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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/reduce/remove_block_reduction_opportunity_finder.h"
#include "source/reduce/remove_block_reduction_opportunity.h"
namespace spvtools {
namespace reduce {
std::string RemoveBlockReductionOpportunityFinder::GetName() const {
return "RemoveBlockReductionOpportunityFinder";
}
std::vector<std::unique_ptr<ReductionOpportunity>>
RemoveBlockReductionOpportunityFinder::GetAvailableOpportunities(
opt::IRContext* context, uint32_t target_function) const {
std::vector<std::unique_ptr<ReductionOpportunity>> result;
// Consider every block in every relevant function.
for (auto* function : GetTargetFunctions(context, target_function)) {
for (auto bi = function->begin(); bi != function->end(); ++bi) {
if (IsBlockValidOpportunity(context, function, &bi)) {
result.push_back(MakeUnique<RemoveBlockReductionOpportunity>(
context, function, &*bi));
}
}
}
return result;
}
bool RemoveBlockReductionOpportunityFinder::IsBlockValidOpportunity(
opt::IRContext* context, opt::Function* function,
opt::Function::iterator* bi) {
assert(*bi != function->end() && "Block iterator was out of bounds");
// Don't remove first block; we don't want to end up with no blocks.
if (*bi == function->begin()) {
return false;
}
// Don't remove blocks with references.
if (context->get_def_use_mgr()->NumUsers((*bi)->id()) > 0) {
return false;
}
// Don't remove blocks whose instructions have outside references.
if (!BlockInstructionsHaveNoOutsideReferences(context, *bi)) {
return false;
}
return true;
}
bool RemoveBlockReductionOpportunityFinder::
BlockInstructionsHaveNoOutsideReferences(
opt::IRContext* context, const opt::Function::iterator& bi) {
// Get all instructions in block.
std::unordered_set<uint32_t> instructions_in_block;
for (const opt::Instruction& instruction : *bi) {
instructions_in_block.insert(instruction.unique_id());
}
// For each instruction...
for (const opt::Instruction& instruction : *bi) {
// For each use of the instruction...
bool no_uses_outside_block = context->get_def_use_mgr()->WhileEachUser(
&instruction, [&instructions_in_block](opt::Instruction* user) -> bool {
// If the use is in this block, continue (return true). Otherwise, we
// found an outside use; return false (and stop).
return instructions_in_block.find(user->unique_id()) !=
instructions_in_block.end();
});
if (!no_uses_outside_block) {
return false;
}
}
return true;
}
} // namespace reduce
} // namespace spvtools
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