[PATCH] Optimize (X >> N) {>,>=,<,<=} C in the combiner (PR tree-optimization/20517)

[Eric Botcazou]

> 2010-09-09  Jakub Jelinek  <jakub@redhat.com>
>
> 	PR tree-optimization/20517
> 	* combine.c (simplify_comparison): Optimize (X >> N) {>,>=,<,<+} C
> 	even if low N bits of X aren't known to be zero.

OK on principle, but can we avoid the code duplication by ORing the comparison 
on low bits with !equality_comparison_p and setting the low order bits in the 
shifted constant only for the appropriate codes?

-- 
Eric Botcazou