Print which output didn't have dependence. (#29047)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29047
When a tuple is returned, it is helpful to know specifically
which output was the culprit.
Actually, it was somewhat /more/ helpful to actually see the
contents of the tensor which didn't have dependence (or, e.g.,
the backtrace of the code that populated it), but that seemed
a step too far.
ghstack-source-id: 93091993
Test Plan:
manually tested because I was debugging an incorrect
trace and looked to see that the output number was indeed identifying
the correct tensor.
Reviewed By: dreiss
Differential Revision: D18274323
fbshipit-source-id: f1551bb03a3cdfa58b9e7f95736d53f317f53d5e
