[clang] [clang][SYCL] Add sycl_external attribute and restrict emitting device code (PR #140282)

[Tom Honermann via cfe-commits]

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@@ -16275,6 +16297,13 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
     }
   }
 
+  if (FD && !FD->isInvalidDecl() && FD->hasAttr<SYCLExternalAttr>()) {
+    SYCLExternalAttr *SEAttr = FD->getAttr<SYCLExternalAttr>();
+    if (FD->isDeletedAsWritten())
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tahonermann wrote:

Sindhu and I previously discussed that and concluded that would be undesirable in template scenarios. In non-dependent cases, diagnosing a defaulted-as-deleted case would probably be ok, but seemed enough of an edge case not to bother since an ODR-use of the deleted function would be diagnosed anyway.

https://github.com/llvm/llvm-project/pull/140282