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// 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.
#include "source/fuzz/fuzzer_pass_outline_functions.h"
#include <vector>
#include "source/fuzz/fuzzer_util.h"
#include "source/fuzz/instruction_descriptor.h"
#include "source/fuzz/transformation_outline_function.h"
#include "source/fuzz/transformation_split_block.h"
namespace spvtools {
namespace fuzz {
FuzzerPassOutlineFunctions::FuzzerPassOutlineFunctions(
opt::IRContext* ir_context, TransformationContext* transformation_context,
FuzzerContext* fuzzer_context,
protobufs::TransformationSequence* transformations,
bool ignore_inapplicable_transformations)
: FuzzerPass(ir_context, transformation_context, fuzzer_context,
transformations, ignore_inapplicable_transformations) {}
void FuzzerPassOutlineFunctions::Apply() {
std::vector<opt::Function*> original_functions;
for (auto& function : *GetIRContext()->module()) {
original_functions.push_back(&function);
}
for (auto& function : original_functions) {
if (!GetFuzzerContext()->ChoosePercentage(
GetFuzzerContext()->GetChanceOfOutliningFunction())) {
continue;
}
std::vector<opt::BasicBlock*> blocks;
for (auto& block : *function) {
blocks.push_back(&block);
}
auto entry_block = MaybeGetEntryBlockSuitableForOutlining(
blocks[GetFuzzerContext()->RandomIndex(blocks)]);
if (!entry_block) {
// The chosen block is not suitable to be the entry block of a region that
// will be outlined.
continue;
}
auto dominator_analysis = GetIRContext()->GetDominatorAnalysis(function);
auto postdominator_analysis =
GetIRContext()->GetPostDominatorAnalysis(function);
std::vector<opt::BasicBlock*> candidate_exit_blocks;
for (auto postdominates_entry_block = entry_block;
postdominates_entry_block != nullptr;
postdominates_entry_block = postdominator_analysis->ImmediateDominator(
postdominates_entry_block)) {
// Consider the block if it is dominated by the entry block, ignore it if
// it is a continue target.
if (dominator_analysis->Dominates(entry_block,
postdominates_entry_block) &&
!GetIRContext()->GetStructuredCFGAnalysis()->IsContinueBlock(
postdominates_entry_block->id())) {
candidate_exit_blocks.push_back(postdominates_entry_block);
}
}
if (candidate_exit_blocks.empty()) {
continue;
}
auto exit_block = MaybeGetExitBlockSuitableForOutlining(
candidate_exit_blocks[GetFuzzerContext()->RandomIndex(
candidate_exit_blocks)]);
if (!exit_block) {
// The block chosen is not suitable
continue;
}
auto region_blocks = TransformationOutlineFunction::GetRegionBlocks(
GetIRContext(), entry_block, exit_block);
std::map<uint32_t, uint32_t> input_id_to_fresh_id;
for (auto id : TransformationOutlineFunction::GetRegionInputIds(
GetIRContext(), region_blocks, exit_block)) {
input_id_to_fresh_id[id] = GetFuzzerContext()->GetFreshId();
}
std::map<uint32_t, uint32_t> output_id_to_fresh_id;
for (auto id : TransformationOutlineFunction::GetRegionOutputIds(
GetIRContext(), region_blocks, exit_block)) {
output_id_to_fresh_id[id] = GetFuzzerContext()->GetFreshId();
}
TransformationOutlineFunction transformation(
entry_block->id(), exit_block->id(),
/*new_function_struct_return_type_id*/
GetFuzzerContext()->GetFreshId(),
/*new_function_type_id*/ GetFuzzerContext()->GetFreshId(),
/*new_function_id*/ GetFuzzerContext()->GetFreshId(),
/*new_function_region_entry_block*/
GetFuzzerContext()->GetFreshId(),
/*new_caller_result_id*/ GetFuzzerContext()->GetFreshId(),
/*new_callee_result_id*/ GetFuzzerContext()->GetFreshId(),
/*input_id_to_fresh_id*/ input_id_to_fresh_id,
/*output_id_to_fresh_id*/ output_id_to_fresh_id);
MaybeApplyTransformation(transformation);
}
}
opt::BasicBlock*
FuzzerPassOutlineFunctions::MaybeGetEntryBlockSuitableForOutlining(
opt::BasicBlock* entry_block) {
// If the entry block is a loop header, we need to get or create its
// preheader and make it the entry block, if possible.
if (entry_block->IsLoopHeader()) {
auto predecessors =
GetIRContext()->cfg()->preds(entry_block->GetLabel()->result_id());
if (predecessors.size() < 2) {
// The header only has one predecessor (the back-edge block) and thus
// it is unreachable. The block cannot be adjusted to be suitable for
// outlining.
return nullptr;
}
// Get or create a suitable preheader and make it become the entry block.
entry_block =
GetOrCreateSimpleLoopPreheader(entry_block->GetLabel()->result_id());
}
assert(!entry_block->IsLoopHeader() &&
"The entry block cannot be a loop header at this point.");
// If the entry block starts with OpPhi or OpVariable, try to split it.
if (entry_block->begin()->opcode() == spv::Op::OpPhi ||
entry_block->begin()->opcode() == spv::Op::OpVariable) {
// Find the first non-OpPhi and non-OpVariable instruction.
auto non_phi_or_var_inst = &*entry_block->begin();
while (non_phi_or_var_inst->opcode() == spv::Op::OpPhi ||
non_phi_or_var_inst->opcode() == spv::Op::OpVariable) {
non_phi_or_var_inst = non_phi_or_var_inst->NextNode();
}
// Split the block.
uint32_t new_block_id = GetFuzzerContext()->GetFreshId();
ApplyTransformation(TransformationSplitBlock(
MakeInstructionDescriptor(GetIRContext(), non_phi_or_var_inst),
new_block_id));
// The new entry block is the newly-created block.
entry_block = &*entry_block->GetParent()->FindBlock(new_block_id);
}
return entry_block;
}
opt::BasicBlock*
FuzzerPassOutlineFunctions::MaybeGetExitBlockSuitableForOutlining(
opt::BasicBlock* exit_block) {
// The exit block must not be a continue target.
assert(!GetIRContext()->GetStructuredCFGAnalysis()->IsContinueBlock(
exit_block->id()) &&
"A candidate exit block cannot be a continue target.");
// If the exit block is a merge block, try to split it and return the second
// block in the pair as the exit block.
if (GetIRContext()->GetStructuredCFGAnalysis()->IsMergeBlock(
exit_block->id())) {
uint32_t new_block_id = GetFuzzerContext()->GetFreshId();
// Find the first non-OpPhi instruction, after which to split.
auto split_before = &*exit_block->begin();
while (split_before->opcode() == spv::Op::OpPhi) {
split_before = split_before->NextNode();
}
if (!MaybeApplyTransformation(TransformationSplitBlock(
MakeInstructionDescriptor(GetIRContext(), split_before),
new_block_id))) {
return nullptr;
}
return &*exit_block->GetParent()->FindBlock(new_block_id);
}
return exit_block;
}
} // namespace fuzz
} // namespace spvtools
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