[llvm] [CodeGen] Support start/stop in CodeGenPassBuilder (PR #70912)

[via llvm-commits]

================
@@ -175,73 +183,82 @@ template <typename DerivedT> class CodeGenPassBuilder {
   // Function object to maintain state while adding codegen IR passes.
   class AddIRPass {
   public:
-    AddIRPass(ModulePassManager &MPM) : MPM(MPM) {}
+    AddIRPass(ModulePassManager &MPM, const DerivedT &PB) : MPM(MPM), PB(PB) {}
     ~AddIRPass() {
       if (!FPM.isEmpty())
         MPM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM)));
     }
 
-    template <typename PassT> void operator()(PassT &&Pass) {
+    template <typename PassT>
+    void operator()(PassT &&Pass, StringRef Name = PassT::name()) {
       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) {
+        if (!PB.runBeforeAdding(Name))
+          return;
+
         FPM.addPass(std::forward<PassT>(Pass));
+
+        for (auto &C : PB.AfterCallbacks)
+          C(Name);
       } else {
         // Add Module Pass
+        if (!PB.runBeforeAdding(Name))
+          return;
+
         if (!FPM.isEmpty()) {
           MPM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM)));
           FPM = FunctionPassManager();
         }
         MPM.addPass(std::forward<PassT>(Pass));
+
+        for (auto &C : PB.AfterCallbacks)
+          C(Name);
       }
     }
 
   private:
     ModulePassManager &MPM;
     FunctionPassManager FPM;
+    const DerivedT &PB;
   };
 
   // Function object to maintain state while adding codegen machine passes.
   class AddMachinePass {
   public:
-    AddMachinePass(MachineFunctionPassManager &PM) : PM(PM) {}
+    AddMachinePass(MachineFunctionPassManager &PM, const DerivedT &PB)
+        : PM(PM), PB(PB) {}
 
     template <typename PassT> void operator()(PassT &&Pass) {
       static_assert(
           is_detected<has_key_t, PassT>::value,
           "Machine function pass must define a static member variable `Key`.");
-      for (auto &C : BeforeCallbacks)
-        if (!C(&PassT::Key))
-          return;
+
+      if (!PB.runBeforeAdding(PassT::name()))
+        return;
+
       PM.addPass(std::forward<PassT>(Pass));
-      for (auto &C : AfterCallbacks)
-        C(&PassT::Key);
+
+      for (auto &C : PB.AfterCallbacks)
+        C(PassT::name());
     }
 
     template <typename PassT> void insertPass(MachinePassKey *ID, PassT Pass) {
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paperchalice wrote:

Currently AMDGPU, Hexagon, PowerPC and RISCV uses `insertPass` to adjust the regalloc pipeline, we need add extension points after `PHIElimination`, `TwoAddressInstruction`, `MachineScheduler`, `RenameIndependentSubregs`, `LiveVariables` and `DetectDeadLanes`.

https://github.com/llvm/llvm-project/pull/70912