[MLIR,OpenMP][NFCI] Removed loop for accessing regions of ParallelOp

[SouraVX]

Summary

ParallelOp has only one region associated with it.

[ftynse]

Thanks for the clean-up!

[kiranchandramohan]

Thanks @SouraVX.

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

ModuleTranslation::convertOmpParallel(Operation &opInst,
   auto bodyGenCB = [&](InsertPointTy allocaIP, InsertPointTy codeGenIP,
                        llvm::BasicBlock &continuationIP) {
     llvm::LLVMContext &llvmContext = llvmModule->getContext();
 
     llvm::BasicBlock *codeGenIPBB = codeGenIP.getBlock();
     llvm::Instruction *codeGenIPBBTI = codeGenIPBB->getTerminator();
 
     builder.SetInsertPoint(codeGenIPBB);
-
-    for (auto &region : opInst.getRegions()) {
-      for (auto &bb : region) {
-        auto *llvmBB = llvm::BasicBlock::Create(
-            llvmContext, "omp.par.region", codeGenIP.getBlock()->getParent());
-        blockMapping[&bb] = llvmBB;
-      }
+    // ParallelOp has only `1` region associated with it.
+    auto &region = cast<omp::ParallelOp>(opInst).getRegion();
 
       // Then, convert blocks one by one in topological order to ensure
       // defs are converted before uses.
       llvm::SetVector<Block *> blocks = topologicalSort(region);
       for (auto indexedBB : llvm::enumerate(blocks)) {
         Block *bb = indexedBB.value();
         llvm::BasicBlock *curLLVMBB = blockMapping[bb];
         if (bb->isEntryBlock())
for (auto &bb : region) {
             builder.SetInsertPoint(curLLVMBB);
             builder.CreateBr(&continuationIP);
           }
         }
       }
       // Finally, after all blocks have been traversed and values mapped,
       // connect the PHI nodes to the results of preceding blocks.
       connectPHINodes(region, valueMapping, blockMapping);
-    }
   };
 
   // TODO: Perform appropriate actions according to the data-sharing
   // attribute (shared, private, firstprivate, ...) of variables.
   // Currently defaults to shared.
   auto privCB = [&](InsertPointTy allocaIP, InsertPointTy codeGenIP,
                     llvm::Value &vPtr,
                     llvm::Value *&replacementValue) -> InsertPointTy {