beam_reorder: Eliminate compiler crash

c288ab87 added beam_reorder to move get_tuple_element instructions.

Compiling code such as the following would crash the compiler:

  alloc(_U1, _U2, R) ->
    V = R#alloc.version,
    Res = id(V),
    _ = id(0),
    Res.

The crash would occur because the following two instructions:

    {get_tuple_element,{x,2},1,{x,1}}.
    {allocate_zero,1,2}.

were swapped and rewritten to:

    {allocate_zero,1,1}.
    {get_tuple_element,{x,2},1,{x,1}}.

That transformation is not safe because the allocate_zero instruction
would kill {x,2}, which is the register that is holding the reference
to the tuple. Only do the transformation when the tuple reference is
in an x register with a lower number than the destination register.

1 files changed, 69 insertions, 0 deletions

diff --git a/lib/compiler/test/beam_reorder_SUITE.erl b/lib/compiler/test/beam_reorder_SUITE.erl
new file mode 100644
index 0000000000..4b2262f65b
--- /dev/null
+++ b/lib/compiler/test/beam_reorder_SUITE.erl
@@ -0,0 +1,69 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2015. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+-module(beam_reorder_SUITE).
+
+-export([all/0,suite/0,groups/0,init_per_suite/1,end_per_suite/1,
+	 init_per_group/2,end_per_group/2,
+	 alloc/1]).
+
+suite() -> [{ct_hooks,[ts_install_cth]}].
+
+all() ->
+    test_lib:recompile(?MODULE),
+    [{group,p}].
+
+groups() ->
+    [{p,[parallel],
+      [alloc
+      ]}].
+
+init_per_suite(Config) ->
+    Config.
+
+end_per_suite(_Config) ->
+    ok.
+
+init_per_group(_GroupName, Config) ->
+    Config.
+
+end_per_group(_GroupName, Config) ->
+    Config.
+
+-record(alloc, {version}).
+
+alloc(_Config) ->
+    {ok,42} = alloc_a(1, 2, #alloc{version=42}),
+    {a,b,c} = alloc_b(1, 2, #alloc{version={a,b,c}}),
+    ok.
+
+alloc_a(_U1, _U2, R) ->
+    V = R#alloc.version,
+    Res = id({ok,V}),
+    _ = id(0),
+    Res.
+
+alloc_b(_U1, _U2, R) ->
+    V = R#alloc.version,
+    Res = id(V),
+    _ = id(0),
+    Res.
+
+id(I) ->
+    I.