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// Copyright (c) 2017 The Khronos Group Inc.
// Copyright (c) 2017 Valve Corporation
// Copyright (c) 2017 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/local_single_block_elim_pass.h"
#include <vector>
#include "source/opt/iterator.h"
namespace spvtools {
namespace opt {
namespace {
const uint32_t kStoreValIdInIdx = 1;
} // anonymous namespace
bool LocalSingleBlockLoadStoreElimPass::HasOnlySupportedRefs(uint32_t ptrId) {
if (supported_ref_ptrs_.find(ptrId) != supported_ref_ptrs_.end()) return true;
if (get_def_use_mgr()->WhileEachUser(ptrId, [this](Instruction* user) {
SpvOp op = user->opcode();
if (IsNonPtrAccessChain(op) || op == SpvOpCopyObject) {
if (!HasOnlySupportedRefs(user->result_id())) {
return false;
}
} else if (op != SpvOpStore && op != SpvOpLoad && op != SpvOpName &&
!IsNonTypeDecorate(op)) {
return false;
}
return true;
})) {
supported_ref_ptrs_.insert(ptrId);
return true;
}
return false;
}
bool LocalSingleBlockLoadStoreElimPass::LocalSingleBlockLoadStoreElim(
Function* func) {
// Perform local store/load, load/load and store/store elimination
// on each block
bool modified = false;
std::vector<Instruction*> instructions_to_kill;
std::unordered_set<Instruction*> instructions_to_save;
for (auto bi = func->begin(); bi != func->end(); ++bi) {
var2store_.clear();
var2load_.clear();
auto next = bi->begin();
for (auto ii = next; ii != bi->end(); ii = next) {
++next;
switch (ii->opcode()) {
case SpvOpStore: {
// Verify store variable is target type
uint32_t varId;
Instruction* ptrInst = GetPtr(&*ii, &varId);
if (!IsTargetVar(varId)) continue;
if (!HasOnlySupportedRefs(varId)) continue;
// If a store to the whole variable, remember it for succeeding
// loads and stores. Otherwise forget any previous store to that
// variable.
if (ptrInst->opcode() == SpvOpVariable) {
// If a previous store to same variable, mark the store
// for deletion if not still used.
auto prev_store = var2store_.find(varId);
if (prev_store != var2store_.end() &&
instructions_to_save.count(prev_store->second) == 0) {
instructions_to_kill.push_back(prev_store->second);
modified = true;
}
bool kill_store = false;
auto li = var2load_.find(varId);
if (li != var2load_.end()) {
if (ii->GetSingleWordInOperand(kStoreValIdInIdx) ==
li->second->result_id()) {
// We are storing the same value that already exists in the
// memory location. The store does nothing.
kill_store = true;
}
}
if (!kill_store) {
var2store_[varId] = &*ii;
var2load_.erase(varId);
} else {
instructions_to_kill.push_back(&*ii);
modified = true;
}
} else {
assert(IsNonPtrAccessChain(ptrInst->opcode()));
var2store_.erase(varId);
var2load_.erase(varId);
}
} break;
case SpvOpLoad: {
// Verify store variable is target type
uint32_t varId;
Instruction* ptrInst = GetPtr(&*ii, &varId);
if (!IsTargetVar(varId)) continue;
if (!HasOnlySupportedRefs(varId)) continue;
uint32_t replId = 0;
if (ptrInst->opcode() == SpvOpVariable) {
// If a load from a variable, look for a previous store or
// load from that variable and use its value.
auto si = var2store_.find(varId);
if (si != var2store_.end()) {
replId = si->second->GetSingleWordInOperand(kStoreValIdInIdx);
} else {
auto li = var2load_.find(varId);
if (li != var2load_.end()) {
replId = li->second->result_id();
}
}
} else {
// If a partial load of a previously seen store, remember
// not to delete the store.
auto si = var2store_.find(varId);
if (si != var2store_.end()) instructions_to_save.insert(si->second);
}
if (replId != 0) {
// replace load's result id and delete load
context()->KillNamesAndDecorates(&*ii);
context()->ReplaceAllUsesWith(ii->result_id(), replId);
instructions_to_kill.push_back(&*ii);
modified = true;
} else {
if (ptrInst->opcode() == SpvOpVariable)
var2load_[varId] = &*ii; // register load
}
} break;
case SpvOpFunctionCall: {
// Conservatively assume all locals are redefined for now.
