Index: llvm/tools/clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- llvm/tools/clang/include/clang/Basic/DiagnosticGroups.td
+++ llvm/tools/clang/include/clang/Basic/DiagnosticGroups.td
@@ -519,6 +519,7 @@
 def ZeroLengthArray : DiagGroup<"zero-length-array">;
 def GNUZeroLineDirective : DiagGroup<"gnu-zero-line-directive">;
 def GNUZeroVariadicMacroArguments : DiagGroup<"gnu-zero-variadic-macro-arguments">;
+def GNUVecElemSize : DiagGroup<"gnu-vec-elem-size">;
 def Fallback : DiagGroup<"fallback">;
 
 // This covers both the deprecated case (in C++98)
@@ -758,7 +759,8 @@
                             GNUStringLiteralOperatorTemplate,
                             GNUUnionCast, GNUVariableSizedTypeNotAtEnd,
                             ZeroLengthArray, GNUZeroLineDirective,
-                            GNUZeroVariadicMacroArguments]>;
+                            GNUZeroVariadicMacroArguments,
+                            GNUVecElemSize]>;
 // A warning group for warnings about code that clang accepts but gcc doesn't.
 def GccCompat : DiagGroup<"gcc-compat">;
 
Index: llvm/tools/clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- llvm/tools/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ llvm/tools/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2301,6 +2301,9 @@
   "cannot convert between vector and non-scalar values (%0 and %1)">;
 def err_typecheck_vector_lengths_not_equal : Error<
   "vector operands do not have the same number of elements (%0 and %1)">;
+def warn_typecheck_vector_element_sizes_not_equal : Warning<
+  "vector operands do not have the same elements sizes (%0 and %1)">,
+  InGroup<GNUVecElemSize>, DefaultIgnore;
 def err_ext_vector_component_exceeds_length : Error<
   "vector component access exceeds type %0">;
 def err_ext_vector_component_name_illegal : Error<
Index: llvm/tools/clang/lib/Sema/SemaExpr.cpp
===================================================================
--- llvm/tools/clang/lib/Sema/SemaExpr.cpp
+++ llvm/tools/clang/lib/Sema/SemaExpr.cpp
@@ -8784,6 +8784,65 @@
         << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
       return QualType();
     }
+    if (!S.LangOpts.OpenCL && !S.LangOpts.ZVector) {
+      const BuiltinType *LHSBT = LHSEleType->getAs<clang::BuiltinType>();
+      const BuiltinType *RHSBT = RHSEleType->getAs<clang::BuiltinType>();
+      if (LHSBT != RHSBT) {
+        BuiltinType::Kind LHSKind = LHSBT->getKind();
+        BuiltinType::Kind RHSKind = RHSBT->getKind();
+        bool DiffSizes = true;
+        switch (LHSKind) {
+        case BuiltinType::Char_S:
+          DiffSizes =
+              RHSKind != BuiltinType::Char_U && RHSKind != BuiltinType::UChar;
+          break;
+        case BuiltinType::Char_U:
+          DiffSizes =
+              RHSKind != BuiltinType::Char_S && RHSKind != BuiltinType::UChar;
+          break;
+        case BuiltinType::UChar:
+          DiffSizes =
+              RHSKind != BuiltinType::Char_U && RHSKind != BuiltinType::Char_S;
+          break;
+        case BuiltinType::Short:
+          DiffSizes = RHSKind != BuiltinType::UShort;
+          break;
+        case BuiltinType::UShort:
+          DiffSizes = RHSKind != BuiltinType::Short;
+          break;
+        case BuiltinType::Int:
+          DiffSizes = RHSKind != BuiltinType::UInt;
+          break;
+        case BuiltinType::UInt:
+          DiffSizes = RHSKind != BuiltinType::Int;
+          break;
+        case BuiltinType::Long:
+          DiffSizes = RHSKind != BuiltinType::ULong;
+          break;
+        case BuiltinType::ULong:
+          DiffSizes = RHSKind != BuiltinType::Long;
+          break;
+        case BuiltinType::LongLong:
+          DiffSizes = RHSKind != BuiltinType::ULongLong;
+          break;
+        case BuiltinType::ULongLong:
+          DiffSizes = RHSKind != BuiltinType::LongLong;
+          break;
+        default:
+          DiffSizes = true;
+          break;
+        }
+        if (DiffSizes) {
+          S.Diag(Loc, diag::warn_typecheck_vector_element_sizes_not_equal)
+              << LHS.get()->getType() << RHS.get()->getType()
+              << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
+          if (S.Diags.getDiagnosticLevel(
+                  diag::warn_typecheck_vector_element_sizes_not_equal, Loc) ==
+              DiagnosticsEngine::Level::Error)
+            return QualType();
+        }
+      }
+    }
   } else {
     // ...else expand RHS to match the number of elements in LHS.
     QualType VecTy =
Index: llvm/tools/clang/test/Sema/vecshift.c
===================================================================
--- llvm/tools/clang/test/Sema/vecshift.c
+++ llvm/tools/clang/test/Sema/vecshift.c
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -fsyntax-only -DERR -Werror-gnu-vec-elem-size -verify %s
 
 typedef __attribute__((__ext_vector_type__(8))) char vector_char8;
 typedef __attribute__((__ext_vector_type__(8))) short vector_short8;
@@ -48,16 +49,30 @@
   vus8 = 1 << vus8;
 
   vc8 = vc8 << vc8;
+#ifdef ERR
+  vi8 = vi8 << vuc8; // expected-error {{vector operands do not have the same elements sizes}}
+  vuc8 = vuc8 << vi8; // expected-error {{vector operands do not have the same elements sizes}}
+  vus8 = vus8 << vui8; // expected-error {{vector operands do not have the same elements sizes}}
+  vui8 = vui8 << vs8; // expected-error {{vector operands do not have the same elements sizes}}
+#else
   vi8 = vi8 << vuc8;
   vuc8 = vuc8 << vi8;
   vus8 = vus8 << vui8;
   vui8 = vui8 << vs8;
+#endif
 
   vc8 <<= vc8;
+#ifdef ERR
+  vi8 <<= vuc8; // expected-error {{vector operands do not have the same elements sizes}}
+  vuc8 <<= vi8; // expected-error {{vector operands do not have the same elements sizes}}
+  vus8 <<= vui8; // expected-error {{vector operands do not have the same elements sizes}}
+  vui8 <<= vs8; // expected-error {{vector operands do not have the same elements sizes}}
+#else
   vi8 <<= vuc8;
   vuc8 <<= vi8;
   vus8 <<= vui8;
   vui8 <<= vs8;
+#endif
 
   c <<= vc8; // expected-error {{assigning to 'char' from incompatible type}}
   i <<= vuc8; // expected-error {{assigning to 'int' from incompatible type}}