[clang] [SYCL] Basic diagnostics for the sycl_kernel_entry_point attribute. (PR #120327)

[Erich Keane via cfe-commits]

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@@ -1134,8 +1134,18 @@ void ASTDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
   // the presence of a sycl_kernel_entry_point attribute, register it so that
   // associated metadata is recreated.
   if (FD->hasAttr<SYCLKernelEntryPointAttr>()) {
+    const auto *SKEPAttr = FD->getAttr<SYCLKernelEntryPointAttr>();
     ASTContext &C = Reader.getContext();
-    C.registerSYCLEntryPointFunction(FD);
+    const SYCLKernelInfo *SKI = C.findSYCLKernelInfo(SKEPAttr->getKernelName());
+    if (SKI) {
+      if (!declaresSameEntity(FD, SKI->getKernelEntryPointDecl())) {
+        Reader.Diag(FD->getLocation(), diag::err_sycl_kernel_name_conflict);
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erichkeane wrote:

Is this not a diagnostic we could do elsewhere?  A diagnostic in the middle of serialization is REALLY strange, and I don't know why we even have that ability. It seems to me that PCH/Modules shouldn't cause diagnostics like this.

https://github.com/llvm/llvm-project/pull/120327