[PATCH] Generate better location ranges for some register-described variables.

[Adrian Prantl]

When determining ChangingRegs, we should also ignore the function's epilogue. Otherwise we will drop debug info for (e.g., spilled) variables [FrameIndex+Offset], because the frame pointer itself is restored in the epilogue and thus marked as changing when it really isn't. Unfortunately there is no FrameSetup flag for epilogue instructions, but I think it would be safe to just make an exception for the frame pointer.

Also I realized we need to have the spiller insert DBG_VALUEs after reloads, but that's only tangentially related.

http://reviews.llvm.org/D3933