diff --git a/bolt/include/bolt/Profile/DataAggregator.h b/bolt/include/bolt/Profile/DataAggregator.h
index 6ff1a66e76c6..f6374eadf019 100644
--- a/bolt/include/bolt/Profile/DataAggregator.h
+++ b/bolt/include/bolt/Profile/DataAggregator.h
@@ -146,6 +146,14 @@ private:
   std::unordered_map<uint64_t, uint64_t> BasicSamples;
   std::vector<PerfMemSample> MemSamples;
 
+  /// Filter pre-aggregated entries belonging to a DSO with this buildid.
+  /// Set when processing a shared library, empty implies main binary.
+  StringRef FilterBuildID;
+  /// Per-DSO samples breakdown: buildid -> sample count.
+  StringMap<uint64_t> DSOSamples;
+  /// Cross-DSO branch counts: (FromDSO -> ToDSO) -> branch count.
+  std::unordered_map<std::pair<StringRef, StringRef>, uint64_t> CrossDSOSamples;
+
   template <typename T> void clear(T &Container) {
     T TempContainer;
     TempContainer.swap(Container);
@@ -579,6 +587,7 @@ private:
   void printBranchSamplesDiagnostics() const;
   void printBasicSamplesDiagnostics(uint64_t OutOfRangeSamples) const;
   void printBranchStacksDiagnostics(uint64_t IgnoredSamples) const;
+  void printDSODiagnostics() const;
 
   /// Get instruction at \p Addr either from containing binary function or
   /// disassemble in-place, and invoke \p Callback on resulting MCInst.
diff --git a/bolt/lib/Profile/DataAggregator.cpp b/bolt/lib/Profile/DataAggregator.cpp
index c770656dbadf..abf9ec4f5aa9 100644
--- a/bolt/lib/Profile/DataAggregator.cpp
+++ b/bolt/lib/Profile/DataAggregator.cpp
@@ -392,6 +392,20 @@ void DataAggregator::parsePreAggregated() {
   ParsingBuf = FileBuf->getBuffer();
   Col = 0;
   Line = 1;
+
+  // When processing a shared object, filter pre-aggregated entries by buildid.
+  if (BC && !BC->HasFixedLoadAddress &&
+      BC->getFilename().ends_with(".so")) {
+    if (auto FileBID = BC->getFileBuildID()) {
+      FilterBuildID = *FileBID;
+      outs() << "PERF2BOLT: filtering pre-aggregated data for buildid "
+             << *FileBID << "\n";
+    } else {
+      errs() << "PERF2BOLT-WARNING: cannot read buildid from input binary, "
+                "won't filter pre-aggregated data\n";
+    }
+  }
+
   if (parsePreAggregatedLBRSamples()) {
     errs() << "PERF2BOLT: failed to parse samples\n";
     exit(1);
@@ -735,6 +749,8 @@ void DataAggregator::processProfile(BinaryContext &BC) {
   else
     processBranchEvents();
 
+  printDSODiagnostics();
+
   processMemEvents();
 
   // Mark all functions with registered events as having a valid profile.
@@ -1438,14 +1454,27 @@ std::error_code DataAggregator::parseAggregatedLBREntry() {
     return std::error_code();
   }
 
+  int64_t Count = Counters[0];
+  int64_t Mispreds = Counters[1];
+
+  if (Addr[0]) {
+    // Per-DSO sample count
+    DSOSamples[Addr[0]->Name] += Count;
+    // Cross-DSO branch count
+    if (Addr[1] && Addr[1]->Name != Addr[0]->Name)
+      CrossDSOSamples[{Addr[0]->Name, Addr[1]->Name}] += Count;
+  }
+
+  // Reset external addresses.
+  for (std::optional<Location> &Loc : Addr)
+    if (Loc && Loc->Name != FilterBuildID)
+      Loc->Offset = Trace::EXTERNAL;
+
   const uint64_t FromOffset = Addr[0]->Offset;
   BinaryFunction *FromFunc = getBinaryFunctionContainingAddress(FromOffset);
   if (FromFunc)
     FromFunc->setHasProfileAvailable();
 
-  int64_t Count = Counters[0];
-  int64_t Mispreds = Counters[1];
-
   /// Record basic IP sample into \p BasicSamples and return.
   if (Type == SAMPLE) {
     BasicSamples[FromOffset] += Count;
@@ -1662,6 +1691,70 @@ void DataAggregator::printBranchStacksDiagnostics(
               "were attributed to the input binary\n";
 }
 
+void DataAggregator::printDSODiagnostics() const {
+  // No buildids (except main binary).
+  if (DSOSamples.size() == 1)
+    return;
+
+  // Main binary: show DSOs covering 95th percentile of sample count.
+  if (FilterBuildID.empty()) {
+    // Sort DSOs by sample count.
+    std::vector<std::pair<std::string, uint64_t>> DSOs;
+    DSOs.reserve(DSOSamples.size());
+    for (const auto &[DSO, Count] : DSOSamples)
+      DSOs.emplace_back(DSO, Count);
+    llvm::sort(DSOs, llvm::less_second());
+
+    outs() << "PERF2BOLT: DSOs covering 95th percentile by samples:\n";
+    uint64_t CumulativeCount = 0;
+    for (auto &[DSO, Count] : llvm::reverse(DSOs)) {
+      CumulativeCount += Count;
+      if (DSO.empty())
+        DSO = "(binary)";
+      outs() << "\t" << DSO << ": " << Count << " samples, "
+             << format("%.1f%%", Count * 100.0f / NumTotalSamples)
+             << " of total, "
+             << format("%.1f%%", CumulativeCount * 100.0f / NumTotalSamples)
+             << " cumulative\n";
+      if (CumulativeCount * 100 >= NumTotalSamples * 95)
+        break;
+    }
+  }
+
+  // Cross-DSO branches: show DSO pairs covering 95th percentile of branch count.
+  if (CrossDSOSamples.size() > 1) {
+    // Sort DSO pairs by branch count.
+    std::vector<std::pair<std::pair<std::string, std::string>, uint64_t>>
+        XDSOs;
+    XDSOs.reserve(CrossDSOSamples.size());
+    // For main binary, include all DSOs. For FilterBuildID case, only include
+    // branches belonging to that DSO.
+    uint64_t NumTotalBranches = 0;
+    for (const auto &[FromTo, Count] : CrossDSOSamples) {
+      bool ShouldInclude = FilterBuildID.empty() || FromTo.first == FilterBuildID;
+      if (!ShouldInclude)
+        continue;
+      NumTotalBranches += Count;
+      XDSOs.emplace_back(FromTo, Count);
+    }
+    llvm::sort(XDSOs, llvm::less_second());
+
+    outs() << "PERF2BOLT: DSO pairs covering 95th percentile of branches:\n";
+    uint64_t CumulativeCount = 0;
+    for (auto &[FromTo, Count] : llvm::reverse(XDSOs)) {
+      CumulativeCount += Count;
+      outs() << "\t" << FromTo.first << " -> " << FromTo.second << ": " << Count
+             << " branches, "
+             << format("%.1f%%", Count * 100.0f / NumTotalBranches)
+             << " of total, "
+             << format("%.1f%%", CumulativeCount * 100.0f / NumTotalBranches)
+             << " cumulative\n";
+      if (CumulativeCount * 100 >= NumTotalBranches * 95)
+        break;
+    }
+  }
+}
+
 std::error_code DataAggregator::parseBranchEvents() {
   std::string BranchEventTypeStr =
       opts::ArmSPE ? "SPE branch events in brstack-format" : "branch events";