1 files changed, 35 insertions, 11 deletions

diff --git a/lib/Transforms/Instrumentation/InstrProfiling.cpp b/lib/Transforms/Instrumentation/InstrProfiling.cpp
index 9b70f95480e4..22076f04d6ad 100644
--- a/lib/Transforms/Instrumentation/InstrProfiling.cpp
+++ b/lib/Transforms/Instrumentation/InstrProfiling.cpp
@@ -13,7 +13,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/Transforms/InstrProfiling.h"
+#include "llvm/Transforms/Instrumentation/InstrProfiling.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
@@ -271,8 +271,8 @@ public:
         break;
     }
 
-    DEBUG(dbgs() << Promoted << " counters promoted for loop (depth="
-                 << L.getLoopDepth() << ")\n");
+    LLVM_DEBUG(dbgs() << Promoted << " counters promoted for loop (depth="
+                      << L.getLoopDepth() << ")\n");
     return Promoted != 0;
   }
 
@@ -430,9 +430,24 @@ void InstrProfiling::promoteCounterLoadStores(Function *F) {
   }
 }
 
-bool InstrProfiling::run(Module &M, const TargetLibraryInfo &TLI) {
-  bool MadeChange = false;
+/// Check if the module contains uses of any profiling intrinsics.
+static bool containsProfilingIntrinsics(Module &M) {
+  if (auto *F = M.getFunction(
+          Intrinsic::getName(llvm::Intrinsic::instrprof_increment)))
+    if (!F->use_empty())
+      return true;
+  if (auto *F = M.getFunction(
+          Intrinsic::getName(llvm::Intrinsic::instrprof_increment_step)))
+    if (!F->use_empty())
+      return true;
+  if (auto *F = M.getFunction(
+          Intrinsic::getName(llvm::Intrinsic::instrprof_value_profile)))
+    if (!F->use_empty())
+      return true;
+  return false;
+}
 
+bool InstrProfiling::run(Module &M, const TargetLibraryInfo &TLI) {
   this->M = &M;
   this->TLI = &TLI;
   NamesVar = nullptr;
@@ -443,6 +458,15 @@ bool InstrProfiling::run(Module &M, const TargetLibraryInfo &TLI) {
                               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.
@@ -464,8 +488,7 @@ bool InstrProfiling::run(Module &M, const TargetLibraryInfo &TLI) {
   for (Function &F : M)
     MadeChange |= lowerIntrinsics(&F);
 
-  if (GlobalVariable *CoverageNamesVar =
-          M.getNamedGlobal(getCoverageUnusedNamesVarName())) {
+  if (CoverageNamesVar) {
     lowerCoverageData(CoverageNamesVar);
     MadeChange = true;
   }
@@ -476,7 +499,6 @@ bool InstrProfiling::run(Module &M, const TargetLibraryInfo &TLI) {
   emitVNodes();
   emitNameData();
   emitRegistration();
-  emitRuntimeHook();
   emitUses();
   emitInitialization();
   return true;
@@ -669,6 +691,7 @@ static bool needsRuntimeRegistrationOfSectionRange(const Module &M) {
   // Use linker script magic to get data/cnts/name start/end.
   if (Triple(M.getTargetTriple()).isOSLinux() ||
       Triple(M.getTargetTriple()).isOSFreeBSD() ||
+      Triple(M.getTargetTriple()).isOSFuchsia() ||
       Triple(M.getTargetTriple()).isPS4CPU())
     return false;
 
@@ -892,15 +915,15 @@ void InstrProfiling::emitRegistration() {
   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());
@@ -925,6 +948,7 @@ void InstrProfiling::emitRuntimeHook() {
 
   // Mark the user variable as used so that it isn't stripped out.
   UsedVars.push_back(User);
+  return true;
 }
 
 void InstrProfiling::emitUses() {