[Sema] Fixes for enum handling for tautological comparison diagnostics

[lebedev.ri]

Summary

As Mattias Eriksson has reported in PR35009, in C, for enums, the underlying type should
be used when checking for the tautological comparison, unlike C++, where the enumerator
values define the value range. So if not in CPlusPlus mode, use the enum underlying type.

Also, i have discovered a problem (a crash) when evaluating tautological-ness of the following comparison:

enum A { A_a = 0 };
if (a < 0) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
return 0;

This affects both the C and C++, but after the first fix, only C++ code was affected.
That was also fixed, while preserving (i think?) the proper diagnostic output.

And while there, attempt to enhance the test coverage.
Yes, some tests got moved around, sorry about that :)

Fixes PR35009

[efriedma]

lib/Sema/SemaChecking.cpp

8612 ↗

(On Diff #119653)

Why are you changing this here, as opposed to changing IntRange::forValueOfCanonicalType?

[Rakete1111]

lib/Sema/SemaChecking.cpp

8610 ↗

(On Diff #119653)

Please drop the braces.

8616 ↗

(On Diff #119653)

You missed a dot at the end.

8665 ↗

(On Diff #119653)

You can define Result lower down (and make it const).

8713 ↗

(On Diff #119653)

Same as before. Also, shouldn't this be a function instead of duplicating the same code two times?

test/Sema/outof-range-enum-constant-compare.c

1 ↗

(On Diff #119653)

I don't know what the convention is, but I would prefer to use platform independent tests wherever possible. I couldn't find a flag to change the underlying type of an enum, so I'm not sure if my suggestion is even feasible.

[lebedev.ri]

Addressed review notes.

For C++, enum handling clearly needs more work, because not all tautological comparisons are actually diagnosed,
so there is no clang/test/Sema/outof-range-enum-constant-compare.cpp, clang/test/Sema/tautological-constant-enum-compare.cpp for this very reason.

[aaron.ballman]

lib/Sema/SemaChecking.cpp

8185 ↗

(On Diff #119705)

For enum types in C code, use the underlying datatype.

8186 ↗

(On Diff #119705)

Can use const auto * here.

8188 ↗

(On Diff #119705)

Here as well.

8189 ↗

(On Diff #119705)

For enum types in C++,

8593 ↗

(On Diff #119705)

Both is not very descriptive -- I think Zero might be an improvement.

[lebedev.ri]

Address review notes.

lib/Sema/SemaChecking.cpp

8186 ↗

(On Diff #119705)

I do agree that as per coding style, that is preferred but the rest of the class would still use the
explicitly-spelled types, and IMO not deviating from local coding style in small changes might be best?

(clang-tidy does not complain about this, but maybe that is because it is not aware of this LLVM internal type casting functions)

But if you insist i will change it.

8593 ↗

(On Diff #119705)

But then it will be confusing what is the difference between Zero and Min for unsigned types.
I think i should just clarify the comment here.

8612 ↗

(On Diff #119653)

No particular reason. Initially i had trouble with moving it into IntRange::forValueOfCanonicalType(),
so i left that in the state that you saw. Now done.

test/Sema/outof-range-enum-constant-compare.c

1 ↗

(On Diff #119653)

https://reviews.llvm.org/D38101?id=118143#inline-338796
That is exactly the flag to change the underlying type of an enum.
I believe the RUN lines are correct here.

[aaron.ballman]

lib/Sema/SemaChecking.cpp

8593 ↗

(On Diff #119757)

when -> When

8619 ↗

(On Diff #119757)

Instead of default constructing the Optional, you should use llvm::None instead.

8186 ↗

(On Diff #119705)

Consistency is best, so you might as well leave it. A follow-up NFC commit would be fine if you wanted to switch everything to auto.

8593 ↗

(On Diff #119705)

Okay, that comment adds sufficient clarity for me.

[lebedev.ri]

Address review notes.

lib/Sema/SemaChecking.cpp

8619 ↗

(On Diff #119757)

Thank you for the suggestion, i did not really know about llvm::None.
However only the last return can be enhanced:

clang/lib/Sema/SemaChecking.cpp:8619:23: error: incompatible operand types ('(anonymous namespace)::LimitType' and 'llvm::NoneType')
    return Value == 0 ? LimitType::Both : llvm::None;
                      ^ ~~~~~~~~~~~~~~~   ~~~~~~~~~~

[aaron.ballman]

LGTM!

lib/Sema/SemaChecking.cpp

8619 ↗

(On Diff #119757)

Blech, that's because there's no common type for the :? operator. I think it'd be worse to split this into multiple statements just to use llvm::None, so it's fine as-is.

cfe/trunk/lib/Sema/SemaChecking.cpp

static IntRange forValueOfCanonicalType(ASTContext &C, const Type *T) {
 
     if (const VectorType *VT = dyn_cast<VectorType>(T))
       T = VT->getElementType().getTypePtr();
     if (const ComplexType *CT = dyn_cast<ComplexType>(T))
       T = CT->getElementType().getTypePtr();
     if (const AtomicType *AT = dyn_cast<AtomicType>(T))
       T = AT->getValueType().getTypePtr();
 
-    // For enum types, use the known bit width of the enumerators.
-    if (const EnumType *ET = dyn_cast<EnumType>(T)) {
+    if (!C.getLangOpts().CPlusPlus) {
+      // For enum types in C code, use the underlying datatype.
+      if (const EnumType *ET = dyn_cast<EnumType>(T))
+        T = ET->getDecl()->getIntegerType().getDesugaredType(C).getTypePtr();
+    } else if (const EnumType *ET = dyn_cast<EnumType>(T)) {
+      // For enum types in C++, use the known bit width of the enumerators.
       EnumDecl *Enum = ET->getDecl();
       // In C++11, enums without definitions can have an explicitly specified
       // underlying type.  Use this type to compute the range.
       if (!Enum->isCompleteDefinition())
         return IntRange(C.getIntWidth(QualType(T, 0)),
                         !ET->isSignedIntegerOrEnumerationType());
 
       unsigned NumPositive = Enum->getNumPositiveBits();
bool isNonBooleanUnsignedValue(Expr *E) {
   // is an integer type; and is either unsigned after implicit casts,
   // or was unsigned before implicit casts.
   return isNonBooleanIntegerValue(E) &&
          (!E->getType()->isSignedIntegerType() ||
           !E->IgnoreParenImpCasts()->getType()->isSignedIntegerType());
 }
 
 enum class LimitType {
-  Max, // e.g. 32767 for short
-  Min  // e.g. -32768 for short
+  Max = 1U << 0U,  // e.g. 32767 for short
+  Min = 1U << 1U,  // e.g. -32768 for short
+  Both = Max | Min // When the value is both the Min and the Max limit at the
+                   // same time; e.g. in C++, A::a in enum A { a = 0 };
 };
 
