SPIRV-Tools/source/opt/vector_dce.cpp

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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/vector_dce.h"
#include <utility>
namespace spvtools {
namespace opt {
namespace {
const uint32_t kExtractCompositeIdInIdx = 0;
const uint32_t kInsertObjectIdInIdx = 0;
const uint32_t kInsertCompositeIdInIdx = 1;
} // namespace
Pass::Status VectorDCE::Process() {
bool modified = false;
for (Function& function : *get_module()) {
modified |= VectorDCEFunction(&function);
}
return (modified ? Status::SuccessWithChange : Status::SuccessWithoutChange);
}
bool VectorDCE::VectorDCEFunction(Function* function) {
LiveComponentMap live_components;
FindLiveComponents(function, &live_components);
return RewriteInstructions(function, live_components);
}
void VectorDCE::FindLiveComponents(Function* function,
LiveComponentMap* live_components) {
std::vector<WorkListItem> work_list;
// Prime the work list. We will assume that any instruction that does
// not result in a vector is live.
//
// Extending to structures and matrices is not as straight forward because of
// the nesting. We cannot simply us a bit vector to keep track of which
// components are live because of arbitrary nesting of structs.
function->ForEachInst(
[&work_list, this, live_components](Instruction* current_inst) {
if (current_inst->IsOpenCL100DebugInstr()) {
return;
}
if (!HasVectorOrScalarResult(current_inst) ||
!context()->IsCombinatorInstruction(current_inst)) {
MarkUsesAsLive(current_inst, all_components_live_, live_components,
&work_list);
}
});
// Process the work list propagating liveness.
for (uint32_t i = 0; i < work_list.size(); i++) {
WorkListItem current_item = work_list[i];
Instruction* current_inst = current_item.instruction;
switch (current_inst->opcode()) {
case SpvOpCompositeExtract:
MarkExtractUseAsLive(current_inst, current_item.components,
live_components, &work_list);
break;
case SpvOpCompositeInsert:
MarkInsertUsesAsLive(current_item, live_components, &work_list);
break;
case SpvOpVectorShuffle:
MarkVectorShuffleUsesAsLive(current_item, live_components, &work_list);
break;
case SpvOpCompositeConstruct:
MarkCompositeContructUsesAsLive(current_item, live_components,
&work_list);
break;
default:
if (current_inst->IsScalarizable()) {
MarkUsesAsLive(current_inst, current_item.components, live_components,
&work_list);
} else {
MarkUsesAsLive(current_inst, all_components_live_, live_components,
&work_list);
}
break;
}
}
}
void VectorDCE::MarkExtractUseAsLive(const Instruction* current_inst,
const utils::BitVector& live_elements,
LiveComponentMap* live_components,
std::vector<WorkListItem>* work_list) {
analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
uint32_t operand_id =
current_inst->GetSingleWordInOperand(kExtractCompositeIdInIdx);
Instruction* operand_inst = def_use_mgr->GetDef(operand_id);
if (HasVectorOrScalarResult(operand_inst)) {
WorkListItem new_item;
new_item.instruction = operand_inst;
if (current_inst->NumInOperands() < 2) {
new_item.components = live_elements;
} else {
new_item.components.Set(current_inst->GetSingleWordInOperand(1));
}
AddItemToWorkListIfNeeded(new_item, live_components, work_list);
}
}
void VectorDCE::MarkInsertUsesAsLive(
const VectorDCE::WorkListItem& current_item,
LiveComponentMap* live_components,
std::vector<VectorDCE::WorkListItem>* work_list) {
analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
if (current_item.instruction->NumInOperands() > 2) {
uint32_t insert_position =
current_item.instruction->GetSingleWordInOperand(2);
// Add the elements of the composite object that are used.
uint32_t operand_id = current_item.instruction->GetSingleWordInOperand(
kInsertCompositeIdInIdx);
Instruction* operand_inst = def_use_mgr->GetDef(operand_id);
WorkListItem new_item;
new_item.instruction = operand_inst;
new_item.components = current_item.components;
new_item.components.Clear(insert_position);
AddItemToWorkListIfNeeded(new_item, live_components, work_list);
// Add the element being inserted if it is used.
if (current_item.components.Get(insert_position)) {
uint32_t obj_operand_id =
current_item.instruction->GetSingleWordInOperand(
kInsertObjectIdInIdx);
Instruction* obj_operand_inst = def_use_mgr->GetDef(obj_operand_id);
WorkListItem new_item_for_obj;
new_item_for_obj.instruction = obj_operand_inst;
new_item_for_obj.components.Set(0);
AddItemToWorkListIfNeeded(new_item_for_obj, live_components, work_list);
}
} else {
// If there are no indices, then this is a copy of the object being
// inserted.
