Google Git
Sign in
llvm/llvm-project/a5757c5b65f1894de16f549212b1c37793312703/./mlir/lib/Dialect/Linalg/Transforms/DropUnitDims.cpp
blob: 023ea277bcf4991744dd236ceb04a2312f88b34c [file] [log] [blame]
//===- DropUnitDims.cpp - Pass to drop use of unit-extent for broadcasting ===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file implements patterns/pass to remove usage of unit-extent dimensions
// to specify broadcasting in favor of more canonical representation of the
// computation
//
//===----------------------------------------------------------------------===//
#include "mlir/Dialect/Linalg/Passes.h"
#include "mlir/Dialect/Affine/IR/AffineOps.h"
#include "mlir/Dialect/Arith/IR/Arith.h"
#include "mlir/Dialect/Linalg/IR/Linalg.h"
#include "mlir/Dialect/Linalg/Transforms/Transforms.h"
#include "mlir/Dialect/Linalg/Utils/Utils.h"
#include "mlir/Dialect/MemRef/Transforms/Transforms.h"
#include "mlir/Dialect/Tensor/IR/Tensor.h"
#include "mlir/Dialect/Tensor/Transforms/Transforms.h"
#include "mlir/Dialect/Tensor/Utils/Utils.h"
#include "mlir/IR/AffineExpr.h"
#include "mlir/IR/AffineMap.h"
#include "mlir/IR/BuiltinTypes.h"
#include "mlir/Transforms/FoldUtils.h"
#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
namespace mlir {
#define GEN_PASS_DEF_LINALGFOLDUNITEXTENTDIMSPASS
#include "mlir/Dialect/Linalg/Passes.h.inc"
} // namespace mlir
#define DEBUG_TYPE "linalg-drop-unit-dims"
using namespace mlir;
using namespace mlir::linalg;
namespace {
/// Pattern to move init operands to ins when all the loops are parallel and
/// blockArgument corresponding to init is used in the region. This is a fix-up
/// when unit reduction dimensions are all folded away. In this context, it
/// becomes a elementwise generic op. E.g., it converts
///
/// %0 = tensor.empty() : tensor<1x1xf32>
/// %1 = linalg.fill
/// ins(%cst : f32)
/// outs(%0 : tensor<1x1xf32>) -> tensor<1x1xf32>
/// %2 = linalg.generic {indexing_maps = [affine_map<(d0) -> (0, d0, 0, 0)>,
/// affine_map<(d0) -> (0, d0)>],
/// iterator_types = ["parallel"]}
/// ins(%arg0 : tensor<1x?x1x1xf32>)
/// outs(%1 : tensor<1x1xf32>) {
/// ^bb0(%in: f32, %out: f32):
/// %3 = arith.addf %in, %out : f32
/// linalg.yield %3 : f32
/// } -> tensor<1x1xf32>
///
/// into
///
/// %0 = tensor.empty() : tensor<1x1xf32>
/// %1 = linalg.fill
/// ins(%cst : f32)
/// outs(%0 : tensor<1x1xf32>) -> tensor<1x1xf32>
/// %2 = tensor.empty() : tensor<1x1xf32>
/// %3 = linalg.generic {indexing_maps = [affine_map<(d0) -> (0, d0, 0, 0)>,
/// affine_map<(d0) -> (0, d0)>,
/// affine_map<(d0) -> (0, d0)>],
/// iterator_types = ["parallel"]}
/// ins(%arg0, %1 : tensor<1x?x1x1xf32>, tensor<1x1xf32>)
/// outs(%2 : tensor<1x1xf32>) {
/// ^bb0(%in: f32, %in_0: f32, %out: f32):
/// %4 = arith.addf %in, %in_0 : f32
/// linalg.yield %4 : f32
/// } -> tensor<1x1xf32>
struct MoveInitOperandsToInput : public OpRewritePattern<GenericOp> {
using OpRewritePattern<GenericOp>::OpRewritePattern;
LogicalResult matchAndRewrite(GenericOp genericOp,
PatternRewriter &rewriter) const override {
if (!genericOp.hasPureTensorSemantics())
return failure();
if (genericOp.getNumParallelLoops() != genericOp.getNumLoops())
return failure();
auto outputOperands = genericOp.getDpsInitsMutable();
SetVector<OpOperand *> candidates;
for (OpOperand &op : outputOperands) {
if (genericOp.getMatchingBlockArgument(&op).use_empty())
continue;
candidates.insert(&op);
}
if (candidates.empty())
return failure();
// Compute the modified indexing maps.
