[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:

Why would incompatibilities and ability to provide useful error messages be dependent on the flag being in the frontend? Is it that the backend can't actually reliably point the finger at the specific flag causing the conflict, so a message would be diluted to "sampling won't work with this"?

(probably a subject for a different forum tho)

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