LoopFusion.cpp File Reference

#include "mlir/Dialect/Affine/Passes.h"
#include "mlir/Dialect/Affine/Analysis/AffineStructures.h"
#include "mlir/Dialect/Affine/Analysis/LoopAnalysis.h"
#include "mlir/Dialect/Affine/Analysis/Utils.h"
#include "mlir/Dialect/Affine/LoopFusionUtils.h"
#include "mlir/Dialect/Affine/LoopUtils.h"
#include "mlir/Dialect/Affine/Utils.h"
#include "mlir/Dialect/MemRef/IR/MemRef.h"
#include "mlir/IR/AffineExpr.h"
#include "mlir/IR/AffineMap.h"
#include "mlir/IR/Builders.h"
#include "mlir/Transforms/Passes.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <iomanip>
#include <optional>
#include <sstream>
#include "mlir/Dialect/Affine/Passes.h.inc"

Go to the source code of this file.

Namespaces
	mlir
	Include the generated interface declarations.
	mlir::affine

Macros
#define	GEN_PASS_DEF_AFFINELOOPFUSION
#define	DEBUG_TYPE   "affine-fusion"

Functions
static bool	canRemoveSrcNodeAfterFusion (unsigned srcId, unsigned dstId, const ComputationSliceState &fusionSlice, Operation *fusedLoopInsPoint, const DenseSet< Value > &escapingMemRefs, const MemRefDependenceGraph &mdg)
	Returns true if node 'srcId' can be removed after fusing it with node 'dstId'. More...
static void	getProducerCandidates (unsigned dstId, const MemRefDependenceGraph &mdg, SmallVectorImpl< unsigned > &srcIdCandidates)
	Returns in 'srcIdCandidates' the producer fusion candidates for consumer 'dstId'. More...
static void	gatherProducerConsumerMemrefs (unsigned srcId, unsigned dstId, const MemRefDependenceGraph &mdg, DenseSet< Value > &producerConsumerMemrefs)
	Returns in 'producerConsumerMemrefs' the memrefs involved in a producer-consumer dependence between 'srcId' and 'dstId'. More...
static bool	isEscapingMemref (Value memref, Block *block)
	A memref escapes in the context of the fusion pass if either: More...
static void	gatherEscapingMemrefs (unsigned id, const MemRefDependenceGraph &mdg, DenseSet< Value > &escapingMemRefs)
	Returns in 'escapingMemRefs' the memrefs from affine store ops in node 'id' that escape the block or are accessed in a non-affine way. More...
static void	sinkSequentialLoops (MemRefDependenceGraph::Node *node)
static Operation *	getDominanceFilterForPrivateMemRefRepl (Block *sliceInsertionBlock, ArrayRef< Operation * > producerStores)
	Get the operation that should act as a dominance filter while replacing memref uses with a private memref for which producerStores and sliceInsertionBlock are provided. More...
static std::optional< double >	getAdditionalComputeFraction (AffineForOp srcForOp, AffineForOp dstForOp, unsigned depth, ArrayRef< ComputationSliceState > depthSliceUnions, int64_t &sliceCost, int64_t &fusedLoopNestComputeCost)
	Returns the amount of additional (redundant) computation that will be done as a fraction of the total computation if srcForOp is fused into dstForOp at depth depth. More...
static Value	createPrivateMemRef (AffineForOp forOp, ArrayRef< Operation * > storeOps, unsigned dstLoopDepth, std::optional< unsigned > fastMemorySpace, Block *sliceInsertionBlock, uint64_t localBufSizeThreshold)
static bool	isFusionProfitable (AffineForOp srcForOp, ArrayRef< Operation * > producerStores, AffineForOp dstForOp, ArrayRef< ComputationSliceState > depthSliceUnions, unsigned maxLegalFusionDepth, unsigned *dstLoopDepth, double computeToleranceThreshold)

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "affine-fusion"

Definition at line 43 of file LoopFusion.cpp.

GEN_PASS_DEF_AFFINELOOPFUSION

#define GEN_PASS_DEF_AFFINELOOPFUSION

Definition at line 38 of file LoopFusion.cpp.

Function Documentation

canRemoveSrcNodeAfterFusion()

static bool canRemoveSrcNodeAfterFusion ( unsigned  srcId, unsigned  dstId, const ComputationSliceState &  fusionSlice, Operation *  fusedLoopInsPoint, const DenseSet< Value > &  escapingMemRefs, const MemRefDependenceGraph &  mdg  )

static

Returns true if node 'srcId' can be removed after fusing it with node 'dstId'.

The node can be removed if any of the following conditions are met:

1. 'srcId' has no output dependences after fusion and no escaping memrefs.
2. 'srcId' has no output dependences after fusion, has escaping memrefs and the fusion slice is maximal.
3. 'srcId' has output dependences after fusion, the fusion slice is maximal and the fusion insertion point dominates all the dependences.

Definition at line 77 of file LoopFusion.cpp.

References mlir::Operation::getBlock(), mlir::affine::MemRefDependenceGraph::getNode(), mlir::Operation::isBeforeInBlock(), mlir::affine::ComputationSliceState::isMaximal(), mlir::affine::MemRefDependenceGraph::Node::op, and mlir::affine::MemRefDependenceGraph::outEdges.

createPrivateMemRef()

static Value createPrivateMemRef ( AffineForOp  forOp, ArrayRef< Operation * >  storeOps, unsigned  dstLoopDepth, std::optional< unsigned >  fastMemorySpace, Block *  sliceInsertionBlock, uint64_t  localBufSizeThreshold  )

static

Definition at line 334 of file LoopFusion.cpp.

