SPIRV-Tools/source/opt/desc_sroa.cpp

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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/opt/desc_sroa.h"
#include "source/util/string_utils.h"
namespace spvtools {
namespace opt {
Pass::Status DescriptorScalarReplacement::Process() {
bool modified = false;
std::vector<Instruction*> vars_to_kill;
for (Instruction& var : context()->types_values()) {
if (IsCandidate(&var)) {
modified = true;
if (!ReplaceCandidate(&var)) {
return Status::Failure;
}
vars_to_kill.push_back(&var);
}
}
for (Instruction* var : vars_to_kill) {
context()->KillInst(var);
}
return (modified ? Status::SuccessWithChange : Status::SuccessWithoutChange);
}
bool DescriptorScalarReplacement::IsCandidate(Instruction* var) {
if (var->opcode() != SpvOpVariable) {
return false;
}
uint32_t ptr_type_id = var->type_id();
Instruction* ptr_type_inst =
context()->get_def_use_mgr()->GetDef(ptr_type_id);
if (ptr_type_inst->opcode() != SpvOpTypePointer) {
return false;
}
uint32_t var_type_id = ptr_type_inst->GetSingleWordInOperand(1);
Instruction* var_type_inst =
context()->get_def_use_mgr()->GetDef(var_type_id);
if (var_type_inst->opcode() != SpvOpTypeArray &&
var_type_inst->opcode() != SpvOpTypeStruct) {
return false;
}
// All structures with descriptor assignments must be replaced by variables,
// one for each of their members - with the exceptions of buffers.
// Buffers are represented as structures, but we shouldn't replace a buffer
// with its elements. All buffers have offset decorations for members of their
// structure types.
bool has_offset_decoration = false;
context()->get_decoration_mgr()->ForEachDecoration(
var_type_inst->result_id(), SpvDecorationOffset,
[&has_offset_decoration](const Instruction&) {
has_offset_decoration = true;
});
if (has_offset_decoration) {
return false;
}
bool has_desc_set_decoration = false;
context()->get_decoration_mgr()->ForEachDecoration(
var->result_id(), SpvDecorationDescriptorSet,
[&has_desc_set_decoration](const Instruction&) {
has_desc_set_decoration = true;
});
if (!has_desc_set_decoration) {
return false;
}
bool has_binding_decoration = false;
context()->get_decoration_mgr()->ForEachDecoration(
var->result_id(), SpvDecorationBinding,
[&has_binding_decoration](const Instruction&) {
has_binding_decoration = true;
});
if (!has_binding_decoration) {
return false;
}
return true;
}
bool DescriptorScalarReplacement::ReplaceCandidate(Instruction* var) {
std::vector<Instruction*> access_chain_work_list;
std::vector<Instruction*> load_work_list;
bool failed = !get_def_use_mgr()->WhileEachUser(
var->result_id(),
[this, &access_chain_work_list, &load_work_list](Instruction* use) {
if (use->opcode() == SpvOpName) {
return true;
}
if (use->IsDecoration()) {
return true;
}
switch (use->opcode()) {
case SpvOpAccessChain:
case SpvOpInBoundsAccessChain:
access_chain_work_list.push_back(use);
return true;
case SpvOpLoad:
load_work_list.push_back(use);
return true;
default:
context()->EmitErrorMessage(
"Variable cannot be replaced: invalid instruction", use);
return false;
}
return true;
});
if (failed) {
return false;
}
for (Instruction* use : access_chain_work_list) {
if (!ReplaceAccessChain(var, use)) {
return false;
}
}
for (Instruction* use : load_work_list) {
if (!ReplaceLoadedValue(var, use)) {
return false;
}
}
return true;
}
bool DescriptorScalarReplacement::ReplaceAccessChain(Instruction* var,
Instruction* use) {
if (use->NumInOperands() <= 1) {
context()->EmitErrorMessage(
"Variable cannot be replaced: invalid instruction", use);
return false;
}
uint32_t idx_id = use->GetSingleWordInOperand(1);
const analysis::Constant* idx_const =
context()->get_constant_mgr()->FindDeclaredConstant(idx_id);
if (idx_const == nullptr) {
context()->EmitErrorMessage("Variable cannot be replaced: invalid index",
use);
return false;
}
uint32_t idx = idx_const->GetU32();
uint32_t replacement_var = GetReplacementVariable(var, idx);
if (use->NumInOperands() == 2) {
// We are not indexing into the replacement variable. We can replaces the
// access chain with the replacement varibale itself.
context()->ReplaceAllUsesWith(use->result_id(), replacement_var);
context()->KillInst(use);
return true;
}
// We need to build a new access chain with the replacement variable as the
// base address.
