Fix Vec256<T>::abs() for floating point when applied on -0.0 (#26422)
Summary:
Currently when a Vec256<T> (base) object contains -0.0, Vec256<T>::abs()
would not produce 0.0, but -0.0 instead. This commit fixes this issue.
This bug will mostly affect CPUs without AVX support, such as ARM,
PowerPC, and older Intel models.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26422
Differential Revision: D17607346
fbshipit-source-id: e8d4595f0e88ad93018a61f89b9e3dcada485358
