From 773e3d0f4a2d978a7ec6be9ed639eb1941d92d6c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 30 Jul 2019 08:34:51 +0200
Subject: Fix compiler crash when compiling with +no_type_opt

If the `no_type_opt` option was given, the compiler would crash when
attempting to compile containing with a `try`...`after` construct,
such as this code:

    foo() ->
        try
            make_ref()
        after
            ok
        end.

To avoid having this bug re-appear, test the `no_type_opt` option
in the test suites.

https://bugs.erlang.org/browse/ERL-997
---
 lib/compiler/src/beam_ssa_opt.erl | 18 +++++++++++++++---
 lib/compiler/src/compile.erl      |  7 +++++--
 2 files changed, 20 insertions(+), 5 deletions(-)

(limited to 'lib/compiler/src')

diff --git a/lib/compiler/src/beam_ssa_opt.erl b/lib/compiler/src/beam_ssa_opt.erl
index 229edc6a1d..d87c66c272 100644
--- a/lib/compiler/src/beam_ssa_opt.erl
+++ b/lib/compiler/src/beam_ssa_opt.erl
@@ -1939,12 +1939,24 @@ verify_merge_is(_) ->
 
 is_merge_allowed(_, #b_blk{}, #b_blk{is=[#b_set{op=peek_message}|_]}) ->
     false;
-is_merge_allowed(L, #b_blk{last=#b_br{}}=Blk, #b_blk{}) ->
+is_merge_allowed(L, #b_blk{last=#b_br{}}=Blk, #b_blk{is=Is}) ->
     %% The predecessor block must have exactly one successor (L) for
     %% the merge to be safe.
     case beam_ssa:successors(Blk) of
-        [L] -> true;
-        [_|_] -> false
+        [L] ->
+            case Is of
+                [#b_set{op=phi,args=[_]}|_] ->
+                    %% The type optimizer pass must have been
+                    %% turned off, since it would have removed this
+                    %% redundant phi node. Refuse to merge the blocks
+                    %% to ensure that this phi node remains at the
+                    %% beginning of a block.
+                    false;
+                _ ->
+                    true
+            end;
+        [_|_] ->
+            false
     end;
 is_merge_allowed(_, #b_blk{last=#b_switch{}}, #b_blk{}) ->
     false.
diff --git a/lib/compiler/src/compile.erl b/lib/compiler/src/compile.erl
index 28db8986ff..0325c714d0 100644
--- a/lib/compiler/src/compile.erl
+++ b/lib/compiler/src/compile.erl
@@ -268,8 +268,11 @@ expand_opt(r21, Os) ->
     [no_put_tuple2 | expand_opt(no_bsm3, Os)];
 expand_opt({debug_info_key,_}=O, Os) ->
     [encrypt_debug_info,O|Os];
-expand_opt(no_type_opt, Os) ->
-    [no_ssa_opt_type_start,
+expand_opt(no_type_opt=O, Os) ->
+    %% Be sure to keep the no_type_opt option so that it will
+    %% be recorded in the BEAM file, allowing the test suites
+    %% to recompile the file with this option.
+    [O,no_ssa_opt_type_start,
      no_ssa_opt_type_continue,
      no_ssa_opt_type_finish | Os];
 expand_opt(O, Os) -> [O|Os].
-- 
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