[llvm] [IR][Float8] Add two kinds float8 IR type (PR #89900)

[via llvm-commits]

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@@ -3847,6 +3847,14 @@ Floating-Point Types
    * - Type
      - Description
 
+   * - ``float8e5m2``
+     - 16-bit floating-point value(2-bit significand)
+
+   * - ``float8e4m3fn``
+     - 16-bit floating-point value(3-bit significand), there are no infinity
+       values, and NaN is represented with the exponent and mantissa bits set
+       to all 1s
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JinjinLi868 wrote:

the reference is that https://arxiv.org/pdf/2209.05433. i am not sure that put the website on the LangRef.rst is better or not.

https://github.com/llvm/llvm-project/pull/89900