[clang] [Clang] Eagerly instantiate used constexpr function upon definition. (PR #73463)

[Richard Smith via cfe-commits]

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@@ -8718,6 +8731,18 @@ void ASTReader::ReadPendingInstantiations(
   PendingInstantiations.clear();
 }
 
+void ASTReader::ReadPendingOfInstantiationsForConstexprEntity(
+    const NamedDecl *D, llvm::SmallSetVector<NamedDecl *, 4> &Decls) {
+  for (auto *Redecl : D->redecls()) {
+    DeclID Id = Redecl->getGlobalID();
+    auto It = PendingInstantiationsOfConstexprEntities.find(Id);
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zygoloid wrote:

Maybe skip this lookup for declarations that aren't from an AST file?

https://github.com/llvm/llvm-project/pull/73463