Reapply r294356 ("Keep track of spilled variables in LiveDebugValues").

Was reverted with r294447 due to undefined behavior with negative offsets
in DBG_VALUE instructions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294532 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed