[backported/clang-7][Frontend] Avoid running plugins during code completion parse

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* https://reviews.llvm.org/D46050
* Fixes slow completion if tidy/clazy checks are activated.
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The parsing that is done for code completion is a special case that will
discard any generated diagnostics, so avoid running plugins for this
case in the first place to avoid performance penalties due to the
plugins.

A scenario for this is for example libclang with extra plugins like
tidy.

Change-Id: Ibd325f234823e4650553d2a9a3c20d993d57c87d
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/Frontend/FrontendAction.cpp b/lib/Frontend/FrontendAction.cpp
index 12226b2314..6c95f88bfc 100644
--- a/lib/Frontend/FrontendAction.cpp
+++ b/lib/Frontend/FrontendAction.cpp
@@ -153,6 +153,10 @@ FrontendAction::CreateWrappedASTConsumer(CompilerInstance &CI,
   if (FrontendPluginRegistry::begin() == FrontendPluginRegistry::end())
     return Consumer;
 
+  // If this is a code completion run, avoid invoking the plugin consumers
+  if (CI.hasCodeCompletionConsumer())
+    return Consumer;
+
   // Collect the list of plugins that go before the main action (in Consumers)
   // or after it (in AfterConsumers)
   std::vector<std::unique_ptr<ASTConsumer>> Consumers;