 /// Checks whether Expr 'Constant' may be the
 /// std::numeric_limits<>::max() or std::numeric_limits<>::min()
 /// of the Expr 'Other'. If true, then returns the limit type (min or max).
 /// The Value is the evaluation of Constant
 llvm::Optional<LimitType> IsTypeLimit(Sema &S, Expr *Constant, Expr *Other,
                                       const llvm::APSInt &Value) {
   if (IsEnumConstOrFromMacro(S, Constant))
     return llvm::Optional<LimitType>();
 
   if (isNonBooleanUnsignedValue(Other) && Value == 0)
     return LimitType::Min;
 
   // TODO: Investigate using GetExprRange() to get tighter bounds
   // on the bit ranges.
   QualType OtherT = Other->IgnoreParenImpCasts()->getType();
   if (const auto *AT = OtherT->getAs<AtomicType>())
     OtherT = AT->getValueType();
 
   IntRange OtherRange = IntRange::forValueOfType(S.Context, OtherT);
 
+  // Special-case for C++ for enum with one enumerator with value of 0.
+  if (OtherRange.Width == 0)
+    return Value == 0 ? LimitType::Both : llvm::Optional<LimitType>();
+
   if (llvm::APSInt::isSameValue(
           llvm::APSInt::getMaxValue(OtherRange.Width,
                                     OtherT->isUnsignedIntegerType()),
           Value))
     return LimitType::Max;
 
   if (llvm::APSInt::isSameValue(
           llvm::APSInt::getMinValue(OtherRange.Width,
                                     OtherT->isUnsignedIntegerType()),
           Value))
     return LimitType::Min;
 
-  return llvm::Optional<LimitType>();
+  return llvm::None;
 }
 
 bool HasEnumType(Expr *E) {
   // Strip off implicit integral promotions.
   while (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E)) {
     if (ICE->getCastKind() != CK_IntegralCast &&
         ICE->getCastKind() != CK_NoOp)
       break;
bool CheckTautologicalComparison(Sema &S, BinaryOperator *E, Expr *Constant,
   llvm::Optional<LimitType> ValueType; // Which limit (min/max) is the constant?
 
   if (!(isNonBooleanIntegerValue(Other) &&
         (ValueType = IsTypeLimit(S, Constant, Other, Value))))
     return false;
 
   bool ConstIsLowerBound = (Op == BO_LT || Op == BO_LE) ^ RhsConstant;
   bool ResultWhenConstEqualsOther = (Op == BO_LE || Op == BO_GE);
+  if (ValueType != LimitType::Both) {
     bool ResultWhenConstNeOther =
         ConstIsLowerBound ^ (ValueType == LimitType::Max);
     if (ResultWhenConstEqualsOther != ResultWhenConstNeOther)
       return false; // The comparison is not tautological.
+  } else if (ResultWhenConstEqualsOther == ConstIsLowerBound)
+    return false; // The comparison is not tautological.
 
   const bool Result = ResultWhenConstEqualsOther;
 
   unsigned Diag = (isNonBooleanUnsignedValue(Other) && Value == 0)
                       ? (HasEnumType(Other)
                              ? diag::warn_unsigned_enum_always_true_comparison
                              : diag::warn_unsigned_always_true_comparison)
                       : diag::warn_tautological_constant_compare;

