Optimize based on possible enum class values?

[Mikhail Maltsev]

On 05/19/2016 04:37 AM, ☂Josh Chia (谢任中) wrote:
> Is there a way to tell gcc to assume that the underlying integer value
> is for a valid enum value and optimize accordingly? Even more
> generally, is there a way to give optimization hints to the compiler
> that a variable can only have certain values at a certain point in the
> code?
> 
You can use this idiom to tell GCC that 'condition' is true:

if (!condition)
  __builtin_unreachable();

GCC is able to infer value ranges from conditions like e.g. (x >= a && x <= b).

-- 
Regards,
    Mikhail Maltsev