[PATCH i386] Allow sibcalls in no-PLT PIC

Richard Henderson rth@redhat.com
Tue May 19 20:16:00 GMT 2015


On 05/19/2015 12:35 PM, Rich Felker wrote:
> Why would you recompute it (this requires a fairly expensive call that
> reads or pops its own return address) rather than simply spilling the
> already-computed value and reloading it from the stack?
> 
> The only example I can think of where it might make sense is when you
> don't want to load the address unconditionally because there are
> shrink-wrappable code paths that don't need it, but multple code paths
> that do, in which case they would each load different values. Is this
> the concern you have in mind?

That too.  I was thinking of exception landing pads, i.e. catches and cleanups,
where in the past we've had to re-compute the GOT address.  Though now that I
think on that more, it wasn't x86 that had that particular landing pad trouble.


r~



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