instruction set simulation

Hi,

Does LLVM have any facilities for embedded instruction set simulation?
Ideally I'd like to convert a PowerPC program to LLVM, then run the
LLVM program while being able to interact with the memory space at
each step to emulate external stuff like sensors and network
transceivers.

Is anything like this possible? Are there utilities to transform
various targets, like PowerPC, back to LLVM?

Thanks.

-Tom

See http://www.libcpu.org/ for more information.