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This PR adds `f6E3M2FN` type to mlir. `f6E3M2FN` type is proposed in [OpenCompute MX Specification](https://www.opencompute.org/documents/ocp-microscaling-formats-mx-v1-0-spec-final-pdf). It defines a 6-bit floating point number with bit layout S1E3M2. Unlike IEEE-754 types, there are no infinity or NaN values. ```c f6E3M2FN - Exponent bias: 3 - Maximum stored exponent value: 7 (binary 111) - Maximum unbiased exponent value: 7 - 3 = 4 - Minimum stored exponent value: 1 (binary 001) - Minimum unbiased exponent value: 1 − 3 = −2 - Has Positive and Negative zero - Doesn't have infinity - Doesn't have NaNs Additional details: - Zeros (+/-): S.000.00 - Max normal number: S.111.11 = ±2^(4) x (1 + 0.75) = ±28 - Min normal number: S.001.00 = ±2^(-2) = ±0.25 - Max subnormal number: S.000.11 = ±2^(-2) x 0.75 = ±0.1875 - Min subnormal number: S.000.01 = ±2^(-2) x 0.25 = ±0.0625 ``` Related PRs: - [PR-94735](https://github.com/llvm/llvm-project/pull/94735) [APFloat] Add APFloat support for FP6 data types - [PR-97118](https://github.com/llvm/llvm-project/pull/97118) [MLIR] Add f8E4M3 type - was used as a template for this PR