DebugLoc associated with a machine instruction is used to emit location entries....

DebugLoc associated with a machine instruction is used to emit location entries. DebugLoc associated with a DBG_VALUE is used to identify lexical scope of the variable. After register allocation, while inserting DBG_VALUE remember original debug location for the first instruction and reuse it, otherwise dwarf writer may be mislead in identifying the variable's scope.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124845 91177308-0d34-0410-b5e6-96231b3b80d8