[GCC] Attribute ifunc support in llvm

This patch add support for GCC attribute((ifunc("resolver"))) for
targets that use ELF as object file format. In general ifunc is a
special kind of function alias with type @gnu_indirect_function. Patch
for Clang http://reviews.llvm.org/D15524

Differential Revision: http://reviews.llvm.org/D15525

llvm-svn: 265667

llvm/lib/IR/Module.cpp

@@ -41,6 +41,7 @@ using namespace llvm;
 template class llvm::SymbolTableListTraits<Function>;
 template class llvm::SymbolTableListTraits<GlobalVariable>;
 template class llvm::SymbolTableListTraits<GlobalAlias>;
+template class llvm::SymbolTableListTraits<GlobalIFunc>;
 
 //===----------------------------------------------------------------------===//
 // Primitive Module methods.
@@ -59,6 +60,7 @@ Module::~Module() {
   GlobalList.clear();
   FunctionList.clear();
   AliasList.clear();
+  IFuncList.clear();
   NamedMDList.clear();
   delete ValSymTab;
   delete static_cast<StringMap<NamedMDNode *> *>(NamedMDSymTab);
@@ -250,6 +252,10 @@ GlobalAlias *Module::getNamedAlias(StringRef Name) const {
   return dyn_cast_or_null<GlobalAlias>(getNamedValue(Name));
 }
 
+GlobalIFunc *Module::getNamedIFunc(StringRef Name) const {
+  return dyn_cast_or_null<GlobalIFunc>(getNamedValue(Name));
+}
+
 /// getNamedMetadata - Return the first NamedMDNode in the module with the
 /// specified name. This method returns null if a NamedMDNode with the
 /// specified name is not found.
@@ -438,6 +444,9 @@ void Module::dropAllReferences() {
 
   for (GlobalAlias &GA : aliases())
     GA.dropAllReferences();
+
+  for (GlobalIFunc &GIF : ifuncs())
+    GIF.dropAllReferences();
 }
 
 unsigned Module::getDwarfVersion() const {