[llvm] [mlir] [MLIR][OpenMP] Support basic materialization for `omp.private` ops (PR #81715)

[via llvm-commits]

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@@ -1000,11 +1000,39 @@ convertOmpWsLoop(Operation &opInst, llvm::IRBuilderBase &builder,
   return success();
 }
 
+/// Replace the region arguments of the parallel op (which correspond to private
+/// variables) with the actual private varibles they correspond to. This
+/// prepares the parallel op so that it matches what is expected by the
+/// OMPIRBuilder. Instead of editing the original op in-place, this function
+/// does the required changes to a cloned version which should then be erased by
+/// the caller.
+static omp::ParallelOp
+prepareOmpParallelForPrivatization(omp::ParallelOp opInst) {
+  mlir::OpBuilder cloneBuilder(opInst);
+  omp::ParallelOp opInstClone =
+      llvm::cast<omp::ParallelOp>(cloneBuilder.clone(*opInst));
+
+  Region &region = opInstClone.getRegion();
+  auto privateVars = opInstClone.getPrivateVars();
+
+  auto privateVarsIt = privateVars.begin();
+  // Reduction precede private arguments, so skip them first.
+  unsigned privateArgBeginIdx = opInstClone.getNumReductionVars();
+  unsigned privateArgEndIdx = privateArgBeginIdx + privateVars.size();
+  for (size_t argIdx = privateArgBeginIdx; argIdx < privateArgEndIdx;
+       ++argIdx, ++privateVarsIt)
+    replaceAllUsesInRegionWith(region.getArgument(argIdx), *privateVarsIt,
+                               region);
+  return opInstClone;
+}
+
 /// Converts the OpenMP parallel operation to LLVM IR.
 static LogicalResult
 convertOmpParallel(omp::ParallelOp opInst, llvm::IRBuilderBase &builder,
                    LLVM::ModuleTranslation &moduleTranslation) {
   using InsertPointTy = llvm::OpenMPIRBuilder::InsertPointTy;
+  //omp::ParallelOp opInstClone = prepareOmpParallelForPrivatization(opInst);
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NimishMishra wrote:

Unintentional comment?

https://github.com/llvm/llvm-project/pull/81715