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Re: RFA: ia64 portion of libunwind patch


On Fri, 07 Nov 2003 16:46:59 -0500, Andrew Cagney <ac131313@redhat.com> said:


Andrew> Would it be possible to define the interface so that, when Andrew> dip-> u.ti.table_data is NULL, the code just fetches values Andrew> from memory using the memory callbacks? i.e., don't require Andrew> GDB to fetch the entire table but instead fetch the bits Andrew> that are needed.

Well, it's software, so anything is _possible_, but I'd rather not do
that, because it creates artificial differences between the
(speed-critical) local unwind case and the remote unwind case.
Furthermore, the unwind table is of a known size, relatively small,
and accessed fairly randomly (via binary search), so it is normally
preferable to read the table all at once and I'd rather design the API
for this common case.

Your comparing the self unwind case (i.e., what happens when a program does a "throw") vs the external unwind case (i.e., like what GDB has to do)?


Is fetching the table elements via a function, rather than a direct access, really that significant an overhead?

Andrew



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