups() -> rel_ops,rel_op_combinations, literal_type_tests,basic_andalso_orelse,traverse_dcd, check_qlc_hrl,andalso_semi,t_tuple_size,binary_part, - bad_constants,bad_guards,guard_in_catch,beam_bool_SUITE]}]. + bad_constants,bad_guards,guard_in_catch,beam_bool_SUITE, + repeated_type_tests]}]. init_per_suite(Config) -> test_lib:recompile(?MODULE), @@ -2261,6 +2263,25 @@ maps() -> evidence(#{0 := Charge}) when 0; #{[] => Charge} == #{[] => 42} -> ok. +repeated_type_tests(_Config) -> + binary = repeated_type_test(<<42>>), + bitstring = repeated_type_test(<<1:1>>), + other = repeated_type_test(atom), + ok. + +repeated_type_test(T) -> + %% Test for a bug in beam_ssa_dead. + if is_bitstring(T) -> + if is_binary(T) -> %This test would be optimized away. + binary; + true -> + bitstring + end; + true -> + other + end. + + %% Call this function to turn off constant propagation. id(I) -> I. -- cgit v1.2.3