source/fuzz/transformation_add_dead_break.h

// Copyright (c) 2019 Google LLC
//
// 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.

#ifndef SOURCE_FUZZ_TRANSFORMATION_ADD_DEAD_BREAK_H_
#define SOURCE_FUZZ_TRANSFORMATION_ADD_DEAD_BREAK_H_

#include <vector>

#include "source/fuzz/fact_manager.h"
#include "source/fuzz/protobufs/spirvfuzz_protobufs.h"
#include "source/fuzz/transformation.h"
#include "source/opt/ir_context.h"

namespace spvtools {
namespace fuzz {

class TransformationAddDeadBreak : public Transformation {
 public:
  explicit TransformationAddDeadBreak(
      const protobufs::TransformationAddDeadBreak& message);

  TransformationAddDeadBreak(uint32_t from_block, uint32_t to_block,
                             bool break_condition_value,
                             std::vector<uint32_t> phi_id);

  // - |message_.from_block| must be the id of a block a in the given module.
  // - |message_.to_block| must be the id of a block b in the given module.
  // - if |message_.break_condition_value| holds (does not hold) then
  //   OpConstantTrue (OpConstantFalse) must be present in the module
  // - |message_.phi_ids| must be a list of ids that are all available at
  //   |message_.from_block|
  // - a and b must be in the same function.
  // - b must be a merge block.
  // - a must end with an unconditional branch to some block c.
  // - replacing this branch with a conditional branch to b or c, with
  //   the boolean constant associated with |message_.break_condition_value| as
  //   the condition, and the ids in |message_.phi_ids| used to extend
  //   any OpPhi instructions at b as a result of the edge from a, must
  //   maintain validity of the module.
  //   In particular, the new branch must not lead to violations of the rule
  //   that a use must be dominated by its definition.
  bool IsApplicable(opt::IRContext* context,
                    const FactManager& fact_manager) const override;

  // Replaces the terminator of a with a conditional branch to b or c.
  // The boolean constant associated with |message_.break_condition_value| is
  // used as the condition, and the order of b and c is arranged such that
  // control is guaranteed to jump to c.
  void Apply(opt::IRContext* context, FactManager* fact_manager) const override;

  protobufs::Transformation ToMessage() const override;

 private:
  // Returns true if and only if adding an edge from |bb_from| to
  // |message_.to_block| respects structured control flow.
  bool AddingBreakRespectsStructuredControlFlow(opt::IRContext* context,
                                                opt::BasicBlock* bb_from) const;

  // Used by 'Apply' to actually apply the transformation to the module of
  // interest, and by 'IsApplicable' to do a dry-run of the transformation on a
  // cloned module, in order to check that the transformation leads to a valid
  // module.  This is only invoked by 'IsApplicable' after certain basic
  // applicability checks have been made, ensuring that the invocation of this
  // method is legal.
  void ApplyImpl(opt::IRContext* context) const;

  protobufs::TransformationAddDeadBreak message_;
};

}  // namespace fuzz
}  // namespace spvtools

#endif  // SOURCE_FUZZ_TRANSFORMATION_ADD_DEAD_BREAK_H_