Function LookupExtInst

source/table2.cpp:297–322

}

spv_result_t LookupExtInst(spv_ext_inst_type_t type, const char* name,
                           const ExtInstDesc** desc) {
  auto ir = ExtInstNameRangeForKind(type);
  if (ir.empty()) {
    return SPV_ERROR_INVALID_LOOKUP;
  }

  auto span = ir.apply(kExtInstNames.data());

  // The comparison function knows to use 'name' string to compare against
  // when the value is kSentinel.
  const auto kSentinel = uint32_t(-1);
  const NameIndex needle{{}, kSentinel};
  auto less = [&](const NameIndex& lhs, const NameIndex& rhs) {
    const char* lhs_chars = lhs.index == kSentinel ? name : getChars(lhs.name);
    const char* rhs_chars = rhs.index == kSentinel ? name : getChars(rhs.name);
    return std::strcmp(lhs_chars, rhs_chars) < 0;
  };

  auto where = std::lower_bound(span.begin(), span.end(), needle, less);
  if (where != span.end() && std::strcmp(getChars(where->name), name) == 0) {
    *desc = &kExtInstByValue[where->index];
    return SPV_SUCCESS;
  }
  return SPV_ERROR_INVALID_LOOKUP;
}

// Finds the extended instruction description by opcode value.
// On success, returns SPV_SUCCESS and updates *desc.