Index: clang-tools-extra/trunk/clang-tidy/misc/SuspiciousEnumUsageCheck.cpp
===================================================================
--- clang-tools-extra/trunk/clang-tidy/misc/SuspiciousEnumUsageCheck.cpp
+++ clang-tools-extra/trunk/clang-tidy/misc/SuspiciousEnumUsageCheck.cpp
@@ -42,7 +42,8 @@
     const auto MinMaxVal = std::minmax_element(
         EnumDec->enumerator_begin(), EnumDec->enumerator_end(),
         [](const EnumConstantDecl *E1, const EnumConstantDecl *E2) {
-          return E1->getInitVal() < E2->getInitVal();
+          return llvm::APSInt::compareValues(E1->getInitVal(),
+                                             E2->getInitVal()) < 0;
         });
     MinVal = MinMaxVal.first->getInitVal();
     MaxVal = MinMaxVal.second->getInitVal();
@@ -57,7 +58,8 @@
 static bool hasDisjointValueRange(const EnumDecl *Enum1,
                                   const EnumDecl *Enum2) {
   ValueRange Range1(Enum1), Range2(Enum2);
-  return (Range1.MaxVal < Range2.MinVal) || (Range2.MaxVal < Range1.MinVal);
+  return llvm::APSInt::compareValues(Range1.MaxVal, Range2.MinVal) < 0 ||
+         llvm::APSInt::compareValues(Range2.MaxVal, Range1.MinVal) < 0;
 }
 
 static bool isNonPowerOf2NorNullLiteral(const EnumConstantDecl *EnumConst) {
Index: clang-tools-extra/trunk/test/clang-tidy/misc-suspicious-enum-usage.cpp
===================================================================
--- clang-tools-extra/trunk/test/clang-tidy/misc-suspicious-enum-usage.cpp
+++ clang-tools-extra/trunk/test/clang-tidy/misc-suspicious-enum-usage.cpp
@@ -54,7 +54,7 @@
   int emptytest = EmptyVal | B;
   if (bestDay() | A)
     return 1;
-  // CHECK-MESSAGES: :[[@LINE-2]]:17: warning: enum values are from different enum types 
+  // CHECK-MESSAGES: :[[@LINE-2]]:17: warning: enum values are from different enum types
   if (I | Y)
     return 1;
   // CHECK-MESSAGES: :[[@LINE-2]]:9: warning: enum values are from different enum types
@@ -88,3 +88,9 @@
     return 1;
   return 42;
 }
+
+namespace PR34400 {
+enum { E1 = 0 };
+enum { E2 = -1 };
+enum { l = E1 | E2 };
+}