uint32_t object_id =
current_item.instruction->GetSingleWordInOperand(kInsertObjectIdInIdx);
Instruction* object_inst = def_use_mgr->GetDef(object_id);
WorkListItem new_item;
new_item.instruction = object_inst;
new_item.components = current_item.components;
AddItemToWorkListIfNeeded(new_item, live_components, work_list);
}
}
void VectorDCE::MarkVectorShuffleUsesAsLive(
const WorkListItem& current_item,
VectorDCE::LiveComponentMap* live_components,
std::vector<WorkListItem>* work_list) {
analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
WorkListItem first_operand;
first_operand.instruction =
def_use_mgr->GetDef(current_item.instruction->GetSingleWordInOperand(0));
WorkListItem second_operand;
second_operand.instruction =
def_use_mgr->GetDef(current_item.instruction->GetSingleWordInOperand(1));
analysis::TypeManager* type_mgr = context()->get_type_mgr();
analysis::Vector* first_type =
type_mgr->GetType(first_operand.instruction->type_id())->AsVector();
uint32_t size_of_first_operand = first_type->element_count();
for (uint32_t in_op = 2; in_op < current_item.instruction->NumInOperands();
++in_op) {
uint32_t index = current_item.instruction->GetSingleWordInOperand(in_op);
if (current_item.components.Get(in_op - 2)) {
if (index < size_of_first_operand) {
first_operand.components.Set(index);
} else {
second_operand.components.Set(index - size_of_first_operand);
}
}
}
AddItemToWorkListIfNeeded(first_operand, live_components, work_list);
AddItemToWorkListIfNeeded(second_operand, live_components, work_list);
}
void VectorDCE::MarkCompositeContructUsesAsLive(
VectorDCE::WorkListItem work_item,
VectorDCE::LiveComponentMap* live_components,
std::vector<VectorDCE::WorkListItem>* work_list) {
analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
analysis::TypeManager* type_mgr = context()->get_type_mgr();
uint32_t current_component = 0;
Instruction* current_inst = work_item.instruction;
uint32_t num_in_operands = current_inst->NumInOperands();
for (uint32_t i = 0; i < num_in_operands; ++i) {
uint32_t id = current_inst->GetSingleWordInOperand(i);
Instruction* op_inst = def_use_mgr->GetDef(id);
if (HasScalarResult(op_inst)) {
WorkListItem new_work_item;
new_work_item.instruction = op_inst;
if (work_item.components.Get(current_component)) {
new_work_item.components.Set(0);
}
AddItemToWorkListIfNeeded(new_work_item, live_components, work_list);
current_component++;
} else {
assert(HasVectorResult(op_inst));
WorkListItem new_work_item;
new_work_item.instruction = op_inst;
uint32_t op_vector_size =
type_mgr->GetType(op_inst->type_id())->AsVector()->element_count();
for (uint32_t op_vector_idx = 0; op_vector_idx < op_vector_size;
op_vector_idx++, current_component++) {
if (work_item.components.Get(current_component)) {
new_work_item.components.Set(op_vector_idx);
}
}
AddItemToWorkListIfNeeded(new_work_item, live_components, work_list);
}
}
}
void VectorDCE::MarkUsesAsLive(
Instruction* current_inst, const utils::BitVector& live_elements,
LiveComponentMap* live_components,
std::vector<VectorDCE::WorkListItem>* work_list) {
analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
current_inst->ForEachInId([&work_list, &live_elements, this, live_components,
def_use_mgr](uint32_t* operand_id) {
Instruction* operand_inst = def_use_mgr->GetDef(*operand_id);
if (HasVectorResult(operand_inst)) {
WorkListItem new_item;
new_item.instruction = operand_inst;
new_item.components = live_elements;
AddItemToWorkListIfNeeded(new_item, live_components, work_list);
} else if (HasScalarResult(operand_inst)) {
WorkListItem new_item;
new_item.instruction = operand_inst;
new_item.components.Set(0);
AddItemToWorkListIfNeeded(new_item, live_components, work_list);
}
});
}
bool VectorDCE::HasVectorOrScalarResult(const Instruction* inst) const {
return HasScalarResult(inst) || HasVectorResult(inst);
}
bool VectorDCE::HasVectorResult(const Instruction* inst) const {
analysis::TypeManager* type_mgr = context()->get_type_mgr();
if (inst->type_id() == 0) {
return false;
}
const analysis::Type* current_type = type_mgr->GetType(inst->type_id());
switch (current_type->kind()) {
case analysis::Type::kVector:
return true;
default:
return false;
}
}
bool VectorDCE::HasScalarResult(const Instruction* inst) const {
analysis::TypeManager* type_mgr = context()->get_type_mgr();
if (inst->type_id() == 0) {
return false;
}
const analysis::Type* current_type = type_mgr->GetType(inst->type_id());
switch (current_type->kind()) {
case analysis::Type::kBool:
case analysis::Type::kInteger:
case analysis::Type::kFloat:
return true;
default:
return false;
}
}
bool VectorDCE::RewriteInstructions(
Function* function, const VectorDCE::LiveComponentMap& live_components) {
bool modified = false;
// Kill DebugValue in the middle of the instruction iteration will result
// in accessing a dangling pointer. We keep dead DebugValue instructions
// in |dead_dbg_value| to kill them once after the iteration.
