Specialize BroadcastIndexesRange for the case where there is only 1 contiguous input

[swolchok]

In this case, broadcasting is not possible if I understand correctly.

NOTE TO REVIEWERS: I deleted a failing test because I think it's testing not-actually-existent-in-PyTorch functionality. Please let me know if I've made a mistake. I tried to exercise the behavior that this test implied existed like so:

>>> t = torch.tensor([1, 2, 3])
>>> t2 = torch.tensor(4)
>>> torch.abs(t2, out=t)
<stdin>:1: UserWarning: An output with one or more elements was resized since it had shape [3], which does not match the required output shape []. This behavior is deprecated, and in a future PyTorch release outputs will not be resized unless they have zero elements. You can explicitly reuse an out tensor t by resizing it, inplace, to zero elements with t.resize_(0). (Triggered internally at /Users/runner/work/pytorch/pytorch/pytorch/aten/src/ATen/native/Resize.cpp:38.)
tensor(4)

I think that if the test was correct, the result would have been torch.tensor([1, 2, 3]) with no message. Also, none of our operator tests seem to be failing. Have I missed anything?

[swolchok]

Stack from ghstack (oldest at bottom):

• -> Specialize BroadcastIndexesRange for the case where there is only 1 contiguous input #12023

[pytorch-bot]

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✅ No Failures

As of commit c11e1bd with merge base f673a4b ():
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[swolchok]

This is a size win. Size script results below, cases with no change edited out for brevity.

test/build_size_test.sh

before:

ExecuTorch with portable ops binary size, unstripped:
-rwxr-xr-x  1 swolchok  staff  1377360 Jun 27 17:24 cmake-out/test/size_test_all_ops
__TEXT	__DATA	__OBJC	others	dec	hex
1064960	65536	0	4295278592	4296409088	100160000

after:

ExecuTorch with portable ops binary size, unstripped:
-rwxr-xr-x  1 swolchok  staff  1360464 Jun 27 17:26 cmake-out/test/size_test_all_ops
__TEXT	__DATA	__OBJC	others	dec	hex
1048576	65536	0	4295278592	4296392704	10015c000

test/build_optimized_size_test.sh

before:

ExecuTorch with portable ops binary size, unstripped:
-rwxr-xr-x  1 swolchok  staff  1506384 Jun 27 17:17 cmake-out/test/size_test_all_ops
__TEXT	__DATA	__OBJC	others	dec	hex
1064960	65536	0	4295393280	4296523776	10017c000
ExecuTorch with optimized ops binary size, unstripped:
-rwxr-xr-x  1 swolchok  staff  4958792 Jun 27 17:17 cmake-out/test/size_test_all_optimized_ops
__TEXT	__DATA	__OBJC	others	dec	hex
3702784	65536	0	4296212480	4299980800	1004c8000

after:

ExecuTorch with portable ops binary size, unstripped:
-rwxr-xr-x  1 swolchok  staff  1505872 Jun 27 17:28 cmake-out/test/size_test_all_ops
__TEXT	__DATA	__OBJC	others	dec	hex
1064960	65536	0	4295393280	4296523776	10017c000
ExecuTorch with optimized ops binary size, unstripped:
-rwxr-xr-x  1 swolchok  staff  4941448 Jun 27 17:28 cmake-out/test/size_test_all_optimized_ops
__TEXT	__DATA	__OBJC	others	dec	hex
3686400	65536	0	4296212480	4299964416	1004c4000