Index: llvm/trunk/include/llvm/Transforms/InstrProfiling.h
===================================================================
--- llvm/trunk/include/llvm/Transforms/InstrProfiling.h
+++ llvm/trunk/include/llvm/Transforms/InstrProfiling.h
@@ -109,7 +109,8 @@
   void emitRegistration();
 
   /// Emit the necessary plumbing to pull in the runtime initialization.
-  void emitRuntimeHook();
+  /// Returns true if a change was made.
+  bool emitRuntimeHook();
 
   /// Add uses of our data variables and runtime hook.
   void emitUses();
Index: llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp
+++ llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp
@@ -448,14 +448,6 @@
 }
 
 bool InstrProfiling::run(Module &M, const TargetLibraryInfo &TLI) {
-  // Improve compile time by avoiding linear scans when there is no work.
-  GlobalVariable *CoverageNamesVar =
-      M.getNamedGlobal(getCoverageUnusedNamesVarName());
-  if (!containsProfilingIntrinsics(M) && !CoverageNamesVar)
-    return false;
-
-  bool MadeChange = false;
-
   this->M = &M;
   this->TLI = &TLI;
   NamesVar = nullptr;
@@ -466,6 +458,15 @@
                               MemOPSizeRangeLast);
   TT = Triple(M.getTargetTriple());
 
+  // Emit the runtime hook even if no counters are present.
+  bool MadeChange = emitRuntimeHook();
+
+  // Improve compile time by avoiding linear scans when there is no work.
+  GlobalVariable *CoverageNamesVar =
+      M.getNamedGlobal(getCoverageUnusedNamesVarName());
+  if (!containsProfilingIntrinsics(M) && !CoverageNamesVar)
+    return MadeChange;
+
   // We did not know how many value sites there would be inside
   // the instrumented function. This is counting the number of instrumented
   // target value sites to enter it as field in the profile data variable.
@@ -498,7 +499,6 @@
   emitVNodes();
   emitNameData();
   emitRegistration();
-  emitRuntimeHook();
   emitUses();
   emitInitialization();
   return true;
@@ -914,15 +914,15 @@
   IRB.CreateRetVoid();
 }
 
-void InstrProfiling::emitRuntimeHook() {
+bool InstrProfiling::emitRuntimeHook() {
   // We expect the linker to be invoked with -u<hook_var> flag for linux,
   // for which case there is no need to emit the user function.
   if (Triple(M->getTargetTriple()).isOSLinux())
-    return;
+    return false;
 
   // If the module's provided its own runtime, we don't need to do anything.
   if (M->getGlobalVariable(getInstrProfRuntimeHookVarName()))
-    return;
+    return false;
 
   // Declare an external variable that will pull in the runtime initialization.
   auto *Int32Ty = Type::getInt32Ty(M->getContext());
@@ -947,6 +947,7 @@
 
   // Mark the user variable as used so that it isn't stripped out.
   UsedVars.push_back(User);
+  return true;
 }
 
 void InstrProfiling::emitUses() {
Index: llvm/trunk/test/Instrumentation/InstrProfiling/linkage.ll
===================================================================
--- llvm/trunk/test/Instrumentation/InstrProfiling/linkage.ll
+++ llvm/trunk/test/Instrumentation/InstrProfiling/linkage.ll
@@ -7,6 +7,9 @@
 ; RUN: opt < %s  -mtriple=x86_64-pc-win32-coff -instrprof -S | FileCheck %s --check-prefix=COFF
 ; RUN: opt < %s  -mtriple=x86_64-pc-win32-coff -passes=instrprof -S | FileCheck %s --check-prefix=COFF
 
+; OTHER: @__llvm_profile_runtime = external global i32
+; LINUX-NOT: @__llvm_profile_runtime = external global i32
+
 @__profn_foo = hidden constant [3 x i8] c"foo"
 @__profn_foo_weak = weak hidden constant [8 x i8] c"foo_weak"
 @"__profn_linkage.ll:foo_internal" = internal constant [23 x i8] c"linkage.ll:foo_internal"
@@ -52,9 +55,6 @@
 
 declare void @llvm.instrprof.increment(i8*, i64, i32, i32)
 
-; OTHER: @__llvm_profile_runtime = external global i32
-; LINUX-NOT: @__llvm_profile_runtime = external global i32
-
 ; OTHER: define linkonce_odr hidden i32 @__llvm_profile_runtime_user() {{.*}} {
 ; OTHER:   %[[REG:.*]] = load i32, i32* @__llvm_profile_runtime
 ; OTHER:   ret i32 %[[REG]]
Index: llvm/trunk/test/Instrumentation/InstrProfiling/no-counters.ll
===================================================================
--- llvm/trunk/test/Instrumentation/InstrProfiling/no-counters.ll
+++ llvm/trunk/test/Instrumentation/InstrProfiling/no-counters.ll
@@ -1,10 +1,12 @@
-;; No instrumentation should be emitted if there are no counter increments.
+;; Emit the runtime hook even if there are no counter increments.
 
-; RUN: opt < %s -instrprof -S | FileCheck %s
-; RUN: opt < %s -passes=instrprof -S | FileCheck %s
-; CHECK-NOT: @__profc
-; CHECK-NOT: @__profd
-; CHECK-NOT: @__llvm_profile_runtime
+; RUN: opt < %s -mtriple=x86_64-apple-macosx10.10.0 -instrprof -S | FileCheck %s -check-prefixes=ALL,DARWIN
+; RUN: opt < %s -mtriple=x86_64-apple-macosx10.10.0 -passes=instrprof -S | FileCheck %s -check-prefixes=ALL,DARWIN
+; RUN: opt < %s -mtriple=x86_64-linux-unknown -passes=instrprof -S | FileCheck %s -check-prefixes=ALL,LINUX
+; ALL-NOT: @__profc
+; ALL-NOT: @__profd
+; DARWIN: @__llvm_profile_runtime
+; LINUX-NOT: @__llvm_profile_runtime
 
 define void @foo() {
   ret void
Index: llvm/trunk/test/Instrumentation/InstrProfiling/profiling.ll
===================================================================
--- llvm/trunk/test/Instrumentation/InstrProfiling/profiling.ll
+++ llvm/trunk/test/Instrumentation/InstrProfiling/profiling.ll
@@ -3,6 +3,8 @@
 
 target triple = "x86_64-apple-macosx10.10.0"
 
+; CHECK: @__llvm_profile_runtime = external global i32
+
 @__profn_foo = hidden constant [3 x i8] c"foo"
 ; CHECK-NOT: __profn_foo
 @__profn_bar = hidden constant [4 x i8] c"bar\00"
@@ -35,5 +37,4 @@
 
 declare void @llvm.instrprof.increment(i8*, i64, i32, i32)
 
-; CHECK: @__llvm_profile_runtime = external global i32
 ; CHECK: @llvm.used = appending global {{.*}} @__profd_foo {{.*}} @__profd_bar {{.*}} @__profd_baz {{.*}} section "llvm.metadata"