[MLIR] [XeGPU] Add distribution pattern for vector.constant_mask from Wg To Sg (#168118)

Author: nbpatel

mlir/lib/Dialect/XeGPU/Transforms/XeGPUWgToSgDistribute.cpp

@@ -1285,6 +1285,71 @@ struct WgToSgVectorTransposeOp
   }
 };
 
+// This pattern distributes the vector.constant_mask ops to work at subgroup
+// level.
+struct WgToSgVectorConstantMaskOp
+    : public OpConversionPattern<vector::ConstantMaskOp> {
+  using OpConversionPattern<vector::ConstantMaskOp>::OpConversionPattern;
+
+  LogicalResult
+  matchAndRewrite(vector::ConstantMaskOp op, OneToNOpAdaptor adaptor,
+                  ConversionPatternRewriter &rewriter) const override {
+    xegpu::DistributeLayoutAttr layout =
+        xegpu::getDistributeLayoutAttr(op.getResult());
+    if (!layout || !layout.isForWorkgroup())
+      return failure();
+
+    Location loc = op.getLoc();
+    VectorType type = op.getResult().getType();
+    auto wgShape = type.getShape();
+
+    ArrayRef<int64_t> wgMaskDimSizes = op.getMaskDimSizes();
+
+    // Get subgroup ID.
+    Value sgId =
+        gpu::SubgroupIdOp::create(rewriter, loc, /*upper_bound=*/nullptr);
+    auto sgOffsets =
+        layout.computeDistributedCoords(rewriter, loc, sgId, wgShape);
+    if (failed(sgOffsets))
+      return failure();
+
+    SmallVector<int64_t> sgShape = getSgShapeAndCount(wgShape, layout).first;
+    VectorType resultType = VectorType::get(sgShape, type.getElementType());
+
+    // In each dimension, each subgroup computes its local mask size as:
+    // min(max(wgMaskSize[d] - offset[d], 0), sgDimSize[d])
+    SmallVector<Value> newCreateMaskOps;
+    for (auto offsetSet : *sgOffsets) {
+      SmallVector<Value> maskOperands;
+
+      for (auto [i, wgMaskSize] : llvm::enumerate(wgMaskDimSizes)) {
+        Value wgMaskSizeVal =
+            arith::ConstantIndexOp::create(rewriter, loc, wgMaskSize);
+        Value dimSizeVal =
+            arith::ConstantIndexOp::create(rewriter, loc, sgShape[i]);
+        Value offset = offsetSet[i];
+        Value adjustedMaskSize =
+            arith::SubIOp::create(rewriter, loc, wgMaskSizeVal, offset);
+        Value zero = arith::ConstantIndexOp::create(rewriter, loc, 0);
+        Value nonNegative =
+            arith::MaxSIOp::create(rewriter, loc, adjustedMaskSize, zero);
+        Value sgMaskSize =
+            arith::MinSIOp::create(rewriter, loc, nonNegative, dimSizeVal);
+        maskOperands.push_back(sgMaskSize);
+      }
+
+      auto newCreateMaskOp =
+          vector::CreateMaskOp::create(rewriter, loc, resultType, maskOperands);
+      xegpu::setDistributeLayoutAttr(newCreateMaskOp->getResult(0),
+                                     layout.dropSgLayoutAndData());
+      newCreateMaskOps.push_back(newCreateMaskOp.getResult());
+    }
+
+    rewriter.replaceOpWithMultiple(op, {newCreateMaskOps});
+    return success();
+  }
+};
+
 } // namespace
 
 namespace mlir {
@@ -1299,8 +1364,8 @@ void populateXeGPUWgToSgDistributePatterns(RewritePatternSet &patterns) {
            WgToSgArithConstantOp, WgToSgLoadGatherOpWithOffset,
            WgToSgStoreScatterOpWithOffset, WgToSgLoadMatrixOp,
            WgToSgStoreMatrixOp, WgToSgVectorStepOp, WgToSgVectorShapeCastOp,
-           WgToSgMultiDimReductionOp, WgToSgVectorTransposeOp>(
-          patterns.getContext());
+           WgToSgMultiDimReductionOp, WgToSgVectorTransposeOp,
+           WgToSgVectorConstantMaskOp>(patterns.getContext());
 }
 } // namespace xegpu
 } // namespace mlir
@@ -1427,9 +1492,9 @@ void XeGPUWgToSgDistributePass::runOnOperation() {
         return isLegal(layout);
       });
 
