Re: [Lightning] sse instructions and gcc warnings

[Paolo Bonzini]

On 07/26/2010 08:45 AM, Paulo César Pereira de Andrade wrote:
>    Hi,
>
>    I did some more extra work in the lightning jit code generation
> in my language
> http://code.google.com/p/exl/source/browse/trunk/lib/elightning.c
>
>    It is still basically using lightning only to glue calls to C
> functions, but I added some extra code for statically typed objects
> yesterday and today...
>
>    But about @subject:
> elightning.c:1664: warning: left-hand operand of comma expression has no
> effect
> elightning.c:1664: warning: value computed is not used
>
> any code using the float registers shows those.

These are harmless and kind of inevitable.

 There are some others
> on x86_64 that cannot be masked, due to mixing int32 and void*.

Do you have a small testcase for this?

> A strange one is:
> elightning.c:1616: warning: implicit declaration of function ‘jit_replace’
> elightning.c:1616: warning: nested extern declaration of ‘jit_replace’
>
> that probably is harmless, as it links and works.

It links only because the particular combination involving jit_replace 
was optimized out by the compiler.  I committed a fix, too bad I don't 
really have the time to write a test case too. :(

>    Also about @subject, I needed to add a global function to check
> if a double is zero, because apparently the i387 goes nonsense if
> a function using vector instructions was called.

Argument passing in i387 was buggy, it is kind of impossible to get it 
right due to the stack-like registers. :(

I think I'm going to change it to use SSE always except for argument 
passing.  Would this be a problem?

Paolo