[llvm-branch-commits] [clang] Document CallGraphSection option (PR #119468)

[via llvm-branch-commits]

https://github.com/Prabhuk created https://github.com/llvm/llvm-project/pull/119468

`CallGraphSection` CodeGen option emits the callgraph section. This
patch documents the design, implementation and usage of this option
and the underlying machinery.

Inferring indirect call targets from a binary is challenging without
source-level information. Hence, the reconstruction of a fine-grained
call graph from the binary is unfeasible for indirect/virtual calls.
To address this, CallGraphSection option collects the necessary information
to construct the call graph while the source information is present, and
stores it in a non-code section of the binary.

Original RFC: https://lists.llvm.org/pipermail/llvm-dev/2021-June/151044.html
Updated RFC: https://lists.llvm.org/pipermail/llvm-dev/2021-July/151739.html