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//===- EmptyOpPatterns.cpp - Patterns related to tensor.empty folding ----===//
//
// 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/Tensor/IR/Tensor.h"
#include "mlir/Dialect/Tensor/Transforms/Transforms.h"
#include "mlir/IR/PatternMatch.h"
#include "llvm/Support/Debug.h"
using namespace mlir;
using namespace mlir::tensor;
namespace {
template <typename ReshapeOp>
struct FoldEmptyTensorWithReshapeOp : public OpRewritePattern<ReshapeOp> {
using OpRewritePattern<ReshapeOp>::OpRewritePattern;
LogicalResult matchAndRewrite(ReshapeOp reshapeOp,
PatternRewriter &rewriter) const override {
if (!reshapeOp.getSrc().template getDefiningOp<EmptyOp>())
return failure();
Location loc = reshapeOp.getLoc();
ReifiedRankedShapedTypeDims resultShapes;
if (failed(reifyResultShapes(rewriter, reshapeOp, resultShapes)) ||
!llvm::hasSingleElement(resultShapes))
return failure();
// TODO: Do not drop tensor type encoding.
Value emptyTensor = rewriter.create<EmptyOp>(
loc, resultShapes[0], reshapeOp.getResultType().getElementType());
if (emptyTensor.getType() != reshapeOp.getResultType()) {
rewriter.replaceOpWithNewOp<tensor::CastOp>(
reshapeOp, reshapeOp.getResultType(), emptyTensor);
} else {
rewriter.replaceOp(reshapeOp, emptyTensor);
}
return success();
}
};
/// `tensor.empty` does not define any tensor contents, so a slice of a
/// `tensor.empty` can be canonicalized to a smaller `tensor.empty`.
struct FoldEmptyTensorWithExtractSliceOp
: public OpRewritePattern<ExtractSliceOp> {
using OpRewritePattern<ExtractSliceOp>::OpRewritePattern;
LogicalResult matchAndRewrite(ExtractSliceOp sliceOp,
PatternRewriter &rewriter) const override {
if (!sliceOp.getSource().getDefiningOp<EmptyOp>())
return failure();
// ExtractSliceOp may be rank-reducing; its dynamic sizes must be
// preserved as well as its result type.
auto tensorType = RankedTensorType::get(sliceOp.getType().getShape(),
sliceOp.getType().getElementType(),
sliceOp.getType().getEncoding());
rewriter.replaceOpWithNewOp<EmptyOp>(sliceOp, tensorType,
sliceOp.getSizes());
return success();
}
};
} // namespace
void mlir::tensor::populateFoldTensorEmptyPatterns(
RewritePatternSet &patterns) {
patterns.add<FoldEmptyTensorWithExtractSliceOp,
FoldEmptyTensorWithReshapeOp<tensor::ExpandShapeOp>,
FoldEmptyTensorWithReshapeOp<tensor::CollapseShapeOp>>(
patterns.getContext());
}
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