[clang] [llvm] [InstrPGO] Support cold function coverage instrumentation (PR #109837)

[Reid Kleckner via cfe-commits]

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@@ -1182,8 +1187,13 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
   const bool IsCtxProfUse =
       !UseCtxProfile.empty() && Phase == ThinOrFullLTOPhase::ThinLTOPreLink;
 
+  // Enable cold function coverage instrumentation if
+  // InstrumentColdFuncOnlyPath is provided.
+  const bool IsColdFuncOnlyInstrGen = PGOInstrumentColdFunctionOnly =
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rnk wrote:

Setting this global variable here has introduced a data race detected by TSan when different threads set up different pass pipelines. Was this intentional? Did you mean to use `==` instead of `=`?

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