cfe/trunk/test/Sema/outof-range-enum-constant-compare.c

+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -DUNSIGNED -verify %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -fsyntax-only -DSIGNED -verify %s
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -DUNSIGNED -DSILENCE -Wno-tautological-constant-out-of-range-compare -verify %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -fsyntax-only -DSIGNED -DSILENCE -Wno-tautological-constant-out-of-range-compare -verify %s
+
+int main() {
+  enum A { A_a = 2 };
+  enum A a;
+
+#ifdef SILENCE
+  // expected-no-diagnostics
+#endif
+
+#ifdef UNSIGNED
+#ifndef SILENCE
+  if (a < 4294967296) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always true}}
+    return 0;
+  if (4294967296 >= a) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always true}}
+    return 0;
+  if (a > 4294967296) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always false}}
+    return 0;
+  if (4294967296 <= a) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always false}}
+    return 0;
+  if (a <= 4294967296) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always true}}
+    return 0;
+  if (4294967296 > a) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always true}}
+    return 0;
+  if (a >= 4294967296) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always false}}
+    return 0;
+  if (4294967296 < a) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always false}}
+    return 0;
+  if (a == 4294967296) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always false}}
+    return 0;
+  if (4294967296 != a) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always true}}
+    return 0;
+  if (a != 4294967296) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always true}}
+    return 0;
+  if (4294967296 == a) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always false}}
+    return 0;
+
+  if (a < 4294967296U) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always true}}
+    return 0;
+  if (4294967296U >= a) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always true}}
+    return 0;
+  if (a > 4294967296U) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always false}}
+    return 0;
+  if (4294967296U <= a) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always false}}
+    return 0;
+  if (a <= 4294967296U) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always true}}
+    return 0;
+  if (4294967296U > a) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always true}}
+    return 0;
+  if (a >= 4294967296U) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always false}}
+    return 0;
+  if (4294967296U < a) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always false}}
+    return 0;
+  if (a == 4294967296U) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always false}}
+    return 0;
+  if (4294967296U != a) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always true}}
+    return 0;
+  if (a != 4294967296U) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always true}}
+    return 0;
+  if (4294967296U == a) // expected-warning {{comparison of constant 4294967296 with expression of type 'enum A' is always false}}
+    return 0;
+#else // SILENCE
+  if (a < 4294967296)
+    return 0;
+  if (4294967296 >= a)
+    return 0;
+  if (a > 4294967296)
+    return 0;
+  if (4294967296 <= a)
+    return 0;
+  if (a <= 4294967296)
+    return 0;
+  if (4294967296 > a)
+    return 0;
+  if (a >= 4294967296)
+    return 0;
+  if (4294967296 < a)
+    return 0;
+  if (a == 4294967296)
+    return 0;
+  if (4294967296 != a)
+    return 0;
+  if (a != 4294967296)
+    return 0;
+  if (4294967296 == a)
+    return 0;
+
+  if (a < 4294967296U)
+    return 0;
+  if (4294967296U >= a)
+    return 0;
+  if (a > 4294967296U)
+    return 0;
+  if (4294967296U <= a)
+    return 0;
+  if (a <= 4294967296U)
+    return 0;
+  if (4294967296U > a)
+    return 0;
+  if (a >= 4294967296U)
+    return 0;
+  if (4294967296U < a)
+    return 0;
+  if (a == 4294967296U)
+    return 0;
+  if (4294967296U != a)
+    return 0;
+  if (a != 4294967296U)
+    return 0;
+  if (4294967296U == a)
+    return 0;
+#endif
+#elif defined(SIGNED)
+#ifndef SILENCE
+  if (a < -2147483649) // expected-warning {{comparison of constant -2147483649 with expression of type 'enum A' is always false}}
+    return 0;
+  if (-2147483649 >= a) // expected-warning {{comparison of constant -2147483649 with expression of type 'enum A' is always false}}
+    return 0;
+  if (a > -2147483649) // expected-warning {{comparison of constant -2147483649 with expression of type 'enum A' is always true}}
+    return 0;
+  if (-2147483649 <= a) // expected-warning {{comparison of constant -2147483649 with expression of type 'enum A' is always true}}
+    return 0;
+  if (a <= -2147483649) // expected-warning {{comparison of constant -2147483649 with expression of type 'enum A' is always false}}
+    return 0;
+  if (-2147483649 > a) // expected-warning {{comparison of constant -2147483649 with expression of type 'enum A' is always false}}
+    return 0;
+  if (a >= -2147483649) // expected-warning {{comparison of constant -2147483649 with expression of type 'enum A' is always true}}
+    return 0;
+  if (-2147483649 < a) // expected-warning {{comparison of constant -2147483649 with expression of type 'enum A' is always true}}
+    return 0;
+  if (a == -2147483649) // expected-warning {{comparison of constant -2147483649 with expression of type 'enum A' is always false}}
