Hi all,

Another costs issue that came out of the investigation for PR 65932 is that
sign-extending loads get a higher cost than they should in the arm backend.
The problem is that when handling a sign-extend of a MEM we add the cost
of the load_sign_extend cost field and then recursively add the cost of the inner MEM
rtx, which is bogus. This will end up adding an extra load cost on it.

The solution in this patch is to just remove that recursive step.
With this patch from various CSE dumps I see much more sane costs assign to these
expressions (such as 12 instead of 32 or higher).

Bootstrapped and tested on arm-none-linux-gnueabihf.

Ok for trunk?

Thanks,
Kyrill

2016-04-27  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

     * config/arm/arm.c (arm_new_rtx_costs, SIGN_EXTEND case):
     Don't add cost of inner memory when handling sign-extended
     loads.