[DispatchCreation] Set split reduction size for ArgCompare

Signed-off-by: Bangtian Liu <[email protected]>

Author: bangtianliu

compiler/src/iree/compiler/DispatchCreation/SetSplitReductionSizes.cpp

@@ -6,6 +6,7 @@
 
 #include "iree/compiler/Dialect/LinalgExt/IR/LinalgExtDialect.h"
 #include "iree/compiler/Dialect/LinalgExt/IR/LinalgExtInterfaces.h"
+#include "iree/compiler/Dialect/LinalgExt/IR/LinalgExtOps.h"
 #include "iree/compiler/DispatchCreation/Passes.h"
 #include "llvm/Support/DebugLog.h"
 #include "mlir/Dialect/Linalg/IR/Linalg.h"
@@ -110,6 +111,12 @@ struct SetSplitReductionSizesPass final
         IREE::LinalgExt::setSplitReductionAttribute(tilingOp, *tileSizes);
         return;
       }
+
+      // --- Case 4: arg_compare operations ---
+      if (auto tileSizes = getArgCompareReductionSizes(tilingOp)) {
+        IREE::LinalgExt::setSplitReductionAttribute(tilingOp, *tileSizes);
+        return;
+      }
     });
   }
 
@@ -389,6 +396,40 @@ struct SetSplitReductionSizesPass final
 
     return tileSizes;
   }
+
+  /// Determine split reduction sizes specifically for arg_compare operations.
+  std::optional<SmallVector<int64_t>>
+  getArgCompareReductionSizes(PartialReductionOpInterface op) const {
+    auto argCompareOp =
+        dyn_cast<IREE::LinalgExt::ArgCompareOp>(op.getOperation());
+    if (!argCompareOp) {
+      return std::nullopt;
+    }
+
+    ShapedType inputType = argCompareOp.getInputType();
+    ArrayRef<int64_t> inputShape = inputType.getShape();
+    int64_t reductionDim = argCompareOp.getDimension();
+    int64_t reductionSize = inputShape[reductionDim];
+
+    if (reductionSize == ShapedType::kDynamic) {
+      return std::nullopt;
+    }
+
+    // Only split if reduction is large enough (empirical threshold)
+    const int64_t minSizeToSplit = 1024;
+    if (reductionSize < minSizeToSplit) {
+      return std::nullopt;
+    }
+
+    int64_t tileSize = findSmallestFactorWithLowerBound(
+                           reductionSize, splitReductionTargetSize)
+                           .value_or(reductionSize);
+
+    LDBG() << "arg_compare split: dim=" << reductionDim
+           << " size=" << reductionSize << " tile=" << tileSize;
+
+    return SmallVector<int64_t>{tileSize};
+  }
 };
 } // namespace
 } // namespace mlir::iree_compiler::DispatchCreation

compiler/src/iree/compiler/DispatchCreation/test/set_split_reduction_sizes_outer_reduction.mlir

@@ -179,3 +179,24 @@ util.func public @arg_compare_negative_outer_dynamic_reduction(
 
   util.return %res_val, %res_idx : tensor<64xf32>, tensor<64xindex>
 }
+
+// -----
+
+// CHECK-LABEL: @arg_compare_large_inner_reduction
+util.func public @arg_compare_large_inner_reduction(%arg0: tensor<4x1x128256xf16>)
+    -> tensor<4x1xi32> {
+  // CHECK: iree_linalg_ext.split_reduction = [1336 : index]
+  %init_val = tensor.empty() : tensor<4x1xf16>
+  %init_idx = tensor.empty() : tensor<4x1xi32>
+
+  %res:2 = iree_linalg_ext.arg_compare
+    dimension(2)
+    ins(%arg0 : tensor<4x1x128256xf16>)
+    outs(%init_val, %init_idx : tensor<4x1xf16>, tensor<4x1xi32>) {
+  ^bb0(%arg1: f16, %arg2: f16):
+    %cmp = arith.cmpf ogt, %arg1, %arg2 : f16
+    iree_linalg_ext.yield %cmp : i1
+  } -> tensor<4x1xf16>, tensor<4x1xi32>
+
+  util.return %res#1 : tensor<4x1xi32>
+}