Requesting Help with Optimizing Code

[Kyle Ingraham]

On Thursday, 8 April 2021 at 03:27:12 UTC, Max Haughton wrote:
> Are you making the compiler aware of your machine? Although the 
> obvious point here is vector width (you have AVX-512 from what 
> I can see, however I'm not sure if this is actually a win or 
> not on Skylake W), the compiler is also forced to use a 
> completely generic scheduling model which may or may not yield 
> good code for your procesor. For LDC, you'll want 
> `-mcpu=native`. Also use cross module inlining if you aren't 
> already.

I haven't tried this yet but will give it a go. Ideally I'd want 
performance independent of compilers but could sprinkle this into 
the build config for when LDC is used.

> I also notice in your hot code, you are using function 
> contracts: When contracts are being checked, LDC actually does 
> use them to optimize the code, however in release builds when 
> they are turned off this is not the case. If you are happy to 
> assume that they are true in release builds (I believe you 
> should at least), you can give the compiler this additional 
> information via the use of an intrinsic or similar (with LDC I 
> just use inline IR, on GDC you have __builtin_unreachable()). 
> LDC *will* assume asserts in release builds as far as I have 
> tested, however this still invokes a branch (just not to a 
> proper assert handler)...

Thanks for shining light on a level of optimization that I did 
not know existed. I've got a lot of learning to do in this area. 
Do you have any resources you'd recommend?