[llvm] [docs][TypeProf]Update instrumentation file format document (PR #83309)

[Mingming Liu via llvm-commits]

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@@ -455,6 +497,16 @@ Temporal Profile Traces
 The section is used to carry on temporal profile information from raw profiles.
 See `temporal profiling`_ for the design.
 
+Virtual Table Names
+^^^^^^^^^^^^^^^^^^^^
+This section is used to carry on the names of vtables from raw profiles into
+indexed profiles.
+
+Unlike function names which are stored as keys of `function data`_ hash table,
+vtable names needs to be stored in a standalone section in indexed profiles.
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minglotus-6 wrote:

done.

https://github.com/llvm/llvm-project/pull/83309