Hi,
I noticed recent GCC adds ivdep pragma support. We have our own implementation
for ivdep for a couple of years now. As GCC implementation is much cleaner and
we want to migrate to it. Ivdep is consumed in two places in our
implementation, one is tree-vect-data-refs.c used by vectorizer, the other is
in ddg.c, used by modulo scheduler. In GCC implementation, the former is the
same, but ddg.c doesn't consume ivdep information at all. I think it is
important not to draw redundant cross-iteration dependence if ivdep is
specified in order to improve modulo scheduling performance.
Looking at the code, I wonder whether loop->safelen still keep the correct
information or whether loop structure still remain correct after so many
tree/rtl passes. For example, in sms-schedule of modulo-sched.c
loop_optimizer_init (LOOPS_HAVE_PREHEADERS
| LOOPS_HAVE_RECORDED_EXITS);
Does this mean loop structure is reinitialized? I know there is a flag
(PROP_loops) which is supposed to preserve loop structure. But not sure what
happens after all loop transformation (unrolling, peeling, etc). Is there a
stage loop structure is rebuilt and we lost safelen (ivdep) information, or it
is still safe to use in modulo scheduling pass?
Thanks,
Bingfeng
