Add missing comparison operators to SmallVector

[bkramer]

A unit test would be fantastic.

[frgossen]

Add tests

llvm/include/llvm/ADT/SmallVector.h

public:
   bool operator!=(const SmallVectorImpl &RHS) const {
     return !(*this == RHS);
   }
 
   bool operator<(const SmallVectorImpl &RHS) const {
     return std::lexicographical_compare(this->begin(), this->end(),
                                         RHS.begin(), RHS.end());
   }
+  bool operator>(const SmallVectorImpl &RHS) const { return RHS < *this; }
+  bool operator<=(const SmallVectorImpl &RHS) const { return !(*this > RHS); }
+  bool operator>=(const SmallVectorImpl &RHS) const { return !(*this < RHS); }
 };
 
 template <typename T>
 void SmallVectorImpl<T>::swap(SmallVectorImpl<T> &RHS) {
   if (this == &RHS) return;
 
   // We can only avoid copying elements if neither vector is small.
   if (!this->isSmall() && !RHS.isSmall()) {

llvm/unittests/ADT/SmallVectorTest.cpp

public:
   static int getNumMoveAssignmentCalls() {
     return numMoveAssignmentCalls;
   }
 
   static int getNumCopyAssignmentCalls() {
     return numCopyAssignmentCalls;
   }
 
-  friend bool operator==(const Constructable & c0, const Constructable & c1) {
+  friend bool operator==(const Constructable &c0, const Constructable &c1) {
     return c0.getValue() == c1.getValue();
   }
 
-  friend bool LLVM_ATTRIBUTE_UNUSED
-  operator!=(const Constructable & c0, const Constructable & c1) {
+  friend bool LLVM_ATTRIBUTE_UNUSED operator!=(const Constructable &c0,
+                                               const Constructable &c1) {
     return c0.getValue() != c1.getValue();
   }
+
+  friend bool operator<(const Constructable &c0, const Constructable &c1) {
+    return c0.getValue() < c1.getValue();
+  }
+  friend bool LLVM_ATTRIBUTE_UNUSED operator<=(const Constructable &c0,
+                                               const Constructable &c1) {
+    return c0.getValue() <= c1.getValue();
+  }
+  friend bool LLVM_ATTRIBUTE_UNUSED operator>(const Constructable &c0,
+                                              const Constructable &c1) {
+    return c0.getValue() > c1.getValue();
+  }
+  friend bool LLVM_ATTRIBUTE_UNUSED operator>=(const Constructable &c0,
+                                               const Constructable &c1) {
+    return c0.getValue() >= c1.getValue();
+  }
 };
 
 int Constructable::numConstructorCalls;
 int Constructable::numCopyConstructorCalls;
 int Constructable::numMoveConstructorCalls;
 int Constructable::numDestructorCalls;
 int Constructable::numAssignmentCalls;
 int Constructable::numCopyAssignmentCalls;
EXPECT_EQ(this->theVector.end(),
                                    this->theVector.begin()));
   EXPECT_EQ(this->theVector.begin() + 1,
             this->theVector.insert(this->theVector.begin() + 1,
                                    this->theVector.begin(),
                                    this->theVector.begin()));
 }
 
 // Comparison tests.
-TYPED_TEST(SmallVectorTest, ComparisonTest) {
-  SCOPED_TRACE("ComparisonTest");
+TYPED_TEST(SmallVectorTest, ComparisonEqualityTest) {
+  SCOPED_TRACE("ComparisonEqualityTest");
 
   this->makeSequence(this->theVector, 1, 3);
   this->makeSequence(this->otherVector, 1, 3);
 
   EXPECT_TRUE(this->theVector == this->otherVector);
   EXPECT_FALSE(this->theVector != this->otherVector);
 
   this->otherVector.clear();
   this->makeSequence(this->otherVector, 2, 4);
 
   EXPECT_FALSE(this->theVector == this->otherVector);
   EXPECT_TRUE(this->theVector != this->otherVector);
 }
 
+// Comparison tests.
+TYPED_TEST(SmallVectorTest, ComparisonLessThanTest) {
+  SCOPED_TRACE("ComparisonLessThanTest");
+
+  this->theVector = {1, 2, 4};
+  this->otherVector = {1, 4};
+
+  EXPECT_TRUE(this->theVector < this->otherVector);
+  EXPECT_TRUE(this->theVector <= this->otherVector);
+  EXPECT_FALSE(this->theVector > this->otherVector);
+  EXPECT_FALSE(this->theVector >= this->otherVector);
+
+  EXPECT_FALSE(this->otherVector < this->theVector);
+  EXPECT_FALSE(this->otherVector <= this->theVector);
+  EXPECT_TRUE(this->otherVector > this->theVector);
+  EXPECT_TRUE(this->otherVector >= this->theVector);
+
+  this->otherVector = {1, 2, 4};
+
+  EXPECT_FALSE(this->theVector < this->otherVector);
+  EXPECT_TRUE(this->theVector <= this->otherVector);
+  EXPECT_FALSE(this->theVector > this->otherVector);
+  EXPECT_TRUE(this->theVector >= this->otherVector);
+
+  EXPECT_FALSE(this->otherVector < this->theVector);
+  EXPECT_TRUE(this->otherVector <= this->theVector);
+  EXPECT_FALSE(this->otherVector > this->theVector);
+  EXPECT_TRUE(this->otherVector >= this->theVector);
+}
+
 // Constant vector tests.
 TYPED_TEST(SmallVectorTest, ConstVectorTest) {
   const TypeParam constVector;
 
   EXPECT_EQ(0u, constVector.size());
   EXPECT_TRUE(constVector.empty());
   EXPECT_TRUE(constVector.begin() == constVector.end());
 }