Re: PATCH to read-rtl.c

[Zack Weinberg <zack at codesourcery dot com>]

Gabriel Dos Reis <gdr@integrable-solutions.net> writes:

>   read-rtl.c implements polymorphism here through the use of the
> underlying integer type of enum rtx_code and enum machine_mode, which
> it assumes to be int or unsigned depending on the circumstances.
> Doing so, allows it to define only one kind of structure (macro_group)
> that contains pointer to various functions (to mimic virtual
> functions).  In C++ speak, the game would be that of a class template
> with virtual functions -- though I'm no sure I would actually use
> virtual functios :-).

I'm not enthused about your solution to this problem.  My first
reaction was to say that we should get out of the fake polymorphism
game; there ought to be separate data structures for the mode and code
macros.  However, the naive way to do that would require duplicating
lots of code.  I would like you to investigate further and see if
there is a clever way to make all the types explicit without
duplicating code.

Failing that, I think it would be better to just use inline casts.
There is no readability gain from

#define to_machine_mode(X) ((enum machine_mode) X)

in fact, because one has to go look up the macro definition, it hurts
comprehension.

zw