+    return 0;
+  if (-2147483649 != a) // expected-warning {{comparison of constant -2147483649 with expression of type 'enum A' is always true}}
+    return 0;
+  if (a != -2147483649) // expected-warning {{comparison of constant -2147483649 with expression of type 'enum A' is always true}}
+    return 0;
+  if (-2147483649 == a) // expected-warning {{comparison of constant -2147483649 with expression of type 'enum A' is always false}}
+    return 0;
+
+  if (a < 2147483648) // expected-warning {{comparison of constant 2147483648 with expression of type 'enum A' is always true}}
+    return 0;
+  if (2147483648 >= a) // expected-warning {{comparison of constant 2147483648 with expression of type 'enum A' is always true}}
+    return 0;
+  if (a > 2147483648) // expected-warning {{comparison of constant 2147483648 with expression of type 'enum A' is always false}}
+    return 0;
+  if (2147483648 <= a) // expected-warning {{comparison of constant 2147483648 with expression of type 'enum A' is always false}}
+    return 0;
+  if (a <= 2147483648) // expected-warning {{comparison of constant 2147483648 with expression of type 'enum A' is always true}}
+    return 0;
+  if (2147483648 > a) // expected-warning {{comparison of constant 2147483648 with expression of type 'enum A' is always true}}
+    return 0;
+  if (a >= 2147483648) // expected-warning {{comparison of constant 2147483648 with expression of type 'enum A' is always false}}
+    return 0;
+  if (2147483648 < a) // expected-warning {{comparison of constant 2147483648 with expression of type 'enum A' is always false}}
+    return 0;
+  if (a == 2147483648) // expected-warning {{comparison of constant 2147483648 with expression of type 'enum A' is always false}}
+    return 0;
+  if (2147483648 != a) // expected-warning {{comparison of constant 2147483648 with expression of type 'enum A' is always true}}
+    return 0;
+  if (a != 2147483648) // expected-warning {{comparison of constant 2147483648 with expression of type 'enum A' is always true}}
+    return 0;
+  if (2147483648 == a) // expected-warning {{comparison of constant 2147483648 with expression of type 'enum A' is always false}}
+    return 0;
+#else // SILENCE
+  if (a < -2147483649)
+    return 0;
+  if (-2147483649 >= a)
+    return 0;
+  if (a > -2147483649)
+    return 0;
+  if (-2147483649 <= a)
+    return 0;
+  if (a <= -2147483649)
+    return 0;
+  if (-2147483649 > a)
+    return 0;
+  if (a >= -2147483649)
+    return 0;
+  if (-2147483649 < a)
+    return 0;
+  if (a == -2147483649)
+    return 0;
+  if (-2147483649 != a)
+    return 0;
+  if (a != -2147483649)
+    return 0;
+  if (-2147483649 == a)
+    return 0;
+
+  if (a < 2147483648)
+    return 0;
+  if (2147483648 >= a)
+    return 0;
+  if (a > 2147483648)
+    return 0;
+  if (2147483648 <= a)
+    return 0;
+  if (a <= 2147483648)
+    return 0;
+  if (2147483648 > a)
+    return 0;
+  if (a >= 2147483648)
+    return 0;
+  if (2147483648 < a)
+    return 0;
+  if (a == 2147483648)
+    return 0;
+  if (2147483648 != a)
+    return 0;
+  if (a != 2147483648)
+    return 0;
+  if (2147483648 == a)
+    return 0;
+#endif
+#endif
+}
+
+// https://bugs.llvm.org/show_bug.cgi?id=35009
+int PR35009() {
+  enum A { A_a = 2 };
+  enum A a;
+
+  // in C, this should not warn.
+
+  if (a < 1)
+    return 0;
+  if (1 >= a)
+    return 0;
+  if (a > 1)
+    return 0;
+  if (1 <= a)
+    return 0;
+  if (a <= 1)
+    return 0;
+  if (1 > a)
+    return 0;
+  if (a >= 1)
+    return 0;
+  if (1 < a)
+    return 0;
+  if (a == 1)
+    return 0;
+  if (1 != a)
+    return 0;
+  if (a != 1)
+    return 0;
+  if (1 == a)
+    return 0;
+
+  if (a < 1U)
+    return 0;
+  if (1U >= a)
+    return 0;
+  if (a > 1U)
+    return 0;
+  if (1U <= a)
+    return 0;
+  if (a <= 1U)
+    return 0;
+  if (1U > a)
+    return 0;
+  if (a >= 1U)
+    return 0;
+  if (1U < a)
+    return 0;
+  if (a == 1U)
+    return 0;
+  if (1U != a)
+    return 0;
+  if (a != 1U)
+    return 0;
+  if (1U == a)
+    return 0;
+
+  if (a < 2)
+    return 0;
+  if (2 >= a)
+    return 0;
+  if (a > 2)
+    return 0;
+  if (2 <= a)
+    return 0;
+  if (a <= 2)
+    return 0;
+  if (2 > a)
+    return 0;
+  if (a >= 2)
+    return 0;
+  if (2 < a)
+    return 0;
+  if (a == 2)
+    return 0;
+  if (2 != a)
+    return 0;
+  if (a != 2)
+    return 0;
+  if (2 == a)
+    return 0;
+
+  if (a < 2U)
+    return 0;
+  if (2U >= a)
+    return 0;
+  if (a > 2U)
+    return 0;
+  if (2U <= a)
+    return 0;
+  if (a <= 2U)
+    return 0;
+  if (2U > a)
+    return 0;
+  if (a >= 2U)
+    return 0;
+  if (2U < a)
+    return 0;
+  if (a == 2U)
+    return 0;
+  if (2U != a)
+    return 0;
+  if (a != 2U)
+    return 0;
+  if (2U == a)
+    return 0;
+
+  if (a < 3)
+    return 0;
+  if (3 >= a)
+    return 0;
+  if (a > 3)
+    return 0;
+  if (3 <= a)
+    return 0;
+  if (a <= 3)
+    return 0;
+  if (3 > a)
+    return 0;
+  if (a >= 3)
+    return 0;
+  if (3 < a)
+    return 0;
+  if (a == 3)
+    return 0;
+  if (3 != a)
+    return 0;
+  if (a != 3)
+    return 0;
+  if (3 == a)
+    return 0;
+
+  if (a < 3U)
+    return 0;
+  if (3U >= a)
+    return 0;
+  if (a > 3U)
+    return 0;
+  if (3U <= a)
+    return 0;
+  if (a <= 3U)
+    return 0;
+  if (3U > a)
+    return 0;
+  if (a >= 3U)
+    return 0;
+  if (3U < a)
+    return 0;
+  if (a == 3U)
+    return 0;
+  if (3U != a)
+    return 0;
+  if (a != 3U)
+    return 0;
+  if (3U == a)
+    return 0;
+
+  return 1;
+}

