Optimize Cache Insertion with try_emplace for Reduced Lookups

[ayushpareek2003]

for the functions- insertEntryForFilename() , insertRealPathForFilename()

Replaced Cache.insert() with Cache.try_emplace() to reduce redundant lookups
Improved efficiency by avoiding unnecessary copying of values when the key already exists

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[llvmbot]

@llvm/pr-subscribers-clang

Author: Ayush Pareek (ayushpareek2003)

Changes

for the functions- insertEntryForFilename() , insertRealPathForFilename()

Replaced Cache.insert() with Cache.try_emplace() to reduce redundant lookups
Improved efficiency by avoiding unnecessary copying of values when the key already exists

---

Full diff: https://github.com/llvm/llvm-project/pull/131402.diff

1 Files Affected:

• (modified) clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h (+15-14)

diff --git a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h
index d12814e7c9253..a24ba86dae0ef 100644
--- a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h
+++ b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h
@@ -247,15 +247,16 @@ class DependencyScanningFilesystemLocalCache {
   insertEntryForFilename(StringRef Filename,
                          const CachedFileSystemEntry &Entry) {
     assert(llvm::sys::path::is_absolute_gnu(Filename));
-    auto [It, Inserted] = Cache.insert({Filename, {&Entry, nullptr}});
-    auto &[CachedEntry, CachedRealPath] = It->getValue();
-    if (!Inserted) {
-      // The file is already present in the local cache. If we got here, it only
-      // contains the real path. Let's make sure the entry is populated too.
-      assert((!CachedEntry && CachedRealPath) && "entry already present");
-      CachedEntry = &Entry;
-    }
-    return *CachedEntry;
+
+      auto &[CachedEntry, CachedRealPath] = Cache.try_emplace(
+          Filename, &Entry, nullptr).first->getValue();
+    
+      if (!CachedEntry) {
+        assert((!CachedEntry && CachedRealPath) && "entry already present");
+        CachedEntry = &Entry;
+      }
+    
+      return *CachedEntry;
   }
 
   /// Returns real path associated with the filename or nullptr if none is
@@ -272,14 +273,14 @@ class DependencyScanningFilesystemLocalCache {
   insertRealPathForFilename(StringRef Filename,
                             const CachedRealPath &RealPath) {
     assert(llvm::sys::path::is_absolute_gnu(Filename));
-    auto [It, Inserted] = Cache.insert({Filename, {nullptr, &RealPath}});
-    auto &[CachedEntry, CachedRealPath] = It->getValue();
-    if (!Inserted) {
-      // The file is already present in the local cache. If we got here, it only
-      // contains the entry. Let's make sure the real path is populated too.
+    auto &[CachedEntry, CachedRealPath] = Cache.try_emplace(
+          Filename, nullptr, &RealPath).first->getValue();
+    
+    if (!CachedRealPath) {
       assert((!CachedRealPath && CachedEntry) && "real path already present");
       CachedRealPath = &RealPath;
     }
+    
     return *CachedRealPath;
   }
 };

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff fbf0276b6a7a7a4508c373cf87fc349569652659 28f6d8b6677e32f45f5fa55c7c73df5a841d7127 --extensions h -- clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h

View the diff from clang-format here.

diff --git a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h
index a24ba86dae..08e6a2e678 100644
--- a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h
+++ b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h
@@ -248,15 +248,15 @@ public:
                          const CachedFileSystemEntry &Entry) {
     assert(llvm::sys::path::is_absolute_gnu(Filename));
 
-      auto &[CachedEntry, CachedRealPath] = Cache.try_emplace(
-          Filename, &Entry, nullptr).first->getValue();
-    
-      if (!CachedEntry) {
-        assert((!CachedEntry && CachedRealPath) && "entry already present");
-        CachedEntry = &Entry;
-      }
-    
-      return *CachedEntry;
+    auto &[CachedEntry, CachedRealPath] =
+        Cache.try_emplace(Filename, &Entry, nullptr).first->getValue();
+
+    if (!CachedEntry) {
+      assert((!CachedEntry && CachedRealPath) && "entry already present");
+      CachedEntry = &Entry;
+    }
+
+    return *CachedEntry;
   }
 
   /// Returns real path associated with the filename or nullptr if none is
@@ -273,14 +273,14 @@ public:
   insertRealPathForFilename(StringRef Filename,
                             const CachedRealPath &RealPath) {
     assert(llvm::sys::path::is_absolute_gnu(Filename));
-    auto &[CachedEntry, CachedRealPath] = Cache.try_emplace(
-          Filename, nullptr, &RealPath).first->getValue();
-    
+    auto &[CachedEntry, CachedRealPath] =
+        Cache.try_emplace(Filename, nullptr, &RealPath).first->getValue();
+
     if (!CachedRealPath) {
       assert((!CachedRealPath && CachedEntry) && "real path already present");
       CachedRealPath = &RealPath;
     }
-    
+
     return *CachedRealPath;
   }
 };

[ayushpareek2003]

Removed unnecessary spaces