From 57c4432ed543898676ccc646ab6d556c7e6ea79a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Sat, 21 May 2016 08:57:28 +0200
Subject: beam_reorder: Don't confuse beam_validator

Make sure we don't optimize code such as:

  is_tuple Fail Src
  test_arity Fail Src Arity
  get_tuple_element Src Pos Dst
  is_map Fail Src

If we would reorder the instructions like this:

  is_tuple Fail Src
  test_arity Fail Src Arity
  is_map Fail Src
  get_tuple_element Src Pos Dst

beam_validator would complain that the type for Src is a map
instead of a tuple. Since the code has problems to begin with,
there is no need to do the optimization.
---
 lib/compiler/src/beam_reorder.erl        |  9 +++++++++
 lib/compiler/test/beam_reorder_SUITE.erl | 16 ++++++++++++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/lib/compiler/src/beam_reorder.erl b/lib/compiler/src/beam_reorder.erl
index f1c0b3ef91..6a7c033ec6 100644
--- a/lib/compiler/src/beam_reorder.erl
+++ b/lib/compiler/src/beam_reorder.erl
@@ -87,6 +87,15 @@ reorder_1([{test,_,_,_}=I,
     %% instruction between the test instruction and the select
     %% instruction.
     reorder_1(Is, D, [S,I|Acc]);
+reorder_1([{test,_,{f,_},[Src|_]}=I|Is], D,
+	  [{get_tuple_element,Src,_,_}|_]=Acc) ->
+    %% We want to avoid code that can confuse beam_validator such as:
+    %%   is_tuple Fail Src
+    %%   test_arity Fail Src Arity
+    %%   is_map Fail Src
+    %%   get_tuple_element Src Pos Dst
+    %% Therefore, don't reorder the instructions in such cases.
+    reorder_1(Is, D, [I|Acc]);
 reorder_1([{test,_,{f,L},Ss}=I|Is0], D0,
 	  [{get_tuple_element,_,_,El}=G|Acc0]=Acc) ->
     case member(El, Ss) of
diff --git a/lib/compiler/test/beam_reorder_SUITE.erl b/lib/compiler/test/beam_reorder_SUITE.erl
index 4b2262f65b..ff31f2d3bd 100644
--- a/lib/compiler/test/beam_reorder_SUITE.erl
+++ b/lib/compiler/test/beam_reorder_SUITE.erl
@@ -21,7 +21,7 @@
 
 -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]).
+	 alloc/1,confused_beam_validator/1]).
 
 suite() -> [{ct_hooks,[ts_install_cth]}].
 
@@ -31,7 +31,8 @@ all() ->
 
 groups() ->
     [{p,[parallel],
-      [alloc
+      [alloc,
+       confused_beam_validator
       ]}].
 
 init_per_suite(Config) ->
@@ -65,5 +66,16 @@ alloc_b(_U1, _U2, R) ->
     _ = id(0),
     Res.
 
+confused_beam_validator(_Config) ->
+    {'EXIT',{{badmap,{any}},_}} = (catch efficient({any})),
+    ok.
+
+efficient({Var}=God) ->
+    id(God#{}),
+    catch
+	receive _ ->
+		Var
+	end.
+
 id(I) ->
     I.
-- 
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