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Re: Revisiting the TYPE_IS_SIZETYPE issue
On Mon, May 26, 2008 at 12:23 PM, Paolo Bonzini <bonzini@gnu.org> wrote:
>
>> So my idea (I have this for some time now, but there's always lack
>> of time to implement it ...) is to make the existing tree codes
>> 'may overflow' operations and introduce new tree code variants
>> with the 'does not overflow' semantics. This way we conservatively
>> preserve 'may overflow' in legacy code.
>
> That seems extremely ugly, especially to make fold-const.c aware of that.
> It would be better to make the "overflow definition" a flag for a single
> PLUS_EXPR node (or PLUS rtl).
That obviously doesn't work. As fold operates on "destructed" trees
you have no way of placing the flag somewhere. Or do you want
flags on tree-codes?
Not that I initially thought of that, too. So eventually I thought of
just partition the tree-code space to allow tree-code flags, but essentially
that's an implementation detail of how to name these different tree codes.
Richard.