source/fuzz/transformation_replace_copy_object_with_store_load.cpp

// Copyright (c) 2020 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.

#include "source/fuzz/transformation_replace_copy_object_with_store_load.h"

#include "source/fuzz/fuzzer_util.h"
#include "source/fuzz/instruction_descriptor.h"

namespace spvtools {
namespace fuzz {

TransformationReplaceCopyObjectWithStoreLoad::
    TransformationReplaceCopyObjectWithStoreLoad(
        protobufs::TransformationReplaceCopyObjectWithStoreLoad message)
    : message_(std::move(message)) {}

TransformationReplaceCopyObjectWithStoreLoad::
    TransformationReplaceCopyObjectWithStoreLoad(
        uint32_t copy_object_result_id, uint32_t fresh_variable_id,
        uint32_t variable_storage_class, uint32_t variable_initializer_id) {
  message_.set_copy_object_result_id(copy_object_result_id);
  message_.set_fresh_variable_id(fresh_variable_id);
  message_.set_variable_storage_class(variable_storage_class);
  message_.set_variable_initializer_id(variable_initializer_id);
}

bool TransformationReplaceCopyObjectWithStoreLoad::IsApplicable(
    opt::IRContext* ir_context, const TransformationContext& /*unused*/) const {
  // |message_.fresh_variable_id| must be fresh.
  if (!fuzzerutil::IsFreshId(ir_context, message_.fresh_variable_id())) {
    return false;
  }
  auto copy_object_instruction =
      ir_context->get_def_use_mgr()->GetDef(message_.copy_object_result_id());

  // This must be a defined OpCopyObject instruction.
  if (!copy_object_instruction ||
      copy_object_instruction->opcode() != spv::Op::OpCopyObject) {
    return false;
  }

  // The opcode of the type_id instruction cannot be a OpTypePointer,
  // because we cannot define a pointer to pointer.
  if (ir_context->get_def_use_mgr()
          ->GetDef(copy_object_instruction->type_id())
          ->opcode() == spv::Op::OpTypePointer) {
    return false;
  }

  // A pointer type instruction pointing to the value type must be defined.
  auto pointer_type_id = fuzzerutil::MaybeGetPointerType(
      ir_context, copy_object_instruction->type_id(),
      static_cast<spv::StorageClass>(message_.variable_storage_class()));
  if (!pointer_type_id) {
    return false;
  }

  // Check that initializer is valid.
  const auto* constant_inst =
      ir_context->get_def_use_mgr()->GetDef(message_.variable_initializer_id());
  if (!constant_inst || !spvOpcodeIsConstant(constant_inst->opcode()) ||
      copy_object_instruction->type_id() != constant_inst->type_id()) {
    return false;
  }
  // |message_.variable_storage_class| must be Private or Function.
  return spv::StorageClass(message_.variable_storage_class()) ==
             spv::StorageClass::Private ||
         spv::StorageClass(message_.variable_storage_class()) ==
             spv::StorageClass::Function;
}

void TransformationReplaceCopyObjectWithStoreLoad::Apply(
    opt::IRContext* ir_context,
    TransformationContext* transformation_context) const {
  auto copy_object_instruction =
      ir_context->get_def_use_mgr()->GetDef(message_.copy_object_result_id());
  // |copy_object_instruction| must be defined.
  assert(copy_object_instruction &&
         copy_object_instruction->opcode() == spv::Op::OpCopyObject &&
         "The required OpCopyObject instruction must be defined.");

  opt::BasicBlock* enclosing_block =
      ir_context->get_instr_block(copy_object_instruction);

  // Get id used as a source by the OpCopyObject instruction.
  uint32_t src_operand = copy_object_instruction->GetSingleWordInOperand(0);
  // A pointer type instruction pointing to the value type must be defined.
  auto pointer_type_id = fuzzerutil::MaybeGetPointerType(
      ir_context, copy_object_instruction->type_id(),
      static_cast<spv::StorageClass>(message_.variable_storage_class()));
  assert(pointer_type_id && "The required pointer type must be available.");

  // Adds a global or local variable (according to the storage class).
  if (spv::StorageClass(message_.variable_storage_class()) ==
      spv::StorageClass::Private) {
    opt::Instruction* new_global = fuzzerutil::AddGlobalVariable(
        ir_context, message_.fresh_variable_id(), pointer_type_id,
        spv::StorageClass::Private, message_.variable_initializer_id());
    ir_context->get_def_use_mgr()->AnalyzeInstDefUse(new_global);
  } else {
    opt::Function* function =
        ir_context->get_instr_block(copy_object_instruction)->GetParent();
    opt::Instruction* new_local = fuzzerutil::AddLocalVariable(
        ir_context, message_.fresh_variable_id(), pointer_type_id,
        function->result_id(), message_.variable_initializer_id());
    ir_context->get_def_use_mgr()->AnalyzeInstDefUse(new_local);
    ir_context->set_instr_block(new_local, &*function->begin());
  }

  // First, insert the OpLoad instruction before the OpCopyObject instruction
  // and then insert the OpStore instruction before the OpLoad instruction.
  fuzzerutil::UpdateModuleIdBound(ir_context, message_.fresh_variable_id());
  opt::Instruction* load_instruction =
      copy_object_instruction->InsertBefore(MakeUnique<opt::Instruction>(
          ir_context, spv::Op::OpLoad, copy_object_instruction->type_id(),
          message_.copy_object_result_id(),
          opt::Instruction::OperandList(
              {{SPV_OPERAND_TYPE_ID, {message_.fresh_variable_id()}}})));
  opt::Instruction* store_instruction =
      load_instruction->InsertBefore(MakeUnique<opt::Instruction>(
          ir_context, spv::Op::OpStore, 0, 0,
          opt::Instruction::OperandList(
              {{SPV_OPERAND_TYPE_ID, {message_.fresh_variable_id()}},
               {SPV_OPERAND_TYPE_ID, {src_operand}}})));

  // Register the new instructions with the def-use manager, and record their
  // enclosing block.
  ir_context->get_def_use_mgr()->AnalyzeInstDefUse(store_instruction);
  ir_context->get_def_use_mgr()->AnalyzeInstDefUse(load_instruction);
  ir_context->set_instr_block(store_instruction, enclosing_block);
  ir_context->set_instr_block(load_instruction, enclosing_block);

  // Remove the CopyObject instruction.
  ir_context->KillInst(copy_object_instruction);

  if (!transformation_context->GetFactManager()->IdIsIrrelevant(
          message_.copy_object_result_id()) &&
      !transformation_context->GetFactManager()->IdIsIrrelevant(src_operand)) {
    // Adds the fact that |message_.copy_object_result_id|
    // and src_operand (id used by OpCopyObject) are synonymous.
    transformation_context->GetFactManager()->AddFactDataSynonym(
        MakeDataDescriptor(message_.copy_object_result_id(), {}),
        MakeDataDescriptor(src_operand, {}));
  }
}

protobufs::Transformation
TransformationReplaceCopyObjectWithStoreLoad::ToMessage() const {
  protobufs::Transformation result;
  *result.mutable_replace_copy_object_with_store_load() = message_;
  return result;
}

std::unordered_set<uint32_t>
TransformationReplaceCopyObjectWithStoreLoad::GetFreshIds() const {
  return {message_.fresh_variable_id()};
}

}  // namespace fuzz
}  // namespace spvtools