// TODO(): Handle more optimally
var2store_.clear();
var2load_.clear();
} break;
default:
break;
}
}
}
for (Instruction* inst : instructions_to_kill) {
context()->KillInst(inst);
}
return modified;
}
void LocalSingleBlockLoadStoreElimPass::Initialize() {
// Initialize Target Type Caches
seen_target_vars_.clear();
seen_non_target_vars_.clear();
// Clear collections
supported_ref_ptrs_.clear();
// Initialize extensions whitelist
InitExtensions();
}
bool LocalSingleBlockLoadStoreElimPass::AllExtensionsSupported() const {
// If any extension not in whitelist, return false
for (auto& ei : get_module()->extensions()) {
const char* extName =
reinterpret_cast<const char*>(&ei.GetInOperand(0).words[0]);
if (extensions_whitelist_.find(extName) == extensions_whitelist_.end())
return false;
}
return true;
}
Pass::Status LocalSingleBlockLoadStoreElimPass::ProcessImpl() {
// Assumes relaxed logical addressing only (see instruction.h).
if (context()->get_feature_mgr()->HasCapability(SpvCapabilityAddresses))
return Status::SuccessWithoutChange;
// Do not process if module contains OpGroupDecorate. Additional
// support required in KillNamesAndDecorates().
// TODO(greg-lunarg): Add support for OpGroupDecorate
for (auto& ai : get_module()->annotations())
if (ai.opcode() == SpvOpGroupDecorate) return Status::SuccessWithoutChange;
// If any extensions in the module are not explicitly supported,
// return unmodified.
if (!AllExtensionsSupported()) return Status::SuccessWithoutChange;
// Process all entry point functions
ProcessFunction pfn = [this](Function* fp) {
return LocalSingleBlockLoadStoreElim(fp);
};
bool modified = context()->ProcessEntryPointCallTree(pfn);
return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange;
}
LocalSingleBlockLoadStoreElimPass::LocalSingleBlockLoadStoreElimPass() =
default;
Pass::Status LocalSingleBlockLoadStoreElimPass::Process() {
Initialize();
return ProcessImpl();
}
void LocalSingleBlockLoadStoreElimPass::InitExtensions() {
extensions_whitelist_.clear();
extensions_whitelist_.insert({
"SPV_AMD_shader_explicit_vertex_parameter",
"SPV_AMD_shader_trinary_minmax",
"SPV_AMD_gcn_shader",
"SPV_KHR_shader_ballot",
"SPV_AMD_shader_ballot",
"SPV_AMD_gpu_shader_half_float",
"SPV_KHR_shader_draw_parameters",
"SPV_KHR_subgroup_vote",
"SPV_KHR_16bit_storage",
"SPV_KHR_device_group",
"SPV_KHR_multiview",
"SPV_NVX_multiview_per_view_attributes",
"SPV_NV_viewport_array2",
"SPV_NV_stereo_view_rendering",
"SPV_NV_sample_mask_override_coverage",
"SPV_NV_geometry_shader_passthrough",
"SPV_AMD_texture_gather_bias_lod",
"SPV_KHR_storage_buffer_storage_class",
// SPV_KHR_variable_pointers
// Currently do not support extended pointer expressions
"SPV_AMD_gpu_shader_int16",
"SPV_KHR_post_depth_coverage",
"SPV_KHR_shader_atomic_counter_ops",
"SPV_EXT_shader_stencil_export",
"SPV_EXT_shader_viewport_index_layer",
"SPV_AMD_shader_image_load_store_lod",
"SPV_AMD_shader_fragment_mask",
"SPV_EXT_fragment_fully_covered",
"SPV_AMD_gpu_shader_half_float_fetch",
"SPV_GOOGLE_decorate_string",
"SPV_GOOGLE_hlsl_functionality1",
"SPV_NV_shader_subgroup_partitioned",
"SPV_EXT_descriptor_indexing",
"SPV_NV_fragment_shader_barycentric",
"SPV_NV_compute_shader_derivatives",
"SPV_NV_shader_image_footprint",
"SPV_NV_shading_rate",
"SPV_NV_mesh_shader",
"SPV_NV_ray_tracing",
"SPV_EXT_fragment_invocation_density",
});
}
} // namespace opt
} // namespace spvtools