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//===- LowerVectorMask.cpp - Lower 'vector.mask' operation ----------------===//
//
// 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 target-independent rewrites and utilities to lower the
// 'vector.mask' operation.
//
//===----------------------------------------------------------------------===//
#include "mlir/Dialect/Arith/IR/Arith.h"
#include "mlir/Dialect/Func/IR/FuncOps.h"
#include "mlir/Dialect/Vector/IR/VectorOps.h"
#include "mlir/Dialect/Vector/Transforms/LoweringPatterns.h"
#include "mlir/Dialect/Vector/Transforms/Passes.h"
#include "mlir/IR/PatternMatch.h"
#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
#define DEBUG_TYPE "lower-vector-mask"
namespace mlir {
namespace vector {
#define GEN_PASS_DEF_LOWERVECTORMASKPASS
#include "mlir/Dialect/Vector/Transforms/Passes.h.inc"
} // namespace vector
} // namespace mlir
using namespace mlir;
using namespace mlir::vector;
//===----------------------------------------------------------------------===//
// populateVectorMaskOpLoweringPatterns
//===----------------------------------------------------------------------===//
namespace {
/// Progressive lowering of CreateMaskOp.
/// One:
/// %x = vector.create_mask %a, ... : vector<dx...>
/// is replaced by:
/// %l = vector.create_mask ... : vector<...> ; one lower rank
/// %0 = arith.cmpi "slt", %ci, %a |
/// %1 = select %0, %l, %zeroes |
/// %r = vector.insert %1, %pr [i] | d-times
/// %x = ....
/// until a one-dimensional vector is reached.
class CreateMaskOpLowering : public OpRewritePattern<vector::CreateMaskOp> {
public:
using OpRewritePattern::OpRewritePattern;
LogicalResult matchAndRewrite(vector::CreateMaskOp op,
PatternRewriter &rewriter) const override {
auto dstType = cast<VectorType>(op.getResult().getType());
int64_t rank = dstType.getRank();
if (rank <= 1)
return rewriter.notifyMatchFailure(
op, "0-D and 1-D vectors are handled separately");
if (dstType.getScalableDims().front())
return rewriter.notifyMatchFailure(
op, "Cannot unroll leading scalable dim in dstType");
auto loc = op.getLoc();
int64_t dim = dstType.getDimSize(0);
Value idx = op.getOperand(0);
VectorType lowType = VectorType::Builder(dstType).dropDim(0);
Value trueVal = rewriter.create<vector::CreateMaskOp>(
loc, lowType, op.getOperands().drop_front());
Value falseVal = rewriter.create<arith::ConstantOp>(
loc, lowType, rewriter.getZeroAttr(lowType));
Value result = rewriter.create<arith::ConstantOp>(
loc, dstType, rewriter.getZeroAttr(dstType));
for (int64_t d = 0; d < dim; d++) {
Value bnd =
rewriter.create<arith::ConstantOp>(loc, rewriter.getIndexAttr(d));
Value val = rewriter.create<arith::CmpIOp>(loc, arith::CmpIPredicate::slt,
bnd, idx);
Value sel = rewriter.create<arith::SelectOp>(loc, val, trueVal, falseVal);
result = rewriter.create<vector::InsertOp>(loc, sel, result, d);
}
rewriter.replaceOp(op, result);
return success();
}
};
/// Progressive lowering of ConstantMaskOp.
/// One:
/// %x = vector.constant_mask [a,b]
/// is replaced by:
/// %z = zero-result
/// %l = vector.constant_mask [b]
/// %4 = vector.insert %l, %z[0]
/// ..
/// %x = vector.insert %l, %..[a-1]
/// until a one-dimensional vector is reached. All these operations
/// will be folded at LLVM IR level.
class ConstantMaskOpLowering : public OpRewritePattern<vector::ConstantMaskOp> {
public:
using OpRewritePattern::OpRewritePattern;
LogicalResult matchAndRewrite(vector::ConstantMaskOp op,
PatternRewriter &rewriter) const override {
auto loc = op.getLoc();
auto dstType = op.getType();
auto dimSizes = op.getMaskDimSizes();
int64_t rank = dstType.getRank();
if (rank == 0) {
assert(dimSizes.size() == 1 &&
"Expected exactly one dim size for a 0-D vector");
bool value = dimSizes.front() == 1;
rewriter.replaceOpWithNewOp<arith::ConstantOp>(
op, dstType,
DenseIntElementsAttr::get(VectorType::get({}, rewriter.getI1Type()),
value));
return success();
}
int64_t trueDimSize = dimSizes.front();
if (rank == 1) {
if (trueDimSize == 0 || trueDimSize == dstType.getDimSize(0)) {
// Use constant splat for 'all set' or 'none set' dims.
// This produces correct code for scalable dimensions (it will lower to
// a constant splat).
rewriter.replaceOpWithNewOp<arith::ConstantOp>(
op, DenseElementsAttr::get(dstType, trueDimSize != 0));
} else {
// Express constant 1-D case in explicit vector form:
// [T,..,T,F,..,F].
// Note: The verifier would reject this case for scalable vectors.
SmallVector<bool> values(dstType.getDimSize(0), false);
for (int64_t d = 0; d < trueDimSize; d++)
values[d] = true;
rewriter.replaceOpWithNewOp<arith::ConstantOp>(
op, dstType, rewriter.getBoolVectorAttr(values));
}
return success();
}
if (dstType.getScalableDims().front())
return rewriter.notifyMatchFailure(
op, "Cannot unroll leading scalable dim in dstType");
VectorType lowType = VectorType::Builder(dstType).dropDim(0);
Value trueVal = rewriter.create<vector::ConstantMaskOp>(
loc, lowType, dimSizes.drop_front());
Value result = rewriter.create<arith::ConstantOp>(
loc, dstType, rewriter.getZeroAttr(dstType));
for (int64_t d = 0; d < trueDimSize; d++)
result = rewriter.create<vector::InsertOp>(loc, trueVal, result, d);
rewriter.replaceOp(op, result);
return success();
}
};
} // namespace
void mlir::vector::populateVectorMaskOpLoweringPatterns(
RewritePatternSet &patterns, PatternBenefit benefit) {
patterns.add<CreateMaskOpLowering, ConstantMaskOpLowering>(
patterns.getContext(), benefit);
}
//===----------------------------------------------------------------------===//
// populateVectorMaskLoweringPatternsForSideEffectingOps
//===----------------------------------------------------------------------===//
namespace {
/// The `MaskOpRewritePattern` implements a pattern that follows a two-fold
/// matching:
/// 1. It matches a `vector.mask` operation.
/// 2. It invokes `matchAndRewriteMaskableOp` on `MaskableOpInterface` nested
/// in the matched `vector.mask` operation.
///
/// It is required that the replacement op in the pattern replaces the
/// `vector.mask` operation and not the nested `MaskableOpInterface`. This
/// approach allows having patterns that "stop" at every `vector.mask` operation
/// and actually match the traits of its the nested `MaskableOpInterface`.
template <class SourceOp>
struct MaskOpRewritePattern : OpRewritePattern<MaskOp> {
using OpRewritePattern<MaskOp>::OpRewritePattern;
private:
LogicalResult matchAndRewrite(MaskOp maskOp,
PatternRewriter &rewriter) const final {
auto maskableOp = cast_or_null<MaskableOpInterface>(maskOp.getMaskableOp());
if (!maskableOp)
return failure();
SourceOp sourceOp = dyn_cast<SourceOp>(maskableOp.getOperation());
if (!sourceOp)
return failure();
return matchAndRewriteMaskableOp(sourceOp, maskOp, rewriter);
}
protected:
virtual LogicalResult
matchAndRewriteMaskableOp(SourceOp sourceOp, MaskingOpInterface maskingOp,
PatternRewriter &rewriter) const = 0;
};
/// Lowers a masked `vector.transfer_read` operation.
