copying memory in phobos

[Mike Wey]

On 04/08/2014 02:35 PM, Mike wrote:
> On Tuesday, 8 April 2014 at 11:56:43 UTC, ketmar wrote:
>>> I understand that.  But why is dest[] = src[] not good enough for
>>> run-time?
>> 'cause some compilers (gcc, for example) has memcpy() as 'intrinsic'
>> and generates better inline code for it sometimes. it's just a small
>> hint for compiler backend, and faster code is good, isn't it? ;-)
>
> a[] = b[] causes the compiler to generate a call to _d_arraycopy, and
> _d_arraycopy calls, you guessed it, memcpy!  (verified with GDC 4.8.2)
> So, there is no performance benefit calling memcpy directly.  It's going
> to be called anyway.

_d_arraycopy does check if the source and destination are of equal 
length and that they don't overlap before calling memcpy.
Although i don't know how much that impacts the performance.

> I'm beginning to believe that, at least in the code I posted, memcpy can
> be replaced by the array syntax, removing a dependency on the C library.

-- 
Mike Wey