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//===- ConvertConst.cpp - Quantizes constant ops --------------------------===//
//
// Copyright 2019 The MLIR Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// =============================================================================
#include "mlir/Dialect/QuantOps/Passes.h"
#include "mlir/Dialect/QuantOps/QuantOps.h"
#include "mlir/Dialect/QuantOps/QuantizeUtils.h"
#include "mlir/Dialect/QuantOps/UniformSupport.h"
#include "mlir/IR/Attributes.h"
#include "mlir/IR/Matchers.h"
#include "mlir/IR/PatternMatch.h"
#include "mlir/IR/StandardTypes.h"
#include "mlir/Pass/Pass.h"
#include "mlir/StandardOps/Ops.h"
using namespace mlir;
using namespace mlir::quant;
namespace {
class ConvertConstPass : public FunctionPass<ConvertConstPass> {
public:
void runOnFunction() override;
};
class QuantizedConstRewrite : public RewritePattern {
public:
struct State : PatternState {
QuantizedType quantizedElementType;
Attribute value;
};
QuantizedConstRewrite(MLIRContext *context)
: RewritePattern(QuantizeCastOp::getOperationName(), 1, context) {}
PatternMatchResult match(Operation *op) const override;
void rewrite(Operation *op, std::unique_ptr<PatternState> baseState,
PatternRewriter &rewriter) const override;
};
} // end anonymous namespace
/// Matches a [constant] -> [qbarrier] where the qbarrier results type is
/// quantized and the operand type is quantizable.
PatternMatchResult QuantizedConstRewrite::match(Operation *op) const {
State state;
// Is the operand a constant?
auto qbarrier = cast<QuantizeCastOp>(op);
if (!matchPattern(qbarrier.arg(), m_Constant(&state.value))) {
return matchFailure();
}
// 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();
state.quantizedElementType =
QuantizedType::getQuantizedElementType(qbarrierResultType);
if (!state.quantizedElementType) {
return matchFailure();
}
if (!QuantizedType::castToStorageType(qbarrierResultType)) {
return matchFailure();
}
// 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 (!state.quantizedElementType.isCompatibleExpressedType(
qbarrier.arg()->getType())) {
return matchFailure();
}
// Is the constant value a type expressed in a way that we support?
if (!state.value.isa<FloatAttr>() && !state.value.isa<SplatElementsAttr>() &&
!state.value.isa<DenseElementsAttr>() &&
!state.value.isa<SparseElementsAttr>()) {
return matchFailure();
}
return matchSuccess(llvm::make_unique<State>(std::move(state)));
}
void QuantizedConstRewrite::rewrite(Operation *op,
std::unique_ptr<PatternState> baseState,
PatternRewriter &rewriter) const {
auto state = static_cast<State *>(baseState.get());
Type newConstValueType;
Attribute newConstValue = quantizeAttr(
state->value, state->quantizedElementType, newConstValueType);
if (!newConstValue) {
return;
}
auto *origConstOp = op->getOperand(0);
// 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 =
FusedLoc::get({origConstOp->getDefiningOp()->getLoc(), op->getLoc()},
rewriter.getContext());
auto newConstOp =
rewriter.create<ConstantOp>(fusedLoc, newConstValueType, newConstValue);
rewriter.replaceOpWithNewOp<StorageCastOp>(
{origConstOp}, op, *op->result_type_begin(), newConstOp);
}
void ConvertConstPass::runOnFunction() {
OwningRewritePatternList patterns;
auto &func = getFunction();
auto *context = &getContext();
patterns.push_back(llvm::make_unique<QuantizedConstRewrite>(context));
applyPatternsGreedily(func, std::move(patterns));
}
FunctionPassBase *mlir::quant::createConvertConstPass() {
return new ConvertConstPass();
}
static PassRegistration<ConvertConstPass>
pass("quant-convert-const",
"Converts constants followed by qbarrier to actual quantized values");
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