75 lines
3.0 KiB
C
75 lines
3.0 KiB
C
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//===- MatmulOptimizer.h -------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef POLLY_MATMULOPTIMIZER_H
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#define POLLY_MATMULOPTIMIZER_H
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#include "isl/isl-noexceptions.h"
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namespace llvm {
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class TargetTransformInfo;
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}
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namespace polly {
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struct Dependences;
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/// Apply the BLIS matmul optimization pattern if possible.
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///
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/// Make the loops containing the matrix multiplication be the innermost
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/// loops and apply the BLIS matmul optimization pattern. BLIS implements
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/// gemm as three nested loops around a macro-kernel, plus two packing
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/// routines. The macro-kernel is implemented in terms of two additional
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/// loops around a micro-kernel. The micro-kernel is a loop around a rank-1
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/// (i.e., outer product) update.
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///
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/// For a detailed description please see [1].
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///
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/// The order of the loops defines the data reused in the BLIS implementation
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/// of gemm ([1]). In particular, elements of the matrix B, the second
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/// operand of matrix multiplication, are reused between iterations of the
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/// innermost loop. To keep the reused data in cache, only elements of matrix
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/// A, the first operand of matrix multiplication, should be evicted during
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/// an iteration of the innermost loop. To provide such a cache replacement
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/// policy, elements of the matrix A can, in particular, be loaded first and,
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/// consequently, be least-recently-used.
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///
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/// In our case matrices are stored in row-major order instead of
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/// column-major order used in the BLIS implementation ([1]). It affects only
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/// on the form of the BLIS micro kernel and the computation of its
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/// parameters. In particular, reused elements of the matrix B are
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/// successively multiplied by specific elements of the matrix A.
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///
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/// Refs.:
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/// [1] - Analytical Modeling is Enough for High Performance BLIS
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/// Tze Meng Low, Francisco D Igual, Tyler M Smith, Enrique S Quintana-Orti
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/// Technical Report, 2014
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/// http://www.cs.utexas.edu/users/flame/pubs/TOMS-BLIS-Analytical.pdf
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///
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/// @see ScheduleTreeOptimizer::createMicroKernel
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/// @see ScheduleTreeOptimizer::createMacroKernel
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/// @see getMicroKernelParams
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/// @see getMacroKernelParams
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///
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/// TODO: Implement the packing transformation.
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///
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/// @param Node The node that contains a band to be optimized. The node
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/// is required to successfully pass
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/// ScheduleTreeOptimizer::isMatrMultPattern.
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/// @param TTI Target Transform Info.
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/// @param D The dependencies.
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///
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/// @returns The transformed schedule or nullptr if the optimization
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/// cannot be applied.
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isl::schedule_node
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tryOptimizeMatMulPattern(isl::schedule_node Node,
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const llvm::TargetTransformInfo *TTI,
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const Dependences *D);
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} // namespace polly
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#endif // POLLY_MATMULOPTIMIZER_H
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