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Why is debug_insn built into DDG?
- From: "Bingfeng Mei" <bmei at broadcom dot com>
- To: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Cc: "aoliva at redhat dot com" <aoliva at redhat dot com>
- Date: Thu, 15 Jul 2010 07:47:32 -0700
- Subject: Why is debug_insn built into DDG?
Hello,
I started to look at VTA recently and check whether our port passes
the -fcompare-debug test. Our port contains some extra passes for
our VLIW target.
What I have trouble is with our modulo scheduling pass (based on
IMS algorithm). I noticed that debug_insns are built into DDG,
and has ANTI-dependence edge drawn between other instruction and them.
This dependencies will affect calculation of ASAP, ALAP etc, therefore
affect ordering algorithm and final scheduling results. Why these
debug_insns are needed in the DDG in the first place? They are skipped
during scheduling anyway. Isn't it waste of compilation time?
Thanks,
Bingfeng