Method getScratch

src/e9tool/e9metadata.cpp:219–243

* Get a suitable scratch register. */

     * Get a suitable scratch register.
     */
    Register getScratch(const Register *exclude = nullptr)
    {
        Register reg = REGISTER_INVALID;
        for (const auto &entry: info)
        {
            int regno = getRegIdx(entry.first);
            if (regno < 0 || regno == FLAGS_IDX || regno == RSP_IDX ||
                    regno == RIP_IDX)
                continue;
            bool found = false;
            for (unsigned i = 0; !found && exclude != nullptr &&
                    exclude[i] != REGISTER_INVALID; i++)
                found = (entry.first == exclude[i]);
            if (found)
                continue;
            const RegInfo &rinfo = entry.second;
            if (rinfo.used)
                continue;
            if (rinfo.clobbered)
                return entry.first;
            if (rinfo.saved)
                reg = entry.first;
        }
        return reg;
    }

    /*
     * Emulate a register push.