dmd codegen improvements

[Etienne Cimon via Digitalmars-d]

On Tuesday, 18 August 2015 at 10:45:49 UTC, Walter Bright wrote:
> So if you're comparing code generated by dmd/gdc/ldc, and 
> notice something that dmd could do better at (1, 2 or 3), 
> please let me know. Often this sort of thing is low hanging 
> fruit that is fairly easily inserted into the back end.

I think someone mentioned how other compilers unroll loops at 
more than 2 levels.

Other than that, there was a recent Java vs D thread which showed 
it orders of magnitude faster on vtable calls. So I think the 
most amazing feature would be to allow profiling & sampling to 
compile with samples and select which functions to inline or do 
some magic around vtable pointers like what Java is doing.

Finally, I'm going to write this down here and haven't had time 
to look more into it but I've never been able to compile Botan 
with optimizations on DMD64 Win64 VS2013 
(https://github.com/etcimon/botan), it's really strange having a 
crypto library that you can't optimize, building -O -g also gives 
me a ccog.c ICE error. I think it might be something about `asm 
pure` that uses some locals, does that eliminate the function 
call parameters?