3 files changed, 32 insertions, 1 deletions
diff --git a/llvm/lib/IR/ModuleSummaryIndex.cpp b/llvm/lib/IR/ModuleSummaryIndex.cpp
index ce74c00766f..4c4466f9a90 100644
--- a/llvm/lib/IR/ModuleSummaryIndex.cpp
+++ b/llvm/lib/IR/ModuleSummaryIndex.cpp
@@ -13,10 +13,14 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/IR/ModuleSummaryIndex.h"
+#include "llvm/ADT/SCCIterator.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
+FunctionSummary FunctionSummary::ExternalNode =
+    FunctionSummary::makeDummyFunctionSummary({});
 bool ValueInfo::isDSOLocal() const {
   // Need to check all summaries are local in case of hash collisions.
   return getSummaryList().size() &&
@@ -80,6 +84,26 @@ bool ModuleSummaryIndex::isGUIDLive(GlobalValue::GUID GUID) const {
   return false;
 }
 
+// TODO: write a graphviz dumper for SCCs (see ModuleSummaryIndex::exportToDot)
+// then delete this function and update its tests
+LLVM_DUMP_METHOD
+void ModuleSummaryIndex::dumpSCCs(raw_ostream &O) {
+  for (scc_iterator<ModuleSummaryIndex *> I =
+           scc_begin<ModuleSummaryIndex *>(this);
+       !I.isAtEnd(); ++I) {
+    O << "SCC (" << utostr(I->size()) << " node" << (I->size() == 1 ? "" : "s")
+      << ") {\n";
+    for (const ValueInfo V : *I) {
+      FunctionSummary *F = nullptr;
+      if (V.getSummaryList().size())
+        F = cast<FunctionSummary>(V.getSummaryList().front().get());
+      O << " " << (F == nullptr ? "External" : "") << " " << utostr(V.getGUID())
+        << (I.hasLoop() ? " (has loop)" : "") << "\n";
+    }
+    O << "}\n";
+  }
+}
+
 namespace {
 struct Attributes {
   void add(const Twine &Name, const Twine &Value,
diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index 1047b8ddeb4..94baee63b0e 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -50,6 +50,10 @@ using namespace object;
 
 #define DEBUG_TYPE "lto"
 
+static cl::opt<bool>
+    DumpThinCGSCCs("dump-thin-cg-sccs", cl::init(false), cl::Hidden,
+                   cl::desc("Dump the SCCs in the ThinLTO index's callgraph"));
+
 // The values are (type identifier, summary) pairs.
 typedef DenseMap<
     GlobalValue::GUID,
@@ -1141,6 +1145,9 @@ Error LTO::runThinLTO(AddStreamFn AddStream, NativeObjectCache Cache) {
       ThinLTO.ModuleMap.size());
   StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
 
+  if (DumpThinCGSCCs)
+    ThinLTO.CombinedIndex.dumpSCCs(outs());
+
   if (Conf.OptLevel > 0)
     ComputeCrossModuleImport(ThinLTO.CombinedIndex, ModuleToDefinedGVSummaries,
                              ImportLists, ExportLists);
diff --git a/llvm/lib/Transforms/IPO/FunctionImport.cpp b/llvm/lib/Transforms/IPO/FunctionImport.cpp
index f886a161bae..aade726994f 100644
--- a/llvm/lib/Transforms/IPO/FunctionImport.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionImport.cpp
@@ -18,8 +18,8 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringMap.h"
-#include "llvm/ADT/StringSet.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringSet.h"
 #include "llvm/Bitcode/BitcodeReader.h"
 #include "llvm/IR/AutoUpgrade.h"
 #include "llvm/IR/Constants.h"