cfe/trunk/test/Sema/tautological-constant-enum-compare.c

+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -DUNSIGNED -verify %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -fsyntax-only -DSIGNED -verify %s
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -DUNSIGNED -DSILENCE -Wno-tautological-constant-compare -verify %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -fsyntax-only -DSIGNED -DSILENCE -Wno-tautological-constant-compare -verify %s
+
+int main() {
+  enum A { A_a = 2 };
+  enum A a;
+
+#ifdef SILENCE
+  // expected-no-diagnostics
+#endif
+
+#ifdef UNSIGNED
+#ifndef SILENCE
+  if (a < 0) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
+    return 0;
+  if (0 >= a)
+    return 0;
+  if (a > 0)
+    return 0;
+  if (0 <= a) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
+    return 0;
+  if (a <= 0)
+    return 0;
+  if (0 > a) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
+    return 0;
+  if (a >= 0) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+    return 0;
+  if (0 < a)
+    return 0;
+
+  if (a < 0U) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
+    return 0;
+  if (0U >= a)
+    return 0;
+  if (a > 0U)
+    return 0;
+  if (0U <= a) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
+    return 0;
+  if (a <= 0U)
+    return 0;
+  if (0U > 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 true}}
+    return 0;
+  if (0U < a)
+    return 0;
+
+  if (a < 4294967295)
+    return 0;
+  if (4294967295 >= a) // expected-warning {{comparison 4294967295 >= 'enum A' is always true}}
+    return 0;
+  if (a > 4294967295) // expected-warning {{comparison 'enum A' > 4294967295 is always false}}
+    return 0;
+  if (4294967295 <= a)
+    return 0;
+  if (a <= 4294967295) // expected-warning {{comparison 'enum A' <= 4294967295 is always true}}
+    return 0;
+  if (4294967295 > a)
+    return 0;
+  if (a >= 4294967295)
+    return 0;
+  if (4294967295 < a) // expected-warning {{comparison 4294967295 < 'enum A' is always false}}
+    return 0;
+
+  if (a < 4294967295U)
+    return 0;
+  if (4294967295U >= a) // expected-warning {{comparison 4294967295 >= 'enum A' is always true}}
+    return 0;
+  if (a > 4294967295U) // expected-warning {{comparison 'enum A' > 4294967295 is always false}}
+    return 0;
+  if (4294967295U <= a)
+    return 0;
+  if (a <= 4294967295U) // expected-warning {{comparison 'enum A' <= 4294967295 is always true}}
+    return 0;
+  if (4294967295U > a)
+    return 0;
+  if (a >= 4294967295U)
+    return 0;
+  if (4294967295U < a) // expected-warning {{comparison 4294967295 < 'enum A' is always false}}
+    return 0;
+#else // SILENCE
+  if (a < 0)
+    return 0;
+  if (0 >= a)
+    return 0;
+  if (a > 0)
+    return 0;
+  if (0 <= a)
+    return 0;
+  if (a <= 0)
+    return 0;
+  if (0 > a)
+    return 0;
+  if (a >= 0)
+    return 0;
+  if (0 < a)
+    return 0;
+
+  if (a < 0U)
+    return 0;
+  if (0U >= a)
+    return 0;
+  if (a > 0U)
+    return 0;
+  if (0U <= a)
+    return 0;
+  if (a <= 0U)
+    return 0;
+  if (0U > a)
+    return 0;
+  if (a >= 0U)
+    return 0;
+  if (0U < a)
+    return 0;
+
+  if (a < 4294967295)
+    return 0;
+  if (4294967295 >= a)
+    return 0;
+  if (a > 4294967295)
+    return 0;
+  if (4294967295 <= a)
+    return 0;
+  if (a <= 4294967295)
+    return 0;
+  if (4294967295 > a)
+    return 0;
+  if (a >= 4294967295)
+    return 0;
+  if (4294967295 < a)
+    return 0;
+
+  if (a < 4294967295U)
+    return 0;
+  if (4294967295U >= a)
+    return 0;
+  if (a > 4294967295U)
+    return 0;
+  if (4294967295U <= a)
+    return 0;
+  if (a <= 4294967295U)
+    return 0;
+  if (4294967295U > a)
+    return 0;
+  if (a >= 4294967295U)
+    return 0;
+  if (4294967295U < a)
+    return 0;
+#endif
+#elif defined(SIGNED)
+#ifndef SILENCE
+  if (a < -2147483648) // expected-warning {{comparison 'enum A' < -2147483648 is always false}}
+    return 0;
+  if (-2147483648 >= a)
+    return 0;
+  if (a > -2147483648)
+    return 0;
+  if (-2147483648 <= a) // expected-warning {{comparison -2147483648 <= 'enum A' is always true}}
+    return 0;
+  if (a <= -2147483648)
+    return 0;
+  if (-2147483648 > a) // expected-warning {{comparison -2147483648 > 'enum A' is always false}}
+    return 0;
+  if (a >= -2147483648) // expected-warning {{comparison 'enum A' >= -2147483648 is always true}}
+    return 0;
+  if (-2147483648 < a)
+    return 0;
+
+  if (a < 2147483647)
+    return 0;
+  if (2147483647 >= a) // expected-warning {{comparison 2147483647 >= 'enum A' is always true}}
+    return 0;
+  if (a > 2147483647) // expected-warning {{comparison 'enum A' > 2147483647 is always false}}
+    return 0;
+  if (2147483647 <= a)
+    return 0;
+  if (a <= 2147483647) // expected-warning {{comparison 'enum A' <= 2147483647 is always true}}
+    return 0;
+  if (2147483647 > a)
+    return 0;
+  if (a >= 2147483647)
+    return 0;
+  if (2147483647 < a) // expected-warning {{comparison 2147483647 < 'enum A' is always false}}
+    return 0;
+
+  if (a < 2147483647U)
+    return 0;
+  if (2147483647U >= a) // expected-warning {{comparison 2147483647 >= 'enum A' is always true}}
+    return 0;
+  if (a > 2147483647U) // expected-warning {{comparison 'enum A' > 2147483647 is always false}}
+    return 0;
+  if (2147483647U <= a)
+    return 0;
+  if (a <= 2147483647U) // expected-warning {{comparison 'enum A' <= 2147483647 is always true}}
+    return 0;
+  if (2147483647U > a)
+    return 0;
+  if (a >= 2147483647U)
+    return 0;
+  if (2147483647U < a) // expected-warning {{comparison 2147483647 < 'enum A' is always false}}
+    return 0;
+#else // SILENCE
+  if (a < -2147483648)
+    return 0;
+  if (-2147483648 >= a)
+    return 0;
+  if (a > -2147483648)
+    return 0;
+  if (-2147483648 <= a)
+    return 0;
+  if (a <= -2147483648)
+    return 0;
+  if (-2147483648 > a)
+    return 0;
+  if (a >= -2147483648)
+    return 0;
+  if (-2147483648 < a)
+    return 0;
+
+  if (a < 2147483647)
+    return 0;
+  if (2147483647 >= a)
+    return 0;
+  if (a > 2147483647)
+    return 0;
+  if (2147483647 <= a)
+    return 0;
+  if (a <= 2147483647)
+    return 0;
+  if (2147483647 > a)
+    return 0;
+  if (a >= 2147483647)
+    return 0;
+  if (2147483647 < a)
+    return 0;
+
+  if (a < 2147483647U)
+    return 0;
+  if (2147483647U >= a)
+    return 0;
+  if (a > 2147483647U)
+    return 0;
+  if (2147483647U <= a)
+    return 0;
+  if (a <= 2147483647U)
+    return 0;
+  if (2147483647U > a)
+    return 0;
+  if (a >= 2147483647U)
+    return 0;
+  if (2147483647U < a)
+    return 0;
+#endif
+#endif
+
+  return 1;
+}
+
+// https://bugs.llvm.org/show_bug.cgi?id=35009
+int PR35009() {
+  enum A { A_a = 2 };
+  enum A a;
+
+  // in C, this should not warn.
+
+  if (a < 1)
+    return 0;
+  if (1 >= a)
+    return 0;
+  if (a > 1)
+    return 0;
+  if (1 <= a)
+    return 0;
+  if (a <= 1)
+    return 0;
+  if (1 > a)
+    return 0;
+  if (a >= 1)
+    return 0;
+  if (1 < a)
+    return 0;
+  if (a == 1)
+    return 0;
+  if (1 != a)
+    return 0;
+  if (a != 1)
+    return 0;
+  if (1 == a)
+    return 0;
+
+  if (a < 1U)
+    return 0;
+  if (1U >= a)
+    return 0;
+  if (a > 1U)
+    return 0;
+  if (1U <= a)
+    return 0;
+  if (a <= 1U)
+    return 0;
+  if (1U > a)
+    return 0;
+  if (a >= 1U)
+    return 0;
+  if (1U < a)
+    return 0;
+  if (a == 1U)
+    return 0;
+  if (1U != a)
+    return 0;
+  if (a != 1U)
+    return 0;
+  if (1U == a)
+    return 0;
+
+  if (a < 2)
+    return 0;
+  if (2 >= a)
+    return 0;
+  if (a > 2)
+    return 0;
+  if (2 <= a)
+    return 0;
+  if (a <= 2)
+    return 0;
+  if (2 > a)
+    return 0;
+  if (a >= 2)
+    return 0;
+  if (2 < a)
+    return 0;
+  if (a == 2)
+    return 0;
+  if (2 != a)
+    return 0;
+  if (a != 2)
+    return 0;
+  if (2 == a)
+    return 0;
+
+  if (a < 2U)
+    return 0;
+  if (2U >= a)
+    return 0;
+  if (a > 2U)
+    return 0;
+  if (2U <= a)
+    return 0;
+  if (a <= 2U)
+    return 0;
+  if (2U > a)
+    return 0;
+  if (a >= 2U)
+    return 0;
+  if (2U < a)
+    return 0;
+  if (a == 2U)
+    return 0;
+  if (2U != a)
+    return 0;
+  if (a != 2U)
+    return 0;
+  if (2U == a)
+    return 0;
+
+  if (a < 3)
+    return 0;
+  if (3 >= a)
+    return 0;
+  if (a > 3)
+    return 0;
+  if (3 <= a)
+    return 0;
+  if (a <= 3)
+    return 0;
+  if (3 > a)
+    return 0;
+  if (a >= 3)
+    return 0;
+  if (3 < a)
+    return 0;
+  if (a == 3)
+    return 0;
+  if (3 != a)
+    return 0;
+  if (a != 3)
+    return 0;
+  if (3 == a)
+    return 0;
+
+  if (a < 3U)
+    return 0;
+  if (3U >= a)
+    return 0;
+  if (a > 3U)
+    return 0;
+  if (3U <= a)
+    return 0;
+  if (a <= 3U)
+    return 0;
+  if (3U > a)
+    return 0;
+  if (a >= 3U)
+    return 0;
+  if (3U < a)
+    return 0;
+  if (a == 3U)
+    return 0;
+  if (3U != a)
+    return 0;
+  if (a != 3U)
+    return 0;
+  if (3U == a)
+    return 0;
+
+  return 1;
+}

