fuchsia / third_party / polly / eb0a81fa94e55c40a4a4d7b316e787ccd8129b71 / . / include / polly / ScheduleOptimizer.h

//===- polly/ScheduleOptimizer.h - The Schedule Optimizer -------*- 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 POLLY_SCHEDULEOPTIMIZER_H | |

#define POLLY_SCHEDULEOPTIMIZER_H | |

#include "llvm/ADT/ArrayRef.h" | |

#include "isl/isl-noexceptions.h" | |

namespace llvm { | |

class TargetTransformInfo; | |

} // namespace llvm | |

struct isl_schedule_node; | |

/// Parameters of the micro kernel. | |

/// | |

/// Parameters, which determine sizes of rank-1 (i.e., outer product) update | |

/// used in the optimized matrix multiplication. | |

struct MicroKernelParamsTy { | |

int Mr; | |

int Nr; | |

}; | |

/// Parameters of the macro kernel. | |

/// | |

/// Parameters, which determine sizes of blocks of partitioned matrices | |

/// used in the optimized matrix multiplication. | |

struct MacroKernelParamsTy { | |

int Mc; | |

int Nc; | |

int Kc; | |

}; | |

namespace polly { | |

struct Dependences; | |

class MemoryAccess; | |

class Scop; | |

/// Additional parameters of the schedule optimizer. | |

/// | |

/// Target Transform Info and the SCoP dependencies used by the schedule | |

/// optimizer. | |

struct OptimizerAdditionalInfoTy { | |

const llvm::TargetTransformInfo *TTI; | |

const Dependences *D; | |

}; | |

/// Parameters of the matrix multiplication operands. | |

/// | |

/// Parameters, which describe access relations that represent operands of the | |

