Index: include/clang/Basic/DiagnosticGroups.td
===================================================================
--- include/clang/Basic/DiagnosticGroups.td
+++ include/clang/Basic/DiagnosticGroups.td
@@ -428,6 +428,7 @@
 def StringPlusChar : DiagGroup<"string-plus-char">;
 def StrncatSize : DiagGroup<"strncat-size">;
 def TautologicalUnsignedZeroCompare : DiagGroup<"tautological-unsigned-zero-compare">;
+def TautologicalUnsignedEnumZeroCompare : DiagGroup<"tautological-unsigned-enum-zero-compare">;
 def TautologicalOutOfRangeCompare : DiagGroup<"tautological-constant-out-of-range-compare">;
 def TautologicalPointerCompare : DiagGroup<"tautological-pointer-compare">;
 def TautologicalOverlapCompare : DiagGroup<"tautological-overlap-compare">;
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -5893,19 +5893,26 @@
   "%select{non-|}1static data member %2 declared const here|"
   "member function %q1 is declared const here}0">;
 
+def warn_lunsigned_always_true_comparison : Warning<
+  "comparison of unsigned expression %0 is always %select{false|true}1">,
+  InGroup<TautologicalUnsignedZeroCompare>;
+def warn_runsigned_always_true_comparison : Warning<
+  "comparison of %0 unsigned expression is always %select{false|true}1">,
+  InGroup<TautologicalUnsignedZeroCompare>;
+def warn_lunsigned_enum_always_true_comparison : Warning<
+  "comparison of unsigned enum expression %0 is always %select{false|true}1">,
+  InGroup<TautologicalUnsignedEnumZeroCompare>;
+def warn_runsigned_enum_always_true_comparison : Warning<
+  "comparison of %0 unsigned enum expression is always %select{false|true}1">,
+  InGroup<TautologicalUnsignedEnumZeroCompare>;
+
 def warn_mixed_sign_comparison : Warning<
   "comparison of integers of different signs: %0 and %1">,
   InGroup<SignCompare>, DefaultIgnore;
-def warn_lunsigned_always_true_comparison : Warning<
-  "comparison of unsigned%select{| enum}2 expression %0 is always %1">,
-  InGroup<TautologicalUnsignedZeroCompare>;
 def warn_out_of_range_compare : Warning<
   "comparison of %select{constant %0|true|false}1 with " 
   "%select{expression of type %2|boolean expression}3 is always "
   "%select{false|true}4">, InGroup<TautologicalOutOfRangeCompare>;
-def warn_runsigned_always_true_comparison : Warning<
-  "comparison of %0 unsigned%select{| enum}2 expression is always %1">,
-  InGroup<TautologicalUnsignedZeroCompare>;
 def warn_comparison_of_mixed_enum_types : Warning<
   "comparison of two values with different enumeration types"
   "%diff{ ($ and $)|}0,1">,
Index: lib/Sema/SemaChecking.cpp
===================================================================
--- lib/Sema/SemaChecking.cpp
+++ lib/Sema/SemaChecking.cpp
@@ -8583,35 +8583,69 @@
 
   // bool values are handled by DiagnoseOutOfRangeComparison().
 
-  BinaryOperatorKind op = E->getOpcode();
   if (E->isValueDependent())
     return false;
 
   Expr *LHS = E->getLHS();
   Expr *RHS = E->getRHS();
 
-  bool Match = true;
+  enum IsEnum { False = false, True = true, SizeOfIsEnum };
+  struct TautologicalComparison {
+    Expr *&Value;
+    BinaryOperatorKind op;
+    Expr *&Const;
+    std::array<unsigned, SizeOfIsEnum> DiagID;
+    const char *cmp;
+    bool Result;
+  };
 
