Index: lib/Transforms/Instrumentation/EfficiencySanitizer.cpp
===================================================================
--- lib/Transforms/Instrumentation/EfficiencySanitizer.cpp
+++ lib/Transforms/Instrumentation/EfficiencySanitizer.cpp
@@ -102,6 +102,21 @@
   return Options;
 }
 
+// Create a constant for Str so that we can pass it to the run-time lib.
+static GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str,
+                                                    bool AllowMerging) {
+  Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
+  // We use private linkage for module-local strings. If they can be merged
+  // with another one, we set the unnamed_addr attribute.
+  GlobalVariable *GV =
+    new GlobalVariable(M, StrConst->getType(), true,
+                       GlobalValue::PrivateLinkage, StrConst, "");
+  if (AllowMerging)
+    GV->setUnnamedAddr(true);
+  GV->setAlignment(1);  // Strings may not be merged w/o setting align 1.
+  return GV;
+}
+
 /// EfficiencySanitizer: instrument each module to find performance issues.
 class EfficiencySanitizer : public ModulePass {
 public:
@@ -115,6 +130,7 @@
 private:
   bool initOnModule(Module &M);
   void initializeCallbacks(Module &M);
+  void createCacheFragGV(Module &M, SmallVector<Constant *, 4> &ToolInfoVec);
   GlobalVariable *createEsanInitToolGV(Module &M);
   void createDestructor(Module &M, GlobalVariable *GV);
   bool runOnFunction(Function &F, Module &M);
@@ -204,15 +220,39 @@
                             IRB.getInt32Ty(), IntptrTy, nullptr));
 }
 
+// Create the global variable for the cache-fragmentation tool.
+void EfficiencySanitizer::createCacheFragGV(
+    Module &M, SmallVector<Constant *, 4> &ToolInfoVec) {
+  assert(Options.ToolType == EfficiencySanitizerOptions::ESAN_CacheFrag);
+  // FIXME: expand ToolInfoVec for the cache-fragmentation tool.
+}
+
 // Create the tool-specific global variable passed to EsanInit and EsanExit.
 GlobalVariable *EfficiencySanitizer::createEsanInitToolGV(Module &M) {
-  GlobalVariable *GV = nullptr;
-  // FIXME: create the tool specific global variable.
-  if (GV == nullptr) {
-    GV = new GlobalVariable(M, IntptrTy, true, GlobalVariable::InternalLinkage,
-                            Constant::getNullValue(IntptrTy));
-  }
-  return GV;
+  // This structure contains tool-specific information about each compilation
+  // unit (module) and is passed to the runtime library.
+  // This structure should be kept consistent with the tool-specific struct
+  // in the runtime library.
+  // struct ToolInfo {
+  //   const char *UnitName;
+  //   // expanding for the specific tool.
+  //   ...
+  // };
+  SmallVector<Constant *, 4> ToolInfoVec;
+  // Compilation unit name.
+  ToolInfoVec.push_back(
+      ConstantExpr::getPointerCast(
+          createPrivateGlobalForString(M, M.getModuleIdentifier(), true),
+          Type::getInt8PtrTy(*Ctx)));
+  // Expanding ToolInfo for the specific tool.
+  if (Options.ToolType == EfficiencySanitizerOptions::ESAN_CacheFrag)
+    createCacheFragGV(M, ToolInfoVec);
+  // Create the global variable.
+  Constant *ToolInfo = ConstantStruct::getAnon(ToolInfoVec);
+  auto *ToolInfoGV = new GlobalVariable(M, ToolInfo->getType(), true,
+                                        GlobalVariable::InternalLinkage,
+                                        ToolInfo);
+  return ToolInfoGV;
 }
 
 void EfficiencySanitizer::createDestructor(Module &M, GlobalVariable *GV) {