Function GetConstantUniformValue

source/opt/const_folding_rules.cpp:1079–1118

Get a singular uniform value, which is repeated when the |type| is a vector.

// Get a singular uniform value, which is repeated when the |type| is a vector.
const analysis::Constant* GetConstantUniformValue(
    analysis::ConstantManager* const_mgr, const analysis::Type* type,
    std::optional<double> f = {}, std::optional<uint64_t> i = {}) {
  const analysis::Constant* uniform = nullptr;
  bool is_vector = false;
  const analysis::Type* base_type = type;

  if (base_type->AsVector()) {
    is_vector = true;
    base_type = base_type->AsVector()->element_type();
  }

  if (f && base_type->AsFloat()) {
    if (base_type->AsFloat()->width() == 32) {
      uniform = const_mgr->GetConstant(
          base_type, utils::FloatProxy<float>((float)f.value()).GetWords());
    } else if (base_type->AsFloat()->width() == 64) {
      uniform = const_mgr->GetConstant(
          base_type, utils::FloatProxy<double>(f.value()).GetWords());
    }
  } else if (i && base_type->AsInteger()) {
    uniform =
        const_mgr->GenerateIntegerConstant(base_type->AsInteger(), i.value());
  }

  if (!uniform) {
    return nullptr;
  }

  if (is_vector) {
    Instruction* uniform_inst = const_mgr->GetDefiningInstruction(uniform);
    if (!uniform_inst) return nullptr;

    uint32_t uniform_id = uniform_inst->result_id();
    uniform =
        const_mgr->GetConstant(type, std::vector<uint32_t>(4, uniform_id));
  }

  return uniform;
}

//  x /  x =  1
// -x /  x = -1