[clang-tools-extra] [clang-tidy][NFC] optimize cache for config option (PR #121406)

[Congcong Cai via cfe-commits]

https://github.com/HerrCai0907 updated https://github.com/llvm/llvm-project/pull/121406

>From 8f8e8c5141fcb6b6d468c80cf3ceb4fdd88eecca Mon Sep 17 00:00:00 2001
From: Congcong Cai <congcongcai0907 at 163.com>
Date: Wed, 1 Jan 2025 01:11:36 +0800
Subject: [PATCH] [clang-tidy][NFC] optimize cache for config option

Current implement will cache ConfigOptions for each path, it will create lots of copy of options when project have deep nested folder structure.
New implement use vector to store options and only cache the index to reduce memory usage and avoid meanless copy
---
 .../clang-tidy/ClangTidyOptions.cpp           | 47 ++++++++++---------
 .../clang-tidy/ClangTidyOptions.h             |  5 +-
 2 files changed, 28 insertions(+), 24 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/ClangTidyOptions.cpp b/clang-tools-extra/clang-tidy/ClangTidyOptions.cpp
index 445c7f85c900c6..9ecb255d916e9b 100644
--- a/clang-tools-extra/clang-tidy/ClangTidyOptions.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidyOptions.cpp
@@ -337,33 +337,34 @@ FileOptionsBaseProvider::FileOptionsBaseProvider(
 void FileOptionsBaseProvider::addRawFileOptions(
     llvm::StringRef AbsolutePath, std::vector<OptionsSource> &CurOptions) {
   auto CurSize = CurOptions.size();
-
   // Look for a suitable configuration file in all parent directories of the
   // file. Start with the immediate parent directory and move up.
-  StringRef Path = llvm::sys::path::parent_path(AbsolutePath);
-  for (StringRef CurrentPath = Path; !CurrentPath.empty();
-       CurrentPath = llvm::sys::path::parent_path(CurrentPath)) {
-    std::optional<OptionsSource> Result;
-
-    auto Iter = CachedOptions.find(CurrentPath);
-    if (Iter != CachedOptions.end())
-      Result = Iter->second;
-
-    if (!Result)
-      Result = tryReadConfigFile(CurrentPath);
-
-    if (Result) {
-      // Store cached value for all intermediate directories.
-      while (Path != CurrentPath) {
+  StringRef RootPath = llvm::sys::path::parent_path(AbsolutePath);
+  auto MemorizedConfigFile =
+      [this, &RootPath](StringRef CurrentPath) -> std::optional<OptionsSource> {
+    auto Iter = CachedOptions.Memorized.find(CurrentPath);
+    if (Iter != CachedOptions.Memorized.end())
+      return CachedOptions.Storage[Iter->second];
+    std::optional<OptionsSource> OptionsSource = tryReadConfigFile(CurrentPath);
+    if (OptionsSource) {
+      const size_t Index = CachedOptions.Storage.size();
+      CachedOptions.Storage.emplace_back(OptionsSource.value());
+      while (RootPath != CurrentPath) {
         LLVM_DEBUG(llvm::dbgs()
-                   << "Caching configuration for path " << Path << ".\n");
-        if (!CachedOptions.count(Path))
-          CachedOptions[Path] = *Result;
-        Path = llvm::sys::path::parent_path(Path);
+                   << "Caching configuration for path " << RootPath << ".\n");
+        CachedOptions.Memorized[RootPath] = Index;
+        RootPath = llvm::sys::path::parent_path(RootPath);
       }
-      CachedOptions[Path] = *Result;
-
-      CurOptions.push_back(*Result);
+      CachedOptions.Memorized[CurrentPath] = Index;
+      RootPath = llvm::sys::path::parent_path(CurrentPath);
+    }
+    return OptionsSource;
+  };
+  for (StringRef CurrentPath = RootPath; !CurrentPath.empty();
+       CurrentPath = llvm::sys::path::parent_path(CurrentPath)) {
+    if (std::optional<OptionsSource> Result =
+            MemorizedConfigFile(CurrentPath)) {
+      CurOptions.emplace_back(Result.value());
       if (!Result->first.InheritParentConfig.value_or(false))
         break;
     }
diff --git a/clang-tools-extra/clang-tidy/ClangTidyOptions.h b/clang-tools-extra/clang-tidy/ClangTidyOptions.h
index 85d5a02ebbc1bc..568f60cf98b21f 100644
--- a/clang-tools-extra/clang-tidy/ClangTidyOptions.h
+++ b/clang-tools-extra/clang-tidy/ClangTidyOptions.h
@@ -241,7 +241,10 @@ class FileOptionsBaseProvider : public DefaultOptionsProvider {
   /// \c ConfigHandlers.
   std::optional<OptionsSource> tryReadConfigFile(llvm::StringRef Directory);
 
-  llvm::StringMap<OptionsSource> CachedOptions;
+  struct OptionsCache {
+    llvm::StringMap<size_t> Memorized;
+    llvm::SmallVector<OptionsSource, 4U> Storage;
+  } CachedOptions;
   ClangTidyOptions OverrideOptions;
   ConfigFileHandlers ConfigHandlers;
   llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS;