[Lightning] Re: Some questions about minor changes

[Paolo Bonzini]

On 09/24/2010 10:16 AM, Paulo César Pereira de Andrade wrote:
>    About the questions:
> o Is it a problem to use byte or word opcodes, i.e. will it cause some kind
>    of register stall, or something, like setting %al or testing %ax, when only
>    that is used, e.g. setting %al as "hidden" counter of xmm registers used
>    when calling a varargs function, or test %ax after fnstw?

I think it's good as long as you read the small register after possibly 
writing the large one.  Writing the small register and reading the large 
one later has performance penalties, instead.

> o Would it be a good idea to either add new interfaces, or change the
>    existing one? e.g. jit_prepare and jit_prolog would be better with 3
>    arguments,to properly calculate the stack offsets, when keeping the stack 
> aligned at
>    16 bytes, otherwise, it requires a not so clear logic, to "intercept" the
>    first call to jit_pusharg_t, jit_arg_t and/or jit_allocai.

Can you explain exactly why?
>    I understand that, to some extent, I am adding significant extra
> complexity to lightning, by adding support to any number of arguments
> for example.

No, your work is much appreciated, even though I'm wondering myself if 
you wouldn't have made your life easier by using LLVM...

Paolo