Reapply r128045 and r128051 with fixes.

Reapply r128045 and r128051 with fixes.

This will extend the ranges of debug info variables in registers until they are
clobbered.

Fix 1: Don't mistake DBG_VALUE instructions referring to incoming arguments on
the stack with DBG_VALUE instructions referring to variables in the frame
pointer. This fixes the gdb test-suite failure.

Fix 2: Don't trace through copies to physical registers setting up call
arguments. These registers are call clobbered, and the source register is more
likely to be a callee-saved register that can be extended through the call
instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128114 91177308-0d34-0410-b5e6-96231b3b80d8