[Tooling] Add a isSingleProcess() helper to ToolExecutor

Summary:
Used in clangd's symbol builder to optimize for the common
shared-memory executor case.

Reviewers: ioeric

Reviewed By: ioeric

Subscribers: kadircet, cfe-commits

Differential Revision: https://reviews.llvm.org/D51164

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@340599 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Tooling/AllTUsExecution.h

@@ -45,6 +45,8 @@ class AllTUsToolExecutor : public ToolExecutor {
 
   StringRef getExecutorName() const override { return ExecutorName; }
 
+  bool isSingleProcess() const override { return true; }
+
   using ToolExecutor::execute;
 
   llvm::Error

include/clang/Tooling/Execution.h

@@ -114,6 +114,13 @@ class ToolExecutor {
   /// Returns the name of a specific executor.
   virtual StringRef getExecutorName() const = 0;
 
+  /// Should return true iff executor runs all actions in a single process.
+  /// Clients can use this signal to find out if they can collect results
+  /// in-memory (e.g. to avoid serialization costs of using ToolResults).
+  /// The single-process executors can still run multiple threads, but all
+  /// executions are guaranteed to share the same memory.
+  virtual bool isSingleProcess() const = 0;
+
   /// Executes each action with a corresponding arguments adjuster.
   virtual llvm::Error
   execute(llvm::ArrayRef<

include/clang/Tooling/StandaloneExecution.h

@@ -52,6 +52,8 @@ class StandaloneToolExecutor : public ToolExecutor {
 
   StringRef getExecutorName() const override { return ExecutorName; }
 
+  bool isSingleProcess() const override { return true; }
+
   using ToolExecutor::execute;
 
   llvm::Error

unittests/Tooling/ExecutionTest.cpp

@@ -96,6 +96,8 @@ class TestToolExecutor : public ToolExecutor {
 
   StringRef getExecutorName() const override { return ExecutorName; }
 
+  bool isSingleProcess() const override { return true; }
+
   llvm::Error
   execute(llvm::ArrayRef<std::pair<std::unique_ptr<FrontendActionFactory>,
                                    ArgumentsAdjuster>>) override {