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// Copyright (c) 2022 The Khronos Group Inc.
// Copyright (c) 2022 LunarG Inc.
//
// 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/eliminate_dead_output_stores_pass.h"
#include "source/opt/instruction.h"
#include "source/opt/ir_context.h"
namespace spvtools {
namespace opt {
namespace {
constexpr uint32_t kDecorationLocationInIdx = 2;
constexpr uint32_t kOpDecorateMemberMemberInIdx = 1;
constexpr uint32_t kOpDecorateBuiltInLiteralInIdx = 2;
constexpr uint32_t kOpDecorateMemberBuiltInLiteralInIdx = 3;
constexpr uint32_t kOpAccessChainIdx0InIdx = 1;
constexpr uint32_t kOpConstantValueInIdx = 0;
} // namespace
Pass::Status EliminateDeadOutputStoresPass::Process() {
// Current functionality assumes shader capability
if (!context()->get_feature_mgr()->HasCapability(spv::Capability::Shader))
return Status::SuccessWithoutChange;
Pass::Status status = DoDeadOutputStoreElimination();
return status;
}
void EliminateDeadOutputStoresPass::InitializeElimination() {
kill_list_.clear();
}
bool EliminateDeadOutputStoresPass::IsLiveBuiltin(uint32_t bi) {
return live_builtins_->find(bi) != live_builtins_->end();
}
bool EliminateDeadOutputStoresPass::AnyLocsAreLive(uint32_t start,
uint32_t count) {
auto finish = start + count;
for (uint32_t u = start; u < finish; ++u) {
if (live_locs_->find(u) != live_locs_->end()) return true;
}
return false;
}
void EliminateDeadOutputStoresPass::KillAllStoresOfRef(Instruction* ref) {
analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
if (ref->opcode() == spv::Op::OpStore) {
kill_list_.push_back(ref);
return;
}
assert((ref->opcode() == spv::Op::OpAccessChain ||
ref->opcode() == spv::Op::OpInBoundsAccessChain) &&
"unexpected use of output variable");
def_use_mgr->ForEachUser(ref, [this](Instruction* user) {
if (user->opcode() == spv::Op::OpStore) kill_list_.push_back(user);
});
}
void EliminateDeadOutputStoresPass::KillAllDeadStoresOfLocRef(
Instruction* ref, Instruction* var) {
analysis::TypeManager* type_mgr = context()->get_type_mgr();
analysis::DecorationManager* deco_mgr = context()->get_decoration_mgr();
analysis::LivenessManager* live_mgr = context()->get_liveness_mgr();
// Find variable location if present.
uint32_t start_loc = 0;
auto var_id = var->result_id();
bool no_loc = deco_mgr->WhileEachDecoration(
var_id, uint32_t(spv::Decoration::Location),
[&start_loc](const Instruction& deco) {
assert(deco.opcode() == spv::Op::OpDecorate && "unexpected decoration");
start_loc = deco.GetSingleWordInOperand(kDecorationLocationInIdx);
return false;
});
// Find patch decoration if present
bool is_patch = !deco_mgr->WhileEachDecoration(
var_id, uint32_t(spv::Decoration::Patch), [](const Instruction& deco) {
if (deco.opcode() != spv::Op::OpDecorate)
assert(false && "unexpected decoration");
return false;
});
// Compute offset and final type of reference. If no location found
// or any stored locations are live, return without removing stores.
auto ptr_type = type_mgr->GetType(var->type_id())->AsPointer();
assert(ptr_type && "unexpected var type");
auto var_type = ptr_type->pointee_type();
uint32_t ref_loc = start_loc;
auto curr_type = var_type;
if (ref->opcode() == spv::Op::OpAccessChain ||
ref->opcode() == spv::Op::OpInBoundsAccessChain) {
live_mgr->AnalyzeAccessChainLoc(ref, &curr_type, &ref_loc, &no_loc,
is_patch, /* input */ false);
}
if (no_loc || AnyLocsAreLive(ref_loc, live_mgr->GetLocSize(curr_type)))
return;
// Kill all stores based on this reference
KillAllStoresOfRef(ref);
}
void EliminateDeadOutputStoresPass::KillAllDeadStoresOfBuiltinRef(
Instruction* ref, Instruction* var) {
auto deco_mgr = context()->get_decoration_mgr();
auto def_use_mgr = context()->get_def_use_mgr();
auto type_mgr = context()->get_type_mgr();
auto live_mgr = context()->get_liveness_mgr();
// Search for builtin decoration of base variable
uint32_t builtin = uint32_t(spv::BuiltIn::Max);
auto var_id = var->result_id();
(void)deco_mgr->WhileEachDecoration(
var_id, uint32_t(spv::Decoration::BuiltIn),
[&builtin](const Instruction& deco) {
assert(deco.opcode() == spv::Op::OpDecorate && "unexpected decoration");
builtin = deco.GetSingleWordInOperand(kOpDecorateBuiltInLiteralInIdx);
return false;
});
// If analyzed builtin and not live, kill stores.
