compiler/plugins/input/StableHLO/Conversion/LegalizeToLinalgUtils.cpp

// Copyright 2022 The IREE Authors
//
// Licensed 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

// Implements utilities for lowering StableHLO dialect to Linalg dialect.

#include "compiler/plugins/input/StableHLO/Conversion/LegalizeToLinalgUtils.h"

#include <algorithm>
#include <numeric>
#include <string>
#include <utility>

#include "mlir/Dialect/Bufferization/IR/Bufferization.h"
#include "mlir/Dialect/SparseTensor/IR/SparseTensor.h"
#include "mlir/Dialect/Tensor/IR/Tensor.h"
#include "mlir/IR/BuiltinTypes.h"
#include "stablehlo/dialect/ChloOps.h"
#include "stablehlo/dialect/StablehloOps.h"

namespace mlir::iree_compiler::stablehlo {
namespace {
bool hasIntegralShapeType(Operation *op) {
  auto stp = llvm::dyn_cast<ShapedType>(op->getOperand(0).getType());
  return stp && stp.getElementType().isIntOrIndex();
}

} // namespace

SmallVector<utils::IteratorType, 3>
getParallelAndReductionIterators(unsigned nLoops, unsigned nReduction) {
  SmallVector<utils::IteratorType, 3> res(nLoops - nReduction,
                                          utils::IteratorType::parallel);
  res.append(nReduction, utils::IteratorType::reduction);
  return res;
}

SmallVector<utils::IteratorType, 3>
getNParallelLoopsAttrs(unsigned nParallelLoops) {
  return getParallelAndReductionIterators(nParallelLoops, 0);
}

Value getEmptySparseTensor(OpBuilder &b, Location loc, ShapedType type,
                           ArrayRef<Value> dynSizes) {
  return b.create<bufferization::AllocTensorOp>(
      loc, llvm::cast<TensorType>(type), dynSizes,
      /*copy=*/Value(),
      /*memory_space=*/IntegerAttr());
}

Value getEmptyTensor(OpBuilder &b, Location loc, ShapedType type,
                     ArrayRef<Value> dynSizes) {
  return b.create<tensor::EmptyOp>(
      loc, type.getShape(), type.getElementType(), dynSizes,
      llvm::cast<RankedTensorType>(type).getEncoding());
}

Value getEmptyTensorFor(OpBuilder &b, Location loc, ShapedType resultType,
                        Operation *op, ValueRange operands) {
  bool isSparse = sparse_tensor::getSparseTensorEncoding(resultType) != nullptr;
  // Collect the sizes for a ranked tensor to be passed as parameter to a
  // new tensor initialization operation. This operation only needs the
  // dynamic sizes.
  SmallVector<Value> sizes;
  if (resultType.hasRank() && !resultType.hasStaticShape()) {
    // Ask the op for its output shape.
    auto shapeSource = cast<InferShapedTypeOpInterface>(op);
    SmallVector<Value, 1> reifiedShapes;
    (void)shapeSource.reifyReturnTypeShapes(b, operands, reifiedShapes);
    assert(reifiedShapes.size() == 1 && "Expected one reified result");
    // Construct sizes for the required dimensions.
    for (const auto &en : llvm::enumerate(resultType.getShape())) {
      if (!ShapedType::isDynamic(en.value()))
        continue;
      sizes.push_back(b.create<tensor::ExtractOp>(
          loc, reifiedShapes[0],
          ValueRange{b.create<arith::ConstantIndexOp>(loc, en.index())}));
    }
  }
  return isSparse ? getEmptySparseTensor(b, loc, resultType, sizes)
                  : getEmptyTensor(b, loc, resultType, sizes);
}

Value coerceTensorShape(OpBuilder &builder, Location loc,
                        TypedValue<ShapedType> value, ShapedType targetType) {
  return builder.createOrFold<tensor::CastOp>(
      loc, targetType.cloneWith(std::nullopt, value.getType().getElementType()),
      value);
}

LogicalResult verifyHloOpBufferOrTensorSemantics(Operation *op) {
  auto isRankedTensor = [](Value val) {
    return isa<RankedTensorType>(val.getType());
  };
  if (!llvm::all_of(op->getOperands(), isRankedTensor))
    return failure();
  return success(llvm::all_of(op->getResults(), isRankedTensor));
}

Value fillTensorWithZeros(OpBuilder &builder, Location loc, Value tensor) {
  auto type = cast<ShapedType>(tensor.getType());
  Value zero;
  // Complex numbers are a special case.
  if (auto complexType = llvm::dyn_cast<ComplexType>(type.getElementType())) {
    auto zeroElement = builder.getZeroAttr(complexType.getElementType());
    auto zeroAttr = builder.getArrayAttr({zeroElement, zeroElement});
    zero = builder.create<complex::ConstantOp>(loc, complexType, zeroAttr);
  } else {
    auto zeroAttr = builder.getZeroAttr(type.getElementType());
    zero = builder.create<arith::ConstantOp>(loc, zeroAttr);
  }
  return builder.create<linalg::FillOp>(loc, zero, tensor).result();
}

Value preSparsify(Operation *op, llvm::SmallVector<Value, 2> &values, Type rtp,
                  OpBuilder *b) {
  // Apply for semi-ring operations that lower to elaborate code
  // (any sign-op, or an integral abs-op).
  // TODO(peiming, ajcbik): these all can potentially be optimized by applying
  // value transform on sparse_tenosr.value memref
  if (isa<mlir::stablehlo::SignOp, mlir::stablehlo::NegOp>(op) ||
      (isa<mlir::stablehlo::AbsOp>(op) && hasIntegralShapeType(op)) ||
      isa<chlo::AsinOp, chlo::AsinhOp, chlo::AtanOp, chlo::AtanhOp,
          chlo::BesselI1eOp, chlo::SinhOp, chlo::TanOp>(op)) {
    if (!sparse_tensor::getSparseTensorEncoding(op->getResult(0).getType()) &&
        !sparse_tensor::getSparseTensorEncoding(op->getOperand(0).getType()))
      return Value();
    Location loc = op->getLoc();
    auto semiring = b->create<sparse_tensor::UnaryOp>(loc, rtp, values[0]);
    Type itp = values[0].getType();
    Block *present = b->createBlock(&semiring.getPresentRegion(), {}, itp, loc);
    b->setInsertionPointToStart(&semiring.getPresentRegion().front());
    values[0] = present->getArgument(0);
    return semiring;
  }
  return Value();
}

Value postSparsify(Operation *op, Value semiring, Value result, OpBuilder *b) {
  if (semiring) {
    b->create<sparse_tensor::YieldOp>(op->getLoc(), result);
    b->setInsertionPointAfter(semiring.getDefiningOp());
    return semiring;
  }
  return result;
}

bool allOperandsAreScalarTensors(Operation *op) {
  return llvm::all_of(op->getOperands(), [](Value operand) {
    auto operandTy = llvm::dyn_cast<ShapedType>(operand.getType());
    return operandTy && operandTy.getRank() == 0;
  });
}

bool isInBodyOfLinalgOps(Operation *op) {
  auto *parentOp = op->getParentRegion()->getParentOp();
  return parentOp->getDialect() ==
         parentOp->getContext()->getLoadedDialect<linalg::LinalgDialect>();
}

SmallVector<int64_t> extract1DVector(DenseIntElementsAttr elements) {
  SmallVector<int64_t> ret;
  for (const APInt &element : elements) {
    ret.push_back(element.getLimitedValue());
  }
  return ret;
}

} // namespace mlir::iree_compiler::stablehlo