[Reland][CPU] Add ops for float8 linear

[Xia-Weiwen]

Reland #3052 which is reverted by 5cbbd73

Revert reason: compiler is complaining about switch...case of bool values.

This PR fixes the issue by converting switch...case to if...else

[pytorch-bot]

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[Xia-Weiwen]

Hi @jcaip @jerryzh168 Could you please import this patch to check if the error is gone in your internal checks? Thanks.

[Xia-Weiwen]

Hi @jerryzh168 Thanks for approving. Do you still need to import it?

[jcaip]

Thanks for fixing this @Xia-Weiwen! This is still failing some tests, I'm seeing:

fbcode/pytorch/ao/torchao/csrc/cpu/aten_kernels/float8_linear.cpp:509:44: error: capturing a structured binding is not yet supported in OpenMP
  509 |     at::native::data_index_init(begin, mc, Mc_parallel, nc, Nc);
      |                                            ^
fbcode/pytorch/ao/torchao/csrc/cpu/aten_kernels/float8_linear.cpp:456:37: note: 'Mc_parallel' declared here
  456 |   auto [parallel_on_M, block_m, Mc, Mc_parallel] = get_m_blocking(M);
      |                                     ^
fbcode/pytorch/ao/torchao/csrc/cpu/aten_kernels/float8_linear.cpp:512:24: error: capturing a structured binding is not yet supported in OpenMP
  512 |       int64_t mc_end = parallel_on_M ? mc + 1 : Mc;
      |                        ^
fbcode/pytorch/ao/torchao/csrc/cpu/aten_kernels/float8_linear.cpp:456:9: note: 'parallel_on_M' declared here
  456 |   auto [parallel_on_M, block_m, Mc, Mc_parallel] = get_m_blocking(M);
      |         ^
fbcode/pytorch/ao/torchao/csrc/cpu/aten_kernels/float8_linear.cpp:512:49: error: capturing a structured binding is not yet supported in OpenMP
  512 |       int64_t mc_end = parallel_on_M ? mc + 1 : Mc;
      |                                                 ^
fbcode/pytorch/ao/torchao/csrc/cpu/aten_kernels/float8_linear.cpp:456:33: note: 'Mc' declared here
  456 |   auto [parallel_on_M, block_m, Mc, Mc_parallel] = get_m_blocking(M);
      |                                 ^
fbcode/pytorch/ao/torchao/csrc/cpu/aten_kernels/float8_linear.cpp:515:32: error: capturing a structured binding is not yet supported in OpenMP
  515 |         int64_t m_size = mci * block_m + block_m > M ? M - mci * block_m : block_m;
      |                                ^
fbcode/pytorch/ao/torchao/csrc/cpu/aten_kernels/float8_linear.cpp:456:24: note: 'block_m' declared here
  456 |   auto [parallel_on_M, block_m, Mc, Mc_parallel] = get_m_blocking(M);
      |                        ^
4 errors generated.

@jerryzh168 Long term I think we need to update our C++ linting to be as strict as whatever upstream dependencies we have, so we can find these issues earlier.

[facebook-github-bot]

@jcaip has imported this pull request. If you are a Meta employee, you can view this in D83564232.

[Xia-Weiwen]

Hi @jcaip Thanks for the feedback. I could not see the errors you saw, even not as warnings. I use the following environment to build Torchao:

• Ubuntu 22.04.3 LTS
• GCC 12.3.0
• Python 3.10
• CMD: USE_CPU_KERNELS=1 python setup.py develop

I can only see the following warnings:

• warning: ignoring attributes on template argument '__m512' [-Wignored-attributes]
• warning: ignoring attributes on template argument '__m256i' [-Wignored-attributes]
• warning: "Py_LIMITED_API" redefined

And these warnings are not from the files this PR adds.
Can you please share the environment, configuration and command to build Torchao so that I can reproduce these errors and fix them in advance? Thanks.