[libcxx-commits] [libcxx] [libc++] Implement std::gcd using the binary version (PR #77747)

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https://github.com/AdvenamTacet approved this pull request.

I have no more performance concerns and LGTM % two hanging comments.

Please add to test values numbers around limits instead of only limits:
```cpp
      std::numeric_limits<Input>::min(),
      std::numeric_limits<Input>::min() + 1,
      std::numeric_limits<Input>::min() + 2,
      std::numeric_limits<Input>::max(),
      std::numeric_limits<Input>::max() - 1,
      std::numeric_limits<Input>::max() - 2,
```
could you also comment on that change:
```diff
-      return -static_cast<_Result>(__t);
+      return static_cast<_Result>(-static_cast<std::make_unsigned_t<_Result>>(__t));
```
Why that change? When does it change the result?

https://github.com/llvm/llvm-project/pull/77747