i * i is nonnegative
Tue Mar 19 16:41:00 GMT 2013
On Tue, 19 Mar 2013, Jeff Law wrote:
> On 03/19/2013 10:08 AM, Marc Glisse wrote:
>> this patch extends the property that x*x is non-negative, which was
>> already known for floats, to integers with undefined overflow.
>> 2013-03-19 Marc Glisse <firstname.lastname@example.org>
>> PR tree-optimization/56355
>> * fold-const.c (tree_binary_nonnegative_warnv_p) <MULT_EXPR>:
>> Also handle integers with undefined overflow.
>> * gcc.dg/pr56355-1.c: New file.
> Fine for the trunk. Though I would suggest waiting for http service & web
> archives to return before committing.
> BTW, did you check if VRP creates a non-negative range for this case as well?
It doesn't :-(
It would probably need to be done in extract_range_from_binary_expr since
extract_range_from_binary_expr_1 does not see the expression, maybe after
calling extract_range_from_binary_expr_1, and we would remove the negative
part of the interval it returned.
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