std::vector<Instruction*> dead_dbg_value;
function->ForEachInst([&modified, this, live_components,
&dead_dbg_value](Instruction* current_inst) {
if (!context()->IsCombinatorInstruction(current_inst)) {
return;
}
auto live_component = live_components.find(current_inst->result_id());
if (live_component == live_components.end()) {
// If this instruction is not in live_components then it does not
// produce a vector, or it is never referenced and ADCE will remove
// it. No point in trying to differentiate.
return;
}
// If no element in the current instruction is used replace it with an
// OpUndef.
if (live_component->second.Empty()) {
modified = true;
MarkDebugValueUsesAsDead(current_inst, &dead_dbg_value);
uint32_t undef_id = this->Type2Undef(current_inst->type_id());
context()->KillNamesAndDecorates(current_inst);
context()->ReplaceAllUsesWith(current_inst->result_id(), undef_id);
context()->KillInst(current_inst);
return;
}
switch (current_inst->opcode()) {
case SpvOpCompositeInsert:
modified |= RewriteInsertInstruction(
current_inst, live_component->second, &dead_dbg_value);
break;
case SpvOpCompositeConstruct:
// TODO: The members that are not live can be replaced by an undef
// or constant. This will remove uses of those values, and possibly
// create opportunities for ADCE.
break;
default:
// Do nothing.
break;
}
});
for (auto* i : dead_dbg_value) context()->KillInst(i);
return modified;
}
bool VectorDCE::RewriteInsertInstruction(
Instruction* current_inst, const utils::BitVector& live_components,
std::vector<Instruction*>* dead_dbg_value) {
// If the value being inserted is not live, then we can skip the insert.
if (current_inst->NumInOperands() == 2) {
// If there are no indices, then this is the same as a copy.
context()->KillNamesAndDecorates(current_inst->result_id());
uint32_t object_id =
current_inst->GetSingleWordInOperand(kInsertObjectIdInIdx);
context()->ReplaceAllUsesWith(current_inst->result_id(), object_id);
return true;
}
uint32_t insert_index = current_inst->GetSingleWordInOperand(2);
if (!live_components.Get(insert_index)) {
MarkDebugValueUsesAsDead(current_inst, dead_dbg_value);
context()->KillNamesAndDecorates(current_inst->result_id());
uint32_t composite_id =
current_inst->GetSingleWordInOperand(kInsertCompositeIdInIdx);
context()->ReplaceAllUsesWith(current_inst->result_id(), composite_id);
return true;
}
// If the values already in the composite are not used, then replace it with
// an undef.
utils::BitVector temp = live_components;
temp.Clear(insert_index);
if (temp.Empty()) {
context()->ForgetUses(current_inst);
uint32_t undef_id = Type2Undef(current_inst->type_id());
current_inst->SetInOperand(kInsertCompositeIdInIdx, {undef_id});
context()->AnalyzeUses(current_inst);
return true;
}
return false;
}
void VectorDCE::MarkDebugValueUsesAsDead(
Instruction* composite, std::vector<Instruction*>* dead_dbg_value) {
context()->get_def_use_mgr()->ForEachUser(
composite, [&dead_dbg_value](Instruction* use) {
if (use->GetOpenCL100DebugOpcode() == OpenCLDebugInfo100DebugValue)
dead_dbg_value->push_back(use);
});
}
void VectorDCE::AddItemToWorkListIfNeeded(
WorkListItem work_item, VectorDCE::LiveComponentMap* live_components,
std::vector<WorkListItem>* work_list) {
Instruction* current_inst = work_item.instruction;
auto it = live_components->find(current_inst->result_id());
if (it == live_components->end()) {
live_components->emplace(
std::make_pair(current_inst->result_id(), work_item.components));
work_list->emplace_back(work_item);
} else {
if (it->second.Or(work_item.components)) {
work_list->emplace_back(work_item);
}
}
}
} // namespace opt
} // namespace spvtools