text: // 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_access_chain_convert_pass.h"
  
  #include "ir_builder.h"
  #include "ir_context.h"
  #include "iterator.h"
  
  namespace spvtools {
  namespace opt {
  
  namespace {
  
  const uint32_t kStoreValIdInIdx = 1;
  const uint32_t kAccessChainPtrIdInIdx = 0;
  const uint32_t kConstantValueInIdx = 0;
  const uint32_t kTypeIntWidthInIdx = 0;
  
  }  // anonymous namespace
  
  void LocalAccessChainConvertPass::BuildAndAppendInst(
      SpvOp opcode, uint32_t typeId, uint32_t resultId,
      const std::vector<Operand>& in_opnds,
      std::vector<std::unique_ptr<Instruction>>* newInsts) {
    std::unique_ptr<Instruction> newInst(
        new Instruction(context(), opcode, typeId, resultId, in_opnds));
    get_def_use_mgr()->AnalyzeInstDefUse(&*newInst);
    newInsts->emplace_back(std::move(newInst));
  }
  
  uint32_t LocalAccessChainConvertPass::BuildAndAppendVarLoad(
      const Instruction* ptrInst, uint32_t* varId, uint32_t* varPteTypeId,
      std::vector<std::unique_ptr<Instruction>>* newInsts) {
    const uint32_t ldResultId = TakeNextId();
    *varId = ptrInst->GetSingleWordInOperand(kAccessChainPtrIdInIdx);
    const Instruction* varInst = get_def_use_mgr()->GetDef(*varId);
    assert(varInst->opcode() == SpvOpVariable);
    *varPteTypeId = GetPointeeTypeId(varInst);
    BuildAndAppendInst(SpvOpLoad, *varPteTypeId, ldResultId,
                       {{spv_operand_type_t::SPV_OPERAND_TYPE_ID, {*varId}}},
                       newInsts);
    return ldResultId;
  }
  
  void LocalAccessChainConvertPass::AppendConstantOperands(
      const Instruction* ptrInst, std::vector<Operand>* in_opnds) {
    uint32_t iidIdx = 0;
    ptrInst->ForEachInId([&iidIdx, &in_opnds, this](const uint32_t* iid) {
      if (iidIdx > 0) {
        const Instruction* cInst = get_def_use_mgr()->GetDef(*iid);
        uint32_t val = cInst->GetSingleWordInOperand(kConstantValueInIdx);
        in_opnds->push_back(
            {spv_operand_type_t::SPV_OPERAND_TYPE_LITERAL_INTEGER, {val}});
      }
      ++iidIdx;
    });
  }
  
  void LocalAccessChainConvertPass::ReplaceAccessChainLoad(
      const Instruction* address_inst, Instruction* original_load) {
    // Build and append load of variable in ptrInst
    std::vector<std::unique_ptr<Instruction>> new_inst;
    uint32_t varId;
    uint32_t varPteTypeId;
    const uint32_t ldResultId =
        BuildAndAppendVarLoad(address_inst, &varId, &varPteTypeId, &new_inst);
    context()->get_decoration_mgr()->CloneDecorations(
        original_load->result_id(), ldResultId, {SpvDecorationRelaxedPrecision});
    original_load->InsertBefore(std::move(new_inst));
  
    // Rewrite |original_load| into an extract.
    Instruction::OperandList new_operands;
  
    // copy the result id and the type id to the new operand list.
    new_operands.emplace_back(original_load->GetOperand(0));
    new_operands.emplace_back(original_load->GetOperand(1));
  
    new_operands.emplace_back(
        Operand({spv_operand_type_t::SPV_OPERAND_TYPE_ID, {ldResultId}}));
    AppendConstantOperands(address_inst, &new_operands);
    original_load->SetOpcode(SpvOpCompositeExtract);
    original_load->ReplaceOperands(new_operands);
    context()->UpdateDefUse(original_load);
  }
  
  void LocalAccessChainConvertPass::GenAccessChainStoreReplacement(
      const Instruction* ptrInst, uint32_t valId,
      std::vector<std::unique_ptr<Instruction>>* newInsts) {
    // Build and append load of variable in ptrInst
    uint32_t varId;
    uint32_t varPteTypeId;
    const uint32_t ldResultId =
        BuildAndAppendVarLoad(ptrInst, &varId, &varPteTypeId, newInsts);
    context()->get_decoration_mgr()->CloneDecorations(
        varId, ldResultId, {SpvDecorationRelaxedPrecision});
  
    // Build and append Insert
    const uint32_t insResultId = TakeNextId();
    std::vector<Operand> ins_in_opnds = {
        {spv_operand_type_t::SPV_OPERAND_TYPE_ID, {valId}},
        {spv_operand_type_t::SPV_OPERAND_TYPE_ID, {ldResultId}}};
    AppendConstantOperands(ptrInst, &ins_in_opnds);
    BuildAndAppendInst(SpvOpCompositeInsert, varPteTypeId, insResultId,
                       ins_in_opnds, newInsts);
  
    context()->get_decoration_mgr()->CloneDecorations(
        varId, insResultId, {SpvDecorationRelaxedPrecision});
  
