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// Copyright (c) 2020 Vasyl Teliman
//
// 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_swap_conditional_branch_operands.h"
#include "source/fuzz/fuzzer_util.h"
#include "source/fuzz/instruction_descriptor.h"
namespace spvtools {
namespace fuzz {
TransformationSwapConditionalBranchOperands::
TransformationSwapConditionalBranchOperands(
protobufs::TransformationSwapConditionalBranchOperands message)
: message_(std::move(message)) {}
TransformationSwapConditionalBranchOperands::
TransformationSwapConditionalBranchOperands(
const protobufs::InstructionDescriptor& instruction_descriptor,
uint32_t fresh_id) {
*message_.mutable_instruction_descriptor() = instruction_descriptor;
message_.set_fresh_id(fresh_id);
}
bool TransformationSwapConditionalBranchOperands::IsApplicable(
opt::IRContext* ir_context, const TransformationContext& /*unused*/) const {
const auto* inst =
FindInstruction(message_.instruction_descriptor(), ir_context);
return fuzzerutil::IsFreshId(ir_context, message_.fresh_id()) && inst &&
inst->opcode() == spv::Op::OpBranchConditional;
}
void TransformationSwapConditionalBranchOperands::Apply(
opt::IRContext* ir_context, TransformationContext* /*unused*/) const {
auto* branch_inst =
FindInstruction(message_.instruction_descriptor(), ir_context);
assert(branch_inst);
auto* block = ir_context->get_instr_block(branch_inst);
assert(block);
// Compute the last instruction in the |block| that allows us to insert
// OpLogicalNot above it.
auto iter = fuzzerutil::GetIteratorForInstruction(block, branch_inst);
if (!fuzzerutil::CanInsertOpcodeBeforeInstruction(spv::Op::OpLogicalNot,
iter)) {
// There might be a merge instruction before OpBranchConditional.
--iter;
}
assert(fuzzerutil::CanInsertOpcodeBeforeInstruction(spv::Op::OpLogicalNot,
iter) &&
"We should now be able to insert spv::Op::OpLogicalNot before |iter|");
// Get the instruction whose result is used as a condition for
// OpBranchConditional.
const auto* condition_inst = ir_context->get_def_use_mgr()->GetDef(
branch_inst->GetSingleWordInOperand(0));
assert(condition_inst);
// We are swapping the labels in OpBranchConditional. This means that we must
// invert the guard as well. We are using OpLogicalNot for that purpose here.
auto new_instruction = MakeUnique<opt::Instruction>(
ir_context, spv::Op::OpLogicalNot, condition_inst->type_id(),
message_.fresh_id(),
opt::Instruction::OperandList{
{SPV_OPERAND_TYPE_ID, {condition_inst->result_id()}}});
auto new_instruction_ptr = new_instruction.get();
iter.InsertBefore(std::move(new_instruction));
fuzzerutil::UpdateModuleIdBound(ir_context, message_.fresh_id());
// Update OpBranchConditional condition operand.
branch_inst->GetInOperand(0).words[0] = message_.fresh_id();
// Swap label operands.
std::swap(branch_inst->GetInOperand(1), branch_inst->GetInOperand(2));
// Additionally, swap branch weights if present.
if (branch_inst->NumInOperands() > 3) {
std::swap(branch_inst->GetInOperand(3), branch_inst->GetInOperand(4));
}
ir_context->get_def_use_mgr()->AnalyzeInstDefUse(new_instruction_ptr);
ir_context->set_instr_block(new_instruction_ptr, block);
ir_context->get_def_use_mgr()->EraseUseRecordsOfOperandIds(branch_inst);
ir_context->get_def_use_mgr()->AnalyzeInstUse(branch_inst);
// No analyses need to be invalidated since the transformation is local to a
// block and the def-use and instruction-to-block mappings have been updated.
}
protobufs::Transformation
TransformationSwapConditionalBranchOperands::ToMessage() const {
protobufs::Transformation result;
*result.mutable_swap_conditional_branch_operands() = message_;
return result;
}
std::unordered_set<uint32_t>
TransformationSwapConditionalBranchOperands::GetFreshIds() const {
return {message_.fresh_id()};
}
} // namespace fuzz
} // namespace spvtools
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