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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/reduce_load_size.h"
#include <set>
#include <vector>
#include "source/opt/instruction.h"
#include "source/opt/ir_builder.h"
#include "source/opt/ir_context.h"
#include "source/util/bit_vector.h"
namespace spvtools {
namespace opt {
namespace {
constexpr uint32_t kExtractCompositeIdInIdx = 0;
constexpr uint32_t kVariableStorageClassInIdx = 0;
constexpr uint32_t kLoadPointerInIdx = 0;
} // namespace
Pass::Status ReduceLoadSize::Process() {
bool modified = false;
for (auto& func : *get_module()) {
func.ForEachInst([&modified, this](Instruction* inst) {
if (inst->opcode() == spv::Op::OpCompositeExtract) {
if (ShouldReplaceExtract(inst)) {
modified |= ReplaceExtract(inst);
}
}
});
}
return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange;
}
bool ReduceLoadSize::ReplaceExtract(Instruction* inst) {
assert(inst->opcode() == spv::Op::OpCompositeExtract &&
"Wrong opcode. Should be OpCompositeExtract.");
analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
analysis::TypeManager* type_mgr = context()->get_type_mgr();
analysis::ConstantManager* const_mgr = context()->get_constant_mgr();
uint32_t composite_id =
inst->GetSingleWordInOperand(kExtractCompositeIdInIdx);
Instruction* composite_inst = def_use_mgr->GetDef(composite_id);
if (composite_inst->opcode() != spv::Op::OpLoad) {
return false;
}
analysis::Type* composite_type = type_mgr->GetType(composite_inst->type_id());
if (composite_type->kind() == analysis::Type::kVector ||
composite_type->kind() == analysis::Type::kMatrix) {
return false;
}
Instruction* var = composite_inst->GetBaseAddress();
if (var == nullptr || var->opcode() != spv::Op::OpVariable) {
return false;
}
spv::StorageClass storage_class = static_cast<spv::StorageClass>(
var->GetSingleWordInOperand(kVariableStorageClassInIdx));
switch (storage_class) {
case spv::StorageClass::Uniform:
case spv::StorageClass::UniformConstant:
case spv::StorageClass::Input:
break;
default:
return false;
}
// Create a new access chain and load just after the old load.
// We cannot create the new access chain load in the position of the extract
// because the storage may have been written to in between.
InstructionBuilder ir_builder(
inst->context(), composite_inst,
IRContext::kAnalysisInstrToBlockMapping | IRContext::kAnalysisDefUse);
uint32_t pointer_to_result_type_id =
type_mgr->FindPointerToType(inst->type_id(), storage_class);
assert(pointer_to_result_type_id != 0 &&
"We did not find the pointer type that we need.");
analysis::Integer int_type(32, false);
const analysis::Type* uint32_type = type_mgr->GetRegisteredType(&int_type);
std::vector<uint32_t> ids;
for (uint32_t i = 1; i < inst->NumInOperands(); ++i) {
uint32_t index = inst->GetSingleWordInOperand(i);
const analysis::Constant* index_const =
const_mgr->GetConstant(uint32_type, {index});
ids.push_back(const_mgr->GetDefiningInstruction(index_const)->result_id());
}
Instruction* new_access_chain = ir_builder.AddAccessChain(
pointer_to_result_type_id,
composite_inst->GetSingleWordInOperand(kLoadPointerInIdx), ids);
// TODO(1841): Handle id overflow.
Instruction* new_load =
ir_builder.AddLoad(inst->type_id(), new_access_chain->result_id());
context()->ReplaceAllUsesWith(inst->result_id(), new_load->result_id());
context()->KillInst(inst);
return true;
}
bool ReduceLoadSize::ShouldReplaceExtract(Instruction* inst) {
analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
Instruction* op_inst = def_use_mgr->GetDef(
inst->GetSingleWordInOperand(kExtractCompositeIdInIdx));
if (op_inst->opcode() != spv::Op::OpLoad) {
return false;
}
auto cached_result = should_replace_cache_.find(op_inst->result_id());
if (cached_result != should_replace_cache_.end()) {
return cached_result->second;
}
bool all_elements_used = false;
std::set<uint32_t> elements_used;
all_elements_used =
!def_use_mgr->WhileEachUser(op_inst, [&elements_used](Instruction* use) {
if (use->IsCommonDebugInstr()) return true;
if (use->opcode() != spv::Op::OpCompositeExtract ||
use->NumInOperands() == 1) {
return false;
}
elements_used.insert(use->GetSingleWordInOperand(1));
return true;
});
bool should_replace = false;
if (all_elements_used) {
should_replace = false;
} else if (1.0 <= replacement_threshold_) {
should_replace = true;
} else {
analysis::ConstantManager* const_mgr = context()->get_constant_mgr();
analysis::TypeManager* type_mgr = context()->get_type_mgr();
analysis::Type* load_type = type_mgr->GetType(op_inst->type_id());
uint32_t total_size = 1;
switch (load_type->kind()) {
case analysis::Type::kArray: {
const analysis::Constant* size_const =
const_mgr->FindDeclaredConstant(load_type->AsArray()->LengthId());
if (size_const) {
assert(size_const->AsIntConstant());
total_size = size_const->GetU32();
} else {
// The size is spec constant, so it is unknown at this time. Assume
// it is very large.
total_size = UINT32_MAX;
}
} break;
case analysis::Type::kStruct:
total_size = static_cast<uint32_t>(
load_type->AsStruct()->element_types().size());
break;
default:
break;
}
double percent_used = static_cast<double>(elements_used.size()) /
static_cast<double>(total_size);
should_replace = (percent_used < replacement_threshold_);
}
should_replace_cache_[op_inst->result_id()] = should_replace;
return should_replace;
}
} // namespace opt
} // namespace spvtools
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