Index: llvm/trunk/lib/IR/ModuleSummaryIndex.cpp
===================================================================
--- llvm/trunk/lib/IR/ModuleSummaryIndex.cpp
+++ llvm/trunk/lib/IR/ModuleSummaryIndex.cpp
@@ -14,11 +14,17 @@
 
 #include "llvm/IR/ModuleSummaryIndex.h"
 #include "llvm/ADT/SCCIterator.h"
+#include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
+#define DEBUG_TYPE "module-summary-index"
+
+STATISTIC(ReadOnlyLiveGVars,
+          "Number of live global variables marked read only");
+
 FunctionSummary FunctionSummary::ExternalNode =
     FunctionSummary::makeDummyFunctionSummary({});
 bool ValueInfo::isDSOLocal() const {
@@ -160,6 +166,14 @@
           GVS->setReadOnly(false);
       propagateConstantsToRefs(S.get());
     }
+#if LLVM_ENABLE_STATS
+  for (auto &P : *this)
+    if (P.second.SummaryList.size())
+      if (auto *GVS = dyn_cast<GlobalVarSummary>(
+              P.second.SummaryList[0]->getBaseObject()))
+        if (isGlobalValueLive(GVS) && GVS->isReadOnly())
+          ReadOnlyLiveGVars++;
+#endif
 }
 
 // TODO: write a graphviz dumper for SCCs (see ModuleSummaryIndex::exportToDot)
Index: llvm/trunk/test/ThinLTO/X86/index-const-prop.ll
===================================================================
--- llvm/trunk/test/ThinLTO/X86/index-const-prop.ll
+++ llvm/trunk/test/ThinLTO/X86/index-const-prop.ll
@@ -3,13 +3,18 @@
 ;  2. Make a local copy of internal definition if all accesses to it are readonly. This allows constant
 ;     folding it during optimziation phase.
 
+; -stats requires asserts
+; REQUIRES: asserts
+
 ; RUN: opt -module-summary %s -o %t1.bc
 ; RUN: opt -module-summary %p/Inputs/index-const-prop.ll -o %t2.bc
 ; RUN: llvm-lto -thinlto-action=thinlink -o %t3.index.bc %t1.bc %t2.bc
-; RUN: llvm-lto -thinlto-action=import -exported-symbol=main  %t1.bc -thinlto-index=%t3.index.bc -o %t1.imported.bc
+; RUN: llvm-lto -thinlto-action=import -exported-symbol=main  %t1.bc -thinlto-index=%t3.index.bc -o %t1.imported.bc -stats 2>&1 | FileCheck %s --check-prefix=STATS
 ; RUN: llvm-dis %t1.imported.bc -o - | FileCheck %s --check-prefix=IMPORT
 ; RUN: llvm-lto -thinlto-action=optimize %t1.imported.bc -o - | llvm-dis - -o - | FileCheck %s --check-prefix=OPTIMIZE
 
+; STATS: 2 module-summary-index - Number of live global variables marked read only
+
 ; Check that we don't internalize gBar when it is exported
 ; RUN: llvm-lto -thinlto-action=import -exported-symbol main -exported-symbol gBar  %t1.bc -thinlto-index=%t3.index.bc -o %t1.imported2.bc
 ; RUN: llvm-dis %t1.imported2.bc -o - | FileCheck %s --check-prefix=IMPORT2
@@ -28,6 +33,10 @@
 
 @gBar = external global i32
 
+; Should not be counted in the stats of live read only variables since it is
+; dead and will be dropped anyway.
+@gDead = internal unnamed_addr global i32 1, align 4
+
 define i32 @main() local_unnamed_addr {
   %call = tail call i32 bitcast (i32 (...)* @foo to i32 ()*)()
   %call1 = tail call i32 bitcast (i32 (...)* @bar to i32 ()*)()