merge revision(s) 63868,63870: [Backport #14897]

	Fix a bug of peephole optimization

	```
	  if   L1
	L0:
	  jump L2
	L1:
	  ...
	L2:
	```

	was wrongly optimized to:

	```
	  unless L2
	L0:
	L1:
	  ...
	L2:
	```

	To make it conservative, this optimization is now disabled when there is
	any label between `if` and `jump` instructions.
	Fixes [Bug #14897].

	compile.c: remove unreachable jump only

	* compile.c (iseq_peephole_optimize): remove unreachable jump
	  instruction only.  if it is labeled and referred from other
	  instructions, it is reachable and must not be removed.
	  [ruby-core:87830] [Bug #14897]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@64893 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 13 insertions, 0 deletions

diff --git a/test/ruby/test_optimization.rb b/test/ruby/test_optimization.rb
index ecc4ba425f..d4557ddbbb 100644
--- a/test/ruby/test_optimization.rb
+++ b/test/ruby/test_optimization.rb
@@ -730,4 +730,17 @@ class TestRubyOptimization < Test::Unit::TestCase
       tap {true || tap {}}
     end;
   end
+
+  def test_jump_elimination_with_optimized_out_block
+    x = Object.new
+    def x.bug(obj)
+      if obj || obj
+        obj = obj
+      else
+        raise "[ruby-core:87830] [Bug #14897]"
+      end
+      obj
+    end
+    assert_equal(:ok, x.bug(:ok))
+  end
 end