Instruction::OperandList new_operands;
// Same result id and result type.
new_operands.emplace_back(use->GetOperand(0));
new_operands.emplace_back(use->GetOperand(1));
// Use the replacement variable as the base address.
new_operands.push_back({SPV_OPERAND_TYPE_ID, {replacement_var}});
// Drop the first index because it is consumed by the replacment, and copy the
// rest.
for (uint32_t i = 4; i < use->NumOperands(); i++) {
new_operands.emplace_back(use->GetOperand(i));
}
use->ReplaceOperands(new_operands);
context()->UpdateDefUse(use);
return true;
}
uint32_t DescriptorScalarReplacement::GetReplacementVariable(Instruction* var,
uint32_t idx) {
auto replacement_vars = replacement_variables_.find(var);
if (replacement_vars == replacement_variables_.end()) {
uint32_t ptr_type_id = var->type_id();
Instruction* ptr_type_inst = get_def_use_mgr()->GetDef(ptr_type_id);
assert(ptr_type_inst->opcode() == SpvOpTypePointer &&
"Variable should be a pointer to an array or structure.");
uint32_t pointee_type_id = ptr_type_inst->GetSingleWordInOperand(1);
Instruction* pointee_type_inst = get_def_use_mgr()->GetDef(pointee_type_id);
const bool is_array = pointee_type_inst->opcode() == SpvOpTypeArray;
const bool is_struct = pointee_type_inst->opcode() == SpvOpTypeStruct;
assert((is_array || is_struct) &&
"Variable should be a pointer to an array or structure.");
// For arrays, each array element should be replaced with a new replacement
// variable
if (is_array) {
uint32_t array_len_id = pointee_type_inst->GetSingleWordInOperand(1);
const analysis::Constant* array_len_const =
context()->get_constant_mgr()->FindDeclaredConstant(array_len_id);
assert(array_len_const != nullptr && "Array length must be a constant.");
uint32_t array_len = array_len_const->GetU32();
replacement_vars = replacement_variables_
.insert({var, std::vector<uint32_t>(array_len, 0)})
.first;
}
// For structures, each member should be replaced with a new replacement
// variable
if (is_struct) {
const uint32_t num_members = pointee_type_inst->NumInOperands();
replacement_vars =
replacement_variables_
.insert({var, std::vector<uint32_t>(num_members, 0)})
.first;
}
}
if (replacement_vars->second[idx] == 0) {
replacement_vars->second[idx] = CreateReplacementVariable(var, idx);
}
return replacement_vars->second[idx];
}
uint32_t DescriptorScalarReplacement::CreateReplacementVariable(
Instruction* var, uint32_t idx) {
// The storage class for the new variable is the same as the original.
SpvStorageClass storage_class =
static_cast<SpvStorageClass>(var->GetSingleWordInOperand(0));
// The type for the new variable will be a pointer to type of the elements of
// the array.
uint32_t ptr_type_id = var->type_id();
Instruction* ptr_type_inst = get_def_use_mgr()->GetDef(ptr_type_id);
assert(ptr_type_inst->opcode() == SpvOpTypePointer &&
"Variable should be a pointer to an array or structure.");
uint32_t pointee_type_id = ptr_type_inst->GetSingleWordInOperand(1);
Instruction* pointee_type_inst = get_def_use_mgr()->GetDef(pointee_type_id);
const bool is_array = pointee_type_inst->opcode() == SpvOpTypeArray;
const bool is_struct = pointee_type_inst->opcode() == SpvOpTypeStruct;
assert((is_array || is_struct) &&
"Variable should be a pointer to an array or structure.");
uint32_t element_type_id =
is_array ? pointee_type_inst->GetSingleWordInOperand(0)
: pointee_type_inst->GetSingleWordInOperand(idx);
uint32_t ptr_element_type_id = context()->get_type_mgr()->FindPointerToType(
element_type_id, storage_class);
// Create the variable.
uint32_t id = TakeNextId();
std::unique_ptr<Instruction> variable(
new Instruction(context(), SpvOpVariable, ptr_element_type_id, id,
std::initializer_list<Operand>{
{SPV_OPERAND_TYPE_STORAGE_CLASS,
{static_cast<uint32_t>(storage_class)}}}));
context()->AddGlobalValue(std::move(variable));
// Copy all of the decorations to the new variable. The only difference is
// the Binding decoration needs to be adjusted.
for (auto old_decoration :
get_decoration_mgr()->GetDecorationsFor(var->result_id(), true)) {
assert(old_decoration->opcode() == SpvOpDecorate);
std::unique_ptr<Instruction> new_decoration(
old_decoration->Clone(context()));
new_decoration->SetInOperand(0, {id});
uint32_t decoration = new_decoration->GetSingleWordInOperand(1u);
if (decoration == SpvDecorationBinding) {
uint32_t new_binding = new_decoration->GetSingleWordInOperand(2);
if (is_array) {
new_binding += idx * GetNumBindingsUsedByType(ptr_element_type_id);
}
if (is_struct) {
// The binding offset that should be added is the sum of binding numbers
// used by previous members of the current struct.
for (uint32_t i = 0; i < idx; ++i) {
new_binding += GetNumBindingsUsedByType(
pointee_type_inst->GetSingleWordInOperand(i));
}
}
new_decoration->SetInOperand(2, {new_binding});
}
context()->AddAnnotationInst(std::move(new_decoration));
}
// Create a new OpName for the replacement variable.
