Interesting performance results on Crc port from zlib

[Igor]

On Sunday, 24 January 2021 at 17:55:20 UTC, welkam wrote:
> On Sunday, 24 January 2021 at 16:23:24 UTC, Igor wrote:
>> ldc2 -c -O3 source/crc32.d test/test.d
>
> Edited the command for clarity. As I suspected the compiler can 
> see the whole programs source code and because of that it can 
> perform better optimizations. If you tried to compile C version 
> with link time optimizations you might get similar results.

It seems you are right. I edited the example.c that comes with 
zlib to just do CRC calculation 100_000 times on 4K buffer and 
compiled it with its make file. But it first made a libz.a static 
lib and then it compiled example.c and linked them together. This 
resulted in executable that still calculates CRC in 262ms. But 
then I included crc32.c directly into example.c and compiled it 
as single compilation unit and now it does the job in 96ms. Same 
happened when I linked it with static lib using gcc -flto so LTO 
is used.

I had no idea this can have such big impact on performance. 
That's it, I am just using source libraries from now on :D