[clang] [clang][DependencyScanning] Implementation of `CompilerInstanceWithContext` to Improve By-Name Queries (PR #164345)

[Jan Svoboda via cfe-commits]

================
@@ -151,14 +151,44 @@ class DependencyScanningTool {
       LookupModuleOutputCallback LookupModuleOutput,
       std::optional<llvm::MemoryBufferRef> TUBuffer = std::nullopt);
 
-  /// Given a compilation context specified via the Clang driver command-line,
-  /// gather modular dependencies of module with the given name, and return the
-  /// information needed for explicit build.
-  llvm::Expected<TranslationUnitDeps> getModuleDependencies(
-      StringRef ModuleName, const std::vector<std::string> &CommandLine,
-      StringRef CWD, const llvm::DenseSet<ModuleID> &AlreadySeen,
+  /// The following three methods provide a new interface to perform
+  /// by name dependency scan. The new interface's intention is to improve
+  /// dependency scanning performance when a sequence of name is looked up
+  /// with the same current working directory and the command line.
+
+  /// @brief Initializing the context and the compiler instance.
+  ///        This method must be called before calling
+  ///        computeDependenciesByNameWithContext.
+  /// @param CWD The current working directory used during the scan.
+  /// @param CommandLine The commandline used for the scan.
+  /// @return Error if the initializaiton fails.
+  llvm::Error initializeCompilerInstacneWithContext(
----------------
jansvoboda11 wrote:

```suggestion
  llvm::Error initializeCompilerInstanceWithContext(
```

https://github.com/llvm/llvm-project/pull/164345