[all-commits] [llvm/llvm-project] ffa5ce: Add arith expansion of f8E8M0 type for extf/trunc ...

[Umang Yadav via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ffa5ce04d0a5440f939881e0e329a173d486dd68
      https://github.com/llvm/llvm-project/commit/ffa5ce04d0a5440f939881e0e329a173d486dd68
  Author: Umang Yadav <29876643+umangyadav at users.noreply.github.com>
  Date:   2025-05-22 (Thu, 22 May 2025)

  Changed paths:
    M mlir/include/mlir/Dialect/Arith/Transforms/Passes.h
    M mlir/include/mlir/Dialect/Arith/Transforms/Passes.td
    M mlir/lib/Dialect/Arith/Transforms/ExpandOps.cpp
    M mlir/test/Dialect/Arith/expand-ops.mlir

  Log Message:
  -----------
  Add arith expansion of f8E8M0 type for extf/trunc ops (#140332)

F8E8M0 floating type is supposed to represent biased exponent bits of
F32 type in OCP Micro scaling floating point formats.


https://www.opencompute.org/documents/ocp-microscaling-formats-mx-v1-0-spec-final-pdf

This PR expands `arith.truncf` and `arith.extf` to support this
behavior.

For the `arith.truncf` thing to note here is that F8E8M0FNU type has one
NaN representation which is encoded as `0xFF`. Therefore alll kinds of
NaNs and +/-Inf in Float32Type would map to NaN in F8E8M0FNU. F8E8M0FNU
doesn't have a sign bit therefore it is a lossy and irreversible
downcast.

cc: @krzysz00  @MaheshRavishankar @Muzammiluddin-Syed-ECE



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