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ivdep pragma not used in ddg.c?
- From: Bingfeng Mei <bmei at broadcom dot com>
- To: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Date: Wed, 9 Jul 2014 10:49:15 +0000
- Subject: ivdep pragma not used in ddg.c?
- Authentication-results: sourceware.org; auth=none
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
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?