SPE doesn't have a fmadd instruction, so don't bother hoisting a
multiply and add sequence to this, as it'd become just a library call.
Hoisting happens too late for the CTR usability test to veto using the CTR
in a loop, and results in an assert "Invalid PPC CTR loop!".
A test is forthcoming. This may be the wrong approach, and a better approach
may be instead to use a feature flag, or something else, for the CPU. However,
since the "traditional" FPU and all its derivatives have fmadd, I didn't see it
necessary for solving this problem. There may be additional CTR related
problems on SPE, though, that I haven't found yet.