[clangd] Cache include fixes for diagnostics caused by the same unresolved name or incomplete type.

Summary:
Multiple diagnostics can be caused by the same unresolved name or incomplete type,
especially if the code is copy-pasted without #includes. The cache can avoid making
repetitive index requests, and thus reduce latency and allow more diagnostics to be
fixed (we limit the number of index requests for each parse).

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D58239

llvm-svn: 354268

1 files changed, 13 insertions, 1 deletions

diff --git a/clang-tools-extra/clangd/IncludeFixer.h b/clang-tools-extra/clangd/IncludeFixer.h
index da292b56b00..f1eac45d9b3 100644
--- a/clang-tools-extra/clangd/IncludeFixer.h
+++ b/clang-tools-extra/clangd/IncludeFixer.h
@@ -21,6 +21,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/ADT/Optional.h"
+#include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include <memory>
 
@@ -51,7 +52,7 @@ private:
   std::vector<Fix> fixIncompleteType(const Type &T) const;
 
   /// Generates header insertion fixes for all symbols. Fixes are deduplicated.
-  std::vector<Fix> fixesForSymbols(llvm::ArrayRef<Symbol> Syms) const;
+  std::vector<Fix> fixesForSymbols(const SymbolSlab &Syms) const;
 
   struct UnresolvedName {
     std::string Name;   // E.g. "X" in foo::X.
@@ -79,6 +80,17 @@ private:
   // These collect the last unresolved name so that we can associate it with the
   // diagnostic.
   llvm::Optional<UnresolvedName> LastUnresolvedName;
+
+  // There can be multiple diagnostics that are caused by the same unresolved
+  // name or incomplete type in one parse, especially when code is
+  // copy-and-pasted without #includes. We cache the index results based on
+  // index requests.
+  mutable llvm::StringMap<SymbolSlab> FuzzyFindCache;
+  mutable llvm::DenseMap<SymbolID, SymbolSlab> LookupCache;
+  // Returns None if the number of index requests has reached the limit.
+  llvm::Optional<const SymbolSlab *>
+  fuzzyFindCached(const FuzzyFindRequest &Req) const;
+  llvm::Optional<const SymbolSlab *> lookupCached(const SymbolID &ID) const;
 };
 
 } // namespace clangd