Remove optional for veiw_fn during View Tracking (#50067)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50067
Fixes #49257
Using the `Callgrind` to test the performance.
```python
import torch
import timeit
from torch.utils.benchmark import Timer
timer = Timer("x.view({100, 5, 20});", setup="torch::Tensor x = torch::ones({10, 10, 100});", language="c++", timer=timeit.default_timer)
res = timer.collect_callgrind(number=10)
```
### Nightly
```python
torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.CallgrindStats object at 0x7f7949138c40>
x.view({100, 5, 20});
setup: torch::Tensor x = torch::ones({10, 10, 100});
All Noisy symbols removed
Instructions: 42310 42310
Baseline: 0 0
10 runs per measurement, 1 thread
Warning: PyTorch was not built with debug symbols.
Source information may be limited. Rebuild with
REL_WITH_DEB_INFO=1 for more detailed results.
```
### Current
```python
<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.CallgrindStats object at 0x7f78f271a580>
x.view({100, 5, 20});
setup: torch::Tensor x = torch::ones({10, 10, 100});
All Noisy symbols removed
Instructions: 42480 42480
Baseline: 0 0
10 runs per measurement, 1 thread
Warning: PyTorch was not built with debug symbols.
Source information may be limited. Rebuild with
REL_WITH_DEB_INFO=1 for more detailed results.
```
### Compare
There are 170 instructions reduced
```python
torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f7941b7a7c0>
970 ???:torch::autograd::as_view(at::Tensor const&, at::Tensor const&, bool, bool, std::function<at::Tensor (at::Tensor const&)>, torch::autograd::CreationMeta, bool)
240 ???:torch::autograd::ViewInfo::~ViewInfo()
180 ???:torch::autograd::ViewInfo::ViewInfo(at::Tensor, std::function<at::Tensor (at::Tensor const&)>)
130 ???:torch::autograd::make_variable_differentiable_view(at::Tensor const&, c10::optional<torch::autograd::ViewInfo>, c10::optional<torch::autograd::ViewInfo>, torch::autograd::CreationMeta, bool)
105 /tmp/benchmark_utils_jit_build_69e2f1710544485588feeca0719a3a57/timer_cpp_4435526292782672407/timer_src.cpp:main
100 ???:std::function<at::Tensor (at::Tensor const&)>::function(std::function<at::Tensor (at::Tensor const&)> const&)
70 ???:torch::autograd::DifferentiableViewMeta::~DifferentiableViewMeta()
70 ???:torch::autograd::DifferentiableViewMeta::DifferentiableViewMeta(c10::TensorImpl*, c10::optional<torch::autograd::ViewInfo>, c10::optional<torch::autograd::ViewInfo>, torch::autograd::CreationMeta)
-100 ???:c10::optional_base<torch::autograd::ViewInfo>::optional_base(c10::optional_base<torch::autograd::ViewInfo>&&)
-105 /tmp/benchmark_utils_jit_build_2e75f38b553e42eba00523a86ad9aa05/timer_cpp_3360771523810516633/timer_src.cpp:main
-120 ???:torch::autograd::ViewInfo::ViewInfo(at::Tensor, c10::optional<std::function<at::Tensor (at::Tensor const&)> >)
-210 ???:c10::optional_base<std::function<at::Tensor (at::Tensor const&)> >::~optional_base()
-240 ???:c10::optional_base<torch::autograd::ViewInfo>::~optional_base()
-920 ???:torch::autograd::as_view(at::Tensor const&, at::Tensor const&, bool, bool, c10::optional<std::function<at::Tensor (at::Tensor const&)> >, torch::autograd::CreationMeta, bool)
```
Test Plan: Imported from OSS
Reviewed By: albanD
Differential Revision: D25900495
Pulled By: ejguan
fbshipit-source-id: dedd30e69db6b48601a18ae98d6b28faeae30d90
