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

[Joshua Cranmer 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)
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jcranmer-intel wrote:

These are 8-bit types, no?

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