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digitalmars.D.bugs - [Issue 21041] New: core.bitop.byteswap(ushort) should used ROL/ROR


          Issue ID: 21041
           Summary: core.bitop.byteswap(ushort) should used ROL/ROR
                    instead of XCHG
           Product: D
           Version: D2
          Hardware: x86_64
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: safety0ff.bugz gmail.com

ROL/ROR should provide better performance and less constraints for register

The claim of better performance is based on:
 - https://www.agner.org/optimize/instruction_tables.pdf
 - Looking at gcc & llvm compiler output

The only disadvantage I see is that the instruction is longer.

Jul 11 2020