    // Build and append Store
    BuildAndAppendInst(SpvOpStore, 0, 0,
                       {{spv_operand_type_t::SPV_OPERAND_TYPE_ID, {varId}},
                        {spv_operand_type_t::SPV_OPERAND_TYPE_ID, {insResultId}}},
                       newInsts);
  }
  
  bool LocalAccessChainConvertPass::IsConstantIndexAccessChain(
      const Instruction* acp) const {
    uint32_t inIdx = 0;
    return acp->WhileEachInId([&inIdx, this](const uint32_t* tid) {
      if (inIdx > 0) {
        Instruction* opInst = get_def_use_mgr()->GetDef(*tid);
        if (opInst->opcode() != SpvOpConstant) return false;
      }
      ++inIdx;
      return true;
    });
  }
  
  bool LocalAccessChainConvertPass::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;
  }
  
  void LocalAccessChainConvertPass::FindTargetVars(Function* func) {
    for (auto bi = func->begin(); bi != func->end(); ++bi) {
      for (auto ii = bi->begin(); ii != bi->end(); ++ii) {
        switch (ii->opcode()) {
          case SpvOpStore:
          case SpvOpLoad: {
            uint32_t varId;
            Instruction* ptrInst = GetPtr(&*ii, &varId);
            if (!IsTargetVar(varId)) break;
            const SpvOp op = ptrInst->opcode();
            // Rule out variables with non-supported refs eg function calls
            if (!HasOnlySupportedRefs(varId)) {
              seen_non_target_vars_.insert(varId);
              seen_target_vars_.erase(varId);
              break;
            }
            // Rule out variables with nested access chains
            // TODO(): Convert nested access chains
            if (IsNonPtrAccessChain(op) && ptrInst->GetSingleWordInOperand(
                                               kAccessChainPtrIdInIdx) != varId) {
              seen_non_target_vars_.insert(varId);
              seen_target_vars_.erase(varId);
              break;
            }
            // Rule out variables accessed with non-constant indices
            if (!IsConstantIndexAccessChain(ptrInst)) {
              seen_non_target_vars_.insert(varId);
              seen_target_vars_.erase(varId);
              break;
            }
          } break;
          default:
            break;
        }
      }
    }
  }
  
  bool LocalAccessChainConvertPass::ConvertLocalAccessChains(Function* func) {
    FindTargetVars(func);
    // Replace access chains of all targeted variables with equivalent
    // extract and insert sequences
    bool modified = false;
    for (auto bi = func->begin(); bi != func->end(); ++bi) {
      std::vector<Instruction*> dead_instructions;
      for (auto ii = bi->begin(); ii != bi->end(); ++ii) {
        switch (ii->opcode()) {
          case SpvOpLoad: {
            uint32_t varId;
            Instruction* ptrInst = GetPtr(&*ii, &varId);
            if (!IsNonPtrAccessChain(ptrInst->opcode())) break;
            if (!IsTargetVar(varId)) break;
            std::vector<std::unique_ptr<Instruction>> newInsts;
            ReplaceAccessChainLoad(ptrInst, &*ii);
            modified = true;
          } break;
          case SpvOpStore: {
            uint32_t varId;
            Instruction* ptrInst = GetPtr(&*ii, &varId);
            if (!IsNonPtrAccessChain(ptrInst->opcode())) break;
            if (!IsTargetVar(varId)) break;
            std::vector<std::unique_ptr<Instruction>> newInsts;
            uint32_t valId = ii->GetSingleWordInOperand(kStoreValIdInIdx);
            GenAccessChainStoreReplacement(ptrInst, valId, &newInsts);
            dead_instructions.push_back(&*ii);
            ++ii;
            ii = ii.InsertBefore(std::move(newInsts));
            ++ii;
            ++ii;
            modified = true;
          } break;
          default:
            break;
        }
      }
  
      while (!dead_instructions.empty()) {
        Instruction* inst = dead_instructions.back();
        dead_instructions.pop_back();
        DCEInst(inst, [&dead_instructions](Instruction* other_inst) {
          auto i = std::find(dead_instructions.begin(), dead_instructions.end(),
                             other_inst);
          if (i != dead_instructions.end()) {
            dead_instructions.erase(i);
          }
        });
      }
    }
    return modified;
  }
  
  void LocalAccessChainConvertPass::Initialize() {
    // Initialize Target Variable Caches
    seen_target_vars_.clear();
    seen_non_target_vars_.clear();
  
    // Initialize collections
    supported_ref_ptrs_.clear();
  
    // Initialize extension whitelist
    InitExtensions();
  }
  
  bool LocalAccessChainConvertPass::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 LocalAccessChainConvertPass::ProcessImpl() {
    // If non-32-bit integer type in module, terminate processing
    // TODO(): Handle non-32-bit integer constants in access chains
    for (const Instruction& inst : get_module()->types_values())
      if (inst.opcode() == SpvOpTypeInt &&
          inst.GetSingleWordInOperand(kTypeIntWidthInIdx) != 32)
        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;
    // 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 ConvertLocalAccessChains(fp);
    };
    bool modified = ProcessEntryPointCallTree(pfn, get_module());
    return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange;
  }
  
  LocalAccessChainConvertPass::LocalAccessChainConvertPass() {}
  
  Pass::Status LocalAccessChainConvertPass::Process() {
    Initialize();
    return ProcessImpl();
  }
  
  void LocalAccessChainConvertPass::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",
    });
  }
  
  }  // namespace opt
  }  // namespace spvtools
  