[Issue 21023] New: 64 bit BSWAP instruction not supported by code generator

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21023

          Issue ID: 21023
           Summary: 64 bit BSWAP instruction not supported by code
                    generator
           Product: D
           Version: D2
          Hardware: x86_64
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: bugzilla at digitalmars.com

References:

BSWAP for 64 bits is emulated here:

  https://github.com/dlang/druntime/blob/master/src/core/bitop.d#L509

The instruction reference for it:

  https://www.felixcloutier.com/x86/bswap

Performance problems evident here:

  https://github.com/dlang/phobos/pull/7534/files

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