[llvm] [mlir] [mlir][OpenMP] - Implement lowering from MLIR to LLVMIR for `private` clause on `target` constructs (PR #105471)

[Sergio Afonso via llvm-commits]

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@@ -3241,12 +3242,140 @@ convertOmpTarget(Operation &opInst, llvm::IRBuilderBase &builder,
   DataLayout dl = DataLayout(opInst.getParentOfType<ModuleOp>());
   SmallVector<Value> mapVars = targetOp.getMapVars();
   llvm::Function *llvmOutlinedFn = nullptr;
-
   // TODO: It can also be false if a compile-time constant `false` IF clause is
   // specified.
   bool isOffloadEntry =
       isTargetDevice || !ompBuilder->Config.TargetTriples.empty();
 
+  if (!targetOp.getPrivateVars().empty()) {
+    OperandRange privateVars = targetOp.getPrivateVars();
+    std::optional<mlir::ArrayAttr> privateSyms = targetOp.getPrivateSyms();
+    auto &targetRegion = opInst.getRegion(0);
+    auto &firstTargetBlock = targetRegion.front();
+    auto *regionArgsStart = firstTargetBlock.getArguments().begin();
+    auto *privArgsStart = regionArgsStart + targetOp.getMapVars().size();
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skatrak wrote:

Just as a heads-up, I'm planning to create a PR stack this week to revamp the handling of clause-related block arguments such as these. At that point we won't have to worry so much about the order they appear in, but instead we'll be able to access them through an MLIR interface.

https://github.com/llvm/llvm-project/pull/105471