New transformation: ReplaceKernels

[MichaelSt98]

Replace configured kernel calls with alternative routines.

Conceptually, the transformation walks each call site in the processed routine, looks for names listed in replace_kernels_map, resolves the replacement routine, and reconstructs the actual argument list against the replacement signature. When the original call target is unresolved in the IR, the transformation also tries to resolve the original routine from source so that remapping can still be done against the original dummy argument names instead of the raw actual expressions. Once the replacement call has been rebuilt, the transformation updates imports/includes to match the new callee and optionally marks the replacement routine as blocked for further scheduler traversal.

Description

This pull request introduces comprehensive tests for the new ReplaceKernels transformation and ensures it is imported as part of the main transformation package. The main focus is on verifying the correct remapping of kernel routine arguments, handling of optional arguments, import rewriting, plan generation, and pipeline integration.

Testing and Validation of ReplaceKernels Transformation

New test suite for kernel replacement:

• Added test_replace_kernel.py containing multiple tests that cover argument remapping, handling of optional arguments, include/import rewriting, plan output, and integration in a pipeline. This ensures the ReplaceKernels transformation works as expected across a variety of scenarios.

Integration with transformation package:

• Exposed replace_kernel transformation in the main loki.transformations package by importing it in __init__.py, making it available for general use.

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[github-actions]

Documentation for this branch can be viewed at https://sites.ecmwf.int/docs/loki/692/index.html

[codecov]

Codecov Report

❌ Patch coverage is 90.59140% with 35 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.18%. Comparing base (bfad794) to head (0a031fd).
⚠️ Report is 13 commits behind head on main.

Files with missing lines	Patch %	Lines
loki/transformations/replace_kernel.py	87.26%	34 Missing ⚠️
loki/transformations/tests/test_replace_kernel.py	99.03%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #692      +/-   ##
==========================================
- Coverage   94.19%   94.18%   -0.02%     
==========================================
  Files         288      290       +2     
  Lines       47496    47997     +501     
==========================================
+ Hits        44741    45204     +463     
- Misses       2755     2793      +38     

Flag	Coverage Δ
lint_rules	96.40% <ø> (ø)
loki	94.15% <90.59%> (-0.02%)	⬇️

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