path tracing benchmark

[Christian Kamm]

bearophile wrote:

> Trass3r:
> 
>> I ported smallpt to D some time ago and now that I've working versions of
>> LDC2 and GDC2 I did a quick comparison:
> 
> I have converted to D many of the commonly found benchmarks, this is my
> version: http://codepad.org/ZbmSfseY
> 
> If I compile it with with LDC1 with Link Time Optimization + Interning:
> ldc -O3 -release -inline -output-bc smallpt2_d.d
> 
> opt -std-compile-opts smallpt2_d.bc > smallpt2_do.bc
> 
> llvm-ld -native -ltango-base-ldc -ltango-user-ldc -ldl -lm -lpthread
> -internalize-public-api-list=_Dmain -o=smallpt2_do smallpt2_do.bc
> 
> I produce a binary that's faster than the C++ version (22.7 seconds
> instead of 29 seconds).

bearophile, just out of interest, what's the performance like if you ran 
ldmd -O3 -release -inline smallpt2_d.d ? If everything worked right -std-
compile-opts should do the same that LDC does at -O3. And why would 
internalizing _Dmain have a noticable performance impact?