[llvm] Windows Filesystem fs::status Conditionally Call GetFileAttributes (PR #78118)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-support

@llvm/pr-subscribers-platform-windows

Author: Haydn Trigg (HaydnTrigg)

<details>
<summary>Changes</summary>

Rather than conditionally using the output from GetFileAttributesW move the branch to avoid calling GetFileAttributesW entirely if not required. This avoids hitting IO an extra time for a small performance improvement.

---
Full diff: https://github.com/llvm/llvm-project/pull/78118.diff


1 Files Affected:

- (modified) llvm/lib/Support/Windows/Path.inc (+9-8) 


``````````diff
diff --git a/llvm/lib/Support/Windows/Path.inc b/llvm/lib/Support/Windows/Path.inc
index 2bf68b7972e746..6598586545ddd0 100644
--- a/llvm/lib/Support/Windows/Path.inc
+++ b/llvm/lib/Support/Windows/Path.inc
@@ -777,14 +777,15 @@ std::error_code status(const Twine &path, file_status &result, bool Follow) {
   if (std::error_code ec = widenPath(path8, path_utf16))
     return ec;
 
-  DWORD attr = ::GetFileAttributesW(path_utf16.begin());
-  if (attr == INVALID_FILE_ATTRIBUTES)
-    return getStatus(INVALID_HANDLE_VALUE, result);
-
-  DWORD Flags = FILE_FLAG_BACKUP_SEMANTICS;
-  // Handle reparse points.
-  if (!Follow && (attr & FILE_ATTRIBUTE_REPARSE_POINT))
-    Flags |= FILE_FLAG_OPEN_REPARSE_POINT;
+  if (!Follow) {
+    DWORD attr = ::GetFileAttributesW(path_utf16.begin());
+    if (attr == INVALID_FILE_ATTRIBUTES)
+      return getStatus(INVALID_HANDLE_VALUE, result);
+    
+    // Handle reparse points.
+    if (attr & FILE_ATTRIBUTE_REPARSE_POINT)
+      Flags |= FILE_FLAG_OPEN_REPARSE_POINT;
+  }
 
   ScopedFileHandle h(
       ::CreateFileW(path_utf16.begin(), 0, // Attributes only.

``````````

</details>


https://github.com/llvm/llvm-project/pull/78118