[code-reflection] RFR: [hat] Proposal for bfloat16 [v2]

[Gary Frost]

On Wed, 3 Dec 2025 11:53:56 GMT, Juan Fumero <jfumero at openjdk.org> wrote:

>> This PR introduces the type [`bfloat16`](https://cloud.google.com/blog/products/ai-machine-learning/bfloat16-the-secret-to-high-performance-on-cloud-tpus) for HAT.
>> 
>> Testing for OpenCL:
>> 
>> 
>> HAT=SHOW_CODE java -cp hat/job.jar hat.java test ffi-opencl hat.test.TestBFloat16Type
>> 
>> 
>> Testing for CUDA:
>> 
>> 
>> HAT=SHOW_CODE java -cp hat/job.jar hat.java test ffi-cuda hat.test.TestBFloat16Type
>> 
>> 
>> Some tests are expecting to fail due to precision error. We will need to improve the type conversion with round-to-nearest-even for example.
>
> Juan Fumero has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 22 commits:
> 
>  - [hat] abstracting the OpenCL and CUDA code builders
>  - Merge branch 'code-reflection' into hat/type/bfloat16
>  - Merge branch 'code-reflection' into hat/type/bfloat16
>  - [hat] remove custom Op for bfloat
>  - single line imports in hat code builders
>  - single line imports in hat code builders
>  - [hat] test matmul with bfloat16
>  - [hat] dialect for bfloat16 removed
>  - [hat] new test file included in the hat test list
>  - [hat] OpenCL handler for bfloat16 via float convs
>  - ... and 12 more: https://git.openjdk.org/babylon/compare/0a7929cc...ddc932c3

hat/backends/ffi/cuda/src/main/java/hat/backend/ffi/CudaHATKernelBuilder.java line 316:

> 314:         byte f32Mixed = hatF16BinaryOp.getF32();
> 315: 
> 316:         oparen();

you might consider leaning into paren($->$.generateReduceFloat....().) rather than balancing parenthesis yourself.

hat/backends/ffi/cuda/src/main/java/hat/backend/ffi/CudaHATKernelBuilder.java line 334:

> 332: 
> 333:         if (f32Mixed == HATF16BinaryOp.LAST_OP) {
> 334:             cparen();

Looks like separate executaionpaths here can create imbalanced paren?

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PR Review Comment: https://git.openjdk.org/babylon/pull/716#discussion_r2584905562
PR Review Comment: https://git.openjdk.org/babylon/pull/716#discussion_r2584909503