Deprecations & Current Refactoring

This page collects current deprecations in MLIR of API and features we intend to remove soon, as well as large refactoring an migration on-going. We try to list these here for the purpose of helping downstream users keeping up with MLIR development.

Deprecated

Use the free function variants for dyn_cast/cast/isa/…

When casting attributes or type, use the free functions variants, e.g., dyn_cast<T>(x), isa<T>(x), etc. Use of the cast methods variants (e.g., x.dyn_cast<T>()) should be avoided in new code as we’ll remove these methods in the future. Discussion on Discourse

On-going Refactoring & large changes

Past Deprecation and Refactoring

LLVM 17

“Promised Interface” and the need to explicitly register InlinerExtension for the FuncDialect.

We’re tightening the contract around injecting interfaces into the system externally, starting with DialectInterface. As an important visible change at the moment is that if you’re using the inliner with the FuncDialect, you need to call func::registerAllExtensions(registry); when setting up your MLIRContext.

Properties && changes to the generic printing format

See on Discourse.

Properties is a new feature in MLIR that will allow to separate the storage of inherent attributes from the discardable ones. One key visible change is the generic assembly format which gain a new attribute entry in-between < >.

preloadDialectInContext has been deprecated for >1y and was removed

See https://github.com/llvm/llvm-project/commit/9c8db444bc85

If you have an mlir-opt tool and you’re still depending on preloadDialectInContext, you need to revisit your pipeline. This option used with mlir-opt is hiding issues with the pipeline, and indications of missing getDependentDialects(). Discussion on Discourse

Migrating mlir-opt-like tools to use MlirOptMainConfig

See https://github.com/llvm/llvm-project/commit/ffd6f6b91a3

If your mlir-opt-like tool is using the MlirOptMain(int argc, char **argv, ...) entry point you won’t be affected, otherwise, see the Discussion on Discourse

Deprecation of gpu-to-(cubin|hsaco) in favor of GPU compilation attributes

GPU compilation attributes are a completely new mechanism for handling the compilation of GPU modules down to binary or other formats in an extensible way. This mechanism lifts many current restrictions the GPU serialization passes had, like being present only if the CUDA driver is there or not linking to LibDevice.

One key difference is the usage of ptxas or the nvptxcompiler library for compiling PTX to binary; hence the CUDATollkit is required for generating binaries.

For these attributes to work correctly, making registration calls to registerNVVMTargetInterfaceExternalModels, registerROCDLTargetInterfaceExternalModels and registerOffloadingLLVMTranslationInterfaceExternalModels are necessary.

The passes gpu-to-(cubin|hsaco) will be removed in a future release.

LLVM 18

Port uses of LLVM Dialect to opaque pointers

LLVM 17 has stopped officially supporting typed pointers, and MLIRs LLVM Dialect is now in the process of dropping the support as well. This was announced back in February 2023 ( PSA) , and now the final steps, i.e., removing the typed pointers, have started ( PSA). If you are still targeting LLVM dialect with typed pointers, an update to support opaque pointers will be necessary.