Index: clang/include/clang/Sema/Sema.h
===================================================================
--- clang/include/clang/Sema/Sema.h
+++ clang/include/clang/Sema/Sema.h
@@ -11717,6 +11717,7 @@
 
   bool areMatrixTypesOfTheSameDimension(QualType srcTy, QualType destTy);
 
+  bool areVectorTypesSameSize(QualType srcType, QualType destType);
   bool areLaxCompatibleVectorTypes(QualType srcType, QualType destType);
   bool isLaxVectorConversion(QualType srcType, QualType destType);
 
Index: clang/lib/Sema/SemaCast.cpp
===================================================================
--- clang/lib/Sema/SemaCast.cpp
+++ clang/lib/Sema/SemaCast.cpp
@@ -2328,6 +2328,16 @@
       return TC_Success;
     }
 
+    if (Self.LangOpts.OpenCL && !CStyle) {
+      if (DestType->isExtVectorType() || SrcType->isExtVectorType()) {
+        // FIXME: Allow for reinterpret cast between 3 and 4 element vectors
+        if (Self.areVectorTypesSameSize(SrcType, DestType)) {
+          Kind = CK_BitCast;
+          return TC_Success;
+        }
+      }
+    }
+
     // Otherwise, pick a reasonable diagnostic.
     if (!destIsVector)
       msg = diag::err_bad_cxx_cast_vector_to_scalar_different_size;
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -7344,6 +7344,25 @@
          matSrcType->getNumColumns() == matDestType->getNumColumns();
 }
 
+bool Sema::areVectorTypesSameSize(QualType srcTy, QualType destTy) {
+  assert(destTy->isVectorType() || srcTy->isVectorType());
+
+  uint64_t srcLen, destLen;
+  QualType srcEltTy, destEltTy;
+  if (!breakDownVectorType(srcTy, srcLen, srcEltTy))
+    return false;
+  if (!breakDownVectorType(destTy, destLen, destEltTy))
+    return false;
+
+  // ASTContext::getTypeSize will return the size rounded up to a
+  // power of 2, so instead of using that, we need to use the raw
+  // element size multiplied by the element count.
+  uint64_t srcEltSize = Context.getTypeSize(srcEltTy);
+  uint64_t destEltSize = Context.getTypeSize(destEltTy);
+
+  return (srcLen * srcEltSize == destLen * destEltSize);
+}
+
 /// Are the two types lax-compatible vector types?  That is, given
 /// that one of them is a vector, do they have equal storage sizes,
 /// where the storage size is the number of elements times the element
@@ -7362,18 +7381,7 @@
   if (srcTy->isScalarType() && destTy->isExtVectorType()) return false;
   if (destTy->isScalarType() && srcTy->isExtVectorType()) return false;
 
-  uint64_t srcLen, destLen;
-  QualType srcEltTy, destEltTy;
-  if (!breakDownVectorType(srcTy, srcLen, srcEltTy)) return false;
-  if (!breakDownVectorType(destTy, destLen, destEltTy)) return false;
-
-  // ASTContext::getTypeSize will return the size rounded up to a
-  // power of 2, so instead of using that, we need to use the raw
-  // element size multiplied by the element count.
-  uint64_t srcEltSize = Context.getTypeSize(srcEltTy);
-  uint64_t destEltSize = Context.getTypeSize(destEltTy);
-
-  return (srcLen * srcEltSize == destLen * destEltSize);
+  return areVectorTypesSameSize(srcTy, destTy);
 }
 
 /// Is this a legal conversion between two types, one of which is
Index: clang/test/CodeGenOpenCLCXX/reinterpret_cast.clcpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenOpenCLCXX/reinterpret_cast.clcpp
@@ -0,0 +1,17 @@
+//RUN: %clang_cc1 %s -triple spir -emit-llvm -O0 -o - | FileCheck %s
+
+typedef int int2 __attribute__((ext_vector_type(2)));
+typedef int int4 __attribute__((ext_vector_type(4)));
+typedef long long2 __attribute__((ext_vector_type(2)));
+
+//CHECK-LABEL: define{{.*}} spir_func void @_Z3barPU3AS1Dv2_i
+void bar(global int2 *in) {
+  //CHECK: bitcast <2 x i32> %{{[0-9]+}} to i64
+  auto l = reinterpret_cast<long>(in[0]);
+  //CHECK: bitcast i64 %{{[0-9]+}} to <2 x i32>
+  auto i2 = reinterpret_cast<int2>(l);
+
+  int4 i4;
+  //CHECK: bitcast <4 x i32> %{{[0-9]+}} to <2 x i64>
+  auto l2 = reinterpret_cast<long2>(i4);
+}
Index: clang/test/SemaOpenCLCXX/reinterpret-cast.clcpp
===================================================================
--- /dev/null
+++ clang/test/SemaOpenCLCXX/reinterpret-cast.clcpp
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 %s -pedantic -verify -fsyntax-only
+
+typedef int int2 __attribute__((ext_vector_type(2)));
+typedef int int3 __attribute__((ext_vector_type(3)));
+typedef int int4 __attribute__((ext_vector_type(4)));
+
+kernel void foo() {
+  long l1;
+  auto l_to_i2 = reinterpret_cast<int2>(l1);
+  int2 i2;
+  auto i2_to_l = reinterpret_cast<long>(i2);
+  auto i2_to_i = reinterpret_cast<int>(i2); // expected-error{{reinterpret_cast from vector 'int2' (vector of 2 'int' values) to scalar 'int' of different size}}
+
+  reserve_id_t r_id1;
+  auto r_id2 = reinterpret_cast<reserve_id_t>(r_id1); // expected-error{{reinterpret_cast from 'reserve_id_t' to 'reserve_id_t' is not allowed}}
+}