I didn't intend to imply otherwise but I see my wording was unclear. I meant that D generally would be a hit, though it's only really speculation either way.

There is no inherent reason that D code would be slower than C++ code.

I should know, I've written a C++ compiler and know where the bloat is buried, and designed D to eschew features that would be inherently slower than the C++ counterparts.

You can even turn off the runtime array bounds checking.

If you use the same backend... no. They are both native languages with "no room below".

llvm vs icc could be a hit, but that's all really.