[kill-loop] Fix a quadratic bottleneck in loop-unroll

[Andrew Pinski]

> 
> Hi Zdenek, all,
> 
> This patch fixes a problem with -fvariable-expansion-in-unroller.  The
> algorithm to analyze instructions was quadratic.  Fixed by letting df.c
> do the data flow beforehand.  I have bootstrapped and tested this patch
> with "-O2 -funroll{,-all}-loops -fvariable-expansion-in-unroller" on
> x86_64-unknown-linux-gnu.  Zdenek, does the patch look good to you?
> 
> Gr.
> Steven
> 
> 	* loop-unroll.c: Don't include varray.h.  Include df.h.
Make sure you update Makefile.in also.

Thanks,
Andrew Pinski