[compiler-rt] [llvm] [docs][IRPGO]Document two binary formats for IRPGO profiles (PR #76105)

[David Li via llvm-commits]

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+=====================
+IRPGO Profile Format
+=====================
+
+.. contents::
+   :local:
+
+
+Overview
+==========
+
+IR-based instrumentation (IRPGO) and its context-sensitive variant (CS-IRPGO)
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david-xl wrote:

Instrumentation PGO (both IR based and Frontend based).

https://github.com/llvm/llvm-project/pull/76105