Speedup CSE by 5%

[Paolo Bonzini]

 > I didn't see anything abusive. However, the patch below saves 10%
 > completely unnecessary calls for lpgparse.i: There is no need to
 > copy_rtx before calling fold_rtx, as fold_rtx always makes a copy if
 > it changes anything. In the frequent case that it did nothing, we can
 > thus avoid doing any cost computation for the "new" trx folded.

This is mostly reindenting so it should be okay even without a copyright 
assignment.

 > I guess so, too, but I don't think that is solved more easily than
 > trying to reduce the redundance in cse.c overall.

Of course.

What is the speedup with your original patch compared to both patches?

Paolo