VHLO Checklist

See vhlo.md for information about VHLO.

Contributing Incompatible Changes

All changes with compatibility implications must go through the RFC process. This includes adding, deprecating, or renaming a feature. Once the RFC is approved, the following steps must be completed:

1. Bump the Version Number in Version.h and Update the Version Log

Prior to updating VHLO ops, attributes, types, or conversions, increment the minor version number in Version.h, and update the version log in VhloDialect.td

Any new VHLO features added would use this bumped version, for example after bumping 0.10.0 --> 0.11.0, a new op in VhloOps.td would use:

VHLO_Op<"abs_v2", "0.11.0", "current">

2. Add Required VHLO Implementation and Conversions

The exact code needed to integrate a new feature will vary, but for the most part the following will need to change:

• For new ops:
  1. Add the op in VhloOps.td
  2. Add StableHLO → VHLO conversion in StablehloLegalizeToVhlo.cpp
  3. Add VHLO → StableHLO conversion in VhloLegalizeToStablehlo.cpp
• For new versions of existing ops:
  1. Add the op in VhloOps.td
  2. Update StableHLO to VHLO mapping in MapStablehloToVhlo.h
  3. Add a conversion between new and old op versions in VhloToVersion.cpp
• For new types or attributes:
  1. Add the type in VhloTypes.td or the attribute in VhloAttrs.td
  2. Add StableHLO → VHLO conversion in StablehloLegalizeToVhlo.cpp
  3. Add VHLO → StableHLO conversion in VhloLegalizeToStablehlo.cpp

3. Add / Update Unit Tests

The contributor of an incompatible change is responsible for both positive and negative unit tests of the feature, as well as compatibility unit tests.

Compatibility unit testing involves updating stablehlo_legalize_to_vhlo.mlir to ensure that StableHLO round trips with the latest version of VHLO, as well as any additional forward or backward compatibility tests required. For example, if adding a new op at version X with Y = X - 1, add a test file like vhlo_to_version_downgrade_invalid.0_Y_0.mlir that shows the op is unsupported before version X. If adding a new version of an op, add a test file like vhlo_to_version_downgrade.0_Y_0.mlir that shows that the op can be downgraded successfully.

If your op has default attributes, include tests that show that the defaults are serialized and deserialized correctly.

4. Add Versioned Serialization Test

After adding tests to stablehlo_legalize_to_vhlo.mlir, copy the versioned test file with the largest version into a new file at the new version, and add the new tests to that file as well. You will also need to create an associated bytecode file using stablehlo-translate:

export TARGET_VERSION=1.X.0
export TARGET_FILENAME=${TARGET_VERSION//./_}
stablehlo-translate --serialize --target=$TARGET_VERSION --strip-debuginfo stablehlo/tests/vhlo/stablehlo_legalize_to_vhlo.$TARGET_FILENAME.mlir > stablehlo/tests/vhlo/stablehlo_legalize_to_vhlo.$TARGET_FILENAME.mlir.bc