[RFA] optimizing predictable branches on x86

[Paolo Bonzini]

>         /* High branch cost, expand as the bitwise OR of the conditions.
>   	 Do the same if the RHS has side effects, because we're effectively
>   	 turning a TRUTH_OR_EXPR into a TRUTH_ORIF_EXPR.  */
> !       if (BRANCH_COST (!optimize_size, false)>= 4
> ! 	  || TREE_SIDE_EFFECTS (TREE_OPERAND (exp, 1)))

What does BRANCH_COST (!optimize_save, ...) mean?

Related -- could you define auxiliary macros for BRANCH_COST (foo, false)?

Thanks!

Paolo