VectorUtils.h

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//===- VectorUtils.h - Vector Utilities -------------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
 
#ifndef MLIR_DIALECT_VECTOR_UTILS_VECTORUTILS_H_
#define MLIR_DIALECT_VECTOR_UTILS_VECTORUTILS_H_
 
#include "mlir/Dialect/Vector/IR/VectorOps.h"
#include "mlir/IR/BuiltinAttributes.h"
#include "mlir/Support/LLVM.h"
 
#include "llvm/ADT/DenseMap.h"
 
namespace mlir {
 
// Forward declarations.
class AffineMap;
class Block;
class Location;
class OpBuilder;
class Operation;
class ShapedType;
class Value;
class VectorType;
class VectorTransferOpInterface;
 
namespace affine {
class AffineApplyOp;
class AffineForOp;
} // namespace affine
 
namespace vector {
/// Helper function that creates a memref::DimOp or tensor::DimOp depending on
/// the type of `source`.
Value createOrFoldDimOp(OpBuilder &b, Location loc, Value source, int64_t dim);
 
/// Returns two dims that are greater than one if the transposition is applied
/// on a 2D slice. Otherwise, returns a failure.
FailureOr<std::pair<int, int>> isTranspose2DSlice(vector::TransposeOp op);
 
} // namespace vector
 
/// Constructs a permutation map of invariant memref indices to vector
/// dimension.
///
/// If no index is found to be invariant, 0 is added to the permutation_map and
/// corresponds to a vector broadcast along that dimension.
///
/// The implementation uses the knowledge of the mapping of loops to
/// vector dimension. `loopToVectorDim` carries this information as a map with:
///   - keys representing "vectorized enclosing loops";
///   - values representing the corresponding vector dimension.
/// Note that loopToVectorDim is a whole function map from which only enclosing
/// loop information is extracted.
///
/// Prerequisites: `indices` belong to a vectorizable load or store operation
/// (i.e. at most one invariant index along each AffineForOp of
/// `loopToVectorDim`). `insertPoint` is the insertion point for the vectorized
/// load or store operation.
///
/// Example 1:
/// The following MLIR snippet:
///
/// ```mlir
///    affine.for %i3 = 0 to %0 {
///      affine.for %i4 = 0 to %1 {
///        affine.for %i5 = 0 to %2 {
///          %a5 = load %arg0[%i4, %i5, %i3] : memref<?x?x?xf32>
///    }}}
/// ```
///
/// may vectorize with {permutation_map: (d0, d1, d2) -> (d2, d1)} into:
///
/// ```mlir
///    affine.for %i3 = 0 to %0 step 32 {
///      affine.for %i4 = 0 to %1 {
///        affine.for %i5 = 0 to %2 step 256 {
///          %4 = vector.transfer_read %arg0, %i4, %i5, %i3
///               {permutation_map: (d0, d1, d2) -> (d2, d1)} :
///               (memref<?x?x?xf32>, index, index) -> vector<32x256xf32>
///    }}}
/// ```
///
/// Meaning that vector.transfer_read will be responsible for reading the slice:
/// `%arg0[%i4, %i5:%15+256, %i3:%i3+32]` into vector<32x256xf32>.
///
/// Example 2:
/// The following MLIR snippet:
///
/// ```mlir
///    %cst0 = arith.constant 0 : index
///    affine.for %i0 = 0 to %0 {
///      %a0 = load %arg0[%cst0, %cst0] : memref<?x?xf32>
///    }
/// ```
///
/// may vectorize with {permutation_map: (d0) -> (0)} into:
///
/// ```mlir
///    affine.for %i0 = 0 to %0 step 128 {
///      %3 = vector.transfer_read %arg0, %c0_0, %c0_0
///           {permutation_map: (d0, d1) -> (0)} :
///           (memref<?x?xf32>, index, index) -> vector<128xf32>
///    }
/// ````
///
/// Meaning that vector.transfer_read will be responsible of reading the slice
/// `%arg0[%c0, %c0]` into vector<128xf32> which needs a 1-D vector broadcast.
///
AffineMap
makePermutationMap(Block *insertPoint, ArrayRef<Value> indices,
                   const DenseMap<Operation *, unsigned> &loopToVectorDim);
AffineMap
makePermutationMap(Operation *insertPoint, ArrayRef<Value> indices,
                   const DenseMap<Operation *, unsigned> &loopToVectorDim);
 
namespace matcher {
 
/// Matches vector.transfer_read, vector.transfer_write and ops that return a
/// vector type that is a multiple of the sub-vector type. This allows passing
/// over other smaller vector types in the function and avoids interfering with
/// operations on those.
/// This is a first approximation, it can easily be extended in the future.
/// TODO: this could all be much simpler if we added a bit that a vector type to
/// mark that a vector is a strict super-vector but it still does not warrant
/// adding even 1 extra bit in the IR for now.
bool operatesOnSuperVectorsOf(Operation &op, VectorType subVectorType);
 
} // namespace matcher
} // namespace mlir
 
#endif // MLIR_DIALECT_VECTOR_UTILS_VECTORUTILS_H_