Function pick_temp_reg

src/codec.cpp:265–279

pick a per-seed shuffled scratch from the volatile pool that doesn't collide with any caller-supplied register

    // pick a per-seed shuffled scratch from the volatile pool that doesn't
    // collide with any caller-supplied register 
    static std::uint8_t pick_temp_reg(const VMConfig& vm,
                                      std::uint64_t salt,
                                      std::initializer_list<std::uint8_t> avoid) {
        std::array<std::uint8_t, 7> pool{rx::rax, rx::rcx, rx::rdx, rx::r8, rx::r9, rx::r10, rx::r11};
        SeedRng local(vm.cipher_k1() ^ salt);
        shuffle_in_place(pool, local);

        for (std::uint8_t r : pool) {
            bool collide = false;
            for (std::uint8_t a : avoid) if (a == r) { collide = true; break; }
            if (!collide) return r;
        }

        return rx::rdx; // unreachable: pool > avoid
    }

    // mask reg to width_reg's width, stripping the high-byte flag 
    static void emit_mask_to_width(X64Emitter& e, const VMConfig& vm,