std::vector<std::unique_ptr<Instruction>> names_to_add;
for (auto p : context()->GetNames(var->result_id())) {
Instruction* name_inst = p.second;
std::string name_str = utils::MakeString(name_inst->GetOperand(1).words);
if (is_array) {
name_str += "[" + utils::ToString(idx) + "]";
}
if (is_struct) {
Instruction* member_name_inst =
context()->GetMemberName(pointee_type_inst->result_id(), idx);
name_str += ".";
if (member_name_inst)
name_str += utils::MakeString(member_name_inst->GetOperand(2).words);
else
// In case the member does not have a name assigned to it, use the
// member index.
name_str += utils::ToString(idx);
}
std::unique_ptr<Instruction> new_name(new Instruction(
context(), SpvOpName, 0, 0,
std::initializer_list<Operand>{
{SPV_OPERAND_TYPE_ID, {id}},
{SPV_OPERAND_TYPE_LITERAL_STRING, utils::MakeVector(name_str)}}));
Instruction* new_name_inst = new_name.get();
get_def_use_mgr()->AnalyzeInstDefUse(new_name_inst);
names_to_add.push_back(std::move(new_name));
}
// We shouldn't add the new names when we are iterating over name ranges
// above. We can add all the new names now.
for (auto& new_name : names_to_add)
context()->AddDebug2Inst(std::move(new_name));
return id;
}
uint32_t DescriptorScalarReplacement::GetNumBindingsUsedByType(
uint32_t type_id) {
Instruction* type_inst = get_def_use_mgr()->GetDef(type_id);
// If it's a pointer, look at the underlying type.
if (type_inst->opcode() == SpvOpTypePointer) {
type_id = type_inst->GetSingleWordInOperand(1);
type_inst = get_def_use_mgr()->GetDef(type_id);
}
// Arrays consume N*M binding numbers where N is the array length, and M is
// the number of bindings used by each array element.
if (type_inst->opcode() == SpvOpTypeArray) {
uint32_t element_type_id = type_inst->GetSingleWordInOperand(0);
uint32_t length_id = type_inst->GetSingleWordInOperand(1);
const analysis::Constant* length_const =
context()->get_constant_mgr()->FindDeclaredConstant(length_id);
// OpTypeArray's length must always be a constant
assert(length_const != nullptr);
uint32_t num_elems = length_const->GetU32();
return num_elems * GetNumBindingsUsedByType(element_type_id);
}
// The number of bindings consumed by a structure is the sum of the bindings
// used by its members.
if (type_inst->opcode() == SpvOpTypeStruct) {
uint32_t sum = 0;
for (uint32_t i = 0; i < type_inst->NumInOperands(); i++)
sum += GetNumBindingsUsedByType(type_inst->GetSingleWordInOperand(i));
return sum;
}
// All other types are considered to take up 1 binding number.
return 1;
}
bool DescriptorScalarReplacement::ReplaceLoadedValue(Instruction* var,
Instruction* value) {
// |var| is the global variable that has to be eliminated (OpVariable).
// |value| is the OpLoad instruction that has loaded |var|.
// The function expects all users of |value| to be OpCompositeExtract
// instructions. Otherwise the function returns false with an error message.
assert(value->opcode() == SpvOpLoad);
assert(value->GetSingleWordInOperand(0) == var->result_id());
std::vector<Instruction*> work_list;
bool failed = !get_def_use_mgr()->WhileEachUser(
value->result_id(), [this, &work_list](Instruction* use) {
if (use->opcode() != SpvOpCompositeExtract) {
context()->EmitErrorMessage(
"Variable cannot be replaced: invalid instruction", use);
return false;
}
work_list.push_back(use);
return true;
});
if (failed) {
return false;
}
for (Instruction* use : work_list) {
if (!ReplaceCompositeExtract(var, use)) {
return false;
}
}
// All usages of the loaded value have been killed. We can kill the OpLoad.
context()->KillInst(value);
return true;
}
bool DescriptorScalarReplacement::ReplaceCompositeExtract(
Instruction* var, Instruction* extract) {
assert(extract->opcode() == SpvOpCompositeExtract);
// We're currently only supporting extractions of one index at a time. If we
// need to, we can handle cases with multiple indexes in the future.
if (extract->NumInOperands() != 2) {
context()->EmitErrorMessage(
"Variable cannot be replaced: invalid instruction", extract);
return false;
}
uint32_t replacement_var =
GetReplacementVariable(var, extract->GetSingleWordInOperand(1));
// The result type of the OpLoad is the same as the result type of the
// OpCompositeExtract.
uint32_t load_id = TakeNextId();
std::unique_ptr<Instruction> load(
new Instruction(context(), SpvOpLoad, extract->type_id(), load_id,
std::initializer_list<Operand>{
{SPV_OPERAND_TYPE_ID, {replacement_var}}}));
Instruction* load_instr = load.get();
get_def_use_mgr()->AnalyzeInstDefUse(load_instr);
context()->set_instr_block(load_instr, context()->get_instr_block(extract));
extract->InsertBefore(std::move(load));
context()->ReplaceAllUsesWith(extract->result_id(), load_id);
context()->KillInst(extract);
return true;
}
} // namespace opt
} // namespace spvtools