llvm-project/mlir/lib/Dialect/Quant/Transforms/ConvertConst.cpp

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3.6 KiB
C++

//===- ConvertConst.cpp - Quantizes constant ops --------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "PassDetail.h"
#include "mlir/Dialect/Arithmetic/IR/Arithmetic.h"
#include "mlir/Dialect/Quant/Passes.h"
#include "mlir/Dialect/Quant/QuantOps.h"
#include "mlir/Dialect/Quant/QuantizeUtils.h"
#include "mlir/Dialect/Quant/UniformSupport.h"
#include "mlir/IR/BuiltinTypes.h"
#include "mlir/IR/Matchers.h"
#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
using namespace mlir;
using namespace mlir::quant;
namespace {
struct ConvertConstPass : public QuantConvertConstBase<ConvertConstPass> {
void runOnOperation() override;
};
struct QuantizedConstRewrite : public OpRewritePattern<QuantizeCastOp> {
using OpRewritePattern<QuantizeCastOp>::OpRewritePattern;
LogicalResult matchAndRewrite(QuantizeCastOp qbarrier,
PatternRewriter &rewriter) const override;
};
} // namespace
/// Matches a [constant] -> [qbarrier] where the qbarrier results type is
/// quantized and the operand type is quantizable.
LogicalResult
QuantizedConstRewrite::matchAndRewrite(QuantizeCastOp qbarrier,
PatternRewriter &rewriter) const {
Attribute value;
// Is the operand a constant?
if (!matchPattern(qbarrier.arg(), m_Constant(&value))) {
return failure();
}
// Does the qbarrier convert to a quantized type. This will not be true
// if a quantized type has not yet been chosen or if the cast to an equivalent
// storage type is not supported.
Type qbarrierResultType = qbarrier.getResult().getType();
QuantizedType quantizedElementType =
QuantizedType::getQuantizedElementType(qbarrierResultType);
if (!quantizedElementType) {
return failure();
}
if (!QuantizedType::castToStorageType(qbarrierResultType)) {
return failure();
}
// Is the operand type compatible with the expressed type of the quantized
// type? This will not be true if the qbarrier is superfluous (converts
// from and to a quantized type).
if (!quantizedElementType.isCompatibleExpressedType(
qbarrier.arg().getType())) {
return failure();
}
// Is the constant value a type expressed in a way that we support?
if (!value.isa<FloatAttr, DenseElementsAttr, SparseElementsAttr>()) {
return failure();
}
Type newConstValueType;
auto newConstValue =
quantizeAttr(value, quantizedElementType, newConstValueType);
if (!newConstValue) {
return failure();
}
// When creating the new const op, use a fused location that combines the
// original const and the qbarrier that led to the quantization.
auto fusedLoc = rewriter.getFusedLoc(
{qbarrier.arg().getDefiningOp()->getLoc(), qbarrier.getLoc()});
auto newConstOp = rewriter.create<arith::ConstantOp>(
fusedLoc, newConstValueType, newConstValue);
rewriter.replaceOpWithNewOp<StorageCastOp>(qbarrier, qbarrier.getType(),
newConstOp);
return success();
}
void ConvertConstPass::runOnOperation() {
RewritePatternSet patterns(&getContext());
auto func = getOperation();
auto *context = &getContext();
patterns.add<QuantizedConstRewrite>(context);
(void)applyPatternsAndFoldGreedily(func, std::move(patterns));
}
std::unique_ptr<OperationPass<func::FuncOp>>
mlir::quant::createConvertConstPass() {
return std::make_unique<ConvertConstPass>();
}