[MLAS] Enable FP16 for Gelu

[akote123]

Enabled fp16 Gelu for opset20.Gelu uses tanh and ERF functions depending on the approximation method used. Implemented tanh in sve and erf in sve and neon .
Gr3E results: with tanh and erf approximation:

GELU(ms)	Tanh_SVE	ERF_SVE	Tanh_NEON	ERF_NEON
Shape	F32	F16	F32	F16
100	0.007	0.007	0.007	0.007
1000	0.008	0.007	0.012	0.008
1000000	0.076	0.039	0.203	0.07

Gr4 results: with tanh and erf approximation:

GELU(ms)	Tanh_SVE	ERF_SVE	Tanh_NEON	ERF_NEON
Shape	F32	F16	F32	F16
100	0.005	0.005	0.005	0.005
1000	0.006	0.006	0.008	0.006
1000000	0.092	0.046	0.224	0.088

This PR is a joint contribution by:
Aruna K(@akote123)
Abhishek Jain(@abhijain1204fujitsu)
Sanket Kale(@sanketkaleoss )

[Copilot]

Pull request overview

This PR enables FP16 (half-precision floating-point) support for the GELU (Gaussian Error Linear Unit) activation operator in ONNX Runtime opset 20. The implementation provides optimized compute paths using ARM SVE (Scalable Vector Extension) and NEON intrinsics for both tanh and erf approximation methods, with fallback to scalar FP32 computation when vector intrinsics are not available.

Key changes:

• Adds FP16 kernel registration for GELU operator alongside the existing FP32 implementation
• Implements optimized FP16 ERF and TANH kernels using ARM SVE and NEON intrinsics
• Adds comprehensive test coverage for both tanh and erf approximation modes with FP16 inputs

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 27 comments.

Show a summary per file

File	Description
onnxruntime/core/providers/cpu/cpu_execution_provider.cc	Registers typed GELU kernels for float and MLFloat16 types
onnxruntime/core/providers/cpu/tensor/gelu.cc	Implements FP16 GELU computation with SVE/NEON optimizations and scalar fallback
onnxruntime/core/providers/cpu/math/element_wise_ops.cc	Adds FP16 ERF operator support using new SVE/NEON kernels
onnxruntime/test/providers/cpu/activation/activation_op_test.cc	Adds FP16 GELU tests for both tanh and erf approximations
onnxruntime/core/mlas/lib/tanh.cpp	Adds SVE path for FP16 tanh computation
onnxruntime/core/mlas/lib/sve/mlasi_sve.h	Declares SVE FP16 function signatures
onnxruntime/core/mlas/lib/sve/mlas_sve_fp16.h	Adds SVE FP16 intrinsic wrapper functions
onnxruntime/core/mlas/lib/sve/Elementwise_sve_fp16.cpp	Implements SVE FP16 tanh, erf, and GELU kernels
onnxruntime/core/mlas/lib/fp16_common.h	Adds NEON FP16 helper functions for erf computation
onnxruntime/core/mlas/lib/erf.cpp	Implements NEON FP16 erf kernel
onnxruntime/core/mlas/inc/mlas.h	Exports NEON FP16 erf kernel function
cmake/onnxruntime_providers_cpu.cmake	Adds ARM FP16 compile flags for gelu.cc and includes MLAS headers
cmake/onnxruntime_mlas.cmake	Adds SVE FP16 elementwise source and compile flags for erf.cpp

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[hariharans29]

/azp run Linux QNN CI Pipeline,Win_TRT_Minimal_CUDA_Test_CI,Windows ARM64 QNN CI Pipeline,Windows GPU Doc Gen CI Pipeline

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[hariharans29]

/azp run Linux QNN CI Pipeline,Win_TRT_Minimal_CUDA_Test_CI,Windows ARM64 QNN CI Pipeline,Windows GPU Doc Gen CI Pipeline

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[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated 19 comments.

Comments suppressed due to low confidence (1)

onnxruntime/core/providers/cpu/math/element_wise_ops.cc:2034

• The allocator is retrieved but no longer used after switching to the native FP16 ERF implementation. The lines getting the temp space allocator (lines 2032-2034) should be removed as they are now unnecessary.

  // get allocator for temporary buffers
  AllocatorPtr alloc;
  ORT_RETURN_IF_ERROR(context->GetTempSpaceAllocator(&alloc));

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[abhijain1204fujitsu]

@hariharans29 we have pushed the code to resolve all the above comments
Kindly support for further review and merger of the PR

[hariharans29]

@hariharans29 we have pushed the code to resolve all the above comments Kindly support for further review and merger of the PR

Please manually "resolve" Copilot's comments and add comments if you think Copilot's suggestion is not applicable and you re not taking it in. Thanks.

