The Assignment Tracking debug-info feature is outlined in this RFC:
https://discourse.llvm.org/t/
rfc-assignment-tracking-a-better-way-of-specifying-variable-locations-in-ir
In an attempt to preserve more info, don't delete dbg.assign intrinsics that
are considered "out of scope" if they're linked to instructions.
Reviewed By: jmorse
Differential Revision: https://reviews.llvm.org/D133314
OCHyams