int64_t origNumInput = genericOp.getNumDpsInputs();
SmallVector<Value> newInputOperands = genericOp.getDpsInputs();
SmallVector<AffineMap> indexingMaps = genericOp.getIndexingMapsArray();
SmallVector<AffineMap> newIndexingMaps;
newIndexingMaps.append(indexingMaps.begin(),
std::next(indexingMaps.begin(), origNumInput));
for (OpOperand *op : candidates) {
newInputOperands.push_back(op->get());
newIndexingMaps.push_back(genericOp.getMatchingIndexingMap(op));
}
newIndexingMaps.append(std::next(indexingMaps.begin(), origNumInput),
indexingMaps.end());
Location loc = genericOp.getLoc();
SmallVector<Value> newOutputOperands =
llvm::to_vector(genericOp.getDpsInits());
for (OpOperand *op : candidates) {
OpBuilder::InsertionGuard guard(rewriter);
rewriter.setInsertionPointAfterValue(op->get());
auto elemType = cast<ShapedType>(op->get().getType()).getElementType();
auto empty = rewriter.create<tensor::EmptyOp>(
loc, tensor::getMixedSizes(rewriter, loc, op->get()), elemType);
unsigned start = genericOp.getDpsInits().getBeginOperandIndex();
newOutputOperands[op->getOperandNumber() - start] = empty.getResult();
}
auto newOp = rewriter.create<GenericOp>(
loc, genericOp.getResultTypes(), newInputOperands, newOutputOperands,
newIndexingMaps, genericOp.getIteratorTypesArray(),
/*bodyBuild=*/nullptr, linalg::getPrunedAttributeList(genericOp));
OpBuilder::InsertionGuard guard(rewriter);
Region &region = newOp.getRegion();
Block *block = rewriter.createBlock(&region);
IRMapping mapper;
for (auto bbarg : genericOp.getRegionInputArgs())
mapper.map(bbarg, block->addArgument(bbarg.getType(), loc));
for (OpOperand *op : candidates) {
BlockArgument bbarg = genericOp.getMatchingBlockArgument(op);
mapper.map(bbarg, block->addArgument(bbarg.getType(), loc));
}
for (OpOperand &op : outputOperands) {
BlockArgument bbarg = genericOp.getMatchingBlockArgument(&op);
if (candidates.count(&op))
block->addArgument(bbarg.getType(), loc);
else
mapper.map(bbarg, block->addArgument(bbarg.getType(), loc));
}
for (auto &op : genericOp.getBody()->getOperations()) {
rewriter.clone(op, mapper);
}
rewriter.replaceOp(genericOp, newOp.getResults());
return success();
}
};
} // namespace
//===---------------------------------------------------------------------===//
// Drop loops that are unit-extents within Linalg operations.
//===---------------------------------------------------------------------===//
/// Implements a pass that canonicalizes the uses of unit-extent dimensions for
/// broadcasting. For example,
///
/// ```mlir
/// #accesses = [
/// affine_map<(d0, d1) -> (0, d1)>,
/// affine_map<(d0, d1) -> (d0, 0)>,
/// affine_map<(d0, d1) -> (d0, d1)>
/// ]
///
/// #trait = {
/// args_in = 2,
/// args_out = 1,
/// indexing_maps = #accesses,
/// iterator_types = ["parallel", "parallel"],
/// library_call = "some_external_fn"
/// }
///
/// func @broadcast_test(%arg0 : tensor<5xf32>, %arg1 : tensor<5xf32>) ->
/// tensor<5x5xf32>
/// {
/// %0 = linalg.tensor_reshape %arg0 [affine_map<(d0, d1) -> (d0, d1)>] :
/// tensor<5xf32> into tensor<1x5xf32>
/// %1 = linalg.tensor_reshape %arg1 [affine_map<(d0, d1) -> (d0, d1)>] :
/// tensor<5xf32> into tensor<5x1xf32>
/// %2 = linalg.generic #trait %0, %1 {
/// ^bb0(%arg2: f32, %arg3: f32):
/// %3 = arith.addf %arg2, %arg3 : f32
/// linalg.yield %3 : f32
/// } : tensor<1x5xf32>, tensor<5x1xf32> -> tensor<5x5xf32>
/// return %2 : tensor<5x5xf32>
/// }
///
/// would canonicalize to
///
/// ```mlir
/// #accesses = [
/// affine_map<(d0, d1) -> (d1)>,
/// affine_map<(d0, d1) -> (d0)>,
/// affine_map<(d0, d1) -> (d0, d1)>
/// ]
///
/// #trait = {
/// args_in = 2,
/// args_out = 1,
/// indexing_maps = #accesses,
/// iterator_types = ["parallel", "parallel"],
/// library_call = "some_external_fn"
/// }
///
/// func @broadcast_test(%arg0 : tensor<5xf32>, %arg1 : tensor<5xf32>) ->
/// tensor<5x5xf32>
/// {
/// %0 = linalg.generic #trait %arg0, %arg1 {
/// ^bb0(%arg2: f32, %arg3: f32):
/// %3 = arith.addf %arg2, %arg3 : f32
/// linalg.yield %3 : f32
/// } : tensor<5xf32>, tensor<5xf32> -> tensor<5x5xf32>
/// return %0 : tensor<5x5xf32>
/// }
/// Update the index accesses of linalg operations having index semantics.
