[SYCL] Implement sycl_ext_oneapi_fp8 for CRI

[dklochkov-emb]

This PR adds FP8 types for CRI docs.
It adds the first part which includes:

1. Initial implementation
2. Unit tests which check expected behavior and values
3. Unit tests which check the fact of builtin calls.
4. E2E tests of all 3 data types: fp8_e4m3, fp8_e5m2 and fp8_e8m0

[dklochkov-emb]

@intel/llvm-reviewers-runtime please, review

[Copilot]

Pull request overview

This PR introduces initial host-side implementations of OneAPI experimental FP8 types (E4M3, E5M2, E8M0) and adds unit tests validating conversions/encodings plus tests that verify the expected SPIR-V builtin call paths (via mocks) for device-only code paths.

Changes:

• Added sycl::ext::oneapi::experimental FP8 type definitions and conversion logic in a new public header.
• Added unit tests for value/encoding behavior for fp8 E4M3, E5M2, and E8M0 on CPU.
• Added mocked builtin implementations and tests to confirm which builtins are invoked from constructors/conversions.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
sycl/include/sycl/ext/oneapi/experimental/float_8bit/types.hpp	Adds the FP8 type implementations, conversion helpers, and builtin hooks.
sycl/unittests/Extensions/fp8/fp8_e4m3.cpp	Adds host unit tests for E4M3 encoding/conversion behavior.
sycl/unittests/Extensions/fp8/fp8_e5m2.cpp	Adds host unit tests for E5M2 encoding/conversion behavior.
sycl/unittests/Extensions/fp8/fp8_e8m0.cpp	Adds host unit tests for E8M0 encoding/conversion behavior.
sycl/unittests/Extensions/fp8/builtin_mocks.hpp	Provides mock builtin symbols and counters to validate builtin call paths.
sycl/unittests/Extensions/fp8/builtin_call_tests.cpp	Adds tests asserting the expected builtin calls occur (via the mocks).
sycl/unittests/Extensions/fp8/CMakeLists.txt	Registers the new FP8 unit test target and sources.
sycl/unittests/Extensions/CMakeLists.txt	Adds the new fp8 unit test subdirectory to the Extensions suite.

[gmlueck]

Here are my comments so far. I haven't looked at E8M0 yet, or at any of the CPU conversions.

[dm-vodopyanov]

@dklochkov-emb can you please provide status for all failed fp8-related tests in pre-commit?

BTW, I restarted some of the checks due to CI issue, so need to wait a bit for the completion.

[dm-vodopyanov]

Overall, LGTM

[sys-ce-bb]

@intel/llvm-gatekeepers please consider merging

[dklochkov-emb]

@intel/llvm-gatekeepers Please, merge it

[sarnex]

@dklochkov-emb We are seeing postcommit CI failures in check-sycl that seem related

GTEST_OUTPUT=json:/__w/llvm/llvm/build/tools/sycl/unittests/Extensions/fp8/./FP8TypesTests-Non_Preview_Tests-SYCL-Unit-313267-102-106.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=106 GTEST_SHARD_INDEX=102 /__w/llvm/llvm/build/tools/sycl/unittests/Extensions/fp8/./FP8TypesTests-Non_Preview_Tests
--

Script:
--
/__w/llvm/llvm/build/tools/sycl/unittests/Extensions/fp8/./FP8TypesTests-Non_Preview_Tests --gtest_filter=FP8E8M0Test.MarrayBFloat16ToEvenRounding
--
/__w/llvm/llvm/src/sycl/unittests/Extensions/fp8/fp8_e8m0.cpp:488: Failure
Death test: { fp8_e8m0_x2 value(in, rounding::to_even); (void)value; }
    Result: failed to die.
 Error msg:
[  DEATH   ] 


/__w/llvm/llvm/src/sycl/unittests/Extensions/fp8/fp8_e8m0.cpp:488
Death test: { fp8_e8m0_x2 value(in, rounding::to_even); (void)value; }
    Result: failed to die.
 Error msg:
[  DEATH   ] 

https://github.com/intel/llvm/actions/runs/27421671974/job/81048588785

Can you please fix ASAP and if not possible revert? Thanks

[dklochkov-emb]

@sarnex I temporarily disabled tests while bug is not fixed, PR:
#22309