Improve perf for forward AD view handling (#57057)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57057
This PR performs optimization on the ViewInfo handling to remove the need for the "no forward AD mode".
- When the forward and backward ViewInfo are the same, create and store only one of them
Code for timing:
```python
timer = Timer(
stmt='a.view(-1)',
setup='''\
import torch
a = torch.rand(4)''')
res = timer.collect_callgrind(repeats=2, number=10)[1]
```
Difference between master and this PR:
```
# Benchmark at master
<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.CallgrindStats object at 0x7fe33be83690>
a.view(-1)
setup:
import torch
a = torch.rand(4)
All Noisy symbols removed
Instructions: 69286 68442
Baseline: 1332 1188
10 runs per measurement, 1 thread
# Benchmark at this branch
<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.CallgrindStats object at 0x7fe33bd7ec30>
a.view(-1)
setup:
import torch
a = torch.rand(4)
All Noisy symbols removed
Instructions: 69437 68562
Baseline: 1363 1188
10 runs per measurement, 1 thread
# Difference between the two
<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7fe1216e9a00>
160 ???:0x000000000a11c8d0
60 torch::autograd::DifferentiableViewMeta::DifferentiableViewMeta
60 ???:torch::autograd::as_view(at::Tensor const&, at::Tensor const&, bool, bool, std::function<at::Tensor (at::Tensor const&)>, torch::autograd::CreationMeta, bool)
40 ???:0x0000000008e14f50
40 ???:0x0000000008e05bd0
40 ???:0x0000000008e05480
40 ???:0x0000000008e036d0
40 ???:0x0000000008e02720
30 make_variable_differentiable_view
...
-20 ???:0x0000000008e02060
-20 ???:0x0000000008e01fd0
-30 ???:torch::autograd::isForwardADEnabled()
-40 ???:0x0000000008e14f90
-40 ???:0x0000000008e05c00
-40 ???:0x0000000008e054a0
-40 ???:0x0000000008e036f0
-40 ???:0x0000000008e02740
-160 ???:0x000000000a11d8d0
Total: 120
```
Test Plan: Imported from OSS
Reviewed By: zou3519
Differential Revision: D28071505
Pulled By: albanD
fbshipit-source-id: 672b1bdf87d516b6de4f2e36656819cfd6f4c9b9
