ivdep pragma not used in ddg.c?

[Bingfeng Mei <bmei at broadcom dot com>]

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