[llvm] [PassManager][Loop] Merge loop pass manager when add it (PR #135150)

[Arthur Eubanks via llvm-commits]

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@@ -130,6 +130,20 @@ class PassManager<Loop, LoopAnalysisManager, LoopStandardAnalysisResults &,
         new LoopNestPassModelT(std::forward<PassT>(Pass))));
   }
 
+  LLVM_ATTRIBUTE_MINSIZE
+  void addPass(PassManager &&PM) {
+    std::size_t VecSize = PM.IsLoopNestPass.size();
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aeubanks wrote:

```suggestion
    size_t VecSize = PM.IsLoopNestPass.size();
```

https://github.com/llvm/llvm-project/pull/135150