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  1. JDK
  2. JDK-8161210 slowdown in MHs.iteratedLoop handles
  3. JDK-8166840

Synthetic bridge constructor in ArrayList$Itr blocks inlining

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    • Sub-task
    • Resolution: Fixed
    • P4
    • 9
    • None
    • core-libs

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      Description

        As discussed recently on hotspot-compiler-dev[1], having a private class with no default constructor can lead to C2 failing to inline, due to the synthetic bridge constructor using a dummy argument of an uninitialized class. This is really a problem in C2, as well as something which could ultimately be resolved by nestmates...

        However, there is an easy workaround in adding an empty package-private constructor. In the most recently found case - a microbenchmark stressing MethodHandles.iteratedLoop - adding this to ArrayList$Itr lead to a 2.5-3x speedup. It thus makes sense to do this simple change in this particular case as a quick fix and solve the larger C2 issue separately.

        [1] http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2016-September/024407.html

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            Backport - A issue that is required to port a Bug or Feature into another product release. This issue type is generally associated with the main Bug/Feature to represent each individual release of the port. JDK-8166853 Synthetic bridge constructor in ArrayList$Itr blocks inlining

            • P4 - Minor loss of function, or other problem where easy workaround is present.
            • Resolved

            Backport - A issue that is required to port a Bug or Feature into another product release. This issue type is generally associated with the main Bug/Feature to represent each individual release of the port. JDK-8183742 Synthetic bridge constructor in ArrayList$Itr blocks inlining

            • P4 - Minor loss of function, or other problem where easy workaround is present.
            • Resolved

            Backport - A issue that is required to port a Bug or Feature into another product release. This issue type is generally associated with the main Bug/Feature to represent each individual release of the port. JDK-8192482 Synthetic bridge constructor in ArrayList$Itr blocks inlining

            • P4 - Minor loss of function, or other problem where easy workaround is present.
            • Resolved
            relates to

            Bug - A problem which impairs or prevents the functions of the product. JDK-8167005 Comment on the need for an empty constructor in ArrayList$Itr

            • P4 - Minor loss of function, or other problem where easy workaround is present.
            • Closed

            Bug - A problem which impairs or prevents the functions of the product. JDK-8161210 slowdown in MHs.iteratedLoop handles

            • P3 - Major loss of function.
            • Open

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                redestad Claes Redestad
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