Index: llvm/lib/Transforms/IPO/OpenMPOpt.cpp
===================================================================
--- llvm/lib/Transforms/IPO/OpenMPOpt.cpp
+++ llvm/lib/Transforms/IPO/OpenMPOpt.cpp
@@ -385,33 +385,36 @@
     return nullptr;
   }
 
-  /// Helper to initialize all runtime function information for those defined in
-  /// OpenMPKinds.def.
-  void initializeRuntimeFunctions() {
-    // Helper to check the types in the declaration against the expected types.
-    auto CheckTypes = [&](RuntimeFunctionInfo &RFI) {
-      if (!RFI.Declaration)
-        return true;
-
-      Function *F = RFI.Declaration;
-      if (F->getReturnType()->getTypeID() != RFI.ReturnType->getTypeID())
-        return false;
+  /// Returns true if the function declaration \p F matches the runtime
+  /// function types, that is, return type \p RTFRetType, and arguments types
+  /// \p RTFArgTypes. If the runtime function is variadic, \p IsVarArg, the
+  /// comparison is made until the runtime function number of arguments.
+  static bool declMatchesRTFTypes(Function *F, Type *RTFRetType, bool IsVarArg,
+                                  SmallVector<Type *, 8> &RTFArgTypes) {
+    if (!F)
+      return true;
+    if (F->getReturnType() != RTFRetType)
+      return false;
+    if (F->arg_size() < RTFArgTypes.size())
+      return false;
+    if (!IsVarArg && F->arg_size() > RTFArgTypes.size())
+      return false;
 
-      if (F->arg_size() != RFI.getNumArgs())
+    auto RTFTyIt = RTFArgTypes.begin();
+    for (Argument &Arg : F->args()) {
+      if (Arg.getType() != *RTFTyIt)
         return false;
 
-      SmallVector<Type *, 8>::iterator RTFTyIt;
-      RTFTyIt = RFI.ArgumentTypes.begin();
-      for (Argument &Arg : F->args()) {
-        if (Arg.getType()->getTypeID() != (*RTFTyIt)->getTypeID())
-          return false;
-
-        ++RTFTyIt;
-      }
+      if (IsVarArg && ++RTFTyIt == RTFArgTypes.end())
+        break;
+    }
 
-      return true;
-    };
+    return true;
+  }
 
+  /// Helper to initialize all runtime function information for those defined in
+  /// OpenMPKinds.def.
+  void initializeRuntimeFunctions() {
     // Helper to collect all uses of the decleration in the UsesMap.
     auto CollectUses = [&](RuntimeFunctionInfo &RFI) {
       unsigned NumUses = 0;
@@ -439,24 +442,26 @@
 
 #define OMP_RTL(_Enum, _Name, _IsVarArg, _ReturnType, ...)                     \
   {                                                                            \
-    auto &RFI = RFIs[_Enum];                                                   \
-    RFI.Kind = _Enum;                                                          \
-    RFI.Name = _Name;                                                          \
-    RFI.IsVarArg = _IsVarArg;                                                  \
-    RFI.ReturnType = _ReturnType;                                              \
-    RFI.ArgumentTypes = SmallVector<Type *, 8>({__VA_ARGS__});                 \
-    RFI.Declaration = M.getFunction(_Name);                                    \
-    bool TypesMatch = CheckTypes(RFI);                                         \
-    (void)TypesMatch;                                                          \
-    unsigned NumUses = CollectUses(RFI);                                       \
-    (void)NumUses;                                                             \
-    LLVM_DEBUG({                                                               \
-      dbgs() << TAG << RFI.Name << (RFI.Declaration ? "" : " not")             \
-             << " found\n";                                                    \
-      if (RFI.Declaration)                                                     \
-        dbgs() << TAG << "-> got " << NumUses << " uses in "                   \
-               << RFI.UsesMap.size() << " different functions.\n";             \
-    });                                                                        \
+    SmallVector<Type *, 8> ArgsTypes({__VA_ARGS__});                           \
+    Function *F = M.getFunction(_Name);                                        \
+    if (declMatchesRTFTypes(F, _ReturnType, _IsVarArg, ArgsTypes)) {           \
+      auto &RFI = RFIs[_Enum];                                                 \
+      RFI.Kind = _Enum;                                                        \
+      RFI.Name = _Name;                                                        \
+      RFI.IsVarArg = _IsVarArg;                                                \
+      RFI.ReturnType = _ReturnType;                                            \
+      RFI.ArgumentTypes = ArgsTypes;                                           \
+      RFI.Declaration = F;                                                     \
+      unsigned NumUses = CollectUses(RFI);                                     \
+      (void)NumUses;                                                           \
+      LLVM_DEBUG({                                                             \
+        dbgs() << TAG << RFI.Name << (RFI.Declaration ? "" : " not")           \
+              << " found\n";                                                   \
+        if (RFI.Declaration)                                                   \
+          dbgs() << TAG << "-> got " << NumUses << " uses in "                 \
+                << RFI.UsesMap.size() << " different functions.\n";            \
+      });                                                                      \
+    }                                                                          \
   }
 #include "llvm/Frontend/OpenMP/OMPKinds.def"