[hariharans29]

/azp run Linux QNN CI Pipeline,Win_TRT_Minimal_CUDA_Test_CI,Windows ARM64 QNN CI Pipeline,Windows GPU Doc Gen CI Pipeline

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[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated 2 comments.

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[abhijain1204fujitsu]

Hi @hariharans29 ,
Thank you for your previous review comments
We have pushed the changes as per review, kindly support us to check the CI Pipelines and further review the code for merger.

[hariharans29]

Hi @hariharans29 , Thank you for your previous review comments We have pushed the changes as per review, kindly support us to check the CI Pipelines and further review the code for merger.

There are still some unaddressed Copilot comments. Please manually resolve them with a comment as to whether going with Copilot's recommendation or not.

[sanketkaleoss]

Hi @hariharans29 ,
We have pushed the new changes resolving CI failures, kindly support us by restarting the CI pipeline.

[hariharans29]

Hi @hariharans29 , We have pushed the new changes resolving CI failures, kindly support us by restarting the CI pipeline.

As stated above, please resolve all Copilot comments and my old comments. Resolving comments is a gating check for merging a PR.

I ll start another round of CI.

[sanketkaleoss]

Hi @hariharans29 , We have pushed the new changes resolving CI failures, kindly support us by restarting the CI pipeline.

As stated above, please resolve all Copilot comments and my old comments. Resolving comments is a gating check for merging a PR.

I ll start another round of CI.

Thanks, will resolve them.

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[Copilot]

Pull request overview

Copilot reviewed 19 out of 19 changed files in this pull request and generated 5 comments.

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[sanketkaleoss]

@hariharans29 Resolved pending comments and incorporated required suggestion.

[hariharans29]

@hariharans29 Resolved pending comments and incorporated required suggestion.

Overall - LGTM. I just re-opened discussion on one comment (manual aligned alloc and aligned free) - nothing that is a blocker.

I ll seek Copilot's opinion once more and we can merge it soon.

Thanks.

[Copilot]

Pull request overview

Copilot reviewed 19 out of 19 changed files in this pull request and generated no new comments.

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[hariharans29]

/azp run Linux QNN CI Pipeline,Win_TRT_Minimal_CUDA_Test_CI,Windows ARM64 QNN CI Pipeline,Windows GPU Doc Gen CI Pipeline

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[Copilot]

Pull request overview

Copilot reviewed 19 out of 19 changed files in this pull request and generated 5 comments.

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[hariharans29]

Overall looks good to me:

1. I had a question on the open comment (aligned allocator)
2. Copilot has a last set of comments - please check if it adds value
3. I think the pending CI failures have nothing to do with the PR. But can you please double check ?
4. Please resolve any pending old comments so that it is mergeable

Thanks !

[sanketkaleoss]

Overall looks good to me:

1. I had a question on the open comment (aligned allocator)
2. Copilot has a last set of comments - please check if it adds value
3. I think the pending CI failures have nothing to do with the PR. But can you please double check ?
4. Please resolve any pending old comments so that it is mergeable

Thanks !

Hi @hariharans29 , resolved the pending comments and incorporated one of the Copilot suggestions. The CI issues appear to be unrelated, and performance has been preserved across these PR iterations. Thanks.

[hariharans29]

/azp run Linux QNN CI Pipeline,Win_TRT_Minimal_CUDA_Test_CI,Windows ARM64 QNN CI Pipeline,Windows GPU Doc Gen CI Pipeline

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Azure Pipelines successfully started running 2 pipeline(s).

[hariharans29]

Overall looks good to me:

1. I had a question on the open comment (aligned allocator)
2. Copilot has a last set of comments - please check if it adds value
3. I think the pending CI failures have nothing to do with the PR. But can you please double check ?
4. Please resolve any pending old comments so that it is mergeable

Thanks !

Hi @hariharans29 , resolved the pending comments and incorporated one of the Copilot suggestions. The CI issues appear to be unrelated, and performance has been preserved across these PR iterations. Thanks.

Thanks for the contribution. I merged it. I take it you would have tried onnxruntime_mlas_test.exe and onnxruntime_test_all.exe in your env right ?

[sanketkaleoss]

Overall looks good to me:

1. I had a question on the open comment (aligned allocator)
2. Copilot has a last set of comments - please check if it adds value
3. I think the pending CI failures have nothing to do with the PR. But can you please double check ?
4. Please resolve any pending old comments so that it is mergeable

Thanks !

Hi @hariharans29 , resolved the pending comments and incorporated one of the Copilot suggestions. The CI issues appear to be unrelated, and performance has been preserved across these PR iterations. Thanks.

Thanks for the contribution. I merged it. I take it you would have tried onnxruntime_mlas_test.exe and onnxruntime_test_all.exe in your env right ?

I have executed both test suites in my environment, and all tests are passing. Thank you for merging this, and for your continued reviews and suggestions.