Remove static global GCNames from Function.cpp and move it to the Con…

…text

This remove the need for locking when deleting a function.

Differential Revision: http://reviews.llvm.org/D15988

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 257139

llvm/include/llvm/IR/Function.h

@@ -66,7 +66,8 @@ class Function : public GlobalObject, public ilist_node<Function> {
    * bit 2      : HasPrologueData
    * bit 3      : HasPersonalityFn
    * bits 4-13  : CallingConvention
-   * bits 14-15 : [reserved]
+   * bits 14    : HasGC
+   * bits 15 : [reserved]
    */
 
   /// Bits from GlobalObject::GlobalObjectSubclassData.
@@ -220,9 +221,11 @@ class Function : public GlobalObject, public ilist_node<Function> {
 
   /// hasGC/getGC/setGC/clearGC - The name of the garbage collection algorithm
   ///                             to use during code generation.
-  bool hasGC() const;
-  const char *getGC() const;
-  void setGC(const char *Str);
+  bool hasGC() const {
+    return getSubclassDataFromValue() & (1<<14);
+  }
+  const std::string &getGC() const;
+  void setGC(const std::string Str);
   void clearGC();
 
   /// @brief adds the attribute to the list of attributes.

llvm/include/llvm/IR/LLVMContext.h

@@ -93,6 +93,17 @@ class LLVMContext {
   /// tag registered with an LLVMContext has an unique ID.
   uint32_t getOperandBundleTagID(StringRef Tag) const;
 
+
+  /// Define the GC for a function
+  void setGC(const Function &Fn, std::string GCName);
+
+  /// Return the GC for a function
+  const std::string &getGC(const Function &Fn);
+
+  /// Remove the GC for a function
+  void deleteGC(const Function &Fn);
+
+
   typedef void (*InlineAsmDiagHandlerTy)(const SMDiagnostic&, void *Context,
                                          unsigned LocCookie);
 

llvm/lib/IR/Core.cpp

@@ -1722,7 +1722,7 @@ void LLVMSetFunctionCallConv(LLVMValueRef Fn, unsigned CC) {
 
 const char *LLVMGetGC(LLVMValueRef Fn) {
   Function *F = unwrap<Function>(Fn);
-  return F->hasGC()? F->getGC() : nullptr;
+  return F->hasGC()? F->getGC().c_str() : nullptr;
 }
 
 void LLVMSetGC(LLVMValueRef Fn, const char *GC) {

llvm/lib/IR/Function.cpp

@@ -366,47 +366,21 @@ void Function::addDereferenceableOrNullAttr(unsigned i, uint64_t Bytes) {
   setAttributes(PAL);
 }
 
-// Maintain the GC name for each function in an on-the-side table. This saves
-// allocating an additional word in Function for programs which do not use GC
-// (i.e., most programs) at the cost of increased overhead for clients which do
-// use GC.
-static DenseMap<const Function*,PooledStringPtr> *GCNames;
-static StringPool *GCNamePool;
-static ManagedStatic<sys::SmartRWMutex<true> > GCLock;
-
-bool Function::hasGC() const {
-  sys::SmartScopedReader<true> Reader(*GCLock);
-  return GCNames && GCNames->count(this);
-}
-
-const char *Function::getGC() const {
+const std::string &Function::getGC() const {
   assert(hasGC() && "Function has no collector");
-  sys::SmartScopedReader<true> Reader(*GCLock);
-  return *(*GCNames)[this];
+  return getContext().getGC(*this);
 }
 
-void Function::setGC(const char *Str) {
-  sys::SmartScopedWriter<true> Writer(*GCLock);
-  if (!GCNamePool)
-    GCNamePool = new StringPool();
-  if (!GCNames)
-    GCNames = new DenseMap<const Function*,PooledStringPtr>();
-  (*GCNames)[this] = GCNamePool->intern(Str);
+void Function::setGC(const std::string Str) {
+  setValueSubclassDataBit(14, !Str.empty());
+  getContext().setGC(*this, std::move(Str));
 }
 
 void Function::clearGC() {
-  sys::SmartScopedWriter<true> Writer(*GCLock);
-  if (GCNames) {
-    GCNames->erase(this);
-    if (GCNames->empty()) {
-      delete GCNames;
-      GCNames = nullptr;
-      if (GCNamePool->empty()) {
-        delete GCNamePool;
-        GCNamePool = nullptr;
-      }
-    }
-  }
+  if (!hasGC())
+    return;
+  getContext().deleteGC(*this);
+  setValueSubclassDataBit(14, false);
 }
 
 /// Copy all additional attributes (those not needed to create a Function) from

llvm/lib/IR/LLVMContext.cpp

@@ -304,3 +304,19 @@ void LLVMContext::getOperandBundleTags(SmallVectorImpl<StringRef> &Tags) const {
 uint32_t LLVMContext::getOperandBundleTagID(StringRef Tag) const {
   return pImpl->getOperandBundleTagID(Tag);
 }
+
+void LLVMContext::setGC(const Function &Fn, std::string GCName) {
+  auto It = pImpl->GCNames.find(&Fn);
+
+  if (It == pImpl->GCNames.end()) {
+    pImpl->GCNames.insert(std::make_pair(&Fn, std::move(GCName)));
+    return;
+  }
+  It->second = std::move(GCName);
+}
+const std::string &LLVMContext::getGC(const Function &Fn) {
+  return pImpl->GCNames[&Fn];
+}
+void LLVMContext::deleteGC(const Function &Fn) {
+  pImpl->GCNames.erase(&Fn);
+}

llvm/lib/IR/LLVMContextImpl.h

@@ -1027,6 +1027,13 @@ class LLVMContextImpl {
   void getOperandBundleTags(SmallVectorImpl<StringRef> &Tags) const;
   uint32_t getOperandBundleTagID(StringRef Tag) const;
 
+  /// Maintain the GC name for each function.
+  ///
+  /// This saves allocating an additional word in Function for programs which
+  /// do not use GC (i.e., most programs) at the cost of increased overhead for
+  /// clients which do use GC.
+  DenseMap<const Function*, std::string> GCNames;
+
   LLVMContextImpl(LLVMContext &C);
   ~LLVMContextImpl();
 

llvm/lib/Transforms/Scalar/PlaceSafepoints.cpp

@@ -499,7 +499,7 @@ static bool isGCSafepointPoll(Function &F) {
 static bool shouldRewriteFunction(Function &F) {
   // TODO: This should check the GCStrategy
   if (F.hasGC()) {
-    const char *FunctionGCName = F.getGC();
+    const auto &FunctionGCName = F.getGC();
     const StringRef StatepointExampleName("statepoint-example");
     const StringRef CoreCLRName("coreclr");
     return (StatepointExampleName == FunctionGCName) ||

llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp

@@ -2558,7 +2558,7 @@ void RewriteStatepointsForGC::stripNonValidAttributesFromBody(Function &F) {
 static bool shouldRewriteStatepointsIn(Function &F) {
   // TODO: This should check the GCStrategy
   if (F.hasGC()) {
-    const char *FunctionGCName = F.getGC();
+    const auto &FunctionGCName = F.getGC();
     const StringRef StatepointExampleName("statepoint-example");
     const StringRef CoreCLRName("coreclr");
     return (StatepointExampleName == FunctionGCName) ||