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Re: PATCH RFC: Ensure TREE_TYPE (TYPE_MIN_VALUE (t)) == t
Richard Guenther wrote:
> On 4/28/07, Richard Kenner <kenner@vlsi1.ultra.nyu.edu> wrote:
>> > Well, VRP never actually does the type comparison that I wrote. The
>> > real question is whether, given a NEGATE_EXPR applied to 'max', this
>> > test is flawed:
>> >
>> > if (max != TYPE_MIN_VALUE (TREE_TYPE (max)))
>>
>> I wouldn't want to make that assumption. Instead, I'd use something
>> like operand_equal_p so that slight differences in types will be ignored.
>> It's much more robust not to make such assumptions unless you absolutely
>> have to. And there seem to be at least two cases where it's wrong:
>> variants and subtypes.
>
> Yes, for this test I think !tree_int_cst_equal () is the correct thing
> to check.
Me too. I think we should basically never make direct comparisons
(based on pointers) between types or constants; instead, use explicit
comparison functions. Then, we can make the functions do quick pointer
comparisons if that's safe.
--
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713