[clang] [llvm] [InstrPGO] Instrument sampling profile based cold function (PR #109837)

[Mircea Trofin via cfe-commits]

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@@ -1784,6 +1784,12 @@ defm debug_info_for_profiling : BoolFOption<"debug-info-for-profiling",
   PosFlag<SetTrue, [], [ClangOption, CC1Option],
           "Emit extra debug info to make sample profile more accurate">,
   NegFlag<SetFalse>>;
+def fprofile_generate_cold_function_coverage : Flag<["-"], "fprofile-generate-cold-function-coverage">, 
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mtrofin wrote:

I meant, why not just use `clang ... -mllvm -instrument-cold-function-coverage`? Is this a clang - only feature (i.e. rust can't use it?) Is it just for symmetry with the current PGO flags?

https://github.com/llvm/llvm-project/pull/109837