[PATCH] [RFC] Rewrite the way we generate debug locations for variables.

[Alexey Samsonov]

  I don't think we're doing the work of register allocator here, though this may look similar :) Instead of tracking the "liveness" of registers, we're calculating the "liveness" of DBG_VALUE instructions, which are tied to user variables, and only occasionally - to registers.

http://llvm-reviews.chandlerc.com/D2658