Re: [Lightning] Bytecode compiler

[Paolo Bonzini]

On 12/06/2010 08:13 PM, Paulo César Pereira de Andrade wrote:
> o Left to right argument evaluation; when passing arguments
>    in registers, right to left just make things harder than they
>    should be and also unnatural, I managed to get along for
>    x86_64 varargs, but mips n32 abi is really designed to build
>    stack frames left to right. I believe the right to left approach
>    is a remaining of i386 only/initial code, or is working with
>    register windows easier right to left also? Sorry, no experience
>    with sparc...
>    This could also cause some issues with code that jumps from
>    code from one jit_prolog to another, and is the only reason I
>    did make default in my fork the "push_pop" option.

This is fine.  Just allocate all space in jit_prepare and replace push 
with mov.

However, this requires changing the header file name to signify the new ABI.

> o "l" "ell" modifier is 64 bits. "ll" probably would only add
>   confusion, but the idea would be to support 64 bit values
>   on 32 bit.

This is already supported, but you have to use addc/addx manually. 
Multi-word values simply do not belong in a low-level IR such as lightning.

> o The intermediate representation also would have the advantage
>   of being able to do better register allocation, but would require
>   some kind of "virtual registers",

This can be isolated in your IR, it doesn't need to be known to lightning.

> jit_push/jit_pop would not be easily possible,
> I already dislike it :-)

They are deprecated anyway.

Paolo