Robin:
All in all I must say that I am more pleased with the DMD results as I am kind of worried about the LDC allocation test performance ...
I am not sure of the causes of this, but the D GG was improved a little, in the last two compiler versions.
I also had to rewrite parts of the codes as some functions just weren't "pure" or "nothrow" such as the whole things around this.data[] += other.data[].
This because LDC2 is one version of the language behind. It's a temporary problem.
Your multiplicationTest timings with LDC2 seem to have not yet reached the performance of your C++ code. You can take a look at the asm output of both. Perhaps in the D code you have some allocation you are not doing in the C++ code.
Bye, bearophile