static void
replaceUnitDimIndexOps(GenericOp genericOp,
const llvm::SmallDenseSet<unsigned> &unitDims,
RewriterBase &rewriter) {
for (IndexOp indexOp :
llvm::make_early_inc_range(genericOp.getBody()->getOps<IndexOp>())) {
OpBuilder::InsertionGuard guard(rewriter);
rewriter.setInsertionPoint(indexOp);
if (unitDims.count(indexOp.getDim()) != 0) {
rewriter.replaceOpWithNewOp<arith::ConstantIndexOp>(indexOp, 0);
} else {
// Update the dimension of the index operation if needed.
unsigned droppedDims = llvm::count_if(
unitDims, [&](unsigned dim) { return dim < indexOp.getDim(); });
if (droppedDims != 0)
rewriter.replaceOpWithNewOp<IndexOp>(indexOp,
indexOp.getDim() - droppedDims);
}
}
}
/// Expand the given `value` so that the type matches the type of `origDest`.
/// The `reassociation` is used when `rankReductionStrategy` is set to
/// `RankReductionStrategy::ReassociativeReshape`.
static Value
expandValue(RewriterBase &rewriter, Location loc, Value result, Value origDest,
ArrayRef<ReassociationIndices> reassociation,
ControlDropUnitDims::RankReductionStrategy rankReductionStrategy) {
// There are no results for memref outputs.
auto origResultType = cast<RankedTensorType>(origDest.getType());
if (rankReductionStrategy ==
ControlDropUnitDims::RankReductionStrategy::ExtractInsertSlice) {
unsigned rank = origResultType.getRank();
SmallVector<OpFoldResult> offsets(rank, rewriter.getIndexAttr(0));
SmallVector<OpFoldResult> sizes =
tensor::getMixedSizes(rewriter, loc, origDest);
SmallVector<OpFoldResult> strides(rank, rewriter.getIndexAttr(1));
return rewriter.createOrFold<tensor::InsertSliceOp>(
loc, result, origDest, offsets, sizes, strides);
}
assert(rankReductionStrategy ==
ControlDropUnitDims::RankReductionStrategy::ReassociativeReshape &&
"unknown rank reduction strategy");
return rewriter.create<tensor::ExpandShapeOp>(loc, origResultType, result,
reassociation);
}
/// Collapse the given `value` so that the type matches the type of
/// `origOutput`. The `reassociation` is used when `rankReductionStrategy` is
/// set to `RankReductionStrategy::ReassociativeReshape`.
static Value collapseValue(
RewriterBase &rewriter, Location loc, Value operand,
ArrayRef<int64_t> targetShape, ArrayRef<ReassociationIndices> reassociation,
ControlDropUnitDims::RankReductionStrategy rankReductionStrategy) {
if (auto memrefType = dyn_cast<MemRefType>(operand.getType())) {
if (rankReductionStrategy ==
ControlDropUnitDims::RankReductionStrategy::ExtractInsertSlice) {
FailureOr<Value> rankReducingExtract =
memref::SubViewOp::rankReduceIfNeeded(rewriter, loc, operand,
targetShape);
assert(succeeded(rankReducingExtract) && "not a unit-extent collapse");
return *rankReducingExtract;
}
assert(
rankReductionStrategy ==
ControlDropUnitDims::RankReductionStrategy::ReassociativeReshape &&
"unknown rank reduction strategy");
MemRefLayoutAttrInterface layout;
auto targetType = MemRefType::get(targetShape, memrefType.getElementType(),
layout, memrefType.getMemorySpace());
return rewriter.create<memref::CollapseShapeOp>(loc, targetType, operand,
reassociation);
}
if (auto tensorType = dyn_cast<RankedTensorType>(operand.getType())) {
if (rankReductionStrategy ==
ControlDropUnitDims::RankReductionStrategy::ExtractInsertSlice) {
FailureOr<Value> rankReducingExtract =
tensor::ExtractSliceOp::rankReduceIfNeeded(rewriter, loc, operand,
targetShape);
assert(succeeded(rankReducingExtract) && "not a unit-extent collapse");
return *rankReducingExtract;
}
assert(
rankReductionStrategy ==
ControlDropUnitDims::RankReductionStrategy::ReassociativeReshape &&
"unknown rank reduction strategy");
auto targetType =
RankedTensorType::get(targetShape, tensorType.getElementType());
return rewriter.create<tensor::CollapseShapeOp>(loc, targetType, operand,
reassociation);
}
llvm_unreachable("unsupported operand type");
}
/// Compute the modified metadata for an operands of operation
/// whose unit dims are being dropped. Return the new indexing map
/// to use, the shape of the operand in the replacement op
/// and the `reassocation` to use to go from original operand shape
/// to modified operand shape.
