Do not use TYPE_CANONICAL in useless_type_conversion

[Jan Hubicka]

> > Thank you! I commited the patch.
> 
> It breaks the Ada build on x86-64 though:

Hmm, I tested Ada on ppc64 only. I will look into that today.

Honza
> 
> eric@polaris:~/build/gcc/native/gcc/ada/rts> 
> /home/eric/build/gcc/native/./gcc/xgcc -B/home/eric/build/gcc/native/./gcc/ -
> B/home/eric/install/gcc/x86_64-suse-linux/bin/ -
> B/home/eric/install/gcc/x86_64-suse-linux/lib/ -isystem 
> /home/eric/install/gcc/x86_64-suse-linux/include -isystem 
> /home/eric/install/gcc/x86_64-suse-linux/sys-include    -c -g -O2  -fpic  -W -
> Wall -gnatpg -nostdinc   s-regpat.adb -o s-regpat.o
> +===========================GNAT BUG DETECTED==============================+
> | 6.0.0 20151008 (experimental) [trunk revision 228597] (x86_64-suse-linux) 
> GCC error:|
> | in gen_lowpart_common, at emit-rtl.c:1399                                |
> | Error detected around s-regpat.adb:1029:22                               |
> | Please submit a bug report; see http://gcc.gnu.org/bugs.html.            |
> | Use a subject line meaningful to you and us to track the bug.            |
> | Include the entire contents of this bug box in the report.               |
> | Include the exact command that you entered.                              |
> | Also include sources listed below.                                       |
> +==========================================================================+
> 
> -- 
> Eric Botcazou