[llvm] [SHT_LLVM_FUNC_MAP][ObjectYaml]Introduce function address map section and emit dynamic instruction count(ObjectYaml part) (PR #124332)

[James Henderson via llvm-commits]

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@@ -535,6 +535,27 @@ Example of BBAddrMap with PGO data:
    .uleb128  1000                         # BB_3 basic block frequency (only when enabled)
    .uleb128  0                            # BB_3 successors count (only enabled with branch probabilities)
 
+``SHT_LLVM_FUNC_MAP`` Section (function address map)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+This section stores the mapping from the binary address of function to its
+related metadata features. It is used to emit function-level analysis data and
+can be enabled through ``--func-map`` option. The fields are encoded in the
+following format:
+
+#. A version number byte used for backward compatibility.
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jh7370 wrote:

No problem. It's important to get these things right! On the plus side, as long as the first part of an entry is the version byte, if we come up with a better format in the future, all we have to do is bump the version number and ensure the header or first entry has that version byte first again, i.e. the header approach (should you decide to switch in the future for whatever reason) is interchangeable with the version-per-entry approach, assuming you have the correct version byte, since the version-per-entry approach is effectively "header per entry" where the version field is the sole component of the header.

Another consideration: is it important to be able to traverse this structure quickly to find the appropriate entry?

https://github.com/llvm/llvm-project/pull/124332