Index: clang/lib/ASTMatchers/ASTMatchFinder.cpp
===================================================================
--- clang/lib/ASTMatchers/ASTMatchFinder.cpp
+++ clang/lib/ASTMatchers/ASTMatchFinder.cpp
@@ -43,6 +43,11 @@
 // optimize this on.
 static const unsigned MaxMemoizationEntries = 10000;
 
+enum class MatchType {
+  Ancestors,
+  Descendants
+};
+
 // We use memoization to avoid running the same matcher on the same
 // AST node twice.  This struct is the key for looking up match
 // result.  It consists of an ID of the MatcherInterface (for
@@ -60,10 +65,11 @@
   DynTypedNode Node;
   BoundNodesTreeBuilder BoundNodes;
   TraversalKind Traversal = TK_AsIs;
+  MatchType Type;
 
   bool operator<(const MatchKey &Other) const {
-    return std::tie(Traversal, MatcherID, Node, BoundNodes) <
-           std::tie(Other.Traversal, Other.MatcherID, Other.Node,
+    return std::tie(Traversal, Type, MatcherID, Node, BoundNodes) <
+           std::tie(Other.Traversal, Other.Type, Other.MatcherID, Other.Node,
                     Other.BoundNodes);
   }
 };
@@ -446,7 +452,8 @@
                                   BoundNodesTreeBuilder *Builder, int MaxDepth,
                                   TraversalKind Traversal, BindKind Bind) {
     // For AST-nodes that don't have an identity, we can't memoize.
-    if (!Node.getMemoizationData() || !Builder->isComparable())
+    // When doing a single-level match, we don't need to memoize
+    if (!Node.getMemoizationData() || !Builder->isComparable() || MaxDepth == 1)
       return matchesRecursively(Node, Matcher, Builder, MaxDepth, Traversal,
                                 Bind);
 
@@ -456,7 +463,7 @@
     // Note that we key on the bindings *before* the match.
     Key.BoundNodes = *Builder;
     Key.Traversal = Ctx.getParentMapContext().getTraversalKind();
-
+    Key.Type = MatchType::Descendants;
     MemoizationMap::iterator I = ResultCache.find(Key);
     if (I != ResultCache.end()) {
       *Builder = I->second.Nodes;
@@ -693,7 +700,8 @@
                                             BoundNodesTreeBuilder *Builder,
                                             AncestorMatchMode MatchMode) {
     // For AST-nodes that don't have an identity, we can't memoize.
-    if (!Builder->isComparable())
+    // When doing a single-level match, we don't need to memoize
+    if (!Builder->isComparable() || MatchMode == AncestorMatchMode::AMM_ParentOnly)
       return matchesAncestorOfRecursively(Node, Ctx, Matcher, Builder,
                                           MatchMode);
 
@@ -702,6 +710,7 @@
     Key.Node = Node;
     Key.BoundNodes = *Builder;
     Key.Traversal = Ctx.getParentMapContext().getTraversalKind();
+    Key.Type = MatchType::Ancestors;
 
     // Note that we cannot use insert and reuse the iterator, as recursive
     // calls to match might invalidate the result cache iterators.
Index: clang/unittests/ASTMatchers/ASTMatchersTraversalTest.cpp
===================================================================
--- clang/unittests/ASTMatchers/ASTMatchersTraversalTest.cpp
+++ clang/unittests/ASTMatchers/ASTMatchersTraversalTest.cpp
@@ -2864,6 +2864,34 @@
     compoundStmt(hasParent(ifStmt()))));
 }
 
+TEST(MatcherMemoize, HasParentDiffersFromHas) {
+  // Test introduced after detecting a bug in memoization
+  constexpr auto code = "void f() { throw 1; }";
+  EXPECT_TRUE(notMatches(
+    code,
+    cxxThrowExpr(hasParent(expr()))));
+  EXPECT_TRUE(matches(
+    code,
+    cxxThrowExpr(has(expr()))));
+  EXPECT_TRUE(matches(
+    code,
+    cxxThrowExpr(anyOf(hasParent(expr()), has(expr())))));
+}
+
+TEST(MatcherMemoize, HasDiffersFromHasDescendant) {
+  // Test introduced after detecting a bug in memoization
+  constexpr auto code = "void f() { throw 1+1; }";
+  EXPECT_TRUE(notMatches(
+    code,
+    cxxThrowExpr(has(integerLiteral()))));
+  EXPECT_TRUE(matches(
+    code,
+    cxxThrowExpr(hasDescendant(integerLiteral()))));
+  EXPECT_TRUE(notMatches(code, 
+    cxxThrowExpr(allOf(
+      hasDescendant(integerLiteral()),
+      has(integerLiteral())))));
+}
 TEST(HasAncestor, MatchesAllAncestors) {
   EXPECT_TRUE(matches(
     "template <typename T> struct C { static void f() { 42; } };"