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Re: Urgent: bug fixes needed for GCC 3.0.2

>   > I'm not sure.  This is a MEM on the stack, and one that is not
>   > necessarily going to be around for the entire function -- witness
>   > the fact that we are going to overwrite it.  Perhaps I misunderstand
>   > a subtlety of RTX_UNCHANGING_P (quite likely, in fact!) but to me
>   > it doesn't make sense to set it for this MEM; the value there is
>   > likely to change.
>   >
>   > Am I speaking nonsense?
> Well, if it wasn't for the sibcall optimization the stack slot would be
> unchanging.  That's the crux of the issue.

Yes.  Perhaps a good fix, in the 3.0.2 time frame, is to turn off
RTX_UNCHANGING_P if flag_sibling_calls is on.

> If we believe that without the sibcall that having RTX_UNCHANGING_P set is
> correct and desirable, then we need to clear the bit if we have a sibcall
> since the sibcall sequence will overwrite the incoming stack slots.  This
> may (or may not) be a difficult thing to do.

It sounds difficult to me.  Especially to get right the first time.

Mark Mitchell         
CodeSourcery, LLC     

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