struct UnitExtentReplacementInfo {
AffineMap indexMap;
SmallVector<ReassociationIndices> reassociation;
SmallVector<int64_t> targetShape;
};
static UnitExtentReplacementInfo dropUnitExtentFromOperandMetadata(
MLIRContext *context, GenericOp genericOp, OpOperand *opOperand,
llvm::SmallDenseMap<unsigned, unsigned> &oldDimsToNewDimsMap,
ArrayRef<AffineExpr> dimReplacements) {
UnitExtentReplacementInfo info;
ReassociationIndices reassociationGroup;
SmallVector<AffineExpr> newIndexExprs;
AffineMap indexingMap = genericOp.getMatchingIndexingMap(opOperand);
ArrayRef<int64_t> operandShape = genericOp.getShape(opOperand);
ArrayRef<AffineExpr> exprs = indexingMap.getResults();
auto isUnitDim = [&](unsigned dim) {
if (auto dimExpr = dyn_cast<AffineDimExpr>(exprs[dim])) {
unsigned oldPosition = dimExpr.getPosition();
return !oldDimsToNewDimsMap.count(oldPosition);
}
// Handle the other case where the shape is 1, and is accessed using a
// constant 0.
if (operandShape[dim] == 1) {
auto constAffineExpr = dyn_cast<AffineConstantExpr>(exprs[dim]);
return constAffineExpr && constAffineExpr.getValue() == 0;
}
return false;
};
unsigned dim = 0;
while (dim < operandShape.size() && isUnitDim(dim))
reassociationGroup.push_back(dim++);
while (dim < operandShape.size()) {
assert(!isUnitDim(dim) && "expected non unit-extent");
reassociationGroup.push_back(dim);
AffineExpr newExpr = exprs[dim].replaceDims(dimReplacements);
newIndexExprs.push_back(newExpr);
info.targetShape.push_back(operandShape[dim]);
++dim;
// Fold all following dimensions that are unit-extent.
while (dim < operandShape.size() && isUnitDim(dim)) {
reassociationGroup.push_back(dim++);
}
info.reassociation.push_back(reassociationGroup);
reassociationGroup.clear();
}
info.indexMap =
AffineMap::get(oldDimsToNewDimsMap.size(), indexingMap.getNumSymbols(),
newIndexExprs, context);
return info;
}
LogicalResult linalg::dropUnitDims(RewriterBase &rewriter, GenericOp genericOp,
const ControlDropUnitDims &options) {
SmallVector<AffineMap> indexingMaps = genericOp.getIndexingMapsArray();
if (indexingMaps.empty())
return failure();
// 1. Check if any of the iteration dimensions are unit-trip count. They will
// end up being unit-trip count if they are used to index into a unit-dim
// tensor/memref.
AffineMap invertedMap = inversePermutation(concatAffineMaps(indexingMaps));
if (!invertedMap) {
return rewriter.notifyMatchFailure(genericOp,
"invalid indexing maps for operation");
}
SmallVector<int64_t> dims = genericOp.getStaticShape();
// 1a. Get the allowed list of dimensions to drop from the `options`.
SmallVector<unsigned> allowedUnitDims = options.controlFn(genericOp);
if (allowedUnitDims.empty()) {
return rewriter.notifyMatchFailure(
genericOp, "control function returns no allowed unit dims to prune");
}
llvm::SmallDenseSet<unsigned> unitDimsFilter(allowedUnitDims.begin(),
allowedUnitDims.end());
llvm::SmallDenseSet<unsigned> unitDims;
for (const auto &expr : enumerate(invertedMap.getResults())) {
if (AffineDimExpr dimExpr = dyn_cast<AffineDimExpr>(expr.value())) {
if (dims[dimExpr.getPosition()] == 1 &&
unitDimsFilter.count(expr.index()))
unitDims.insert(expr.index());
}
}
// 2. Compute the iterator types of the modified op by dropping the one-trip
// count loops.
