Only truncate leading 1s if the value is too big. (#94521)
If it's just right, broadcasting will do the right thing
automatically.
This helps with unbacked SymInts as I can avoid testing one
equality on the inside.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94521
Approved by: https://github.com/voznesenskym
