compile.c: stop the jump-jump optimization if the second has any event

Fixes [Bug #17868]

compile.c

@@ -2926,7 +2926,8 @@ iseq_peephole_optimize(rb_iseq_t *iseq, LINK_ELEMENT *list, const int do_tailcal
 	}
         else if (iobj != diobj && IS_INSN(&diobj->link) &&
                  IS_INSN_ID(diobj, jump) &&
-		 OPERAND_AT(iobj, 0) != OPERAND_AT(diobj, 0)) {
+		 OPERAND_AT(iobj, 0) != OPERAND_AT(diobj, 0) &&
+                 diobj->insn_info.events == 0) {
 	    /*
 	     *  useless jump elimination:
 	     *     jump LABEL1

test/ruby/test_settracefunc.rb

@@ -2386,4 +2386,19 @@ class TestSetTraceFunc < Test::Unit::TestCase
     EOS
     assert_equal [:return, :unpack], event
   end
+
+  def test_while_in_while
+    lines = []
+
+    TracePoint.new(:line){|tp|
+      next unless target_thread?
+      lines << tp.lineno
+    }.enable{
+      n = 3
+      while n > 0
+        n -= 1 while n > 0
+      end
+    }
+    assert_equal [__LINE__ - 5, __LINE__ - 4, __LINE__ - 3], lines, 'Bug #17868'
+  end
 end