//===- TosaToTensor.cpp - Lowering Tosa to Tensor Dialect -------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// These rewriters lower from the Tosa to the Tensor dialect.
//
//===----------------------------------------------------------------------===//

#include "mlir/Conversion/TosaToTensor/TosaToTensor.h"
#include "mlir/Dialect/Arith/IR/Arith.h"
#include "mlir/Dialect/Tensor/IR/Tensor.h"
#include "mlir/Dialect/Tosa/IR/TosaOps.h"
#include "mlir/IR/PatternMatch.h"
#include "mlir/Transforms/GreedyPatternRewriteDriver.h"

using namespace mlir;
using namespace tosa;

namespace {

class SliceConverter : public OpRewritePattern<tosa::SliceOp> {
public:
  using OpRewritePattern<tosa::SliceOp>::OpRewritePattern;

  LogicalResult matchAndRewrite(tosa::SliceOp sliceOp,
                                PatternRewriter &rewriter) const final {
    Location loc = sliceOp.getLoc();
    Value input = sliceOp.getInput();
    SmallVector<int64_t> strides, sizes;
    ArrayRef<int64_t> starts = sliceOp.getStart();
    strides.resize(sliceOp.getType().template cast<ShapedType>().getRank(), 1);

    SmallVector<Value> dynSizes;
    for (const auto &i : llvm::enumerate(sliceOp.getSize())) {
      int64_t size = i.value();
      size_t index = i.index();
      sizes.push_back(size == -1 ? ShapedType::kDynamic : size);
      if (!ShapedType::isDynamic(sizes.back()))
        continue;

      auto dim = rewriter.create<tensor::DimOp>(loc, input, index);
      auto offset = rewriter.create<arith::ConstantOp>(
          loc, rewriter.getIndexAttr(starts[index]));
      dynSizes.push_back(rewriter.create<arith::SubIOp>(loc, dim, offset));
    }

    auto newSliceOp = rewriter.create<tensor::ExtractSliceOp>(
        sliceOp.getLoc(), sliceOp.getType(), input, ValueRange({}), dynSizes,
        ValueRange({}), rewriter.getDenseI64ArrayAttr(starts),
        rewriter.getDenseI64ArrayAttr(sizes),
        rewriter.getDenseI64ArrayAttr(strides));

    rewriter.replaceOp(sliceOp, newSliceOp.getResult());
    return success();
  }
};

class PadConverter : public OpRewritePattern<tosa::PadOp> {
public:
  using OpRewritePattern<tosa::PadOp>::OpRewritePattern;

  LogicalResult matchAndRewrite(tosa::PadOp padOp,
                                PatternRewriter &rewriter) const final {
    auto loc = padOp.getLoc();
    auto input = padOp.getInput1();
    auto padding = padOp.getPadding();

    ShapedType inputTy = input.getType().cast<ShapedType>();
    Type elementTy = inputTy.getElementType();
    int64_t rank = inputTy.getRank();

    // Setup the default constantAttr.

    Value padConstant;

    if (padOp.getPadConst()) {
      padConstant = rewriter.createOrFold<tensor::ExtractOp>(
          loc, padOp.getPadConst(), ValueRange({}));
    } else {
      Attribute constantAttr;
      if (elementTy.isa<FloatType>()) {
        constantAttr = rewriter.getFloatAttr(elementTy, 0.0);
      } else if (elementTy.isa<IntegerType>() && !padOp.getQuantizationInfo()) {
        constantAttr = rewriter.getIntegerAttr(elementTy, 0);
      } else if (elementTy.isa<IntegerType>() && padOp.getQuantizationInfo()) {
        int64_t value = padOp.getQuantizationInfo()->getInputZp();
        constantAttr = rewriter.getIntegerAttr(elementTy, value);
      }
      if (constantAttr)
        padConstant = rewriter.create<arith::ConstantOp>(loc, constantAttr);
    }

    if (!padConstant) {
      return rewriter.notifyMatchFailure(
          padOp, "tosa.pad was unable to determine the pad constant value.");
    }

    Value lowIndex =
        rewriter.create<arith::ConstantOp>(loc, rewriter.getIndexAttr(0));
    Value highIndex =
        rewriter.create<arith::ConstantOp>(loc, rewriter.getIndexAttr(1));

    SmallVector<OpFoldResult, 3> lowValues;
    SmallVector<OpFoldResult, 3> highValues;

    lowValues.reserve(rank);
    highValues.reserve(rank);

    for (int i = 0; i < rank; i++) {
      Value inputIndex = rewriter.createOrFold<arith::ConstantIndexOp>(loc, i);
      Value lowVal = rewriter.createOrFold<tensor::ExtractOp>(
          loc, padding, ValueRange({inputIndex, lowIndex}));
      Value highVal = rewriter.createOrFold<tensor::ExtractOp>(
          loc, padding, ValueRange({inputIndex, highIndex}));

      lowVal = rewriter.createOrFold<arith::IndexCastOp>(
          loc, rewriter.getIndexType(), lowVal);
      highVal = rewriter.createOrFold<arith::IndexCastOp>(
          loc, rewriter.getIndexType(), highVal);

      lowValues.push_back(lowVal);
      highValues.push_back(highVal);
    }

    auto newPadOp = rewriter.create<tensor::PadOp>(
        loc, padOp.getType(), input, lowValues, highValues, padConstant);

    rewriter.replaceOp(padOp, newPadOp.getResult());
    return success();
  }
};

} // namespace

void mlir::tosa::populateTosaToTensorConversionPatterns(
    RewritePatternSet *patterns) {
  patterns->add<SliceConverter, PadConverter>(patterns->getContext());
}