RFA: Avoid creating garbage CONSTs in cselib.c

[Richard Sandiford]

Steven Bosscher <stevenb.gcc@gmail.com> writes:
>> It looks like ~1.5% to ~2% of all rtl created comes from wrap_constant
>> in cselib.c.  Not a huge amount, but it's easy to avoid.
>>
>> Tested on x86_64-linux-gnu.  OK to install?
>
> Nice patch. OK after also testing this on an autoinc target.

OK, installed after comparing the asm output before and after the patch
on gcc.torture, gcc.dg and g++.dg for arm-eabi.  There were no differences.

Thanks,
Richard