SmallVector<utils::IteratorType> newIteratorTypes;
llvm::SmallDenseMap<unsigned, unsigned> oldDimToNewDimMap;
SmallVector<AffineExpr> dimReplacements;
unsigned newDims = 0;
for (auto [index, attr] :
llvm::enumerate(genericOp.getIteratorTypesArray())) {
if (unitDims.count(index)) {
dimReplacements.push_back(
getAffineConstantExpr(0, rewriter.getContext()));
} else {
newIteratorTypes.push_back(attr);
oldDimToNewDimMap[index] = newDims;
dimReplacements.push_back(
getAffineDimExpr(newDims, rewriter.getContext()));
newDims++;
}
}
// 3. For each of the operands, find the
// - modified affine map to use.
// - shape of the operands after the unit-dims are dropped.
// - the reassociation indices used to convert from the original
// operand type to modified operand (needed only when using reshapes
// for rank reduction strategy)
// Note that the indexing maps might need changing even if there are no
// unit dimensions that are dropped to handle cases where `0` is used to
// access a unit-extent tensor. Consider moving this out of this specific
// transformation as a stand-alone transformation. Kept here right now due
// to legacy.
SmallVector<AffineMap> newIndexingMaps;
SmallVector<SmallVector<ReassociationIndices>> reassociations;
SmallVector<SmallVector<int64_t>> targetShapes;
SmallVector<bool> collapsed;
auto hasCollapsibleType = [](OpOperand &operand) {
Type operandType = operand.get().getType();
if (auto memrefOperandType = dyn_cast_or_null<MemRefType>(operandType)) {
return memrefOperandType.getLayout().isIdentity();
}
if (auto tensorOperandType = dyn_cast<RankedTensorType>(operandType)) {
return tensorOperandType.getEncoding() == nullptr;
}
return false;
};
for (OpOperand &opOperand : genericOp->getOpOperands()) {
auto indexingMap = genericOp.getMatchingIndexingMap(&opOperand);
ArrayRef<int64_t> shape = genericOp.getShape(&opOperand);
if (!hasCollapsibleType(opOperand)) {
AffineMap newIndexingMap = indexingMap.replaceDimsAndSymbols(
dimReplacements, ArrayRef<AffineExpr>{}, oldDimToNewDimMap.size(), 0);
newIndexingMaps.push_back(newIndexingMap);
targetShapes.push_back(llvm::to_vector(shape));
collapsed.push_back(false);
reassociations.push_back({});
continue;
}
auto replacementInfo = dropUnitExtentFromOperandMetadata(
rewriter.getContext(), genericOp, &opOperand, oldDimToNewDimMap,
dimReplacements);
reassociations.push_back(replacementInfo.reassociation);
newIndexingMaps.push_back(replacementInfo.indexMap);
targetShapes.push_back(replacementInfo.targetShape);
collapsed.push_back(!(replacementInfo.indexMap.getNumResults() ==
indexingMap.getNumResults()));
}
// Abort if the indexing maps of the result operation are not invertible
// (i.e. not legal) or if no dimension was reduced.
if (newIndexingMaps == indexingMaps ||
!inversePermutation(concatAffineMaps(newIndexingMaps)))
return failure();
Location loc = genericOp.getLoc();
// 4. For each of the operands, collapse the operand to convert
// from original shape to shape in the modified operation if needed,
// either through use of reshapes or rank-reducing slices as
// specified in `options`.
SmallVector<Value> newOperands;
for (OpOperand &opOperand : genericOp->getOpOperands()) {
int64_t idx = opOperand.getOperandNumber();
if (!collapsed[idx]) {
newOperands.push_back(opOperand.get());
continue;
}
newOperands.push_back(collapseValue(rewriter, loc, opOperand.get(),
targetShapes[idx], reassociations[idx],
options.rankReductionStrategy));
}
// 5. Create the `linalg.generic` operation with the new operands,
// indexing maps, iterator types and result types.
