For Java 9 JDK-8145688 optimized Math.pow. This caused a regression compared to Java 8, which special cased for powers of 2. That special case is missing from Java 9.
See also:
https://www.reddit.com/r/javahelp/comments/7b5erh/i_think_i_found_piece_of_code_which_is_8_times/
            
See also:
https://www.reddit.com/r/javahelp/comments/7b5erh/i_think_i_found_piece_of_code_which_is_8_times/
- duplicates
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                    JDK-8190869 C2: missing strength reduction of Math.pow(x, 2.0D) to x*x -           
- Resolved
 
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- relates to
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                    JDK-8145688 update for x86 pow in the math lib -           
- Resolved
 
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