cfe/trunk/test/Sema/tautological-unsigned-enum-zero-compare.c

-// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -DALL_WARN -verify %s
-// RUN: %clang_cc1 -triple=x86_64-pc-win32 -fsyntax-only -DSIGN_WARN -verify %s
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -DUNSIGNED -verify %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -fsyntax-only -DSIGNED -verify %s
 // RUN: %clang_cc1 -triple=x86_64-pc-win32 -fsyntax-only -Wno-tautological-unsigned-enum-zero-compare -verify %s
 
 // Okay, this is where it gets complicated.
 // Then default enum sigdness is target-specific.
 // On windows, it is signed by default. We do not want to warn in that case.
 
 int main() {
-  enum A { A_foo, A_bar };
+  enum A { A_a = 0 };
   enum A a;
+  enum B { B_a = -1 };
+  enum B b;
 
-#ifdef ALL_WARN
+#ifdef UNSIGNED
   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}}
+  if (0 >= a)
+    return 0;
+  if (a > 0)
     return 0;
   if (0 <= a) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
     return 0;
+  if (a <= 0)
+    return 0;
   if (0 > a) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
     return 0;
+  if (a >= 0) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+    return 0;
+  if (0 < a)
+    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}}
+  if (0U >= a)
+    return 0;
+  if (a > 0U)
     return 0;
   if (0U <= a) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
     return 0;
+  if (a <= 0U)
+    return 0;
   if (0U > a) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
     return 0;
-#elif defined(SIGN_WARN)
-  if (a < 0) // ok
+  if (a >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+    return 0;
+  if (0U < a)
+    return 0;
+
+  if (b < 0)
+    return 0;
+  if (0 >= b)
+    return 0;
+  if (b > 0)
+    return 0;
+  if (0 <= b)
+    return 0;
+  if (b <= 0)
+    return 0;
+  if (0 > b)
+    return 0;
+  if (b >= 0)
+    return 0;
+  if (0 < b)
+    return 0;
+
+  if (b < 0U) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
+    return 0;
+  if (0U >= b)
+    return 0;
+  if (b > 0U)
+    return 0;
+  if (0U <= b) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
+    return 0;
+  if (b <= 0U)
+    return 0;
+  if (0U > b) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
+    return 0;
+  if (b >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
     return 0;
-  if (a >= 0) // ok
+  if (0U < b)
     return 0;
-  if (0 <= a) // ok
+#elif defined(SIGNED)
+  if (a < 0)
+    return 0;
+  if (0 >= a)
+    return 0;
+  if (a > 0)
+    return 0;
+  if (0 <= a)
+    return 0;
+  if (a <= 0)
     return 0;
-  if (0 > a) // ok
+  if (0 > a)
     return 0;
+  if (a >= 0)
+    return 0;
+  if (0 < a)
+    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}}
+  if (0U >= a)
+    return 0;
+  if (a > 0U)
     return 0;
   if (0U <= a) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
     return 0;
+  if (a <= 0U)
+    return 0;
   if (0U > 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 true}}
+    return 0;
+  if (0U < a)
+    return 0;
+
+  if (b < 0)
+    return 0;
+  if (0 >= b)
+    return 0;
+  if (b > 0)
+    return 0;
+  if (0 <= b)
+    return 0;
+  if (b <= 0)
+    return 0;
+  if (0 > b)
+    return 0;
+  if (b >= 0)
+    return 0;
+  if (0 < b)
+    return 0;
+
+  if (b < 0U) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
+    return 0;
+  if (0U >= b)
+    return 0;
+  if (b > 0U)
+    return 0;
+  if (0U <= b) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
+    return 0;
+  if (b <= 0U)
+    return 0;
+  if (0U > b) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
+    return 0;
+  if (b >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+    return 0;
+  if (0U < b)
+    return 0;
 #else
   // expected-no-diagnostics
+
   if (a < 0)
     return 0;
-  if (a >= 0)
+  if (0 >= a)
+    return 0;
+  if (a > 0)
     return 0;
   if (0 <= a)
     return 0;
+  if (a <= 0)
+    return 0;
   if (0 > a)
     return 0;
+  if (a >= 0)
+    return 0;
+  if (0 < a)
+    return 0;
+
   if (a < 0U)
     return 0;
-  if (a >= 0U)
+  if (0U >= a)
+    return 0;
+  if (a > 0U)
     return 0;
   if (0U <= a)
     return 0;
+  if (a <= 0U)
+    return 0;
   if (0U > a)
     return 0;
+  if (a >= 0U)
+    return 0;
+  if (0U < a)
+    return 0;
+
+  if (b < 0)
+    return 0;
+  if (0 >= b)
+    return 0;
+  if (b > 0)
+    return 0;
+  if (0 <= b)
+    return 0;
+  if (b <= 0)
+    return 0;
+  if (0 > b)
+    return 0;
+  if (b >= 0)
+    return 0;
+  if (0 < b)
+    return 0;
+
+  if (b < 0U)
+    return 0;
+  if (0U >= b)
+    return 0;
+  if (b > 0U)
+    return 0;
+  if (0U <= b)
+    return 0;
+  if (b <= 0U)
+    return 0;
+  if (0U > b)
+    return 0;
+  if (b >= 0U)
+    return 0;
+  if (0U < b)
+    return 0;
 #endif
 
