[clang] [CUDA][HIP] Fix overriding of constexpr virtual function (PR #121986)

[Yaxun Liu via cfe-commits]

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@@ -1595,8 +1606,21 @@ static bool IsOverloadOrOverrideImpl(Sema &SemaRef, FunctionDecl *New,
 
         // Allow overloading of functions with same signature and different CUDA
         // target attributes.
-        if (NewTarget != OldTarget)
+        if (NewTarget != OldTarget) {
+          // Special case: non-constexpr function is allowed to override
+          // constexpr virtual function
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yxsamliu wrote:

That seems to be too generic. The implicit host/device attributes are not just added to constexpr functions. They are also added to inherited ctors, e.g. https://godbolt.org/z/PvGfzj5ej . An inherited ctor may have only one implicit device attribute, which should be treated as a device function, like an explicit device attribute. I tends to think the special handling needed by constexpr pure-virtual function is a rare exception.

https://github.com/llvm/llvm-project/pull/121986