tensorflow/compiler/mlir/tools/kernel_gen/transforms/rewrite_tf_framework_assert.cc

/* Copyright 2021 The TensorFlow Authors. All Rights Reserved.

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/ControlFlow/IR/ControlFlowOps.h"  // from @llvm-project
#include "mlir/Dialect/Func/IR/FuncOps.h"  // from @llvm-project
#include "mlir/Transforms/DialectConversion.h"  // from @llvm-project
#include "tensorflow/compiler/mlir/tools/kernel_gen/ir/tf_framework_ops.h"
#include "tensorflow/compiler/mlir/tools/kernel_gen/transforms/passes.h"
#include "tensorflow/compiler/mlir/tools/kernel_gen/transforms/rewriters.h"

namespace mlir {
namespace kernel_gen {
namespace tf_framework {
namespace {

// Converts tf_framework.assert to a conditional branch that reports an error to
// OpKernelContext and creates a fake memref using NullMemRefOp.
class TFAssertOpConverter : public OpConversionPattern<TFAssertOp> {
 public:
  using OpConversionPattern<TFAssertOp>::OpConversionPattern;

  LogicalResult matchAndRewrite(
      TFAssertOp op, OpAdaptor adaptor,
      ConversionPatternRewriter &rewriter) const override {
    Location loc = op.getLoc();

    // Split the block to insert CondBr.
    OpBuilder::InsertPoint ip = rewriter.saveInsertionPoint();
    Block *split_block = rewriter.splitBlock(
        rewriter.getInsertionBlock(), std::next(rewriter.getInsertionPoint()));

    auto func = op->getParentOfType<func::FuncOp>();
    Block *error_reporting_block =
        rewriter.createBlock(&func.getRegion(), {}, {});
    rewriter.create<ReportErrorOp>(loc, adaptor.ctx(), adaptor.error_code(),
                                   adaptor.msg());

    SmallVector<Value, 2> null_memrefs;
    for (auto type : func.getFunctionType().getResults()) {
      null_memrefs.push_back(rewriter.create<NullMemRefOp>(loc, type));
    }
    rewriter.create<func::ReturnOp>(loc, null_memrefs);

    rewriter.restoreInsertionPoint(ip);
    rewriter.replaceOpWithNewOp<cf::CondBranchOp>(
        op, adaptor.arg(), split_block, llvm::None, error_reporting_block,
        llvm::None);
    return success();
  }
};

#define GEN_PASS_CLASSES
#include "tensorflow/compiler/mlir/tools/kernel_gen/transforms/kernel_gen_passes.h.inc"

bool IsNotInsideTfEntryFunction(Operation *op) {
  auto func = op->getParentOfType<func::FuncOp>();
  return !func->hasAttrOfType<UnitAttr>(TFFrameworkDialect::kTFEntryAttrName);
}
// All contained `tf_framework.assert` operations are rewritten into calls to
// `tf_framework.report_error` and the required control flow to make
// execution of the function terminate.
class RewriteTFFrameworkAssertPass
    : public RewriteTFFrameworkAssertBase<RewriteTFFrameworkAssertPass> {
  void getDependentDialects(DialectRegistry &registry) const override {
    registry.insert<mlir::kernel_gen::tf_framework::TFFrameworkDialect>();
  }

 public:
  void runOnOperation() override {
    ModuleOp m = getOperation();

    // Populate patterns.
    MLIRContext *context = &getContext();
    RewritePatternSet patterns(context);
    patterns.add<TFAssertOpConverter>(context);
    PopulateEmbedTFFrameworkAssertPattern(&patterns);

    // Set target.
    ConversionTarget target(getContext());
    target.addLegalDialect<tf_framework::TFFrameworkDialect, func::FuncDialect,
                           cf::ControlFlowDialect>();
    target.addIllegalOp<TFAssertOp>();
    target.addDynamicallyLegalOp<cf::AssertOp>(IsNotInsideTfEntryFunction);

    if (failed(applyPartialConversion(m, target, std::move(patterns)))) {
      signalPassFailure();
    }
  }
};

}  // namespace

std::unique_ptr<OperationPass<ModuleOp> > CreateRewriteTFFrameworkAssert() {
  return std::make_unique<RewriteTFFrameworkAssertPass>();
}

}  // namespace tf_framework
}  // namespace kernel_gen
}  // namespace mlir