[PATCH] D51802: [clangd] Make advanceTo() faster on Posting Lists

[Kirill Bobyrev via Phabricator via cfe-commits]

kbobyrev created this revision.
kbobyrev added reviewers: ioeric, sammccall, ilya-biryukov.
kbobyrev added a project: clang-tools-extra.
Herald added subscribers: kadircet, arphaman, jkorous, MaskRay.

If the current element is already beyond advanceTo()'s DocID, just return 
instead of doing binary search. This simple optimization saves up to 3-4% 
performance,


https://reviews.llvm.org/D51802

Files:
  clang-tools-extra/clangd/index/dex/Iterator.cpp


Index: clang-tools-extra/clangd/index/dex/Iterator.cpp
===================================================================
--- clang-tools-extra/clangd/index/dex/Iterator.cpp
+++ clang-tools-extra/clangd/index/dex/Iterator.cpp
@@ -38,6 +38,8 @@
   /// or higher than the given one.
   void advanceTo(DocID ID) override {
     assert(!reachedEnd() && "DOCUMENT iterator can't advance() at the end.");
+    if (peek() == ID)
+      return;
     Index = std::lower_bound(Index, std::end(Documents), ID);
   }
 



Index: clang-tools-extra/clangd/index/dex/Iterator.cpp
===================================================================
--- clang-tools-extra/clangd/index/dex/Iterator.cpp
+++ clang-tools-extra/clangd/index/dex/Iterator.cpp
@@ -38,6 +38,8 @@
   /// or higher than the given one.
   void advanceTo(DocID ID) override {
     assert(!reachedEnd() && "DOCUMENT iterator can't advance() at the end.");
+    if (peek() == ID)
+      return;
     Index = std::lower_bound(Index, std::end(Documents), ID);
   }
 

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