-  target.addDynamicallyLegalOp<vector::ShapeCastOp, vector::StepOp,
-                               vector::TransposeOp, vector::BroadcastOp,
-                               vector::MultiDimReductionOp>(
+  target.addDynamicallyLegalOp<
+      vector::ShapeCastOp, vector::StepOp, vector::TransposeOp,
+      vector::BroadcastOp, vector::MultiDimReductionOp, vector::ConstantMaskOp>(
       [=](Operation *op) -> bool {
         // Check for either a SliceAttr or LayoutAttr on the result.
         auto layout = xegpu::getDistributeLayoutAttr(op->getResult(0));

mlir/test/Dialect/XeGPU/xegpu-wg-to-sg-unify-ops-rr.mlir

@@ -130,5 +130,13 @@ gpu.module @test_distribution {
     %trans = vector.transpose %load, [1, 0] {layout_result_0 = #xegpu.layout<sg_layout = [4, 8], sg_data = [16, 32], lane_layout = [1, 16], lane_data = [1, 1], order =[1, 0]>} : vector<256x128xf32> to vector<128x256xf32>
       gpu.return
   }
+
+  // CHECK-LABEL: vector_mask_2D
+  gpu.func @vector_mask_2D() {
+    // CHECK-COUNT-4: vector.create_mask {{.*}}, {{.*}} : vector<16x16xi1>
+    // CHECK-NOT: vector.create_mask
+    %constant_mask = vector.constant_mask [16, 16] {layout_result_0 = #xegpu.layout<sg_layout = [8, 4], sg_data = [16, 16]>} : vector<256x128xi1>
+    gpu.return
+  }
 }
 

mlir/test/Dialect/XeGPU/xegpu-wg-to-sg-unify-ops.mlir

@@ -548,6 +548,41 @@ gpu.module @test_distribution {
     gpu.return
   }
 
+  // CHECK-LABEL: vector_mask_1D
+  gpu.func @vector_mask_1D() {
+    // CHECK-DAG: %[[SGID:.*]] = gpu.subgroup_id : index
+    // CHECK-DAG: %[[REMU:.*]] = index.remu %[[SGID]], %[[C2:.*]]
+    // CHECK-DAG: %[[MUL:.*]] = index.mul %[[REMU]], %[[C16:.*]]
+    // CHECK-DAG: %[[REMU2:.*]] = index.remu %[[MUL]], %[[C32:.*]]
+    // CHECK-DAG: %[[SUB:.*]] = arith.subi %[[C8:.*]], %[[REMU2]] : index
+    // CHECK-DAG: %[[MAX:.*]] = arith.maxsi %[[SUB]], %[[C0:.*]] : index
+    // CHECK-DAG: %[[MIN:.*]] = arith.minsi %[[MAX]], %[[C16:.*]] : index
+    // CHECK-DAG: %[[MASK:.*]] = vector.create_mask %[[MIN]] : vector<16xi1>
+    %constant_mask = vector.constant_mask [8] {layout_result_0 = #xegpu.layout<sg_layout = [2], sg_data = [16]>} : vector<32xi1>
+    gpu.return
+  }
+
+  // CHECK-LABEL: vector_mask_2D
+  gpu.func @vector_mask_2D() {
+    // CHECK-DAG: %[[SGID:.*]] = gpu.subgroup_id : index
+    // CHECK-DAG: %[[SGIDX:.*]] = index.remu %[[SGID]], %[[C4:.*]]
+    // CHECK-DAG: %[[SGIDY_TMP:.*]] = index.divu %[[SGID]], %[[C4:.*]]
+    // CHECK-DAG: %[[SGIDY:.*]] = index.remu %[[SGIDY_TMP]], %[[C8:.*]]
+    // CHECK-DAG: %[[ROW:.*]] = index.mul %[[SGIDY]], %[[C32:.*]]
+    // CHECK-DAG: %[[COL:.*]] = index.mul %[[SGIDX]], %[[C32:.*]]
+    // CHECK-DAG: %[[MODROW:.*]] = index.remu %[[ROW]], %[[C256:.*]]
+    // CHECK-DAG: %[[MODCOL:.*]] = index.remu %[[COL]], %[[C128:.*]]
+    // CHECK-DAG: %[[SUBROW:.*]] = arith.subi %[[C16:.*]], %[[MODROW]] : index
+    // CHECK-DAG: %[[MAXROW:.*]] = arith.maxsi %[[SUBROW]], %[[C4:.*]] : index
+    // CHECK-DAG: %[[MINROW:.*]] = arith.minsi %[[MAXROW]], %[[C32:.*]] : index
+    // CHECK-DAG: %[[SUBCOL:.*]] = arith.subi %[[C16:.*]], %[[MODCOL]] : index
+    // CHECK-DAG: %[[MAXCOL:.*]] = arith.maxsi %[[SUBCOL]], %[[C7:.*]] : index
+    // CHECK-DAG: %[[MINCOL:.*]] = arith.minsi %[[MAXCOL]], %[[C32:.*]] : index
+    // CHECK-DAG: %[[MASK:.*]] = vector.create_mask %[[MINROW]], %[[MINCOL]] : vector<32x32xi1>
+    %constant_mask = vector.constant_mask [16, 16] {layout_result_0 = #xegpu.layout<sg_layout = [8, 4], sg_data = [32, 32]>} : vector<256x128xi1>
+    gpu.return
+  }
+
   // CHECK-LABEL: distribute_load_slice_attr
   gpu.func @distribute_load_slice_attr() {
     %2 = memref.alloca() {alignment = 1024} : memref<4096xf32>