[llvm] [NewPM][CodeGen] Add callback style codegen pass builder (PR #108690)

[Matt Arsenault via llvm-commits]

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@@ -114,6 +121,34 @@ struct PassModel : PassConcept<IRUnitT, AnalysisManagerT, ExtraArgTs...> {
 
   bool isRequired() const override { return passIsRequiredImpl<PassT>(); }
 
+  template <typename T>
+  using has_erase_if_t = decltype(std::declval<T &>().eraseIf(
+      std::declval<function_ref<bool(StringRef)>>()));
+
+  template <typename T>
+  std::enable_if_t<is_detected<has_erase_if_t, T>::value>
+  eraseIfImpl(function_ref<bool(StringRef)> Pred) {
+    Pass.eraseIf(Pred);
+  }
+
+  template <typename T>
+  std::enable_if_t<!is_detected<has_erase_if_t, T>::value>
+  eraseIfImpl(function_ref<bool(StringRef)>) {}
+
+  void eraseIf(function_ref<bool(StringRef)> Pred) override {
+    eraseIfImpl<PassT>(Pred);
+  }
+
+  template <typename T>
+  using has_is_empty_t = decltype(std::declval<T &>().isEmpty());
+
+  bool isEmpty() const override {
+    if constexpr (is_detected<has_is_empty_t, PassT>::value)
+      return Pass.isEmpty();
+    else
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arsenm wrote:

No else after return 

https://github.com/llvm/llvm-project/pull/108690