ArrayRef<Value> newInputs =
ArrayRef<Value>(newOperands).take_front(genericOp.getNumDpsInputs());
ArrayRef<Value> newOutputs =
ArrayRef<Value>(newOperands).take_back(genericOp.getNumDpsInits());
SmallVector<Type> resultTypes;
resultTypes.reserve(genericOp.getNumResults());
for (unsigned i : llvm::seq<unsigned>(0, genericOp.getNumResults()))
resultTypes.push_back(newOutputs[i].getType());
GenericOp replacementOp =
rewriter.create<GenericOp>(loc, resultTypes, newInputs, newOutputs,
newIndexingMaps, newIteratorTypes);
rewriter.inlineRegionBefore(genericOp.getRegion(), replacementOp.getRegion(),
replacementOp.getRegion().begin());
// 5a. Replace `linalg.index` operations that refer to the dropped unit
// dimensions.
replaceUnitDimIndexOps(replacementOp, unitDims, rewriter);
// 6. If any result type changes, insert a reshape/slice to convert from the
// original
// type to the new type.
SmallVector<Value> resultReplacements;
for (auto [index, result] : llvm::enumerate(replacementOp.getResults())) {
unsigned opOperandIndex = index + replacementOp.getNumDpsInputs();
Value origDest = genericOp.getDpsInitOperand(index)->get();
if (!collapsed[opOperandIndex]) {
resultReplacements.push_back(result);
continue;
}
resultReplacements.push_back(expandValue(rewriter, loc, result, origDest,
reassociations[opOperandIndex],
options.rankReductionStrategy));
}
rewriter.replaceOp(genericOp, resultReplacements);
return success();
}
namespace {
struct DropUnitDims : public OpRewritePattern<GenericOp> {
DropUnitDims(MLIRContext *context, ControlDropUnitDims options = {},
PatternBenefit benefit = 1)
: OpRewritePattern(context, benefit), options(std::move(options)) {}
LogicalResult matchAndRewrite(GenericOp genericOp,
PatternRewriter &rewriter) const override {
return dropUnitDims(rewriter, genericOp, options);
}
private:
ControlDropUnitDims options;
};
} // namespace
//===---------------------------------------------------------------------===//
// Drop dimensions that are unit-extents within tensor operations.
//===---------------------------------------------------------------------===//
namespace {
struct DropPadUnitDims : public OpRewritePattern<tensor::PadOp> {
DropPadUnitDims(MLIRContext *context, ControlDropUnitDims options = {},
PatternBenefit benefit = 1)
: OpRewritePattern(context, benefit), options(std::move(options)) {}
LogicalResult matchAndRewrite(tensor::PadOp padOp,
PatternRewriter &rewriter) const override {
// 1a. Get the allowed list of dimensions to drop from the `options`.
SmallVector<unsigned> allowedUnitDims = options.controlFn(padOp);
if (allowedUnitDims.empty()) {
return rewriter.notifyMatchFailure(
padOp, "control function returns no allowed unit dims to prune");
}
if (padOp.getSourceType().getEncoding()) {
return rewriter.notifyMatchFailure(
padOp, "cannot collapse dims of tensor with encoding");
}
// Fail for non-constant padding values. The body of the pad could
// depend on the padding indices and/or properties of the padded
// tensor so for now we fail.
// TODO: Support non-constant padding values.
Value paddingVal = padOp.getConstantPaddingValue();
if (!paddingVal) {
return rewriter.notifyMatchFailure(
padOp, "unimplemented: non-constant padding value");
}
ArrayRef<int64_t> sourceShape = padOp.getSourceType().getShape();
int64_t padRank = sourceShape.size();
auto isStaticZero = [](OpFoldResult f) {
std::optional<int64_t> maybeInt = getConstantIntValue(f);
return maybeInt && *maybeInt == 0;
};
llvm::SmallDenseSet<unsigned> unitDimsFilter(allowedUnitDims.begin(),
allowedUnitDims.end());
llvm::SmallDenseSet<unsigned> unitDims;
SmallVector<int64_t> newShape;
SmallVector<OpFoldResult> newLowPad;
SmallVector<OpFoldResult> newHighPad;
for (const auto [dim, size, low, high] :
zip_equal(llvm::seq(static_cast<int64_t>(0), padRank), sourceShape,
padOp.getMixedLowPad(), padOp.getMixedHighPad())) {
if (unitDimsFilter.contains(dim) && size == 1 && isStaticZero(low) &&
isStaticZero(high)) {
unitDims.insert(dim);
} else {
newShape.push_back(size);
newLowPad.push_back(low);
newHighPad.push_back(high);
}
}
if (unitDims.empty()) {
return rewriter.notifyMatchFailure(padOp, "no unit dims to collapse");
}
ReassociationIndices reassociationGroup;
SmallVector<ReassociationIndices> reassociationMap;
int64_t dim = 0;
while (dim < padRank && unitDims.contains(dim))
reassociationGroup.push_back(dim++);
while (dim < padRank) {
assert(!unitDims.contains(dim) && "expected non unit-extent");
reassociationGroup.push_back(dim);
dim++;
// Fold all following dimensions that are unit-extent.
