Re: Lua code generation and optimisation
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- Subject: Re: Lua code generation and optimisation
- From: "David Collier" <myshkin@...>
- Date: Wed, 3 Oct 2012 13:14 +0100 (BST)
Thanks both.
I did appreciate that unless there were language features I hadn't
spotted yet the code would have to get included.
I guess a preprocessor is the only option without a language extension.
I'm feeling my way towards a coding standard for Lua - I find the dynamic
typing makes me want to say we should check the type and range of
arguments to a 'company library routine' on entry, but I also want to be
able to write code for eLua, where the installed code should probably run
without the checks. But I only want one copy of the source to maintain.
I suppose I could write a function "checkargs", and pass it the arguments
and 1-byte statements of what they should be at the head of each routine.
Then I can replace that routine with 'ret'
Or I can dig around for a Lua preprocessor, and try to work out how to
tell eclipse to run it for me each time :-)
D.
> *From:* "Michal Kolodziejczyk" <miko@wp.pl>
> *To:* <lua-l@lists.lua.org>
> *Date:* 2012年10月03日 09:30:00 +0200
>
> On 02.10.2012 18:36, David Collier wrote:
> > I'm thinking about code size.
> >
> > If I write
> >
> > if CheckCarefully and fred > 3
> > then
> > print("help fred is >3 which is a very bad idea in our case")
> > return
> > else
> > <whatever using fred>
> > end
> >
> > Can I set up the value of CheckCarefully so that the compiler can
> > omit
> > the print and omit storing the error string.
>
> What compiler are you writing about? Lua has an interpreter and no
> compiler. LuaJIT has just-in-time compiler, but it "compiles" code
> as it
> runs (so it still needs the full original source/bytecode).
>
> > Or will it always create the strings in the bytecode?
>
> Yes. Check for yourself:
> $ luac -l example.lua
>
> main <example.lua:0,0> (15 instructions, 60 bytes at 0x985bd18)
> 0+ params, 2 slots, 0 upvalues, 0 locals, 6 constants, 0 functions
> 1 [2] GETGLOBAL 0 -1 ; CheckCarefully
> 2 [2] TEST 0 0 0
> 3 [2] JMP 8 ; to 12
> 4 [2] GETGLOBAL 0 -2 ; fred
> 5 [2] LT 0 -3 0 ; 3 -
> 6 [2] JMP 5 ; to 12
> 7 [3] GETGLOBAL 0 -4 ; print
> 8 [3] LOADK 1 -5 ; "help fred is >3 which is a very bad idea
> in our
> case"
> 9 [3] CALL 0 2 1
> 10 [4] RETURN 0 1
> 11 [4] JMP 3 ; to 15
> 12 [6] GETGLOBAL 0 -4 ; print
> 13 [6] LOADK 1 -6 ; "<whatever using fred>"
> 14 [6] CALL 0 2 1
> 15 [7] RETURN 0 1
>
> > If this won't work, anyone got a good way to have code and
> > strings in
> > during testing phase and omitted in deployed code?
>
> You are looking for any kind of preprocessor, echeck out metalua:
> http://metalua.luaforge.net/
>
> Regards,
> miko
>
>
>