Reproduce: this appears in arbitrary command(e.g java -XX:+PrintCompilation Reduced) with arbitrary build mode.

The output of PrintCompilation is ill-formed:

     22 1 3 java.lang.Object::<init> (1 bytes)
     25 2 3 java.lang.String::hashCode (60 bytes)
     25 3 3 java.lang.String::coder (15 bytes)
     27 4 3 Reduced::foo (12 bytes)
     27 5 3 java.lang.Boolean::valueOf (14 bytes)
     27 6 3 java.lang.Boolean::hashCode (8 bytes)
     27 8 4 Reduced::foo (12 bytes)
     27 7 2 java.lang.Boolean::hashCode (14 bytes)
   4 3 Reduced::foo (12 bytes) made not entrant <------missing timestamp
     29 9 % 3 Reduced::main @ 4 (33 bytes)
     29 10 3 Reduced::main (33 bytes)
     29 11 % 4 Reduced::main @ 4 (33 bytes)
   9 % 3 Reduced::main @ 4 (33 bytes) made not entrant
  11 % 4 Reduced::main @ 4 (33 bytes) made not entrant

This seems related to JDK-8272586, which print timestamp optionally.