diff --git a/clang/include/clang/Basic/TargetBuiltins.h b/clang/include/clang/Basic/TargetBuiltins.h
--- a/clang/include/clang/Basic/TargetBuiltins.h
+++ b/clang/include/clang/Basic/TargetBuiltins.h
@@ -157,7 +157,7 @@
     EltType getEltType() const { return (EltType)(Flags & EltTypeMask); }
     bool isPoly() const {
       EltType ET = getEltType();
-      return ET == Poly8 || ET == Poly16;
+      return ET == Poly8 || ET == Poly16 || ET == Poly64;
     }
     bool isUnsigned() const { return (Flags & UnsignedFlag) != 0; }
     bool isQuad() const { return (Flags & QuadFlag) != 0; }
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -3165,6 +3165,7 @@
     case BuiltinType::UShort:
       EltName = "poly16_t";
       break;
+    case BuiltinType::LongLong:
     case BuiltinType::ULongLong:
       EltName = "poly64_t";
       break;
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -7552,15 +7552,16 @@
                         Triple.getArch() == llvm::Triple::aarch64_be;
   if (VecKind == VectorType::NeonPolyVector) {
     if (IsPolyUnsigned) {
-      // AArch64 polynomial vectors are unsigned and support poly64.
+      // AArch64 polynomial vectors are unsigned.
       return BTy->getKind() == BuiltinType::UChar ||
              BTy->getKind() == BuiltinType::UShort ||
              BTy->getKind() == BuiltinType::ULong ||
              BTy->getKind() == BuiltinType::ULongLong;
     } else {
-      // AArch32 polynomial vector are signed.
+      // AArch32 polynomial vectors are signed.
       return BTy->getKind() == BuiltinType::SChar ||
-             BTy->getKind() == BuiltinType::Short;
+             BTy->getKind() == BuiltinType::Short ||
+             BTy->getKind() == BuiltinType::LongLong;
     }
   }
 
diff --git a/clang/utils/TableGen/NeonEmitter.cpp b/clang/utils/TableGen/NeonEmitter.cpp
--- a/clang/utils/TableGen/NeonEmitter.cpp
+++ b/clang/utils/TableGen/NeonEmitter.cpp
@@ -2235,6 +2235,7 @@
   OS << "#else\n";
   OS << "typedef int8_t poly8_t;\n";
   OS << "typedef int16_t poly16_t;\n";
+  OS << "typedef int64_t poly64_t;\n";
   OS << "#endif\n";
 
   // Emit Neon vector typedefs.
@@ -2247,7 +2248,7 @@
   for (auto &TS : TDTypeVec) {
     bool IsA64 = false;
     Type T(TS, ".");
-    if (T.isDouble() || (T.isPoly() && T.getElementSizeInBits() == 64))
+    if (T.isDouble())
       IsA64 = true;
 
     if (InIfdef && !IsA64) {
@@ -2280,7 +2281,7 @@
     for (auto &TS : TDTypeVec) {
       bool IsA64 = false;
       Type T(TS, ".");
-      if (T.isDouble() || (T.isPoly() && T.getElementSizeInBits() == 64))
+      if (T.isDouble())
         IsA64 = true;
 
       if (InIfdef && !IsA64) {