http://d.puremagic.com/issues/show_bug.cgi?id=10402

           Summary: memmove optimization for std.algorithm.copy
           Product: D
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody@puremagic.com
        ReportedBy: tommitissari@hotmail.com


--- Comment #0 from Tommi <tommitissari@hotmail.com> 2013-06-18 05:24:34 PDT ---
Add an optimization for:

Range2 copy(Range1, Range2)(Range1 source, Range2 target);

...to use the c function memmove when it is safe to do so and the two ranges overlap each other (when they don't overlap, a vectorized copy should be faster). As far as I can tell, it is safe to use memmove for copying source over target if all of the following are true:

1) Both ranges are arrays (static or dynamic)
2) Both arrays have the same element type
3) hasElaborateAssign!T is false for the element type T

I haven't benchmarked anything, but all the good C++ standard library implementations of std::copy seem to do this optimization, and I trust that they know what they are doing.

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http://d.puremagic.com/issues/show_bug.cgi?id=10402



--- Comment #1 from Tommi <tommitissari@hotmail.com> 2013-06-18 06:03:11 PDT ---
(In reply to comment #0)
> Add an optimization for:
> 
> Range2 copy(Range1, Range2)(Range1 source, Range2 target);
> 
> ...to use the c function memmove when it is safe to do so and the two ranges overlap each other (when they don't overlap, a vectorized copy should be faster). As far as I can tell, it is safe to use memmove for copying source over target if all of the following are true:
> 
> 1) Both ranges are arrays (static or dynamic)
> 2) Both arrays have the same element type
> 3) hasElaborateAssign!T is false for the element type T
> 
> I haven't benchmarked anything, but all the good C++ standard library implementations of std::copy seem to do this optimization, and I trust that they know what they are doing.

Also, the documentation for std.algorithm.copy should be changed to indicate that the ranges are allowed to overlap if the above conditions hold.

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