From d10fd4596270d7f8503dc46a0a7c229ad08795d2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Fri, 29 Jun 2018 14:14:40 +0200
Subject: Eliminate a crash in the beam_jump pass

https://bugs.erlang.org/browse/ERL-660
---
 lib/compiler/src/beam_utils.erl        |  3 +++
 lib/compiler/test/beam_utils_SUITE.erl | 25 +++++++++++++++++++++++--
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/lib/compiler/src/beam_utils.erl b/lib/compiler/src/beam_utils.erl
index 5510624b2d..30b6dcac8c 100644
--- a/lib/compiler/src/beam_utils.erl
+++ b/lib/compiler/src/beam_utils.erl
@@ -355,6 +355,9 @@ split_even(Rs) -> split_even(Rs, [], []).
 %%                    exit BIF will raise an exception
 %%    used - Reg is used
 
+check_liveness({fr,_}, _, St) ->
+    %% Conservatively always consider the floating point register used.
+    {used,St};
 check_liveness(R, [{block,Blk}|Is], St0) ->
     case check_liveness_block(R, Blk, St0) of
 	{transparent,St1} ->
diff --git a/lib/compiler/test/beam_utils_SUITE.erl b/lib/compiler/test/beam_utils_SUITE.erl
index 3d35b546fc..dee7fb9cf9 100644
--- a/lib/compiler/test/beam_utils_SUITE.erl
+++ b/lib/compiler/test/beam_utils_SUITE.erl
@@ -25,7 +25,8 @@
 	 is_not_killed/1,is_not_used_at/1,
 	 select/1,y_catch/1,otp_8949_b/1,liveopt/1,coverage/1,
          y_registers/1,user_predef/1,scan_f/1,cafu/1,
-         receive_label/1,read_size_file_version/1,not_used/1]).
+         receive_label/1,read_size_file_version/1,not_used/1,
+         is_used_fr/1]).
 -export([id/1]).
 
 suite() -> [{ct_hooks,[ts_install_cth]}].
@@ -52,7 +53,8 @@ groups() ->
        scan_f,
        cafu,
        read_size_file_version,
-       not_used
+       not_used,
+       is_used_fr
       ]}].
 
 init_per_suite(Config) ->
@@ -527,5 +529,24 @@ not_used_p(_C, S, K, L) when is_record(K, k) ->
             id(K)
     end.
 
+is_used_fr(Config) ->
+    1 = is_used_fr(self(), self()),
+    1 = is_used_fr(self(), other),
+    receive 1 -> ok end,
+    receive 1 -> ok end,
+    receive 1 -> ok end,
+    receive 1 -> ok end,
+    ok.
+
+is_used_fr(X, Y) ->
+    %% beam_utils:is_used({fr,R}, Code) would crash.
+    _ = 0 / (X ! 1),
+    _ = case Y of
+            X -> ok;
+            _ -> error
+        end,
+    X ! 1.
+
+
 %% The identity function.
 id(I) -> I.
-- 
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