Add FLOAT8E8M0 data type support in ONNX Runtime (#28381)
### Description
This PR adds support for the `FLOAT8E8M0` data type in ONNX Runtime,
following the same pattern used for existing Float8 types (Float8E4M3FN,
Float8E4M3FNUZ, Float8E5M2, Float8E5M2FNUZ).
#### FLOAT8E8M0 Format
FLOAT8E8M0 is an 8-bit floating point format with:
- 8 exponent bits
- 0 mantissa bits
- No sign bit (all values are positive)
- Values are powers of two: `2^(val - 127)`
- 0xFF is reserved for NaN
- No infinity, no negative values, no denormals
This format is useful as a scaling factor type in microscaling (MX)
quantization formats.
#### Changes
**Core Type Definition**
- `include/onnxruntime/core/common/float8.h` - Added `Float8E8M0` struct
with float conversion routines and `std::numeric_limits` specialization.
The float→Float8E8M0 conversion correctly handles NaN (including
negative NaN) and infinity by checking these special values before
sign-dependent logic, consistent with how `Float8E4M3FN` handles them.
**C API**
- `include/onnxruntime/core/session/onnxruntime_c_api.h` - Added
`ONNX_TENSOR_ELEMENT_DATA_TYPE_FLOAT8E8M0` enum value at ordinal 24 to
match the ONNX protobuf spec (`FLOAT8E8M0 = 24`). Note: `UINT2` and
`INT2` shift to ordinals 25 and 26 respectively to align with the spec.
Language bindings (Java, C#, JS) will need corresponding updates in a
follow-up PR.
**Framework Integration**
- `onnxruntime/core/framework/element_type_lists.h` - Added to
AllFixedSizeIRv9, AllIRv9, AllFloat8 type lists
- `include/onnxruntime/core/framework/to_tensor_proto_element_type.h` -
Added template specialization
- `include/onnxruntime/core/framework/data_types_internal.h` - Added
dispatch cases
- `include/onnxruntime/core/framework/data_types.h` - Added to
IsTensorContainedType and IsSparseTensorContainedType
- `onnxruntime/core/framework/utils.h` - Added
GetONNXTensorElementDataType specialization
- `onnxruntime/core/framework/data_types.cc` - Full type registration
(tensor, sparse, seq, optional, prim)
- `onnxruntime/core/framework/tensorprotoutils.cc` - UnpackTensor, size
calculation, serialization
- `onnxruntime/core/framework/tensor_type_and_shape.cc` - Type mapping
- `onnxruntime/core/framework/onnxruntime_map_type_info.cc` - Type
mapping
**Shared Library Provider Bridge**
- `onnxruntime/core/providers/shared_library/provider_interfaces.h`
-
`onnxruntime/core/providers/shared_library/provider_bridge_provider.cc`
- `onnxruntime/core/providers/shared_library/provider_wrappedtypes.h`
- `onnxruntime/core/session/provider_bridge_ort.cc`
**Tests**
- `onnxruntime/test/framework/float8e8m0_test.cc` - Unit tests for
Float8E8M0 type including conversion, rounding, NaN (positive and
negative), infinity (positive and negative), negative values, operators,
and batch conversion
- `onnxruntime/test/onnx/tensorprotoutils.cc` - Test infrastructure
updates
- `onnxruntime/test/unittest_util/checkers.cc` - Test checker updates
### Motivation and Context
ONNX has added the FLOAT8E8M0 data type. This PR adds the corresponding
support in ONNX Runtime so that models using this data type can be
loaded and processed correctly.
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: tianleiwu <30328909+tianleiwu@users.noreply.github.com>
Co-authored-by: Tianlei Wu <tlwu@microsoft.com>