References mlir::affine::MemRefRegion::compute(), mlir::OpBuilder::create(), mlir::AffineMap::get(), mlir::get(), mlir::getAffineDimExpr(), mlir::affine::MemRefRegion::getConstantBoundingSizeAndShape(), mlir::affine::MemRefRegion::getConstraints(), getDominanceFilterForPrivateMemRefRepl(), mlir::Operation::getLoc(), mlir::affine::getMemRefIntOrFloatEltSizeInBytes(), mlir::presburger::IntegerRelation::getNumDimAndSymbolVars(), mlir::FlatLinearValueConstraints::getValues(), mlir::affine::replaceAllMemRefUsesWith(), and mlir::simplifyAffineExpr().

gatherEscapingMemrefs()

static void gatherEscapingMemrefs ( unsigned  id, const MemRefDependenceGraph &  mdg, DenseSet< Value > &  escapingMemRefs  )

static

Returns in 'escapingMemRefs' the memrefs from affine store ops in node 'id' that escape the block or are accessed in a non-affine way.

Definition at line 217 of file LoopFusion.cpp.

References mlir::affine::MemRefDependenceGraph::block, mlir::affine::MemRefDependenceGraph::getNode(), and isEscapingMemref().

gatherProducerConsumerMemrefs()

static void gatherProducerConsumerMemrefs ( unsigned  srcId, unsigned  dstId, const MemRefDependenceGraph &  mdg, DenseSet< Value > &  producerConsumerMemrefs  )

static

Returns in 'producerConsumerMemrefs' the memrefs involved in a producer-consumer dependence between 'srcId' and 'dstId'.

Definition at line 171 of file LoopFusion.cpp.

References mlir::affine::gatherProducerConsumerMemrefs(), and mlir::affine::MemRefDependenceGraph::getNode().

getAdditionalComputeFraction()

static std::optional<double> getAdditionalComputeFraction ( AffineForOp  srcForOp, AffineForOp  dstForOp, unsigned  depth, ArrayRef< ComputationSliceState >  depthSliceUnions, int64_t &  sliceCost, int64_t &  fusedLoopNestComputeCost  )

static

Returns the amount of additional (redundant) computation that will be done as a fraction of the total computation if srcForOp is fused into dstForOp at depth depth.

The method returns the compute cost of the slice and the fused nest's compute cost in the trailing output arguments.

Definition at line 280 of file LoopFusion.cpp.

References mlir::affine::getComputeCost(), mlir::affine::getFusionComputeCost(), mlir::affine::getLoopNestStats(), and mlir::affine::ComputationSliceState::isEmpty().

Referenced by isFusionProfitable().

getDominanceFilterForPrivateMemRefRepl()

static Operation* getDominanceFilterForPrivateMemRefRepl ( Block *  sliceInsertionBlock, ArrayRef< Operation * >  producerStores  )

static

Get the operation that should act as a dominance filter while replacing memref uses with a private memref for which producerStores and sliceInsertionBlock are provided.

This effectively determines in what part of the IR we should be performing the replacement.

Definition at line 245 of file LoopFusion.cpp.

References mlir::Block::begin(), mlir::Block::findAncestorOpInBlock(), mlir::affine::findInnermostCommonBlockInScope(), and mlir::Operation::isBeforeInBlock().

Referenced by createPrivateMemRef().

getProducerCandidates()

static void getProducerCandidates ( unsigned  dstId, const MemRefDependenceGraph &  mdg, SmallVectorImpl< unsigned > &  srcIdCandidates  )

static

Returns in 'srcIdCandidates' the producer fusion candidates for consumer 'dstId'.

Candidates are sorted by node id order. This order corresponds to the program order when the 'mdg' is created. However, program order is not guaranteed and must not be required by the client. Program order won't be held if the 'mdg' is reused from a previous fusion step or if the node creation order changes in the future to support more advance cases.

Definition at line 136 of file LoopFusion.cpp.

References mlir::affine::MemRefDependenceGraph::getNode(), and mlir::affine::MemRefDependenceGraph::inEdges.

isEscapingMemref()

static bool isEscapingMemref ( Value  memref, Block *  block  )

static

A memref escapes in the context of the fusion pass if either:

1. it (or its alias) is a block argument, or
2. created by an op not known to guarantee alias freedom,
3. it (or its alias) are used by ops other than affine dereferencing ops (e.g., by call op, memref load/store ops, alias creating ops, unknown ops, terminator ops, etc.); such ops do not deference the memref in an affine way.

Definition at line 187 of file LoopFusion.cpp.

References mlir::Value::getDefiningOp(), and mlir::Value::getUsers().

Referenced by gatherEscapingMemrefs().

isFusionProfitable()

static bool isFusionProfitable ( AffineForOp  srcForOp, ArrayRef< Operation * >  producerStores, AffineForOp  dstForOp, ArrayRef< ComputationSliceState >  depthSliceUnions, unsigned  maxLegalFusionDepth, unsigned *  dstLoopDepth, double  computeToleranceThreshold  )

static

Definition at line 498 of file LoopFusion.cpp.

References mlir::affine::MemRefRegion::compute(), getAdditionalComputeFraction(), mlir::affine::getComputeCost(), mlir::Operation::getLoc(), mlir::affine::getLoopNestStats(), mlir::affine::getMemoryFootprintBytes(), mlir::affine::MemRefRegion::getRegionSize(), mlir::affine::ComputationSliceState::isEmpty(), and max().

sinkSequentialLoops()

static void sinkSequentialLoops ( MemRefDependenceGraph::Node *  node )

static

Definition at line 234 of file LoopFusion.cpp.

References mlir::affine::MemRefDependenceGraph::Node::op, and mlir::affine::sinkSequentialLoops().