diff --git a/llvm/lib/ProfileData/SampleProf.cpp b/llvm/lib/ProfileData/SampleProf.cpp
--- a/llvm/lib/ProfileData/SampleProf.cpp
+++ b/llvm/lib/ProfileData/SampleProf.cpp
@@ -371,9 +371,8 @@
 
 void SampleContextTrimmer::canonicalizeContextProfiles() {
   StringSet<> ProfilesToBeRemoved;
-  // Note that StringMap order is guaranteed to be top-down order,
-  // this makes sure we make room for promoted/merged context in the
-  // map, before we move profiles in the map.
+  // Use reference type to reduce unnecessary copying.
+  StringMap<FunctionSamples &> ProfilesToBeAdded;
   for (auto &I : ProfileMap) {
     FunctionSamples &FProfile = I.second;
     StringRef ContextStr = FProfile.getNameWithContext();
@@ -383,17 +382,54 @@
     // Use the context string from FunctionSamples to update the keys of
     // ProfileMap. They can get out of sync after context profile promotion
     // through pre-inliner.
-    auto Ret = ProfileMap.try_emplace(ContextStr, FProfile);
-    assert(Ret.second && "Conext conflict during canonicalization");
-    FProfile = Ret.first->second;
-
-    // Track the context profile to remove
-    ProfilesToBeRemoved.erase(ContextStr);
+    auto Ret = ProfilesToBeAdded.try_emplace(ContextStr, FProfile);
+    (void)Ret;
+    assert(Ret.second && "Context conflict during canonicalization");
     ProfilesToBeRemoved.insert(I.first());
   }
 
+  // There could be a conflict where a context being added is also being
+  // removed. This could happen when a context is promoted to another context
+  // which is also promoted to the third context. For example, given an original
+  // context A @ B @ C that is promoted to B @ C and the original context B @ C
+  // which is promoted to just C, adding B @ C to the profile map while removing
+  // same context (but with different profile) from the map will cause a
+  // conflict. We need to handle the conflict in a correct order. The order we
+  // are taking is
+  //    Insert C (new) into the profile map
+  //    Remove B @ C (old) from the profile
+  //    Insert B @ C (new) from the profile
+  //    Remove A @ B @ C (old) from the profile.
+  // The order matters because a new entry relies on the profile of the
+  // corresponding old entry to construct itself, so as to avoid unnecessary
+  // profile copying. Therefore, removing an old entry before the new entry is
+  // inserted is problematic. The processing order can be figured out by a
+  // simple algorithm that does not handle cyclic dependencies. This should be
+  // fine since we are only targeting context promotion where context strings
+  // are truncated when promoted.
+
+  // Step 1. Insert new contexts that do not exist so far.
+  for (auto &I : ProfilesToBeAdded) {
+    if (!ProfilesToBeRemoved.count(I.first()))
+      ProfileMap.try_emplace(I.first(), I.second);
+  }
+
+  // Step 2. Remove contexts that were not inserted in step 1.
+  for (auto &I : ProfilesToBeRemoved) {
+    if (ProfilesToBeAdded.count(I.first()))
+      ProfileMap.erase(I.first());
+  }
+
+  // Step 3. Insert contexts that were just removed.
+  for (auto &I : ProfilesToBeAdded) {
+    if (ProfilesToBeRemoved.count(I.first()))
+      ProfileMap.try_emplace(I.first(), I.second);
+  }
+
+  // Step 4. Remove the rest contexts.
   for (auto &I : ProfilesToBeRemoved) {
-    ProfileMap.erase(I.first());
+    if (!ProfilesToBeAdded.count(I.first()))
+      ProfileMap.erase(I.first());
   }
 }
 
diff --git a/llvm/tools/llvm-profgen/CSPreInliner.cpp b/llvm/tools/llvm-profgen/CSPreInliner.cpp
--- a/llvm/tools/llvm-profgen/CSPreInliner.cpp
+++ b/llvm/tools/llvm-profgen/CSPreInliner.cpp
@@ -16,11 +16,6 @@
 using namespace llvm;
 using namespace sampleprof;
 
-static cl::opt<bool> EnableCSPreInliner(
-    "csspgo-preinliner", cl::Hidden, cl::init(false),
-    cl::desc("Run a global pre-inliner to merge context profile based on "
-             "estimated global top-down inline decisions"));
-
 // The switches specify inline thresholds used in SampleProfileLoader inlining.
 // TODO: the actual threshold to be tuned here because the size here is based
 // on machine code not LLVM IR.
@@ -179,9 +174,6 @@
 }
 
 void CSPreInliner::run() {
-  if (!EnableCSPreInliner)
-    return;
-
 #ifndef NDEBUG
   auto printProfileNames = [](StringMap<FunctionSamples> &Profiles,
                               bool IsInput) {
diff --git a/llvm/tools/llvm-profgen/ProfileGenerator.cpp b/llvm/tools/llvm-profgen/ProfileGenerator.cpp
--- a/llvm/tools/llvm-profgen/ProfileGenerator.cpp
+++ b/llvm/tools/llvm-profgen/ProfileGenerator.cpp
@@ -48,6 +48,11 @@
     cl::desc("Keep the last K frames while merging cold profile. 1 means the "
              "context-less base profile"));
 
+static cl::opt<bool> EnableCSPreInliner(
+    "csspgo-preinliner", cl::Hidden, cl::init(false),
+    cl::desc("Run a global pre-inliner to merge context profile based on "
+             "estimated global top-down inline decisions"));
+
 extern cl::opt<int> ProfileSummaryCutoffCold;
 
 using namespace llvm;
@@ -401,7 +406,8 @@
 
   // Run global pre-inliner to adjust/merge context profile based on estimated
   // inline decisions.
-  CSPreInliner(ProfileMap, HotCountThreshold, ColdCountThreshold).run();
+  if (EnableCSPreInliner)
+    CSPreInliner(ProfileMap, HotCountThreshold, ColdCountThreshold).run();
 
   // Trim and merge cold context profile using cold threshold above;
   SampleContextTrimmer(ProfileMap)