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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_store_elim_pass.h"
#include "source/cfa.h"
#include "source/latest_version_glsl_std_450_header.h"
#include "source/opt/iterator.h"
namespace spvtools {
namespace opt {
namespace {
const uint32_t kStoreValIdInIdx = 1;
const uint32_t kVariableInitIdInIdx = 1;
} // anonymous namespace
bool LocalSingleStoreElimPass::LocalSingleStoreElim(Function* func) {
bool modified = false;
// Check all function scope variables in |func|.
BasicBlock* entry_block = &*func->begin();
for (Instruction& inst : *entry_block) {
if (inst.opcode() != SpvOpVariable) {
break;
}
modified |= ProcessVariable(&inst);
}
return modified;
}
bool LocalSingleStoreElimPass::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 LocalSingleStoreElimPass::ProcessImpl() {
// Assumes relaxed logical addressing only (see instruction.h)
if (context()->get_feature_mgr()->HasCapability(SpvCapabilityAddresses))
return Status::SuccessWithoutChange;
// Do not process if any disallowed extensions are enabled
if (!AllExtensionsSupported()) return Status::SuccessWithoutChange;
// Process all entry point functions
ProcessFunction pfn = [this](Function* fp) {
return LocalSingleStoreElim(fp);
};
bool modified = context()->ProcessEntryPointCallTree(pfn);
return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange;
}
LocalSingleStoreElimPass::LocalSingleStoreElimPass() = default;
Pass::Status LocalSingleStoreElimPass::Process() {
InitExtensionWhiteList();
return ProcessImpl();
}
void LocalSingleStoreElimPass::InitExtensionWhiteList() {
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",
"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",
"SPV_EXT_physical_storage_buffer",
});
}
bool LocalSingleStoreElimPass::ProcessVariable(Instruction* var_inst) {
std::vector<Instruction*> users;
FindUses(var_inst, &users);
Instruction* store_inst = FindSingleStoreAndCheckUses(var_inst, users);
if (store_inst == nullptr) {
return false;
}
return RewriteLoads(store_inst, users);
}
Instruction* LocalSingleStoreElimPass::FindSingleStoreAndCheckUses(
Instruction* var_inst, const std::vector<Instruction*>& users) const {
// Make sure there is exactly 1 store.
Instruction* store_inst = nullptr;
// If |var_inst| has an initializer, then that will count as a store.
if (var_inst->NumInOperands() > 1) {
store_inst = var_inst;
}
for (Instruction* user : users) {
switch (user->opcode()) {
case SpvOpStore:
// Since we are in the relaxed addressing mode, the use has to be the
// base address of the store, and not the value being store. Otherwise,
// we would have a pointer to a pointer to function scope memory, which
// is not allowed.
if (store_inst == nullptr) {
store_inst = user;
} else {
// More than 1 store.
return nullptr;
}
break;
case SpvOpAccessChain:
case SpvOpInBoundsAccessChain:
if (FeedsAStore(user)) {
// Has a partial store. Cannot propagate that.
return nullptr;
}
break;
case SpvOpLoad:
case SpvOpImageTexelPointer:
case SpvOpName:
case SpvOpCopyObject:
break;
default:
if (!user->IsDecoration()) {
// Don't know if this instruction modifies the variable.
// Conservatively assume it is a store.
return nullptr;
}
break;
}
}
return store_inst;
}
void LocalSingleStoreElimPass::FindUses(
const Instruction* var_inst, std::vector<Instruction*>* users) const {
analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
def_use_mgr->ForEachUser(var_inst, [users, this](Instruction* user) {
users->push_back(user);
if (user->opcode() == SpvOpCopyObject) {
FindUses(user, users);
}
});
}
bool LocalSingleStoreElimPass::FeedsAStore(Instruction* inst) const {
analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
return !def_use_mgr->WhileEachUser(inst, [this](Instruction* user) {
switch (user->opcode()) {
case SpvOpStore:
return false;
case SpvOpAccessChain:
case SpvOpInBoundsAccessChain:
case SpvOpCopyObject:
return !FeedsAStore(user);
case SpvOpLoad:
case SpvOpImageTexelPointer:
case SpvOpName:
return true;
default:
// Don't know if this instruction modifies the variable.
// Conservatively assume it is a store.
return user->IsDecoration();
}
});
}
bool LocalSingleStoreElimPass::RewriteLoads(
Instruction* store_inst, const std::vector<Instruction*>& uses) {
BasicBlock* store_block = context()->get_instr_block(store_inst);
DominatorAnalysis* dominator_analysis =
context()->GetDominatorAnalysis(store_block->GetParent());
uint32_t stored_id;
if (store_inst->opcode() == SpvOpStore)
stored_id = store_inst->GetSingleWordInOperand(kStoreValIdInIdx);
else
stored_id = store_inst->GetSingleWordInOperand(kVariableInitIdInIdx);
std::vector<Instruction*> uses_in_store_block;
bool modified = false;
for (Instruction* use : uses) {
if (use->opcode() == SpvOpLoad) {
if (dominator_analysis->Dominates(store_inst, use)) {
modified = true;
context()->KillNamesAndDecorates(use->result_id());
context()->ReplaceAllUsesWith(use->result_id(), stored_id);
context()->KillInst(use);
}
}
}
return modified;
}
} // namespace opt
} // namespace spvtools