while (dim < padRank && unitDims.contains(dim))
reassociationGroup.push_back(dim++);
reassociationMap.push_back(reassociationGroup);
reassociationGroup.clear();
}
Value collapsedSource =
collapseValue(rewriter, padOp.getLoc(), padOp.getSource(), newShape,
reassociationMap, options.rankReductionStrategy);
auto newPadOp = rewriter.create<tensor::PadOp>(
padOp.getLoc(), /*result=*/Type(), collapsedSource, newLowPad,
newHighPad, paddingVal, padOp.getNofold());
Value dest = padOp.getResult();
if (options.rankReductionStrategy ==
ControlDropUnitDims::RankReductionStrategy::ExtractInsertSlice) {
SmallVector<OpFoldResult> expandedSizes;
int64_t numUnitDims = 0;
for (auto dim : llvm::seq(static_cast<int64_t>(0), padRank)) {
if (unitDims.contains(dim)) {
expandedSizes.push_back(rewriter.getIndexAttr(1));
numUnitDims++;
continue;
}
expandedSizes.push_back(tensor::getMixedSize(
rewriter, padOp.getLoc(), newPadOp, dim - numUnitDims));
}
dest = rewriter.create<tensor::EmptyOp>(
padOp.getLoc(), expandedSizes,
padOp.getResultType().getElementType());
}
Value expandedValue =
expandValue(rewriter, padOp.getLoc(), newPadOp.getResult(), dest,
reassociationMap, options.rankReductionStrategy);
rewriter.replaceOp(padOp, expandedValue);
return success();
}
private:
ControlDropUnitDims options;
};
} // namespace
namespace {
/// Convert `extract_slice` operations to rank-reduced versions.
struct RankReducedExtractSliceOp
: public OpRewritePattern<tensor::ExtractSliceOp> {
using OpRewritePattern<tensor::ExtractSliceOp>::OpRewritePattern;
LogicalResult matchAndRewrite(tensor::ExtractSliceOp sliceOp,
PatternRewriter &rewriter) const override {
RankedTensorType resultType = sliceOp.getType();
SmallVector<OpFoldResult> targetShape;
for (auto size : resultType.getShape())
targetShape.push_back(rewriter.getIndexAttr(size));
auto reassociation = getReassociationMapForFoldingUnitDims(targetShape);
if (!reassociation ||
reassociation->size() == static_cast<size_t>(resultType.getRank()))
return failure();
SmallVector<OpFoldResult> offsets = sliceOp.getMixedOffsets();
SmallVector<OpFoldResult> strides = sliceOp.getMixedStrides();
SmallVector<OpFoldResult> sizes = sliceOp.getMixedSizes();
auto rankReducedType = cast<RankedTensorType>(
tensor::ExtractSliceOp::inferCanonicalRankReducedResultType(
reassociation->size(), sliceOp.getSourceType(), offsets, sizes,
strides));
Location loc = sliceOp.getLoc();
Value newSlice = rewriter.create<tensor::ExtractSliceOp>(
loc, rankReducedType, sliceOp.getSource(), offsets, sizes, strides);
rewriter.replaceOpWithNewOp<tensor::ExpandShapeOp>(
sliceOp, resultType, newSlice, *reassociation);
return success();
}
};
/// Convert `insert_slice` operations to rank-reduced versions.
/// This patterns works with both InsertSliceOp and ParallelInsertSliceOp.
template <typename InsertOpTy>
struct RankReducedInsertSliceOp : public OpRewritePattern<InsertOpTy> {
using OpRewritePattern<InsertOpTy>::OpRewritePattern;
LogicalResult matchAndRewrite(InsertOpTy insertSliceOp,
PatternRewriter &rewriter) const override {
RankedTensorType sourceType = insertSliceOp.getSourceType();
SmallVector<OpFoldResult> targetShape;
for (auto size : sourceType.getShape())
targetShape.push_back(rewriter.getIndexAttr(size));
auto reassociation = getReassociationMapForFoldingUnitDims(targetShape);
if (!reassociation ||
reassociation->size() == static_cast<size_t>(sourceType.getRank()))
return failure();
Location loc = insertSliceOp.getLoc();
tensor::CollapseShapeOp reshapedSource;
{
OpBuilder::InsertionGuard g(rewriter);
// The only difference between InsertSliceOp and ParallelInsertSliceOp
// is the insertion point is just before the ParallelCombiningOp in the
// parallel case.
