[clang] [FMV] Emit the resolver along with the default version definition. (PR #84405)

[Alexandros Lamprineas via cfe-commits]

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@@ -4347,6 +4362,19 @@ void CodeGenModule::emitCPUDispatchDefinition(GlobalDecl GD) {
   }
 }
 
+/// Adds a declaration to the list of multi version functions if not present.
+void CodeGenModule::AddDeferredMultiVersionResolverToEmit(GlobalDecl GD) {
+  const auto *FD = cast<FunctionDecl>(GD.getDecl());
+  assert(FD && "Not a FunctionDecl?");
+
+  if (FD->isTargetVersionMultiVersion()) {
+    StringRef NamePrefix = getMangledName(GD).split('.').first;
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labrinea wrote:

Right, I see. I've just thought of another issue with `getMangledNameImpl()`. Even though it would be more reliable to not split strings, we can't use its return value (std::string) as the key to a DenseSet. But let me double check it.

https://github.com/llvm/llvm-project/pull/84405