[llvm] [Coroutines] Conditional elide coroutines based on hot/cold information (PR #145831)

[Adrian Vogelsgesang via llvm-commits]

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@@ -145,6 +191,37 @@ PreservedAnalyses CoroAnnotationElidePass::run(LazyCallGraph::SCC &C,
       bool IsCallerPresplitCoroutine = Caller->isPresplitCoroutine();
       bool HasAttr = CB->hasFnAttr(llvm::Attribute::CoroElideSafe);
       if (IsCallerPresplitCoroutine && HasAttr) {
+
+        llvm::raw_ostream *OS = nullptr;
+        auto _ = getCoroElidedStatsOStream(OS);
+        assert(OS && "At least we should able to get access to standard error");
+
+        auto &BFI = FAM.getResult<BlockFrequencyAnalysis>(*Caller);
+        if (BFI.getBlockFreq(CB->getParent()) <
+            BFI.getEntryFreq()) {
+          static BranchProbability MinBranchProbability(
+              static_cast<int>(CoroElideBranchRatio * MinBlockCounterExecution),
+              MinBlockCounterExecution);
+
+          auto Prob = BranchProbability::getBranchProbability(
+              BFI.getBlockFreq(CB->getParent()).getFrequency(),
+              BFI.getEntryFreq().getFrequency());
+
+          if (Prob < MinBranchProbability) {
+            *OS << "Not eliding " << *CB
+                << " with estimated probability: " << Prob << "\n";
+            continue;
+          }
+
+          *OS << "BB Prob: \t" << Prob << "\n";
+        } else {
+          *OS << "BB Freq: \t"
+              << BFI.getBlockFreq(CB->getParent()).getFrequency() << "\n";
+          *OS << "Entry Freq: \t" << BFI.getEntryFreq().getFrequency() << "\n";
+        }
+
+        *OS << "eliding " << *CB << "\n";
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vogelsgesang wrote:

should we integrate this information on whether / why a coroutine was elided into the optimization remarks (already used further down in this file)

https://github.com/llvm/llvm-project/pull/145831