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

4 files changed, 35 insertions, 5 deletions

diff --git a/bootstraptest/test_flow.rb b/bootstraptest/test_flow.rb
index 0390062a24..9da6d45cbd 100644
--- a/bootstraptest/test_flow.rb
+++ b/bootstraptest/test_flow.rb
@@ -589,3 +589,13 @@ assert_equal "foo", %q{
   end
   Bug6460.new.m1
 }, '[ruby-dev:46372]'
+
+assert_equal "foo", %q{
+  obj = "foo"
+  if obj || any1
+    any2 = any2
+  else
+    raise obj.inspect
+  end
+  obj
+}, '[ruby-core:87830]'
diff --git a/compile.c b/compile.c
index 2f1e46aaa1..95ba803995 100644
--- a/compile.c
+++ b/compile.c
@@ -2469,6 +2469,8 @@ iseq_peephole_optimize(rb_iseq_t *iseq, LINK_ELEMENT *list, const int do_tailcal
 		  IS_INSN_ID(piobj, branchunless))) {
 	    INSN *pdiobj = (INSN *)get_destination_insn(piobj);
 	    if (niobj == pdiobj) {
+		int refcnt = IS_LABEL(piobj->link.next) ?
+		    ((LABEL *)piobj->link.next)->refcnt : 0;
 		/*
 		 * useless jump elimination (if/unless destination):
 		 *   if   L1
@@ -2486,7 +2488,12 @@ iseq_peephole_optimize(rb_iseq_t *iseq, LINK_ELEMENT *list, const int do_tailcal
 		piobj->insn_id = (IS_INSN_ID(piobj, branchif))
 		  ? BIN(branchunless) : BIN(branchif);
 		replace_destination(piobj, iobj);
-		ELEM_REMOVE(&iobj->link);
+		if (refcnt <= 1) {
+		    ELEM_REMOVE(&iobj->link);
+		}
+		else {
+		    /* TODO: replace other branch destinations too */
+		}
 		return COMPILE_OK;
 	    }
 	    else if (diobj == pdiobj) {
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
diff --git a/version.h b/version.h
index 9a63e01338..230c84ead3 100644
--- a/version.h
+++ b/version.h
@@ -1,10 +1,10 @@
 #define RUBY_VERSION "2.5.2"
-#define RUBY_RELEASE_DATE "2018-09-03"
-#define RUBY_PATCHLEVEL 90
+#define RUBY_RELEASE_DATE "2018-10-01"
+#define RUBY_PATCHLEVEL 91
 
 #define RUBY_RELEASE_YEAR 2018
-#define RUBY_RELEASE_MONTH 9
-#define RUBY_RELEASE_DAY 3
+#define RUBY_RELEASE_MONTH 10
+#define RUBY_RELEASE_DAY 1
 
 #include "ruby/version.h"