if (std::is_same<InsertOpTy, tensor::ParallelInsertSliceOp>::value)
rewriter.setInsertionPoint(insertSliceOp->getParentOp());
reshapedSource = rewriter.create<tensor::CollapseShapeOp>(
loc, insertSliceOp.getSource(), *reassociation);
}
rewriter.replaceOpWithNewOp<InsertOpTy>(
insertSliceOp, reshapedSource, insertSliceOp.getDest(),
insertSliceOp.getMixedOffsets(), insertSliceOp.getMixedSizes(),
insertSliceOp.getMixedStrides());
return success();
}
};
} // namespace
/// Patterns that are used to canonicalize the use of unit-extent dims for
/// broadcasting.
static void
populateFoldUnitExtentDimsViaReshapesPatterns(RewritePatternSet &patterns,
ControlDropUnitDims &options) {
auto *context = patterns.getContext();
patterns.add<DropUnitDims>(context, options);
patterns.add<DropPadUnitDims>(context, options);
// TODO: Patterns unrelated to unit dim folding should be factored out.
patterns.add<RankReducedExtractSliceOp,
RankReducedInsertSliceOp<tensor::InsertSliceOp>,
RankReducedInsertSliceOp<tensor::ParallelInsertSliceOp>>(
context);
linalg::FillOp::getCanonicalizationPatterns(patterns, context);
tensor::CollapseShapeOp::getCanonicalizationPatterns(patterns, context);
tensor::EmptyOp::getCanonicalizationPatterns(patterns, context);
tensor::ExpandShapeOp::getCanonicalizationPatterns(patterns, context);
tensor::populateFoldTensorEmptyPatterns(patterns);
memref::populateResolveRankedShapedTypeResultDimsPatterns(patterns);
memref::populateResolveShapedTypeResultDimsPatterns(patterns);
}
static void
populateFoldUnitExtentDimsViaSlicesPatterns(RewritePatternSet &patterns,
ControlDropUnitDims &options) {
auto *context = patterns.getContext();
options.rankReductionStrategy =
ControlDropUnitDims::RankReductionStrategy::ExtractInsertSlice;
patterns.add<DropUnitDims>(context, options);
patterns.add<DropPadUnitDims>(context, options);
// TODO: Patterns unrelated to unit dim folding should be factored out.
linalg::FillOp::getCanonicalizationPatterns(patterns, context);
tensor::EmptyOp::getCanonicalizationPatterns(patterns, context);
tensor::populateFoldTensorEmptyPatterns(patterns);
memref::populateResolveRankedShapedTypeResultDimsPatterns(patterns);
memref::populateResolveShapedTypeResultDimsPatterns(patterns);
}
void mlir::linalg::populateFoldUnitExtentDimsPatterns(
RewritePatternSet &patterns, linalg::ControlDropUnitDims &options) {
if (options.rankReductionStrategy ==
linalg::ControlDropUnitDims::RankReductionStrategy::ExtractInsertSlice) {
populateFoldUnitExtentDimsViaSlicesPatterns(patterns, options);
} else if (options.rankReductionStrategy ==
linalg::ControlDropUnitDims::RankReductionStrategy::
ReassociativeReshape) {
populateFoldUnitExtentDimsViaReshapesPatterns(patterns, options);
}
}
void mlir::linalg::populateMoveInitOperandsToInputPattern(
RewritePatternSet &patterns) {
patterns.add<MoveInitOperandsToInput>(patterns.getContext());
}
namespace {
/// Pass that removes unit-extent dims within generic ops.
struct LinalgFoldUnitExtentDimsPass
: public impl::LinalgFoldUnitExtentDimsPassBase<
LinalgFoldUnitExtentDimsPass> {
using impl::LinalgFoldUnitExtentDimsPassBase<
LinalgFoldUnitExtentDimsPass>::LinalgFoldUnitExtentDimsPassBase;
void runOnOperation() override {
Operation *op = getOperation();
MLIRContext *context = op->getContext();
RewritePatternSet patterns(context);
ControlDropUnitDims options;
if (useRankReducingSlices) {
options.rankReductionStrategy = linalg::ControlDropUnitDims::
RankReductionStrategy::ExtractInsertSlice;
}
linalg::populateFoldUnitExtentDimsPatterns(patterns, options);
populateMoveInitOperandsToInputPattern(patterns);
(void)applyPatternsAndFoldGreedily(op, std::move(patterns));
}
};
} // namespace