https://issues.dlang.org/show_bug.cgi?id=23605

          Issue ID: 23605
           Summary: The current implementation of powmod is very slow for
                    the ulong type
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: phobos
          Assignee: nobody@puremagic.com
          Reporter: siarhei.siamashka@hotmail.com

Long multiplication with a 128-bit result can be used to optimize https://github.com/dlang/phobos/blob/v2.101.2/std/math/exponential.d#L830-L854

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