Interesting performance results on Crc port from zlib

[Steven Schveighoffer]

On 1/24/21 10:26 AM, Igor wrote:
> I ported zlib way of CRC calculation [1] to D and then I compared its 
> performance to Phobos std.digest.crc and to calling actual zlib 
> implementation through etc.c.zlib: crc32_z and I got some interesting 
> results:
> 
> build type   |  zlib  | phobos | zlibdport |
> --------------------------------------------
> dmd debug    |  240ms |  272ms |     211ms |
> dmd release  |  237ms |  279ms |     202ms |
> ldc debug    |  238ms |  136ms |     264ms |
> ldc release  |  238ms |  132ms |     125ms |
> 
> Calling actual zlib is pretty constant, I guess because it uses 
> precompiled static library. What is really surprising is how much faster 
> is the port from original zlib. Anyone has any idea how can that be?

Probably inlining. If you are using a compiled library, it can't inline 
the code, it has to be an opaque call.

-Steve