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

[Snehasish Kumar 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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snehasish wrote:

> Is it that the backend can't actually reliably point the finger at the specific flag causing the conflict

Yes, if we know that this instrumentation mode should not be mixed with e.g. sanitizers or something else we can enforce these checks early. I don't see a particular downside to adding a frontend flag. The convenience of bundling the 2 lld flags and 3 mllvm flags into a single frontend flag seems like a good enough motivation to do so.

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