[clangd] Symbol index interfaces and an in-memory index implementation.

Summary:
o Index interfaces to support using different index sources (e.g. AST index, global index) for code completion, cross-reference finding etc. This patch focuses on code completion.

The following changes in the original patch has been split out.
o Implement an AST-based index.
o Add an option to replace sema code completion for qualified-id with index-based completion.
o Implement an initial naive code completion index which matches symbols that have the query string as substring.

Reviewers: malaperle, sammccall

Reviewed By: sammccall

Subscribers: hokein, klimek, malaperle, mgorny, ilya-biryukov, cfe-commits

Differential Revision: https://reviews.llvm.org/D40548

llvm-svn: 320688

1 files changed, 41 insertions, 0 deletions

diff --git a/clang-tools-extra/clangd/index/MemIndex.h b/clang-tools-extra/clangd/index/MemIndex.h
new file mode 100644
index 00000000000..24601294da7
--- /dev/null
+++ b/clang-tools-extra/clangd/index/MemIndex.h
@@ -0,0 +1,41 @@
+//===--- MemIndex.h - Dynamic in-memory symbol index. -------------- C++-*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_MEMINDEX_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_MEMINDEX_H
+
+#include "Index.h"
+#include <mutex>
+
+namespace clang {
+namespace clangd {
+
+/// \brief This implements an index for a (relatively small) set of symbols that
+/// can be easily managed in memory.
+class MemIndex : public SymbolIndex {
+public:
+  /// \brief (Re-)Build index for `Symbols`. All symbol pointers must remain
+  /// accessible as long as `Symbols` is kept alive.
+  void build(std::shared_ptr<std::vector<const Symbol *>> Symbols);
+
+  bool fuzzyFind(Context &Ctx, const FuzzyFindRequest &Req,
+                 std::function<void(const Symbol &)> Callback) const override;
+
+private:
+  std::shared_ptr<std::vector<const Symbol *>> Symbols;
+  // Index is a set of symbols that are deduplicated by symbol IDs.
+  // FIXME: build smarter index structure.
+  llvm::DenseMap<SymbolID, const Symbol *> Index;
+  mutable std::mutex Mutex;
+};
+
+} // namespace clangd
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_MEMINDEX_H