[clang] [flang] [llvm] Add IR Profile-Guided Optimization (IR PGO) support to the Flang compiler (PR #136098)

[Tom Eccles via cfe-commits]

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@@ -19,6 +21,7 @@ template <typename T> class Expected;
 template <typename T> class IntrusiveRefCntPtr;
 class Module;
 class MemoryBufferRef;
+extern cl::opt<llvm::PGOOptions::ColdFuncOpt> ClPGOColdFuncAttr;
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tblah wrote:

nit: I would put this `extern` in `BackendUtil.cpp` because it is not part of BackendUtils's public interface to other translation units.

https://github.com/llvm/llvm-project/pull/136098