LLVM goes back to 2003, and Sing# is based on Spec# which is only 2004?
The Wikipedia mentions 2003 and we can assume there was already work going on before.
http://en.wikipedia.org/wiki/Singularity_%28operating_system...
Although the first published papers are indeed from 2004.
It comes from the Singularity OS compiler toolchain, which is older than LLVM.
It is also used to deploy .NET applications as native code on Windows Phone 8 devices.