[all-commits] [llvm/llvm-project] 2c5806: [MLIR] Add f4E2M1FN type (#108877)

[Sergey Kozub via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2c58063435ce4717a949585bc5c32ecf98a77238
      https://github.com/llvm/llvm-project/commit/2c58063435ce4717a949585bc5c32ecf98a77238
  Author: Sergey Kozub <skozub at nvidia.com>
  Date:   2024-09-24 (Tue, 24 Sep 2024)

  Changed paths:
    M mlir/include/mlir-c/BuiltinTypes.h
    M mlir/include/mlir/IR/Builders.h
    M mlir/include/mlir/IR/BuiltinTypes.h
    M mlir/include/mlir/IR/BuiltinTypes.td
    M mlir/include/mlir/IR/CommonTypeConstraints.td
    M mlir/include/mlir/IR/Types.h
    M mlir/lib/AsmParser/TokenKinds.def
    M mlir/lib/AsmParser/TypeParser.cpp
    M mlir/lib/Bindings/Python/IRTypes.cpp
    M mlir/lib/CAPI/IR/BuiltinTypes.cpp
    M mlir/lib/Conversion/LLVMCommon/TypeConverter.cpp
    M mlir/lib/Dialect/Arith/Transforms/EmulateUnsupportedFloats.cpp
    M mlir/lib/IR/AsmPrinter.cpp
    M mlir/lib/IR/Builders.cpp
    M mlir/lib/IR/BuiltinTypes.cpp
    M mlir/lib/IR/MLIRContext.cpp
    M mlir/lib/IR/Types.cpp
    M mlir/python/mlir/_mlir_libs/_mlir/ir.pyi
    M mlir/python/mlir/extras/types.py
    M mlir/test/IR/attribute.mlir
    M mlir/test/Target/LLVMIR/llvmir.mlir
    M mlir/test/python/ir/builtin_types.py
    M mlir/utils/lldb-scripts/mlirDataFormatters.py
    M mlir/utils/tree-sitter-mlir/grammar.js

  Log Message:
  -----------
  [MLIR] Add f4E2M1FN type (#108877)

This PR adds `f4E2M1FN` type to mlir.

`f4E2M1FN` type is proposed in [OpenCompute MX
Specification](https://www.opencompute.org/documents/ocp-microscaling-formats-mx-v1-0-spec-final-pdf).
It defines a 4-bit floating point number with bit layout S1E2M1. Unlike
IEEE-754 types, there are no infinity or NaN values.

```c
f4E2M1FN
- Exponent bias: 1
- Maximum stored exponent value: 3 (binary 11)
- Maximum unbiased exponent value: 3 - 1 = 2
- Minimum stored exponent value: 1 (binary 01)
- Minimum unbiased exponent value: 1 − 1 = 0
- Has Positive and Negative zero
- Doesn't have infinity
- Doesn't have NaNs

Additional details:
- Zeros (+/-): S.00.0
- Max normal number: S.11.1 = ±2^(2) x (1 + 0.5) = ±6.0
- Min normal number: S.01.0 = ±2^(0) = ±1.0
- Min subnormal number: S.00.1 = ±2^(0) x 0.5 = ±0.5
```

Related PRs:
- [PR-95392](https://github.com/llvm/llvm-project/pull/95392) [APFloat]
Add APFloat support for FP4 data type
- [PR-105573](https://github.com/llvm/llvm-project/pull/105573) [MLIR]
Add f6E3M2FN type - was used as a template for this PR
- [PR-107999](https://github.com/llvm/llvm-project/pull/107999) [MLIR]
Add f6E2M3FN type



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