[clang] [llvm] [mlir] [OpenMP] Migrate GPU Reductions CodeGen from Clang to OMPIRBuilder (PR #80343)

[Johannes Doerfert via cfe-commits]

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@@ -1235,27 +1251,56 @@ class OpenMPIRBuilder {
   getTargetEntryUniqueInfo(FileIdentifierInfoCallbackTy CallBack,
                            StringRef ParentName = "");
 
-  /// Functions used to generate reductions. Such functions take two Values
-  /// representing LHS and RHS of the reduction, respectively, and a reference
-  /// to the value that is updated to refer to the reduction result.
-  using ReductionGenTy =
-      function_ref<InsertPointTy(InsertPointTy, Value *, Value *, Value *&)>;
+  /// Enum class for the RedctionGen CallBack type to be used.
+  enum class ReductionGenCBTy { Clang, MLIR };
+
+  /// ReductionGen CallBack for Clang
+  ///
+  /// \param CodeGenIP InsertPoint for CodeGen.
+  /// \param Index Index of the ReductionInfo to generate code for.
+  /// \param LHSPtr Optionally used by Clang to return the LHSPtr it used for
+  /// codegen, used for fixup later.
+  /// \param RHSPtr Optionally used by Clang to
+  /// return the RHSPtr it used for codegen, used for fixup later.
+  /// \param CurFn Optionally used by Clang to pass in the Current Function as
+  /// Clang context may be old.
+  using ReductionGenCBClang =
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jdoerfert wrote:

s/ReductionGenCBClang/ReductionGenClangCBTy

Similarly, elsewhere.

https://github.com/llvm/llvm-project/pull/80343