Initialize INSN_COND

Alexander Monakov amonakov@ispras.ru
Fri Jun 3 17:44:00 GMT 2011



On Thu, 2 Jun 2011, Bernd Schmidt wrote:

> Ok. Although I wonder how sel-sched can end up reusing an entry in
> h_d_i_d? How does it use this machinery? If it's not doing a normal
> forward scan as in sched_analyze, the INSN_COND mechanism may break in
> other ways.

Indeed, that patch did not completely solve the problem, as stale INSN_CONDs
can still be seen (I have a testcase reduced from combine.c).  Selective
scheduler's dependency analysis is certainly not limited to a single pass, as
it will test more dependencies on the fly after e.g. creating bookkeeping.

Was there some particular breakage you had in mind when mentioning that
INSN_CONDs may break in other ways?

Can you tell why you chose to place INSN_CONDs into HDID instead of HID?
HID seems a bit more natural choice to me, and as it explicitely populated
with zeros, it fixes the above combine.c testcase for me.  However, moving
INSN_CONDs to HID breaks sel-sched in a different way because sometimes HID is
not extended early enough; if that approach is generally ok for you, I can see
whether I can produce a working patch in that vein.

FWIW, we have a patch that adds predication support for the selective
scheduler (allowing the scheduler to transform insns into predicated form)
that we plan to submit during this stage1.

Thanks.
Alexander



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