if (builtin != uint32_t(spv::BuiltIn::Max)) {
if (live_mgr->IsAnalyzedBuiltin(builtin) && !IsLiveBuiltin(builtin))
KillAllStoresOfRef(ref);
return;
}
// Search for builtin decoration on indexed member
auto ref_op = ref->opcode();
if (ref_op != spv::Op::OpAccessChain &&
ref_op != spv::Op::OpInBoundsAccessChain) {
return;
}
uint32_t in_idx = kOpAccessChainIdx0InIdx;
analysis::Type* var_type = type_mgr->GetType(var->type_id());
analysis::Pointer* ptr_type = var_type->AsPointer();
auto curr_type = ptr_type->pointee_type();
auto arr_type = curr_type->AsArray();
if (arr_type) {
curr_type = arr_type->element_type();
++in_idx;
}
auto str_type = curr_type->AsStruct();
auto str_type_id = type_mgr->GetId(str_type);
auto member_idx_id = ref->GetSingleWordInOperand(in_idx);
auto member_idx_inst = def_use_mgr->GetDef(member_idx_id);
assert(member_idx_inst->opcode() == spv::Op::OpConstant &&
"unexpected non-constant index");
auto ac_idx = member_idx_inst->GetSingleWordInOperand(kOpConstantValueInIdx);
(void)deco_mgr->WhileEachDecoration(
str_type_id, uint32_t(spv::Decoration::BuiltIn),
[ac_idx, &builtin](const Instruction& deco) {
assert(deco.opcode() == spv::Op::OpMemberDecorate &&
"unexpected decoration");
auto deco_idx =
deco.GetSingleWordInOperand(kOpDecorateMemberMemberInIdx);
if (deco_idx == ac_idx) {
builtin =
deco.GetSingleWordInOperand(kOpDecorateMemberBuiltInLiteralInIdx);
return false;
}
return true;
});
assert(builtin != uint32_t(spv::BuiltIn::Max) && "builtin not found");
// If analyzed builtin and not live, kill stores.
if (live_mgr->IsAnalyzedBuiltin(builtin) && !IsLiveBuiltin(builtin))
KillAllStoresOfRef(ref);
}
Pass::Status EliminateDeadOutputStoresPass::DoDeadOutputStoreElimination() {
// Current implementation only supports vert, tesc, tese, geom shaders
auto stage = context()->GetStage();
if (stage != spv::ExecutionModel::Vertex &&
stage != spv::ExecutionModel::TessellationControl &&
stage != spv::ExecutionModel::TessellationEvaluation &&
stage != spv::ExecutionModel::Geometry)
return Status::Failure;
InitializeElimination();
analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
analysis::TypeManager* type_mgr = context()->get_type_mgr();
analysis::DecorationManager* deco_mgr = context()->get_decoration_mgr();
// Process all output variables
for (auto& var : context()->types_values()) {
if (var.opcode() != spv::Op::OpVariable) {
continue;
}
analysis::Type* var_type = type_mgr->GetType(var.type_id());
analysis::Pointer* ptr_type = var_type->AsPointer();
if (ptr_type->storage_class() != spv::StorageClass::Output) {
continue;
}
// If builtin decoration on variable, process as builtin.
auto var_id = var.result_id();
bool is_builtin = false;
if (deco_mgr->HasDecoration(var_id, uint32_t(spv::Decoration::BuiltIn))) {
is_builtin = true;
} else {
// If interface block with builtin members, process as builtin.
// Strip off outer array type if present.
auto curr_type = ptr_type->pointee_type();
auto arr_type = curr_type->AsArray();
if (arr_type) curr_type = arr_type->element_type();
auto str_type = curr_type->AsStruct();
if (str_type) {
auto str_type_id = type_mgr->GetId(str_type);
if (deco_mgr->HasDecoration(str_type_id,
uint32_t(spv::Decoration::BuiltIn)))
is_builtin = true;
}
}
// For each store or access chain using var, if dead builtin or all its
// locations are dead, kill store or all access chain's stores
def_use_mgr->ForEachUser(
var_id, [this, &var, is_builtin](Instruction* user) {
auto op = user->opcode();
if (op == spv::Op::OpEntryPoint || op == spv::Op::OpName ||
op == spv::Op::OpDecorate)
return;
if (is_builtin)
KillAllDeadStoresOfBuiltinRef(user, &var);
else
KillAllDeadStoresOfLocRef(user, &var);
});
}
for (auto& kinst : kill_list_) context()->KillInst(kinst);
return kill_list_.empty() ? Status::SuccessWithoutChange
: Status::SuccessWithChange;
}
} // namespace opt
} // namespace spvtools
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