[PATCH] D82771: [ASTMatcher] Fix a performance regression: memorize the child match.

[Haojian Wu via Phabricator via cfe-commits]

hokein updated this revision to Diff 274347.
hokein added a comment.

Address comments.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D82771/new/

https://reviews.llvm.org/D82771

Files:
  clang/lib/ASTMatchers/ASTMatchFinder.cpp


Index: clang/lib/ASTMatchers/ASTMatchFinder.cpp
===================================================================
--- clang/lib/ASTMatchers/ASTMatchFinder.cpp
+++ clang/lib/ASTMatchers/ASTMatchFinder.cpp
@@ -45,7 +45,9 @@
 
 enum class MatchType {
   Ancestors,
-  Descendants
+
+  Descendants,
+  Child,
 };
 
 // We use memoization to avoid running the same matcher on the same
@@ -452,8 +454,7 @@
                                   BoundNodesTreeBuilder *Builder, int MaxDepth,
                                   TraversalKind Traversal, BindKind Bind) {
     // For AST-nodes that don't have an identity, we can't memoize.
-    // When doing a single-level match, we don't need to memoize
-    if (!Node.getMemoizationData() || !Builder->isComparable() || MaxDepth == 1)
+    if (!Node.getMemoizationData() || !Builder->isComparable())
       return matchesRecursively(Node, Matcher, Builder, MaxDepth, Traversal,
                                 Bind);
 
@@ -463,7 +464,8 @@
     // Note that we key on the bindings *before* the match.
     Key.BoundNodes = *Builder;
     Key.Traversal = Ctx.getParentMapContext().getTraversalKind();
-    Key.Type = MatchType::Descendants;
+    // Memoize result even doing a single-level match, it might be expensive.
+    Key.Type = MaxDepth == 1 ? MatchType::Child : MatchType::Descendants;
     MemoizationMap::iterator I = ResultCache.find(Key);
     if (I != ResultCache.end()) {
       *Builder = I->second.Nodes;
@@ -700,8 +702,10 @@
                                             BoundNodesTreeBuilder *Builder,
                                             AncestorMatchMode MatchMode) {
     // For AST-nodes that don't have an identity, we can't memoize.
-    // When doing a single-level match, we don't need to memoize
-    if (!Builder->isComparable() || MatchMode == AncestorMatchMode::AMM_ParentOnly)
+    // When doing a single-level match, we don't need to memoize because
+    // ParentMap (in ASTContext) already memoizes the result.
+    if (!Builder->isComparable() ||
+        MatchMode == AncestorMatchMode::AMM_ParentOnly)
       return matchesAncestorOfRecursively(Node, Ctx, Matcher, Builder,
                                           MatchMode);
 


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