I had found weird bugs in Windows x64 not saving XMM4/XMM5:

```
// But, not saving XMM4 and XMM5 breaks things in VS 2010, even though they are volatile regs.
```
3e6df2d7aa8a7995b54e3a49a73083c717e76a90

I found a value was expected to be preserved in XMM4.  I'm not sure if it was a bug in MSVC2010 though.

-[Unknown]