Optimize empty case in Vec::retain

rust-lang · Jul 29, 2024 · 6a6824a · 6a6824a
1 parent 355efac
commit 6a6824a
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
@@ -1711,6 +1711,12 @@ impl<T, A: Allocator> Vec<T, A> {
         F: FnMut(&mut T) -> bool,
     {
         let original_len = self.len();
+
+        if original_len == 0 {
+            // Empty case: explicit return allows better optimization, vs letting compiler infer it
+            return;
+        }
+
         // Avoid double drop if the drop guard is not executed,
         // since we may make some holes during the process.
         unsafe { self.set_len(0) };