Tried release build got ICE, does anyone have a clue what might cause this?

[Random D user via Digitalmars-d-learn]

So I tried to build my project in release for the first time in a 
long while. It takes like 25x longer to compile and finally the 
compiler crashes. It seems to go away if I disable the optimizer.
I get:

tym = x1d
Internal error: backend\cgxmm.c 547
Does anyone have a clue what might trigger this?
I'm asking because my project has grown a bit and I don't really 
have any good way of isolating this.

I'm using dmd 2.068.1 and msvc x64 target.