[libcxx-commits] [libcxx] [libc++] Speed up classic locale (PR #72112)

[Louis Dionne via libcxx-commits]

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@@ -538,16 +549,40 @@ locale::__imp::use_facet(long id) const
 
 // locale
 
+std::atomic<locale::__imp*> locale::__imp::classic_;
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ldionne wrote:

Okay, sold. But even then, after the suggested refactoring we could do this:

```
const locale& locale::classic() {
    static const no_destroy<locale> c(__private_tag{}, []{
        __imp* ptr = &make<__imp>(1u);
        // <comment ...>
        classic_.store(ptr, std::memory_order_relaxed);
    }());
    return c.get();
}
```

I guess that makes this patch and the refactoring orthogonal.

https://github.com/llvm/llvm-project/pull/72112