[llvm] [CodeGen][NPM] Support CodeGenSCCOrder in pipeline (PR #136818)

[Matt Arsenault via llvm-commits]

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@@ -276,20 +302,47 @@ template <typename DerivedT, typename TargetMachineT> class CodeGenPassBuilder {
         MFPM.addPass(std::forward<PassT>(Pass));
       } else {
         // Add Module Pass
-        if (!MFPM.isEmpty()) {
-          MPM.addPass(createModuleToFunctionPassAdaptor(
-              createFunctionToMachineFunctionPassAdaptor(std::move(MFPM))));
-          MFPM = MachineFunctionPassManager();
-        }
-
+        flushMFPMToMPM();
         MPM.addPass(std::forward<PassT>(Pass));
       }
 
       for (auto &C : PB.AfterCallbacks)
         C(Name, MFPM);
     }
 
+    /// Setting this will add passes to the CGSCC pass manager.
+    void requireCGSCCOrder() {
+      if (PB.AddInCGSCCOrder)
+        return;
+      flushMFPMToMPM();
+      PB.AddInCGSCCOrder = true;
+    }
+
+    /// Stop adding passes to the CGSCC pass manager.
+    /// Existing passes won't be removed.
+    void stopAddingInCGSCCOrder() {
+      if (!PB.AddInCGSCCOrder)
+        return;
+      flushMFPMToMPM();
+      PB.AddInCGSCCOrder = false;
+    }
+
   private:
+    void flushMFPMToMPM() {
+      if (!MFPM.isEmpty()) {
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arsenm wrote:

Early return and reduce indent 

https://github.com/llvm/llvm-project/pull/136818