+  if (a == 0)
+    return 0;
+  if (0 != a)
+    return 0;
+  if (a != 0)
+    return 0;
+  if (0 == a)
+    return 0;
+
+  if (a == 0U)
+    return 0;
+  if (0U != a)
+    return 0;
+  if (a != 0U)
+    return 0;
+  if (0U == a)
+    return 0;
+
+  if (b == 0)
+    return 0;
+  if (0 != b)
+    return 0;
+  if (b != 0)
+    return 0;
+  if (0 == b)
+    return 0;
+
+  if (b == 0U)
+    return 0;
+  if (0U != b)
+    return 0;
+  if (b != 0U)
+    return 0;
+  if (0U == b)
+    return 0;
+
   return 1;
 }

cfe/trunk/test/Sema/tautological-unsigned-enum-zero-compare.cpp

-// RUN: %clang_cc1 -std=c++11 -triple=x86_64-pc-linux-gnu -fsyntax-only -DALL_WARN -verify %s
-// RUN: %clang_cc1 -std=c++11 -triple=x86_64-pc-win32 -fsyntax-only -DSIGN_WARN -verify %s
-// RUN: %clang_cc1 -std=c++11 -triple=x86_64-pc-win32 -fsyntax-only -Wno-tautological-unsigned-enum-zero-compare -verify %s
+// RUN: %clang_cc1 -std=c++11 -triple=x86_64-pc-linux-gnu -fsyntax-only -DUNSIGNED -verify %s
+// RUN: %clang_cc1 -std=c++11 -triple=x86_64-pc-win32 -fsyntax-only -DSIGNED -verify %s
+// RUN: %clang_cc1 -std=c++11 -triple=x86_64-pc-win32 -fsyntax-only -DSILENCE -Wno-tautological-unsigned-enum-zero-compare -verify %s
 
 // Okay, this is where it gets complicated.
 // Then default enum sigdness is target-specific.
 // On windows, it is signed by default. We do not want to warn in that case.
 
 int main() {
-  enum A { A_foo, A_bar };
+  enum A { A_foo = 0, A_bar, };
   enum A a;
 
-  enum B : unsigned { B_foo, B_bar };
+  enum B : unsigned { B_foo = 0, B_bar, };
   enum B b;
 
-  enum C : signed { c_foo, c_bar };
+  enum C : signed { C_foo = 0, C_bar, };
   enum C c;
 
-#ifdef ALL_WARN
+#ifdef UNSIGNED
   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}}
+  if (0 >= a)
+    return 0;
+  if (a > 0)
     return 0;
   if (0 <= a) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
     return 0;
+  if (a <= 0)
+    return 0;
   if (0 > a) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
     return 0;
+  if (a >= 0) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+    return 0;
+  if (0 < a)
+    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}}
+  if (0U >= a)
+    return 0;
+  if (a > 0U)
     return 0;
   if (0U <= a) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
     return 0;
+  if (a <= 0U)
+    return 0;
   if (0U > 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 true}}
+    return 0;
+  if (0U < a)
+    return 0;
 
   if (b < 0) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
     return 0;
-  if (b >= 0) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+  if (0 >= b)
+    return 0;
+  if (b > 0)
     return 0;
   if (0 <= b) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
     return 0;
+  if (b <= 0)
+    return 0;
   if (0 > b) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
     return 0;
+  if (b >= 0) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+    return 0;
+  if (0 < b)
+    return 0;
+
   if (b < 0U) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
     return 0;
-  if (b >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+  if (0U >= b)
+    return 0;
+  if (b > 0U)
     return 0;
   if (0U <= b) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
     return 0;
+  if (b <= 0U)
+    return 0;
   if (0U > b) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
     return 0;
+  if (b >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+    return 0;
+  if (0U < b)
+    return 0;
 
-  if (c < 0) // ok
+  if (c < 0)
+    return 0;
+  if (0 >= c) // expected-warning {{comparison 0 >= 'enum C' is always true}}
+    return 0;
+  if (c > 0) // expected-warning {{comparison 'enum C' > 0 is always false}}
+    return 0;
+  if (0 <= c)
+    return 0;
+  if (c <= 0) // expected-warning {{comparison 'enum C' <= 0 is always true}}
     return 0;
-  if (c >= 0) // ok
+  if (0 > c)
     return 0;
-  if (0 <= c) // ok
+  if (c >= 0)
     return 0;
-  if (0 > c) // ok
+  if (0 < c) // expected-warning {{0 < 'enum C' is always false}}
     return 0;
+
   if (c < 0U) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
     return 0;
-  if (c >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+  if (0U >= c)
+    return 0;
+  if (c > 0U)
     return 0;
   if (0U <= c) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
     return 0;
+  if (c <= 0U)
+    return 0;
   if (0U > c) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
     return 0;
-#elif defined(SIGN_WARN)
-  if (a < 0) // ok
+  if (c >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
     return 0;
-  if (a >= 0) // ok
+  if (0U < c)
     return 0;
-  if (0 <= a) // ok
+#elif defined(SIGNED)
+  if (a < 0)
+    return 0;
+  if (0 >= a) // expected-warning {{comparison 0 >= 'enum A' is always true}}
     return 0;
-  if (0 > a) // ok
+  if (a > 0) // expected-warning {{comparison 'enum A' > 0 is always false}}
+    return 0;
+  if (0 <= a)
     return 0;
+  if (a <= 0) // expected-warning {{comparison 'enum A' <= 0 is always true}}
+    return 0;
+  if (0 > a)
+    return 0;
+  if (a >= 0)
+    return 0;
+  if (0 < a) // expected-warning {{comparison 0 < 'enum A' 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}}
+  if (0U >= a)
+    return 0;
+  if (a > 0U)
     return 0;
   if (0U <= a) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
     return 0;
+  if (a <= 0U)
+    return 0;
   if (0U > 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 true}}
+    return 0;
+  if (0U < a)
+    return 0;
 
