DF_DU_CHAIN | DF_UD_CHAIN flags in new-ra

[Mukta Punjani, Noida]

>It's possible that this is a problem with the incremental 
>building.  The
>later rounds of coloring just update the df information, instead of
>rebuilding it from scratch.

The problem doesn't seem to be in the incremental web building but the
initial run itself.

>Because I never used the def-use 
>chains from
>df.c I also didn't test if the updating mechanism works 
>correctly on that
>part of the information.  The strange thing though is, that 
>the allocator
>doesn't make use of this information anyway, so I wonder why 
>it causes any
>errors depending on the existence of it.

No idea about this, but there seems to be some patch at
http://gcc.gnu.org/ml/gcc-patches/2001-09/msg01199.html. Applying this
change in new-regalloc seems to result in another segmentation fault ICE.

>You would have to debug it
>further.  The error itself means, that some sanity check went 
>wrong.  Have
>you tried also with the newregalloc-branch?

This ICE appears on new-regalloc branch.

~ Mukta