[Bug rtl-optimization/33224] failing rtl iv analysis (maybe due to df)

["rakdver at kam dot mff dot cuni dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #7 from rakdver at kam dot mff dot cuni dot cz  2007-08-30 18:09 -------
Subject: Re:  failing rtl iv analysis (maybe due to df)

> The only thing that you are allowed to do with the DF_REF_ID is to get
> it from a df_def
> AFTER YOU ARE SURE THAT THE DEF IS IN THE REGION

OK, this might be the problem; the code takes the defs from the reg->def
lists, and checks whether the defs are set in the reaching def bitmaps.
Naturally, it assumes that when the region is set by df_set_blocks, the
reaching def bitmaps will only contain the defs that belong to the
region (which used to be true before your changes).

Anyway, it would be nice to have some documentation for df (there
is only a short notice in
http://gcc.gnu.org/onlinedocs/gccint/Liveness-information.html#Liveness-information,
which appears wrong given the importance of this api), in particular
pointing out such non-obvious traps would be great.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33224