   if (b < 0) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
     return 0;
-  if (b >= 0) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+  if (0 >= b)
+    return 0;
+  if (b > 0)
     return 0;
   if (0 <= b) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
     return 0;
+  if (b <= 0)
+    return 0;
   if (0 > b) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
     return 0;
+  if (b >= 0) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+    return 0;
+  if (0 < b)
+    return 0;
+
   if (b < 0U) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
     return 0;
-  if (b >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+  if (0U >= b)
+    return 0;
+  if (b > 0U)
     return 0;
   if (0U <= b) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
     return 0;
+  if (b <= 0U)
+    return 0;
   if (0U > b) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
     return 0;
+  if (b >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+    return 0;
+  if (0U < b)
+    return 0;
 
-  if (c < 0) // ok
+  if (c < 0)
     return 0;
-  if (c >= 0) // ok
+  if (0 >= c) // expected-warning {{comparison 0 >= 'enum C' is always true}}
     return 0;
-  if (0 <= c) // ok
+  if (c > 0) // expected-warning {{comparison 'enum C' > 0 is always false}}
+    return 0;
+  if (0 <= c)
     return 0;
-  if (0 > c) // ok
+  if (c <= 0) // expected-warning {{comparison 'enum C' <= 0 is always true}}
+    return 0;
+  if (0 > c)
+    return 0;
+  if (c >= 0)
     return 0;
+  if (0 < c) // expected-warning {{0 < 'enum C' is always false}}
+    return 0;
+
   if (c < 0U) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
     return 0;
-  if (c >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+  if (0U >= c)
+    return 0;
+  if (c > 0U)
     return 0;
   if (0U <= c) // expected-warning {{comparison of 0 <= unsigned enum expression is always true}}
     return 0;
+  if (c <= 0U)
+    return 0;
   if (0U > c) // expected-warning {{comparison of 0 > unsigned enum expression is always false}}
     return 0;
+  if (c >= 0U) // expected-warning {{comparison of unsigned enum expression >= 0 is always true}}
+    return 0;
+  if (0U < c)
+    return 0;
 #else
-  // expected-no-diagnostics
   if (a < 0)
     return 0;
-  if (a >= 0)
+  if (0 >= a) // expected-warning {{comparison 0 >= 'enum A' is always true}}
+    return 0;
+  if (a > 0) // expected-warning {{comparison 'enum A' > 0 is always false}}
     return 0;
   if (0 <= a)
     return 0;
+  if (a <= 0) // expected-warning {{comparison 'enum A' <= 0 is always true}}
+    return 0;
   if (0 > a)
     return 0;
+  if (a >= 0)
+    return 0;
+  if (0 < a) // expected-warning {{comparison 0 < 'enum A' is always false}}
+    return 0;
+
   if (a < 0U)
     return 0;
-  if (a >= 0U)
+  if (0U >= a)
+    return 0;
+  if (a > 0U)
     return 0;
   if (0U <= a)
     return 0;
+  if (a <= 0U)
+    return 0;
   if (0U > a)
     return 0;
+  if (a >= 0U)
+    return 0;
+  if (0U < a)
+    return 0;
 
   if (b < 0)
     return 0;
-  if (b >= 0)
+  if (0 >= b)
+    return 0;
+  if (b > 0)
     return 0;
   if (0 <= b)
     return 0;
+  if (b <= 0)
+    return 0;
   if (0 > b)
     return 0;
+  if (b >= 0)
+    return 0;
+  if (0 < b)
+    return 0;
+
   if (b < 0U)
     return 0;
-  if (b >= 0U)
+  if (0U >= b)
+    return 0;
+  if (b > 0U)
     return 0;
   if (0U <= b)
     return 0;
+  if (b <= 0U)
+    return 0;
   if (0U > b)
     return 0;
+  if (b >= 0U)
+    return 0;
+  if (0U < b)
+    return 0;
 
   if (c < 0)
     return 0;
-  if (c >= 0)
+  if (0 >= c) // expected-warning {{comparison 0 >= 'enum C' is always true}}
+    return 0;
+  if (c > 0) // expected-warning {{comparison 'enum C' > 0 is always false}}
     return 0;
   if (0 <= c)
     return 0;
+  if (c <= 0) // expected-warning {{comparison 'enum C' <= 0 is always true}}
+    return 0;
   if (0 > c)
     return 0;
+  if (c >= 0)
+    return 0;
+  if (0 < c) // expected-warning {{0 < 'enum C' is always false}}
+    return 0;
+
   if (c < 0U)
     return 0;
-  if (c >= 0U)
+  if (0U >= c)
+    return 0;
+  if (c > 0U)
     return 0;
   if (0U <= c)
     return 0;
+  if (c <= 0U)
+    return 0;
   if (0U > c)
     return 0;
+  if (c >= 0U)
+    return 0;
+  if (0U < c)
+    return 0;
+#endif
+
+  return 1;
+}
+
+namespace crash_enum_zero_width {
+int test() {
+  enum A : unsigned {
+    A_foo = 0
+  };
+  enum A a;
+
+  // used to crash in llvm::APSInt::getMaxValue()
+#ifndef SILENCE
+  if (a < 0) // expected-warning {{comparison of unsigned enum expression < 0 is always false}}
+#else
+  if (a > 0)
 #endif
+    return 0;
 
   return 1;
 }
+} // namespace crash_enum_zero_width