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diff --git a/llvm/lib/Analysis/OptimizationRemarkEmitter.cpp b/llvm/lib/Analysis/OptimizationRemarkEmitter.cpp
new file mode 100644
index 00000000000..cd6a9366801
--- /dev/null
+++ b/llvm/lib/Analysis/OptimizationRemarkEmitter.cpp
@@ -0,0 +1,136 @@
+//===- OptimizationRemarkEmitter.cpp - Optimization Diagnostic --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Optimization diagnostic interfaces.  It's packaged as an analysis pass so
+// that by using this service passes become dependent on BFI as well.  BFI is
+// used to compute the "hotness" of the diagnostic message.
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/OptimizationRemarkEmitter.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
+#include "llvm/Analysis/LazyBlockFrequencyInfo.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/IR/DebugInfo.h"
+#include "llvm/IR/DiagnosticInfo.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/LLVMContext.h"
+
+using namespace llvm;
+
+OptimizationRemarkEmitter::OptimizationRemarkEmitter(const Function *F)
+    : F(F), BFI(nullptr) {
+  if (!F->getContext().getDiagnosticsHotnessRequested())
+    return;
+
+  // First create a dominator tree.
+  DominatorTree DT;
+  DT.recalculate(*const_cast<Function *>(F));
+
+  // Generate LoopInfo from it.
+  LoopInfo LI;
+  LI.analyze(DT);
+
+  // Then compute BranchProbabilityInfo.
+  BranchProbabilityInfo BPI;
+  BPI.calculate(*F, LI);
+
+  // Finally compute BFI.
+  OwnedBFI = llvm::make_unique<BlockFrequencyInfo>(*F, BPI, LI);
+  BFI = OwnedBFI.get();
+}
+
+bool OptimizationRemarkEmitter::invalidate(
+    Function &F, const PreservedAnalyses &PA,
+    FunctionAnalysisManager::Invalidator &Inv) {
+  // This analysis has no state and so can be trivially preserved but it needs
+  // a fresh view of BFI if it was constructed with one.
+  if (BFI && Inv.invalidate<BlockFrequencyAnalysis>(F, PA))
+    return true;
+
+  // Otherwise this analysis result remains valid.
+  return false;
+}
+
+Optional<uint64_t> OptimizationRemarkEmitter::computeHotness(const Value *V) {
+  if (!BFI)
+    return None;
+
+  return BFI->getBlockProfileCount(cast<BasicBlock>(V));
+}
+
+void OptimizationRemarkEmitter::computeHotness(
+    DiagnosticInfoIROptimization &OptDiag) {
+  const Value *V = OptDiag.getCodeRegion();
+  if (V)
+    OptDiag.setHotness(computeHotness(V));
+}
+
+void OptimizationRemarkEmitter::emit(
+    DiagnosticInfoOptimizationBase &OptDiagBase) {
+  auto &OptDiag = cast<DiagnosticInfoIROptimization>(OptDiagBase);
+  computeHotness(OptDiag);
+  // If a diagnostic has a hotness value, then only emit it if its hotness
+  // meets the threshold.
+  if (OptDiag.getHotness() &&
+      *OptDiag.getHotness() <
+          F->getContext().getDiagnosticsHotnessThreshold()) {
+    return;
+  }
+
+  F->getContext().diagnose(OptDiag);
+}
+
+OptimizationRemarkEmitterWrapperPass::OptimizationRemarkEmitterWrapperPass()
+    : FunctionPass(ID) {
+  initializeOptimizationRemarkEmitterWrapperPassPass(
+      *PassRegistry::getPassRegistry());
+}
+
+bool OptimizationRemarkEmitterWrapperPass::runOnFunction(Function &Fn) {
+  BlockFrequencyInfo *BFI;
+
+  if (Fn.getContext().getDiagnosticsHotnessRequested())
+    BFI = &getAnalysis<LazyBlockFrequencyInfoPass>().getBFI();
+  else
+    BFI = nullptr;
+
+  ORE = llvm::make_unique<OptimizationRemarkEmitter>(&Fn, BFI);
+  return false;
+}
+
+void OptimizationRemarkEmitterWrapperPass::getAnalysisUsage(
+    AnalysisUsage &AU) const {
+  LazyBlockFrequencyInfoPass::getLazyBFIAnalysisUsage(AU);
+  AU.setPreservesAll();
+}
+
+AnalysisKey OptimizationRemarkEmitterAnalysis::Key;
+
+OptimizationRemarkEmitter
+OptimizationRemarkEmitterAnalysis::run(Function &F,
+                                       FunctionAnalysisManager &AM) {
+  BlockFrequencyInfo *BFI;
+
+  if (F.getContext().getDiagnosticsHotnessRequested())
+    BFI = &AM.getResult<BlockFrequencyAnalysis>(F);
+  else
+    BFI = nullptr;
+
+  return OptimizationRemarkEmitter(&F, BFI);
+}
+
+char OptimizationRemarkEmitterWrapperPass::ID = 0;
+static const char ore_name[] = "Optimization Remark Emitter";
+#define ORE_NAME "opt-remark-emitter"
+
+INITIALIZE_PASS_BEGIN(OptimizationRemarkEmitterWrapperPass, ORE_NAME, ore_name,
+                      false, true)
+INITIALIZE_PASS_DEPENDENCY(LazyBFIPass)
+INITIALIZE_PASS_END(OptimizationRemarkEmitterWrapperPass, ORE_NAME, ore_name,
+                    false, true)