/// matrix multiplication. | |

struct MatMulInfoTy { | |

MemoryAccess *A = nullptr; | |

MemoryAccess *B = nullptr; | |

MemoryAccess *ReadFromC = nullptr; | |

MemoryAccess *WriteToC = nullptr; | |

int i = -1; | |

int j = -1; | |

int k = -1; | |

}; | |

extern bool DisablePollyTiling; | |

} // namespace polly | |

class ScheduleTreeOptimizer { | |

public: | |

/// Apply schedule tree transformations. | |

/// | |

/// This function takes an (possibly already optimized) schedule tree and | |

/// applies a set of additional optimizations on the schedule tree. The | |

/// transformations applied include: | |

/// | |

/// - Tiling | |

/// - Prevectorization | |

/// | |

/// @param Schedule The schedule object the transformations will be applied | |

/// to. | |

/// @param OAI Target Transform Info and the SCoP dependencies. | |

/// @returns The transformed schedule. | |

static isl::schedule | |

optimizeSchedule(isl::schedule Schedule, | |

const polly::OptimizerAdditionalInfoTy *OAI = nullptr); | |

/// Apply schedule tree transformations. | |

/// | |

/// This function takes a node in an (possibly already optimized) schedule | |

/// tree and applies a set of additional optimizations on this schedule tree | |

/// node and its descendants. The transformations applied include: | |

/// | |

/// - Tiling | |

/// - Prevectorization | |

/// | |

/// @param Node The schedule object post-transformations will be applied to. | |

/// @param OAI Target Transform Info and the SCoP dependencies. | |

/// @returns The transformed schedule. | |

static isl::schedule_node | |

optimizeScheduleNode(isl::schedule_node Node, | |

const polly::OptimizerAdditionalInfoTy *OAI = nullptr); | |

/// Decide if the @p NewSchedule is profitable for @p S. | |

/// | |

/// @param S The SCoP we optimize. | |

/// @param NewSchedule The new schedule we computed. | |

/// | |

/// @return True, if we believe @p NewSchedule is an improvement for @p S. | |

static bool isProfitableSchedule(polly::Scop &S, isl::schedule NewSchedule); | |

/// Isolate a set of partial tile prefixes. | |

/// | |

/// This set should ensure that it contains only partial tile prefixes that | |

/// have exactly VectorWidth iterations. | |

/// | |

/// @param Node A schedule node band, which is a parent of a band node, | |

/// that contains a vector loop. | |

/// @return Modified isl_schedule_node. | |

static isl::schedule_node isolateFullPartialTiles(isl::schedule_node Node, | |

int VectorWidth); | |

private: | |

/// Tile a schedule node. | |

/// | |

/// @param Node The node to tile. | |

/// @param Identifier An name that identifies this kind of tiling and | |

/// that is used to mark the tiled loops in the | |

/// generated AST. | |

/// @param TileSizes A vector of tile sizes that should be used for | |

/// tiling. | |

/// @param DefaultTileSize A default tile size that is used for dimensions | |

/// that are not covered by the TileSizes vector. | |

static isl::schedule_node tileNode(isl::schedule_node Node, | |

const char *Identifier, | |

llvm::ArrayRef<int> TileSizes, | |

int DefaultTileSize); | |

/// Tile a schedule node and unroll point loops. | |

/// | |

/// @param Node The node to register tile. | |

/// @param TileSizes A vector of tile sizes that should be used for | |

/// tiling. | |

/// @param DefaultTileSize A default tile size that is used for dimensions | |

static isl::schedule_node applyRegisterTiling(isl::schedule_node Node, | |

llvm::ArrayRef<int> TileSizes, | |

int DefaultTileSize); | |

/// Apply the BLIS matmul optimization pattern. | |

/// | |

/// Make the loops containing the matrix multiplication be the innermost | |

/// loops and apply the BLIS matmul optimization pattern. BLIS implements | |

/// gemm as three nested loops around a macro-kernel, plus two packing | |

/// routines. The macro-kernel is implemented in terms of two additional | |

/// loops around a micro-kernel. The micro-kernel is a loop around a rank-1 | |

/// (i.e., outer product) update. | |

/// | |

/// For a detailed description please see [1]. | |

/// | |

/// The order of the loops defines the data reused in the BLIS implementation | |

/// of gemm ([1]). In particular, elements of the matrix B, the second | |

/// operand of matrix multiplication, are reused between iterations of the | |

/// innermost loop. To keep the reused data in cache, only elements of matrix | |

/// A, the first operand of matrix multiplication, should be evicted during | |

/// an iteration of the innermost loop. To provide such a cache replacement | |

/// policy, elements of the matrix A can, in particular, be loaded first and, | |

/// consequently, be least-recently-used. | |

/// | |

/// In our case matrices are stored in row-major order instead of | |

/// column-major order used in the BLIS implementation ([1]). It affects only | |

/// on the form of the BLIS micro kernel and the computation of its | |

/// parameters. In particular, reused elements of the matrix B are | |

/// successively multiplied by specific elements of the matrix A. | |

/// | |

/// Refs.: | |

/// [1] - Analytical Modeling is Enough for High Performance BLIS | |

/// Tze Meng Low, Francisco D Igual, Tyler M Smith, Enrique S Quintana-Orti | |

/// Technical Report, 2014 | |

/// http://www.cs.utexas.edu/users/flame/pubs/TOMS-BLIS-Analytical.pdf | |

/// | |

/// @see ScheduleTreeOptimizer::createMicroKernel | |

/// @see ScheduleTreeOptimizer::createMacroKernel | |

/// @see getMicroKernelParams | |

/// @see getMacroKernelParams | |

/// | |

/// TODO: Implement the packing transformation. | |

/// | |

/// @param Node The node that contains a band to be optimized. The node | |

/// is required to successfully pass | |

/// ScheduleTreeOptimizer::isMatrMultPattern. | |

/// @param TTI Target Transform Info. | |

/// @param MMI Parameters of the matrix multiplication operands. | |

/// @returns The transformed schedule. | |

static isl::schedule_node | |

optimizeMatMulPattern(isl::schedule_node Node, | |

const llvm::TargetTransformInfo *TTI, | |

polly::MatMulInfoTy &MMI); | |

/// Check if this node is a band node we want to tile. | |

/// | |

/// We look for innermost band nodes where individual dimensions are marked as | |

