[clang] [llvm] [mlir] [OMPIRBuilder] always leave PARALLEL via the same barrier (PR #164586)

[Michael Kruse via llvm-commits]

================
@@ -1800,8 +1779,18 @@ OpenMPIRBuilder::InsertPointOrErrorTy OpenMPIRBuilder::createParallel(
   Instruction *PRegPreFiniTI = PRegPreFiniBB->getTerminator();
 
   InsertPointTy PreFiniIP(PRegPreFiniBB, PRegPreFiniTI->getIterator());
-  if (Error Err = FiniCB(PreFiniIP))
-    return Err;
+  if (!FiniInfo.FiniBB) {
+    if (Error Err = FiniCB(PreFiniIP))
+      return Err;
+  } else {
+    llvm::IRBuilderBase::InsertPointGuard Guard{Builder};
----------------
Meinersbur wrote:

```suggestion
    IRBuilderBase::InsertPointGuard Guard{Builder};
```
We are in the `llvm::` namespace

https://github.com/llvm/llvm-project/pull/164586