[llvm] [CodeGen] Allow `CodeGenPassBuilder` to add module pass after function pass (PR #77084)

[Arthur Eubanks via llvm-commits]

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@@ -175,45 +175,33 @@ template <typename DerivedT> class CodeGenPassBuilder {
   // Function object to maintain state while adding codegen IR passes.
   class AddIRPass {
   public:
-    AddIRPass(ModulePassManager &MPM, bool DebugPM, bool Check = true)
-        : MPM(MPM) {
-      if (Check)
-        AddingFunctionPasses = false;
-    }
+    AddIRPass(ModulePassManager &MPM) : MPM(MPM) {}
     ~AddIRPass() {
-      MPM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM)));
-    }
-
-    // Add Function Pass
-    template <typename PassT>
-    std::enable_if_t<is_detected<is_function_pass_t, PassT>::value>
-    operator()(PassT &&Pass) {
-      if (AddingFunctionPasses && !*AddingFunctionPasses)
-        AddingFunctionPasses = true;
-      FPM.addPass(std::forward<PassT>(Pass));
+      if (!FPM.isEmpty())
+        MPM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM)));
     }
 
-    // Add Module Pass
-    template <typename PassT>
-    std::enable_if_t<is_detected<is_module_pass_t, PassT>::value &&
-                     !is_detected<is_function_pass_t, PassT>::value>
-    operator()(PassT &&Pass) {
-      assert((!AddingFunctionPasses || !*AddingFunctionPasses) &&
-             "could not add module pass after adding function pass");
-      MPM.addPass(std::forward<PassT>(Pass));
+    template <typename PassT> void operator()(PassT &&Pass) {
+      static_assert((is_detected<is_function_pass_t, PassT>::value ||
+                     is_detected<is_module_pass_t, PassT>::value) &&
+                    "Only module pass and function pass are supported.");
+
+      // Add Function Pass
+      if constexpr (is_detected<is_function_pass_t, PassT>::value)
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aeubanks wrote:

for consistency, add braces here when else block uses braces 

https://github.com/llvm/llvm-project/pull/77084