struct MaskedTransferReadOpPattern
: public MaskOpRewritePattern<TransferReadOp> {
public:
using MaskOpRewritePattern<TransferReadOp>::MaskOpRewritePattern;
LogicalResult
matchAndRewriteMaskableOp(TransferReadOp readOp, MaskingOpInterface maskingOp,
PatternRewriter &rewriter) const override {
// TODO: The 'vector.mask' passthru is a vector and 'vector.transfer_read'
// expects a scalar. We could only lower one to the other for cases where
// the passthru is a broadcast of a scalar.
if (maskingOp.hasPassthru())
return rewriter.notifyMatchFailure(
maskingOp, "Can't lower passthru to vector.transfer_read");
// Replace the `vector.mask` operation.
rewriter.replaceOpWithNewOp<TransferReadOp>(
maskingOp.getOperation(), readOp.getVectorType(), readOp.getSource(),
readOp.getIndices(), readOp.getPermutationMap(), readOp.getPadding(),
maskingOp.getMask(), readOp.getInBounds());
return success();
}
};
/// Lowers a masked `vector.transfer_write` operation.
struct MaskedTransferWriteOpPattern
: public MaskOpRewritePattern<TransferWriteOp> {
public:
using MaskOpRewritePattern<TransferWriteOp>::MaskOpRewritePattern;
LogicalResult
matchAndRewriteMaskableOp(TransferWriteOp writeOp,
MaskingOpInterface maskingOp,
PatternRewriter &rewriter) const override {
Type resultType =
writeOp.getResult() ? writeOp.getResult().getType() : Type();
// Replace the `vector.mask` operation.
rewriter.replaceOpWithNewOp<TransferWriteOp>(
maskingOp.getOperation(), resultType, writeOp.getVector(),
writeOp.getSource(), writeOp.getIndices(), writeOp.getPermutationMap(),
maskingOp.getMask(), writeOp.getInBounds());
return success();
}
};
/// Lowers a masked `vector.gather` operation.
struct MaskedGatherOpPattern : public MaskOpRewritePattern<GatherOp> {
public:
using MaskOpRewritePattern<GatherOp>::MaskOpRewritePattern;
LogicalResult
matchAndRewriteMaskableOp(GatherOp gatherOp, MaskingOpInterface maskingOp,
PatternRewriter &rewriter) const override {
Value passthru = maskingOp.hasPassthru()
? maskingOp.getPassthru()
: rewriter.create<arith::ConstantOp>(
gatherOp.getLoc(),
rewriter.getZeroAttr(gatherOp.getVectorType()));
// Replace the `vector.mask` operation.
rewriter.replaceOpWithNewOp<GatherOp>(
maskingOp.getOperation(), gatherOp.getVectorType(), gatherOp.getBase(),
gatherOp.getIndices(), gatherOp.getIndexVec(), maskingOp.getMask(),
passthru);
return success();
}
};
struct LowerVectorMaskPass
: public vector::impl::LowerVectorMaskPassBase<LowerVectorMaskPass> {
using Base::Base;
void runOnOperation() override {
Operation *op = getOperation();
MLIRContext *context = op->getContext();
RewritePatternSet loweringPatterns(context);
populateVectorMaskLoweringPatternsForSideEffectingOps(loweringPatterns);
MaskOp::getCanonicalizationPatterns(loweringPatterns, context);
if (failed(applyPatternsGreedily(op, std::move(loweringPatterns))))
signalPassFailure();
}
void getDependentDialects(DialectRegistry &registry) const override {
registry.insert<vector::VectorDialect>();
}
};
} // namespace
/// Populates instances of `MaskOpRewritePattern` to lower masked operations
/// with `vector.mask`. Patterns should rewrite the `vector.mask` operation and
/// not its nested `MaskableOpInterface`.
void vector::populateVectorMaskLoweringPatternsForSideEffectingOps(
RewritePatternSet &patterns) {
patterns.add<MaskedTransferReadOpPattern, MaskedTransferWriteOpPattern,
MaskedGatherOpPattern>(patterns.getContext());
}
std::unique_ptr<Pass> mlir::vector::createLowerVectorMaskPass() {
return std::make_unique<LowerVectorMaskPass>();
}