[PATCH] D119927: [Clang] [P2025] More exhaustive tests for NRVO

[Arthur O'Dwyer via Phabricator via cfe-commits]

Quuxplusone added inline comments.


================
Comment at: clang/test/CodeGenCXX/nrvo.cpp:1537
+  }
+  return x; // FIXME: NRVO could happen if B == false, but doesn't
+}
----------------
Quuxplusone wrote:
> Nit: `s/if/when/`
Serendipitously, I just ran into almost this exact scenario in D120180, where C++20's `reverse_iterator` wants to do basically
```
    {
      _Iter __tmp = current;
      --__tmp;
      if constexpr (is_pointer_v<_Iter>) {
        return __tmp;
      } else {
        return std::move(__tmp).operator->();
      }
    }
```
and so we want NRVO on `__tmp` in the former case but URVO in the latter case. Of course in that specific case, we "want NRVO" only when `__tmp` is a pointer and thus NRVO doesn't apply anyway because pointers are returned in registers. But it would be nice to have a test case for as-close-as-possible to that pattern, if you don't mind adding one.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D119927/new/

https://reviews.llvm.org/D119927