/// permutable. | |

/// | |

/// @param Node The node to check. | |

static bool isTileableBandNode(isl::schedule_node Node); | |

/// Pre-vectorizes one scheduling dimension of a schedule band. | |

/// | |

/// prevectSchedBand splits out the dimension DimToVectorize, tiles it and | |

/// sinks the resulting point loop. | |

/// | |

/// Example (DimToVectorize=0, VectorWidth=4): | |

/// | |

/// | Before transformation: | |

/// | | |

/// | A[i,j] -> [i,j] | |

/// | | |

/// | for (i = 0; i < 128; i++) | |

/// | for (j = 0; j < 128; j++) | |

/// | A(i,j); | |

/// | |

/// | After transformation: | |

/// | | |

/// | for (it = 0; it < 32; it+=1) | |

/// | for (j = 0; j < 128; j++) | |

/// | for (ip = 0; ip <= 3; ip++) | |

/// | A(4 * it + ip,j); | |

/// | |

/// The goal of this transformation is to create a trivially vectorizable | |

/// loop. This means a parallel loop at the innermost level that has a | |

/// constant number of iterations corresponding to the target vector width. | |

/// | |

/// This transformation creates a loop at the innermost level. The loop has | |

/// a constant number of iterations, if the number of loop iterations at | |

/// DimToVectorize can be divided by VectorWidth. The default VectorWidth is | |

/// currently constant and not yet target specific. This function does not | |

/// reason about parallelism. | |

static isl::schedule_node prevectSchedBand(isl::schedule_node Node, | |

unsigned DimToVectorize, | |

int VectorWidth); | |

/// Apply additional optimizations on the bands in the schedule tree. | |

/// | |

/// We are looking for an innermost band node and apply the following | |

/// transformations: | |

/// | |

/// - Tile the band | |

/// - if the band is tileable | |

/// - if the band has more than one loop dimension | |

/// | |

/// - Prevectorize the schedule of the band (or the point loop in case of | |

/// tiling). | |

/// - if vectorization is enabled | |

/// | |

/// @param Node The schedule node to (possibly) optimize. | |

/// @param User A pointer to forward some use information | |

/// (currently unused). | |

static isl_schedule_node *optimizeBand(isl_schedule_node *Node, void *User); | |

/// Apply additional optimizations on the bands in the schedule tree. | |

/// | |

/// We apply the following | |

/// transformations: | |

/// | |

/// - Tile the band | |

/// - Prevectorize the schedule of the band (or the point loop in case of | |

/// tiling). | |

/// - if vectorization is enabled | |

/// | |

/// @param Node The schedule node to (possibly) optimize. | |

/// @param User A pointer to forward some use information | |

/// (currently unused). | |

static isl::schedule_node standardBandOpts(isl::schedule_node Node, | |

void *User); | |

/// Check if this node contains a partial schedule that could | |

/// probably be optimized with analytical modeling. | |

/// | |

/// isMatrMultPattern tries to determine whether the following conditions | |

/// are true: | |

/// 1. the partial schedule contains only one statement. | |

/// 2. there are exactly three input dimensions. | |

/// 3. all memory accesses of the statement will have stride 0 or 1, if we | |

/// interchange loops (switch the variable used in the inner loop to | |

/// the outer loop). | |

/// 4. all memory accesses of the statement except from the last one, are | |

/// read memory access and the last one is write memory access. | |

/// 5. all subscripts of the last memory access of the statement don't | |

/// contain the variable used in the inner loop. | |

/// If this is the case, we could try to use an approach that is similar to | |

/// the one used to get close-to-peak performance of matrix multiplications. | |

/// | |

/// @param Node The node to check. | |

/// @param D The SCoP dependencies. | |

/// @param MMI Parameters of the matrix multiplication operands. | |

static bool isMatrMultPattern(isl::schedule_node Node, | |

const polly::Dependences *D, | |

polly::MatMulInfoTy &MMI); | |

/// Create the BLIS macro-kernel. | |

/// | |

/// We create the BLIS macro-kernel by applying a combination of tiling | |

/// of dimensions of the band node and interchanging of two innermost | |

/// modified dimensions. The values of of MacroKernelParams's fields are used | |

/// as tile sizes. | |

/// | |

/// @param Node The schedule node to be modified. | |

/// @param MacroKernelParams Parameters of the macro kernel | |

/// to be used as tile sizes. | |

static isl::schedule_node | |

createMacroKernel(isl::schedule_node Node, | |

MacroKernelParamsTy MacroKernelParams); | |

/// Create the BLIS macro-kernel. | |

/// | |

/// We create the BLIS macro-kernel by applying a combination of tiling | |

/// of dimensions of the band node and interchanging of two innermost | |

/// modified dimensions. The values passed in MicroKernelParam are used | |

/// as tile sizes. | |

/// | |

/// @param Node The schedule node to be modified. | |

/// @param MicroKernelParams Parameters of the micro kernel | |

/// to be used as tile sizes. | |

/// @see MicroKernelParamsTy | |

static isl::schedule_node | |

createMicroKernel(isl::schedule_node Node, | |

MicroKernelParamsTy MicroKernelParams); | |

}; | |

/// Build the desired set of partial tile prefixes. | |

/// | |

/// We build a set of partial tile prefixes, which are prefixes of the vector | |

/// loop that have exactly VectorWidth iterations. | |

/// | |

/// 1. Drop all constraints involving the dimension that represents the | |

/// vector loop. | |

/// 2. Constrain the last dimension to get a set, which has exactly VectorWidth | |

/// iterations. | |

/// 3. Subtract loop domain from it, project out the vector loop dimension and | |

/// get a set that contains prefixes, which do not have exactly VectorWidth | |

/// iterations. | |

/// 4. Project out the vector loop dimension of the set that was build on the | |

/// first step and subtract the set built on the previous step to get the | |

/// desired set of prefixes. | |

/// | |

/// @param ScheduleRange A range of a map, which describes a prefix schedule | |

/// relation. | |

isl::set getPartialTilePrefixes(isl::set ScheduleRange, int VectorWidth); | |

#endif // POLLY_SCHEDULEOPTIMIZER_H |