//===- FoldMemRefsOps.cpp - AMDGPU fold memref ops ------------------------===//
//
// 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/AMDGPU/Transforms/Passes.h"

#include "mlir/Dialect/AMDGPU/IR/AMDGPUDialect.h"
#include "mlir/Dialect/Affine/ViewLikeInterfaceUtils.h"
#include "mlir/Dialect/MemRef/IR/MemRef.h"
#include "mlir/Dialect/MemRef/Utils/MemRefUtils.h"
#include "mlir/Transforms/WalkPatternRewriteDriver.h"
#include "llvm/ADT/TypeSwitch.h"

namespace mlir::amdgpu {
#define GEN_PASS_DEF_AMDGPUFOLDMEMREFOPSPASS
#include "mlir/Dialect/AMDGPU/Transforms/Passes.h.inc"

struct AmdgpuFoldMemRefOpsPass final
    : amdgpu::impl::AmdgpuFoldMemRefOpsPassBase<AmdgpuFoldMemRefOpsPass> {
  void runOnOperation() override {
    RewritePatternSet patterns(&getContext());
    populateAmdgpuFoldMemRefOpsPatterns(patterns);
    walkAndApplyPatterns(getOperation(), std::move(patterns));
  }
};

static LogicalResult foldMemrefViewOp(PatternRewriter &rewriter, Location loc,
                                      Value view, mlir::OperandRange indices,
                                      SmallVectorImpl<Value> &resolvedIndices,
                                      Value &memrefBase, StringRef role) {
  Operation *defOp = view.getDefiningOp();
  if (!defOp) {
    return failure();
  }
  return llvm::TypeSwitch<Operation *, LogicalResult>(defOp)
      .Case([&](memref::SubViewOp subviewOp) {
        mlir::affine::resolveIndicesIntoOpWithOffsetsAndStrides(
            rewriter, loc, subviewOp.getMixedOffsets(),
            subviewOp.getMixedStrides(), subviewOp.getDroppedDims(), indices,
            resolvedIndices);
        memrefBase = subviewOp.getSource();
        return success();
      })
      .Case([&](memref::ExpandShapeOp expandShapeOp) {
        mlir::memref::resolveSourceIndicesExpandShape(
            loc, rewriter, expandShapeOp, indices, resolvedIndices, false);
        memrefBase = expandShapeOp.getViewSource();
        return success();
      })
      .Case([&](memref::CollapseShapeOp collapseShapeOp) {
        mlir::memref::resolveSourceIndicesCollapseShape(
            loc, rewriter, collapseShapeOp, indices, resolvedIndices);
        memrefBase = collapseShapeOp.getViewSource();
        return success();
      })
      .Default([&](Operation *op) {
        return rewriter.notifyMatchFailure(
            op, (role + " producer is not one of SubViewOp, ExpandShapeOp, or "
                        "CollapseShapeOp")
                    .str());
      });
}

struct FoldMemRefOpsIntoGatherToLDSOp final : OpRewritePattern<GatherToLDSOp> {
  using Base::Base;
  LogicalResult matchAndRewrite(GatherToLDSOp op,
                                PatternRewriter &rewriter) const override {
    Location loc = op.getLoc();

    SmallVector<Value> sourceIndices, destIndices;
    Value memrefSource, memrefDest;

    auto foldSrcResult =
        foldMemrefViewOp(rewriter, loc, op.getSrc(), op.getSrcIndices(),
                         sourceIndices, memrefSource, "source");

    if (failed(foldSrcResult)) {
      memrefSource = op.getSrc();
      sourceIndices = op.getSrcIndices();
    }

    auto foldDstResult =
        foldMemrefViewOp(rewriter, loc, op.getDst(), op.getDstIndices(),
                         destIndices, memrefDest, "destination");

    if (failed(foldDstResult)) {
      memrefDest = op.getDst();
      destIndices = op.getDstIndices();
    }

    if (failed(foldSrcResult) && failed(foldDstResult))
      return rewriter.notifyMatchFailure(op, "no fold found");

    rewriter.replaceOpWithNewOp<GatherToLDSOp>(
        op, memrefSource, sourceIndices, memrefDest, destIndices,
        op.getTransferType(), op.getAsync());

    return success();
  }
};

template <typename OpTy>
struct FoldMemRefOpsIntoDmaBaseOp final : OpRewritePattern<OpTy> {
  using OpRewritePattern<OpTy>::OpRewritePattern;
  LogicalResult matchAndRewrite(OpTy op,
                                PatternRewriter &rewriter) const override {
    Location loc = op.getLoc();

    SmallVector<Value> globalIndices, ldsIndices;
    Value globalBase, ldsBase;

    LogicalResult didFoldGlobal =
        foldMemrefViewOp(rewriter, loc, op.getGlobal(), op.getGlobalIndices(),
                         globalIndices, globalBase, "global");
    if (failed(didFoldGlobal)) {
      globalBase = op.getGlobal();
      globalIndices = op.getGlobalIndices();
    }

    LogicalResult didFoldLds =
        foldMemrefViewOp(rewriter, loc, op.getLds(), op.getLdsIndices(),
                         ldsIndices, ldsBase, "lds");
    if (failed(didFoldLds)) {
      ldsBase = op.getLds();
      ldsIndices = op.getLdsIndices();
    }

    if (failed(didFoldGlobal) && failed(didFoldLds))
      return rewriter.notifyMatchFailure(op, "no fold found");

    rewriter.replaceOpWithNewOp<OpTy>(op, op.getBase().getType(), globalBase,
                                      globalIndices, ldsBase, ldsIndices);
    return success();
  }
};

struct FoldMemRefOpsIntoTransposeLoadOp final
    : OpRewritePattern<TransposeLoadOp> {
  using Base::Base;
  LogicalResult matchAndRewrite(TransposeLoadOp op,
                                PatternRewriter &rewriter) const override {
    SmallVector<Value> sourceIndices;
    Value memrefSource;

    if (failed(foldMemrefViewOp(rewriter, op.getLoc(), op.getSrc(),
                                op.getSrcIndices(), sourceIndices, memrefSource,
                                "source")))
      return failure();

    rewriter.replaceOpWithNewOp<TransposeLoadOp>(op, op.getResult().getType(),
                                                 memrefSource, sourceIndices);
    return success();
  }
};

void populateAmdgpuFoldMemRefOpsPatterns(RewritePatternSet &patterns,
                                         PatternBenefit benefit) {
  patterns.add<FoldMemRefOpsIntoGatherToLDSOp,
               FoldMemRefOpsIntoDmaBaseOp<MakeDmaBaseOp>,
               FoldMemRefOpsIntoDmaBaseOp<MakeGatherDmaBaseOp>,
               FoldMemRefOpsIntoTransposeLoadOp>(patterns.getContext(),
                                                 benefit);
}
} // namespace mlir::amdgpu