[libcxx-commits] [libcxx] Mark some std::string functions noinline. (PR #72869)

[Louis Dionne via libcxx-commits]

================
@@ -1899,7 +1899,7 @@ private:
     // to call the __init() functions as those are marked as inline which may
     // result in over-aggressive inlining by the compiler, where our aim is
     // to only inline the fast path code directly in the ctor.
-    _LIBCPP_CONSTEXPR_SINCE_CXX20 void __init_copy_ctor_external(const value_type* __s, size_type __sz);
+    _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_NOINLINE void __init_copy_ctor_external(const value_type* __s, size_type __sz);
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ldionne wrote:

IMO comments like this one above explain why we have `_LIBCPP_NOINLINE` on this method:

```
// Slow path for the (inlined) copy constructor for 'long' strings.
// Always externally instantiated and not inlined.
```

Furthermore, these methods all have `_external` in their names which kind of explains why they're not inlined. I'm not sure we need more documentation.

https://github.com/llvm/llvm-project/pull/72869