Use predicates for RTL objects

[Segher Boessenkool]

On Wed, Aug 07, 2019 at 12:15:29PM -0400, Arvind Sankar wrote:
> I would also like to get some comments on the following idea to make the
> code checks more readable: I am thinking of adding
> 	bool rtx_def::is_a (enum rtx_code) const
> This would allow us to make all the rtx_code comparisons more readable
> without having to define individual macros for each.
> i.e.,
> 	REG_P (x)			   => x->is_a (REG)
> 	GET_CODE (x) == PLUS		   => x->is_a (PLUS)
> 	GET_CODE (PATTERN (x)) == SEQUENCE => PATTERN (x)->is_a (SEQUENCE)

That makes things much worse.  Not only is it less readable (IMO), but
the "is_a" idiom is used to check if something is of a certain class,
which is not the case here.

In "GET_CODE (x) == PLUS" it is clear that what the resulting machine
code does is cheap.  With "x->is_a (PLUS)", who knows what is happening
below the covers!

(And "REG_P" and similar are much shorter code to type).


Segher