fix aliasing bug in pixel shuffle/unshuffle (#86608)
Fixes https://github.com/pytorch/pytorch/issues/82235
cc @albanD - `at::pixel_shuffle` and `at::pixel_unshuffle` advertise as being non-aliasing, but they have a C++ decomposition that internally uses reshape(), which means that it might return an alias.
I happened to notice this because a bunch of tests in `test/test_ops.py` failed when I ran locally with a `DEBUG=1` build.
(P.S.: when are we finally gonna get a debug build test in CI? 😃)
I fixed by adding an extra clone, which... is going to be an unnecessary perf hit in the case where the `reshape()` already properly cloned the input. My hope is that this is fine, because this only impacts the composite kernel- we already have a "fast" CPU kernel that does the right thing. Is `pixel_shuffle/unshuffle` commonly used with cuda? Maybe we should just add a fast cuda kernel for it if that's the case.
Alternatively, it seems like it would be nice if `reshape()` accepted an optional argument to unconditionally return a copy. That seems like a rabbit hole that isn't worth going down for now though - I remember a discussion a while ago about making `reshape()` copy-on-write
Pull Request resolved: https://github.com/pytorch/pytorch/pull/86608
Approved by: https://github.com/albanD
