[llvm] [PGO] Sampled instrumentation in PGO to speed up instrumentation binary (PR #69535)

[via llvm-commits]

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@@ -805,6 +808,10 @@ void PassBuilder::addPGOInstrPasses(ModulePassManager &MPM,
   // Do counter promotion at Level greater than O0.
   Options.DoCounterPromotion = true;
   Options.UseBFIInPromotion = IsCS;
+  if (EnableSampledInstr) {
+    Options.Sampling = true;
+    Options.DoCounterPromotion = false;
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xur-llvm wrote:

The reason is mentioned in InstrProfling.C:400.

https://github.com/llvm/llvm-project/pull/69535