Fix reference links, adjust wording slightly

Author: SLTozer

llvm/docs/HowToUpdateDebugInfo.rst

@@ -431,25 +431,27 @@ where the missing source location is intentional. For this, you can use the
 ``debugify`` output. This is enabled in a build of LLVM by setting the CMake
 flag ``-DLLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING=COVERAGE``. When this has been
 set, LLVM will enable runtime tracking of
-:ref:`DebugLoc annotations<_NewInstLocations>`, allowing ``debugify`` to ignore
+:ref:`DebugLoc annotations<NewInstLocations>`, allowing ``debugify`` to ignore
 instructions that have an explicitly recorded reason given for not having a
 source location.
 
 For triaging source location bugs detected with ``debugify``, you may find it
-helpful to instead set the CMake flag
+helpful to instead set the CMake flag to enable "origin tracking",
 ``-DLLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING=COVERAGE_AND_ORIGIN``. This flag adds
 more detail to ``debugify``'s output, by including one or more stacktraces with
 every missing source location, capturing the point at which the empty source
 location was created, and every point at which it was copied to an instruction,
-making it trivial in most cases to find the origin of the underlying bug.
+making it trivial in most cases to find the origin of the underlying bug. If
+using origin tracking, it is recommended to also build LLVM with debug info
+enabled, so that the stacktrace can be accurately symbolized.
 
 .. note::
 
    The coverage tracking feature has been designed primarily for use with the
-   :ref:`original debug info preservation` mode of ``debugify``, and so may not
-   be reliable in other settings. When using this mode, the stacktraces produced
-   by the ``COVERAGE_AND_ORIGIN`` setting will be printed in an easy-to-read
-   format as part of the reports generated by the
+   :ref:`original debug info preservation<OriginalDI>` mode of ``debugify``, and
+   so may not be reliable in other settings. When using this mode, the
+   stacktraces produced by the ``COVERAGE_AND_ORIGIN`` setting will be printed
+   in an easy-to-read format as part of the reports generated by the
    ``llvm-original-di-preservation.py`` script.
 
 .. _OriginalDI: