//===- XeGPUWgToSgDistribute.cpp - XeGPU Workgroup to Subgroup Pass -------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// #include "mlir/Dialect/XeGPU/Transforms/Passes.h" #include "mlir/Dialect/Affine/Utils.h" #include "mlir/Dialect/Arith/IR/Arith.h" #include "mlir/Dialect/Arith/Utils/Utils.h" #include "mlir/Dialect/GPU/IR/GPUDialect.h" #include "mlir/Dialect/Index/IR/IndexDialect.h" #include "mlir/Dialect/Index/IR/IndexOps.h" #include "mlir/Dialect/Math/IR/Math.h" #include "mlir/Dialect/MemRef/IR/MemRef.h" #include "mlir/Dialect/SCF/Transforms/Patterns.h" #include "mlir/Dialect/Utils/IndexingUtils.h" #include "mlir/Dialect/XeGPU/IR/XeGPU.h" #include "mlir/Dialect/XeGPU/Transforms/Transforms.h" #include "mlir/Dialect/XeGPU/Utils/XeGPUUtils.h" #include "mlir/Transforms/DialectConversion.h" #include namespace mlir { namespace xegpu { #define GEN_PASS_DEF_XEGPUWGTOSGDISTRIBUTE #include "mlir/Dialect/XeGPU/Transforms/Passes.h.inc" } // namespace xegpu } // namespace mlir using namespace mlir; namespace { static std::pair, int> getSgShapeAndCount(ArrayRef shape, xegpu::LayoutAttr layout) { int count = 1; SmallVector sgShape(shape); if (layout && layout.isWgLayout()) { DenseI32ArrayAttr sgLayoutAttr = layout.getSgLayout(); auto sgLayout = llvm::to_vector_of(sgLayoutAttr.asArrayRef()); if (DenseI32ArrayAttr sgDataAttr = layout.getSgData()) sgShape = llvm::to_vector_of(sgDataAttr.asArrayRef()); else sgShape = computeShapeRatio(shape, sgLayout).value_or(sgShape); SmallVector distUnit = computeElementwiseMul(sgLayout, sgShape); // Clamp distUnit to the original shape to handle cases where data is // shared among subgroups, which may cause distUnit to exceed the original // shape. for (size_t i = 0; i < distUnit.size(); ++i) distUnit[i] = std::min(shape[i], distUnit[i]); count = computeProduct(shape) / computeProduct(distUnit); } return std::make_pair(sgShape, count); } /// This pattern transforms the CreateNdDescOp to create a subgroup descriptor /// from a workgroup descriptor. It replaces the offsets and sizes with /// appropriate values for the subgroup. /// It uses round-robin assignment to distribute the work to the subgroups. /// Following create_nd_desc operation:, /// %tdesc = xegpu.create_nd_tdesc %src[0, 0] : memref<24x24xf32> /// -> !xegpu.tensor_desc<24x24xf32, #xegpu.layout> /// is converted to 9 subgroup level operations based on the sg_layout & /// sg_data: /// %tdesc = xegpu.create_nd_tdesc %src[off1, off2] : memref<24x24xf32> -> /// !xegpu.tensor_desc<2x2xf32, #xegpu.layout> /// /// The sg_layout and sg_data attributes are dropped after the pass as they are /// no longer needed. /// /// 24x24 matrix distribution example: /// sg_layout = [4, 4], sg_data = [2, 2] /// Each 8x8 matrix within the 24x24 matrix is called a distribution unit. /// dist_unit_shape = [8, 8] --> sg_layout[i] * sg_data[i] /// /// +------------------------+ /// | 8x8 | 8x8 | 8x8 | <- 3 tiles across /// |-----+-----+-----| /// | 8x8 | 8x8 | 8x8 | <- 3 tiles down /// |-----+-----+-----| /// | 8x8 | 8x8 | 8x8 | /// +------------------------+ /// /// Each 8x8 tile is further subdivided among subgroups: /// +------------------------+ /// | 2x2 2x2 2x2 2x2 | <- 4 subgroups across (each handles 2 columns) /// | 2x2 2x2 2x2 2x2 | <- 4 subgroups down (each handles 2 rows) /// | 2x2 2x2 2x2 2x2 | /// | 2x2 2x2 2x2 2x2 | /// +------------------------+ /// /// Since the 24x24 matrix is divided into 8x8 distribution units, there will be /// 9 distribution units (3x3) in total. Hence the 9 subgroup level operations. /// The pass currently has entire distribution logic in the WgToSgCreateNdOp /// pattern and all the other ops just follow. /// TODO: Decouple the distribution logic from WgToSgCreateNdOp for all the /// ops in the pass. struct WgToSgCreateNdOp : public OpConversionPattern { using OpConversionPattern::OpConversionPattern; // Calculate offset for each subgroup SmallVector calculateGlobalOffsets(ConversionPatternRewriter &rewriter, Location loc, const SmallVector &originalOffsets, const SmallVector &localOffset, const SmallVector &distUnitBaseAddr, const SmallVector &distUnitShape) const { assert(localOffset.size() == distUnitBaseAddr.size() && "localOffset and distUnitBaseAddr must have the same rank"); SmallVector globalOffsets(originalOffsets.begin(), originalOffsets.end()); size_t rank = localOffset.size(); for (size_t i = 0; i < rank; ++i) { size_t dimIdx = originalOffsets.size() - rank + i; Value constOffset = rewriter.create(loc, distUnitBaseAddr[i]); Value offset = rewriter.createOrFold(loc, localOffset[i], constOffset); Value modValue = rewriter.create(loc, distUnitShape[i]); Value offsetMod = rewriter.createOrFold(loc, offset, modValue); Value origOffset = getValueOrCreateConstantIndexOp( rewriter, loc, originalOffsets[dimIdx]); Value globalOffset = rewriter.createOrFold(loc, origOffset, offsetMod); globalOffsets[dimIdx] = globalOffset; } return globalOffsets; } LogicalResult matchAndRewrite(xegpu::CreateNdDescOp op, OneToNOpAdaptor adaptor, ConversionPatternRewriter &rewriter) const override { Location loc = op.getLoc(); MLIRContext *ctx = op.getContext(); xegpu::TensorDescType tdescTy = op.getType(); auto layout = dyn_cast(tdescTy.getLayout()); if (!layout) return failure(); Type elemTy = tdescTy.getElementType(); ArrayRef wgShape = tdescTy.getShape(); // sgLayout must be present for workgroup-level distribution. SmallVector sgLayout; if (auto sgLayoutAttr = layout.getSgLayout()) sgLayout = llvm::to_vector_of(sgLayoutAttr.asArrayRef()); else return rewriter.notifyMatchFailure( op, "sgLayout attribute is required in layout"); SmallVector sgShape = getSgShapeAndCount(wgShape, layout).first; // TODO : Handle order attribute // Get the subgroup ID auto linearSgId = rewriter.create(loc, /*upper_bound=*/nullptr); // Create constants for layout dimensions SmallVector sgLayoutDim(sgLayout.size()); SmallVector sgDataDim(sgShape.size()); for (size_t i = 0; i < sgLayout.size(); i++) { sgLayoutDim[i] = rewriter.create(loc, sgLayout[i]); sgDataDim[i] = rewriter.create(loc, sgShape[i]); } auto deLinearizeSgId = affine::delinearizeIndex(rewriter, loc, linearSgId, sgLayoutDim); if (failed(deLinearizeSgId)) return failure(); SmallVector sgIds = *deLinearizeSgId; // Calculate distribution unit shape and local offsets for subgroup SmallVector distUnitShape(sgLayout.size()); SmallVector localOffset(sgLayout.size()); for (size_t i = 0; i < sgLayout.size(); i++) { distUnitShape[i] = std::min(sgLayout[i] * sgShape[i], wgShape[i]); localOffset[i] = rewriter.createOrFold(loc, sgIds[i], sgDataDim[i]); } SmallVector originalOffsets = op.getMixedOffsets(); xegpu::TensorDescType newTdescTy = xegpu::TensorDescType::get(ctx, sgShape, elemTy, tdescTy.getEncoding(), layout.dropSgLayoutAndData()); SmallVector newCreateNdOps; for (SmallVector distUnitBaseAddr : StaticTileOffsetRange(wgShape, distUnitShape)) { SmallVector globalOffsets = calculateGlobalOffsets(rewriter, loc, originalOffsets, localOffset, distUnitBaseAddr, distUnitShape); auto newCreateNdOp = rewriter.create( loc, newTdescTy, op.getSource(), globalOffsets, op.getMixedSizes(), op.getMixedStrides()); newCreateNdOps.push_back(newCreateNdOp); } rewriter.replaceOpWithMultiple(op, {newCreateNdOps}); return success(); } }; /// This pattern transforms the LoadNdOp to load subgroup data. struct WgToSgLoadNdOp : public OpConversionPattern { using OpConversionPattern::OpConversionPattern; LogicalResult matchAndRewrite(xegpu::LoadNdOp op, OneToNOpAdaptor adaptor, ConversionPatternRewriter &rewriter) const override { SmallVector newLoadOps; for (auto src : adaptor.getTensorDesc()) { xegpu::TensorDescType tdescTy = dyn_cast(src.getType()); ArrayRef srcShape = tdescTy.getShape(); VectorType newResTy = VectorType::get(srcShape, tdescTy.getElementType()); auto newLoadOp = rewriter.create(op.getLoc(), newResTy, src, op->getAttrs()); newLoadOps.push_back(newLoadOp); } rewriter.replaceOpWithMultiple(op, {newLoadOps}); return mlir::success(); } }; /// This pattern transforms the StoreNdOp to store to a subgroup descriptor /// It creates a StoreNdOp op to store the updated values to the new subgroup /// src tensor descriptors. struct WgToSgStoreNdOp : public OpConversionPattern { using OpConversionPattern::OpConversionPattern; LogicalResult matchAndRewrite(xegpu::StoreNdOp op, OneToNOpAdaptor adaptor, ConversionPatternRewriter &rewriter) const override { for (auto [v, t] : llvm::zip(adaptor.getValue(), adaptor.getTensorDesc())) rewriter.create(op.getLoc(), v, t, op.getL1HintAttr(), op.getL2HintAttr(), op.getL3HintAttr()); rewriter.eraseOp(op); return success(); } }; /// This pattern transforms the UpdateNdOffsetOp to update the offsets of a /// subgroup descriptor. It creates an UpdateNdOffsetOp op to update the /// offsets of the new subgroup src tensor descriptors. struct WgToSgUpdateNdOffsetOp : public OpConversionPattern { using OpConversionPattern::OpConversionPattern; LogicalResult matchAndRewrite(xegpu::UpdateNdOffsetOp op, OneToNOpAdaptor adaptor, ConversionPatternRewriter &rewriter) const override { llvm::SmallVector newUpdateTileOffsetOps; for (auto tDesc : adaptor.getTensorDesc()) { auto newUpdateTileOffsetOp = rewriter.create( op.getLoc(), tDesc.getType(), tDesc, op.getOffsets(), op.getConstOffsets()); newUpdateTileOffsetOps.push_back(newUpdateTileOffsetOp); } rewriter.replaceOpWithMultiple(op, {newUpdateTileOffsetOps}); return success(); } }; /// This pattern transforms the DpasOp to work at subgroup level. struct WgToSgDpasOp : public OpConversionPattern { using OpConversionPattern::OpConversionPattern; LogicalResult matchAndRewrite(xegpu::DpasOp op, OneToNOpAdaptor adaptor, ConversionPatternRewriter &rewriter) const override { Location loc = op.getLoc(); VectorType resultTy = op.getResult().getType(); if (resultTy.getRank() != 2) return failure(); auto originalLayout = xegpu::getLayoutAttr(op.getResult()); if (!originalLayout) return failure(); size_t i = 0; SmallVector newDpasOps; for (auto aVec : adaptor.getLhs()) { for (auto bVec : adaptor.getRhs()) { llvm::SmallVector operands({aVec, bVec}); Value tmpC; if (op.getAcc()) { tmpC = adaptor.getAcc()[i++]; operands.push_back(tmpC); } ArrayRef aVecShape = llvm::cast(aVec.getType()).getShape(); ArrayRef bVecShape = llvm::cast(bVec.getType()).getShape(); VectorType resTy = VectorType::get({aVecShape[0], bVecShape[1]}, resultTy.getElementType()); tmpC = rewriter.create(loc, resTy, operands); xegpu::setLayoutAttr(cast(tmpC), originalLayout.dropSgLayoutAndData()); newDpasOps.push_back(tmpC); } } rewriter.replaceOpWithMultiple(op, {newDpasOps}); return success(); } }; /// This pattern transforms the PrefetchNdOp to prefetch the subgroup data. struct WgToSgPrefetchNdOp : public OpConversionPattern { using OpConversionPattern::OpConversionPattern; LogicalResult matchAndRewrite(xegpu::PrefetchNdOp op, OneToNOpAdaptor adaptor, ConversionPatternRewriter &rewriter) const override { for (auto src : adaptor.getTensorDesc()) rewriter.create(op.getLoc(), TypeRange(), src, op->getAttrs()); rewriter.eraseOp(op); return success(); } }; // This pattern transforms elementwise ops to work at subgroup level. struct WgToSgElementwiseOp : public ConversionPattern { WgToSgElementwiseOp(MLIRContext *ctx) : ConversionPattern(MatchAnyOpTypeTag(), /*benefit=*/1, ctx) {} LogicalResult matchAndRewrite(Operation *op, ArrayRef operands, ConversionPatternRewriter &rewriter) const override { // Only match ops with elementwise trait and single result. if (!OpTrait::hasElementwiseMappableTraits(op) || op->getNumResults() != 1) return failure(); auto resultType = dyn_cast(op->getResult(0).getType()); assert(resultType && "Expected result to be a VectorType"); ArrayRef wgShape = resultType.getShape(); xegpu::LayoutAttr layout = xegpu::getLayoutAttr(op->getResult(0)); if (!layout || !layout.getSgLayout()) return failure(); SmallVector sgShape = getSgShapeAndCount(wgShape, layout).first; size_t numVariants = operands.empty() ? 0 : operands.front().size(); if (llvm::any_of(operands, [&](const ValueRange &operandVec) { return operandVec.size() != numVariants; })) return failure(); SmallVector newResults; VectorType newResultType = VectorType::get(sgShape, resultType.getElementType()); for (size_t i = 0; i < numVariants; ++i) { SmallVector opOperands; for (auto &operandVec : operands) opOperands.push_back(operandVec[i]); OperationState state(op->getLoc(), op->getName()); state.addOperands(opOperands); state.addTypes(newResultType); // Copy all attributes, but update "layout_result_0" to drop // sgLayout/sgData for (auto attr : op->getAttrs()) { if (auto layout = dyn_cast(attr.getValue())) state.addAttribute(attr.getName(), layout.dropSgLayoutAndData()); else state.addAttribute(attr.getName(), attr.getValue()); } Operation *newOp = rewriter.create(state); newResults.push_back(newOp->getResult(0)); } rewriter.replaceOpWithMultiple(op, {newResults}); return success(); } }; // Handles UnrealizedConversionCastOp generated during // SCFStructuralTypeConversions (step 1). This op may appear as either a // target or source materialization for Vector values, e.g.: // 1. unrealized_cast %1 : vector<256xf32> to vector<16xf32>, ... // 2. unrealized_cast %1 : vector<16xf32>, ... to vector<256xf32> // it could be either 1:N or N:1 cast. In both cases, the pattern // simply forwards the inputs to the outputs using 1:1 or 1:N interface. // for example, the following scf::forOp // ``` // %for = scf.for ... iter_args(%arg1 = %0)->(vector<128x128xf16>) { // %n = use(%arg1): vector<128x128xf16> // scf.yield %n : vector<128x128xf16> // } // ``` // Could be converted to: // ``` // %1 = unrealized_conversion_cast %0 // : vector<128x128xf16> to vector<16x16xf16>, vector<16x16xf16> // %for:2 = scf.for ... iter_args(%arg1 = %1#1, %arg2 = %1#2) // -> (vector<16x16xf16>, vector<16x16xf16) { // %m = unrealized_conversion_cast %arg1, %arg2 // : vector<16x16xf16>, vector<16x16xf16> to vector<128x128xf16> // %n = use(%m): vector<128x128xf16> // %b = unrealized_conversion_cast %n // : vector<128x128xf16> to vector<16x16xf16>, vector<16x16xf16> // scf.yield %b#1, %b#2 : vector<16x16xf16>, vector<16x16xf16> // } // %cast = unrealized_conversion_cast %for:2 // : vector<16x16xf16>, vector<16x16xf16> to vector<128x128xf16> // ``` // TODO: remove it when context-aware type converter is ready. struct UnrealizedConversionCastOpPattern : public OpConversionPattern { using OpConversionPattern< mlir::UnrealizedConversionCastOp>::OpConversionPattern; mlir::LogicalResult matchAndRewrite(mlir::UnrealizedConversionCastOp op, OneToNOpAdaptor adaptor, ConversionPatternRewriter &rewriter) const override { SmallVector inputs = xegpu::flattenValues(adaptor.getInputs()); auto inputTy = dyn_cast(inputs[0].getType()); auto outputTy = dyn_cast(op->getOpResult(0).getType()); if (!inputTy || !outputTy || !llvm::all_equal(op->getResultTypes()) || !llvm::all_equal(ValueRange(inputs).getTypes())) return failure(); // Handles the case "cast %1 : vector<256xf32> to vector<16xf32>, ...". // It is generated by source materialization (e.g., inits to scf forOp). // The input values provided by the adaptor should already be distributed, // and their types should correspond exactly to the result types of the // operation. if (op.getNumOperands() == 1 && llvm::equal(ValueRange(inputs).getTypes(), op->getResultTypes())) { rewriter.replaceOp(op, inputs); return success(); } // Handles the case "cast %1 : vector<16xf32>, ... to vector<256xf32>". // It is generated by target materialization (e.g., arguments/results // of scf forOp). All input values must have the same vector type, and // their shape must be evenly divisible by the output vector's shape // (determined by the nature of the workgroup to subgroup distribution). // TODO: it is not safe to do such forward, since such N:1 cast could be // from others. if (op.getNumResults() == 1 && computeShapeRatio(outputTy.getShape(), inputTy.getShape())) { rewriter.replaceOpWithMultiple(op, {inputs}); return success(); } return mlir::failure(); } }; } // namespace namespace mlir { namespace xegpu { void populateXeGPUWgToSgDistributePatterns(RewritePatternSet &patterns) { patterns.add( patterns.getContext()); } } // namespace xegpu } // namespace mlir namespace { struct XeGPUWgToSgDistributePass : public xegpu::impl::XeGPUWgToSgDistributeBase { void runOnOperation() override; }; } // namespace void XeGPUWgToSgDistributePass::runOnOperation() { // Track existing UnrealizedConversionCastOps SmallVector existingCastOps; getOperation()->walk([&](UnrealizedConversionCastOp castOp) { existingCastOps.push_back(castOp.getOperation()); }); { // Step 1: Apply SCFStructuralTypeConversions to SCF operations with // VectorType operands. This first converts such operands to // RankedTensorType, propagates the layout attribute into the encoding // attribute, and finally converts the RankedTensorType to VectorType based // on the encoding. TypeConverter converter; converter.addConversion([&](Type type) -> Type { return type; }); converter.addConversion( [&](RankedTensorType type, SmallVectorImpl &result) -> std::optional { Type elemTy = type.getElementType(); ArrayRef shape = type.getShape(); int count; SmallVector subShape; std::tie(subShape, count) = getSgShapeAndCount( shape, dyn_cast_if_present(type.getEncoding())); auto newTy = VectorType::get(subShape, elemTy); result.append(count, newTy); return success(); }); xegpu::doSCFStructuralTypeConversionWithTensorType(getOperation(), converter); } // Step 2: Perform workgroup to subgroup distribution for TensorDesc values, // as well as XeGPU, Arith, and Vector operations. MLIRContext *ctx = &getContext(); RewritePatternSet patterns(ctx); ConversionTarget target(*ctx); TypeConverter converter; converter.addConversion([&](Type type) -> Type { return type; }); converter.addConversion( [&](xegpu::TensorDescType type, SmallVectorImpl &result) -> std::optional { Type elemTy = type.getElementType(); ArrayRef shape = type.getShape(); int count; SmallVector subShape; xegpu::LayoutAttr layout = type.getLayoutAttr(); std::tie(subShape, count) = getSgShapeAndCount(shape, layout); if (layout) layout = layout.dropSgLayoutAndData(); auto newTy = xegpu::TensorDescType::get( type.getContext(), subShape, elemTy, type.getEncoding(), layout); result.append(count, newTy); return success(); }); auto getTensorDescType = [](Operation *op) -> xegpu::TensorDescType { if (auto createOp = dyn_cast(op)) return createOp.getType(); if (auto loadOp = dyn_cast(op)) return loadOp.getTensorDescType(); if (auto storeOp = dyn_cast(op)) return storeOp.getTensorDescType(); if (auto updateOp = dyn_cast(op)) return updateOp.getType(); if (auto prefetchOp = dyn_cast(op)) return prefetchOp.getTensorDescType(); return xegpu::TensorDescType(); }; auto isLegal = [&](xegpu::LayoutAttr layout) -> bool { return !layout || !layout.isWgLayout(); }; target.addDynamicallyLegalOp([=](Operation *op) -> bool { auto tdescTy = getTensorDescType(op); auto layout = dyn_cast_if_present(tdescTy.getLayout()); return isLegal(layout); }); target.addDynamicallyLegalOp([=](xegpu::DpasOp op) -> bool { auto layout = xegpu::getLayoutAttr(op.getResult()); return isLegal(layout); }); target.addDynamicallyLegalDialect( [=](Operation *op) -> std::optional { // Only handle elementwise mappable ops if (!OpTrait::hasElementwiseMappableTraits(op)) return true; VectorType resultType = dyn_cast(op->getResult(0).getType()); if (!resultType) return true; // Check if all operands are vectors of the same shape // TODO: Support other types. for (Value operand : op->getOperands()) { VectorType operandType = dyn_cast(operand.getType()); if (!operandType || operandType.getShape() != resultType.getShape()) { return true; } } xegpu::LayoutAttr layout = xegpu::getLayoutAttr(op->getResult(0)); return isLegal(layout); }); target.addDynamicallyLegalOp( [=](UnrealizedConversionCastOp op) { return llvm::is_contained(existingCastOps, op.getOperation()); }); target.markUnknownOpDynamicallyLegal([](Operation *) { return true; }); scf::populateSCFStructuralTypeConversionsAndLegality(converter, patterns, target); xegpu::populateXeGPUWgToSgDistributePatterns(patterns); if (failed( applyPartialConversion(getOperation(), target, std::move(patterns)))) return signalPassFailure(); // Remove sg_layout and sg_data attributes from the Layout // attribute for each VectorType result of the operation. // For Structured Control Flow ops, the layout is simply removed, // since in 1:N case, the layout for new results are missing. // Layout propagation pass will activated. getOperation()->walk([](Operation *op) { for (OpResult result : op->getOpResults()) { std::string name = xegpu::getLayoutName(result); if (auto layout = op->getAttrOfType(name)) { op->removeAttr(name); if (!isa(op)) op->setAttr(name, layout.dropSgLayoutAndData()); } } }); }