lua-users home
lua-l archive

[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index] [Thread Index] 



On 2017-09-06 03:21 PM, Egor Skriptunoff wrote:

On Wed, Sep 6, 2017 at 4:28 PM, Soni L. wrote:

    While playing with the Lua parser I noticed OP_SELF uses an
    unnecessary extra register, but this is only visible if you have
    more than 256 constants.

        771    [258]    LOADK        3 -257    ; "print"
        772    [258]    SELF         1 1 3


This is not a bug.
Instruction "SELF 1 1 -257" is impossible due to limitation of 9 bits per constant index (operand C) for opcode SELF. On the contrary, LOADK can address any constant using 18-bit field (field Bx). That's why all constants except first 256 have to be passed through intermediate register. 




SELF takes 2 inputs and produces 2 outputs, so why's it 1 1 3 and not 1 1 2?

--
Disclaimer: these emails may be made public at any given time, with or without reason. If you don't agree with this, DO NOT REPLY.