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// Copyright (c) 2018 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/opt/struct_cfg_analysis.h"
#include "source/opt/ir_context.h"
namespace {
const uint32_t kMergeNodeIndex = 0;
const uint32_t kContinueNodeIndex = 1;
} // namespace
namespace spvtools {
namespace opt {
StructuredCFGAnalysis::StructuredCFGAnalysis(IRContext* ctx) : context_(ctx) {
// If this is not a shader, there are no merge instructions, and not
// structured CFG to analyze.
if (!context_->get_feature_mgr()->HasCapability(SpvCapabilityShader)) {
return;
}
for (auto& func : *context_->module()) {
AddBlocksInFunction(&func);
}
}
void StructuredCFGAnalysis::AddBlocksInFunction(Function* func) {
if (func->begin() == func->end()) return;
std::list<BasicBlock*> order;
context_->cfg()->ComputeStructuredOrder(func, &*func->begin(), &order);
struct TraversalInfo {
ConstructInfo cinfo;
uint32_t merge_node;
uint32_t continue_node;
};
// Set up a stack to keep track of currently active constructs.
std::vector<TraversalInfo> state;
state.emplace_back();
state[0].cinfo.containing_construct = 0;
state[0].cinfo.containing_loop = 0;
state[0].cinfo.containing_switch = 0;
state[0].cinfo.in_continue = false;
state[0].merge_node = 0;
state[0].continue_node = 0;
for (BasicBlock* block : order) {
if (context_->cfg()->IsPseudoEntryBlock(block) ||
context_->cfg()->IsPseudoExitBlock(block)) {
continue;
}
if (block->id() == state.back().merge_node) {
state.pop_back();
}
// This works because the structured order is designed to keep the blocks in
// the continue construct between the continue header and the merge node.
if (block->id() == state.back().continue_node) {
state.back().cinfo.in_continue = true;
}
bb_to_construct_.emplace(std::make_pair(block->id(), state.back().cinfo));
if (Instruction* merge_inst = block->GetMergeInst()) {
TraversalInfo new_state;
new_state.merge_node =
merge_inst->GetSingleWordInOperand(kMergeNodeIndex);
new_state.cinfo.containing_construct = block->id();
if (merge_inst->opcode() == SpvOpLoopMerge) {
new_state.cinfo.containing_loop = block->id();
new_state.cinfo.containing_switch = 0;
new_state.continue_node =
merge_inst->GetSingleWordInOperand(kContinueNodeIndex);
if (block->id() == new_state.continue_node) {
new_state.cinfo.in_continue = true;
bb_to_construct_[block->id()].in_continue = true;
} else {
new_state.cinfo.in_continue = false;
}
} else {
new_state.cinfo.containing_loop = state.back().cinfo.containing_loop;
new_state.cinfo.in_continue = state.back().cinfo.in_continue;
new_state.continue_node = state.back().continue_node;
if (merge_inst->NextNode()->opcode() == SpvOpSwitch) {
new_state.cinfo.containing_switch = block->id();
} else {
new_state.cinfo.containing_switch =
state.back().cinfo.containing_switch;
}
}
state.emplace_back(new_state);
merge_blocks_.Set(new_state.merge_node);
}
}
}
uint32_t StructuredCFGAnalysis::ContainingConstruct(Instruction* inst) {
uint32_t bb = context_->get_instr_block(inst)->id();
return ContainingConstruct(bb);
}
uint32_t StructuredCFGAnalysis::MergeBlock(uint32_t bb_id) {
uint32_t header_id = ContainingConstruct(bb_id);
if (header_id == 0) {
return 0;
}
BasicBlock* header = context_->cfg()->block(header_id);
Instruction* merge_inst = header->GetMergeInst();
return merge_inst->GetSingleWordInOperand(kMergeNodeIndex);
}
uint32_t StructuredCFGAnalysis::LoopMergeBlock(uint32_t bb_id) {
uint32_t header_id = ContainingLoop(bb_id);
if (header_id == 0) {
return 0;
}
BasicBlock* header = context_->cfg()->block(header_id);
Instruction* merge_inst = header->GetMergeInst();
return merge_inst->GetSingleWordInOperand(kMergeNodeIndex);
}
uint32_t StructuredCFGAnalysis::LoopContinueBlock(uint32_t bb_id) {
uint32_t header_id = ContainingLoop(bb_id);
if (header_id == 0) {
return 0;
}
BasicBlock* header = context_->cfg()->block(header_id);
Instruction* merge_inst = header->GetMergeInst();
return merge_inst->GetSingleWordInOperand(kContinueNodeIndex);
}
uint32_t StructuredCFGAnalysis::SwitchMergeBlock(uint32_t bb_id) {
uint32_t header_id = ContainingSwitch(bb_id);
if (header_id == 0) {
return 0;
}
BasicBlock* header = context_->cfg()->block(header_id);
Instruction* merge_inst = header->GetMergeInst();
return merge_inst->GetSingleWordInOperand(kMergeNodeIndex);
}
bool StructuredCFGAnalysis::IsContinueBlock(uint32_t bb_id) {
assert(bb_id != 0);
return LoopContinueBlock(bb_id) == bb_id;
}
bool StructuredCFGAnalysis::IsInContainingLoopsContinueConstruct(
uint32_t bb_id) {
auto it = bb_to_construct_.find(bb_id);
if (it == bb_to_construct_.end()) {
return false;
}
return it->second.in_continue;
}
bool StructuredCFGAnalysis::IsInContinueConstruct(uint32_t bb_id) {
while (bb_id != 0) {
if (IsInContainingLoopsContinueConstruct(bb_id)) {
return true;
}
bb_id = ContainingLoop(bb_id);
}
return false;
}
bool StructuredCFGAnalysis::IsMergeBlock(uint32_t bb_id) {
return merge_blocks_.Get(bb_id);
}
std::unordered_set<uint32_t>
StructuredCFGAnalysis::FindFuncsCalledFromContinue() {
std::unordered_set<uint32_t> called_from_continue;
std::queue<uint32_t> funcs_to_process;
// First collect the functions that are called directly from a continue
// construct.
for (Function& func : *context_->module()) {
for (auto& bb : func) {
if (IsInContainingLoopsContinueConstruct(bb.id())) {
for (const Instruction& inst : bb) {
if (inst.opcode() == SpvOpFunctionCall) {
funcs_to_process.push(inst.GetSingleWordInOperand(0));
}
}
}
}
}
// Now collect all of the functions that are indirectly called as well.
while (!funcs_to_process.empty()) {
uint32_t func_id = funcs_to_process.front();
funcs_to_process.pop();
Function* func = context_->GetFunction(func_id);
if (called_from_continue.insert(func_id).second) {
context_->AddCalls(func, &funcs_to_process);
}
}
return called_from_continue;
}
} // namespace opt
} // namespace spvtools