-  if (op == BO_LT && isNonBooleanUnsignedValue(LHS) && IsZero(S, RHS)) {
-    S.Diag(E->getOperatorLoc(), diag::warn_lunsigned_always_true_comparison)
-      << "< 0" << "false" << HasEnumType(LHS)
-      << LHS->getSourceRange() << RHS->getSourceRange();
-  } else if (op == BO_GE && isNonBooleanUnsignedValue(LHS) && IsZero(S, RHS)) {
-    S.Diag(E->getOperatorLoc(), diag::warn_lunsigned_always_true_comparison)
-      << ">= 0" << "true" << HasEnumType(LHS)
-      << LHS->getSourceRange() << RHS->getSourceRange();
-  } else if (op == BO_GT && isNonBooleanUnsignedValue(RHS) && IsZero(S, LHS)) {
-    S.Diag(E->getOperatorLoc(), diag::warn_runsigned_always_true_comparison)
-      << "0 >" << "false" << HasEnumType(RHS)
-      << LHS->getSourceRange() << RHS->getSourceRange();
-  } else if (op == BO_LE && isNonBooleanUnsignedValue(RHS) && IsZero(S, LHS)) {
-    S.Diag(E->getOperatorLoc(), diag::warn_runsigned_always_true_comparison)
-      << "0 <=" << "true" << HasEnumType(RHS)
-      << LHS->getSourceRange() << RHS->getSourceRange();
-  } else
-    Match = false;
+  const std::array<const TautologicalComparison, 4> TautologicalComparisons = {{
+      {LHS,
+       BO_LT,
+       RHS,
+       {{diag::warn_lunsigned_always_true_comparison,
+         diag::warn_lunsigned_enum_always_true_comparison}},
+       "< 0",
+       false},
+      {LHS,
+       BO_GE,
+       RHS,
+       {{diag::warn_lunsigned_always_true_comparison,
+         diag::warn_lunsigned_enum_always_true_comparison}},
+       ">= 0",
+       true},
+      {RHS,
+       BO_GT,
+       LHS,
+       {{diag::warn_runsigned_always_true_comparison,
+         diag::warn_runsigned_enum_always_true_comparison}},
+       "0 >",
+       false},
+      {RHS,
+       BO_LE,
+       LHS,
+       {{diag::warn_runsigned_always_true_comparison,
+         diag::warn_runsigned_enum_always_true_comparison}},
+       "0 <=",
+       true},
+  }};
 
-  return Match;
+  BinaryOperatorKind op = E->getOpcode();
+  for (const TautologicalComparison &Check : TautologicalComparisons) {
+    if (Check.op != op)
+      continue;
+
+    if (!(isNonBooleanUnsignedValue(Check.Value) && IsZero(S, Check.Const)))
+      return false;
+
+    S.Diag(E->getOperatorLoc(), Check.DiagID[HasEnumType(Check.Value)])
+        << Check.cmp << Check.Result << LHS->getSourceRange()
+        << RHS->getSourceRange();
+
+    return true;
+  }
+
+  return false;
 }
 
 void DiagnoseOutOfRangeComparison(Sema &S, BinaryOperator *E, Expr *Constant,
Index: test/Sema/compare.c
===================================================================
--- test/Sema/compare.c
+++ test/Sema/compare.c
@@ -308,8 +308,59 @@
 int rdar8511238() {
   enum A { A_foo, A_bar };
   enum A a;
+
+  if (a == 0)
+      return 0;
+  if (a != 0)
+      return 0;
   if (a < 0) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
-    return 0;
+      return 0;
+  if (a <= 0)
+      return 0;
+  if (a > 0)
+      return 0;
+  if (a >= 0) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+      return 0;
+
+  if (0 == a)
+      return 0;
+  if (0 != a)
+      return 0;
+  if (0 < a)
+      return 0;
+  if (0 <= a) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
+      return 0;
+  if (0 > a) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
+      return 0;
+  if (0 >= a)
+      return 0;
+
+  if (a == 0U)
+      return 0;
+  if (a != 0U)
+      return 0;
+  if (a < 0U) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
+      return 0;
+  if (a <= 0U)
+      return 0;
+  if (a > 0U)
+      return 0;
+  if (a >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+      return 0;
+
+  if (0U == a)
+      return 0;
+  if (0U != a)
+      return 0;
+  if (0U < a)
+      return 0;
+  if (0U <= a) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
+      return 0;
+  if (0U > a) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
+      return 0;
+  if (0U >= a)
+      return 0;
+
   return 20;
 }
 
Index: test/Sema/tautological-unsigned-enum-zero-compare.c
===================================================================
--- /dev/null
+++ test/Sema/tautological-unsigned-enum-zero-compare.c
@@ -0,0 +1,46 @@
+// RUN: %clang_cc1 -fsyntax-only -DTEST -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wno-tautological-unsigned-enum-zero-compare -verify %s
+
+int main() {
+  enum A { A_foo, A_bar };
+  enum A a;
+
+#ifdef TEST
+  if (a < 0) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
+    return 0;
+  if (a >= 0) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+    return 0;
+  if (0 <= a) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
+    return 0;
+  if (0 > a) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
+    return 0;
+  if (a < 0U) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
+    return 0;
+  if (a >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+    return 0;
+  if (0U <= a) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
+    return 0;
+  if (0U > a) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
+    return 0;
+#else
+  // expected-no-diagnostics
+  if (a < 0)
+    return 0;
+  if (a >= 0)
+    return 0;
+  if (0 <= a)
+    return 0;
+  if (0 > a)
+    return 0;
+  if (a < 0U)
+    return 0;
+  if (a >= 0U)
+    return 0;
+  if (0U <= a)
+    return 0;
+  if (0U > a)
+    return 0;
+#endif
+
+  return 1;
+}