ScalarEvolution: Recurrences for GEP operations #1525
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This approach seems like the best choice moving forward, and is necessary for supporting getelementptr instructions. Also updates the tests accordingly. In particular, we no longer care about the size of the resulting chrec map in the tests, as a lot more outputs now have computed chrecs than only the loop variables. We still check that the loop variables are in the map in the tests, so no behavior has changed there.
phate
reviewed
Feb 9, 2026
Worked fine locally, but crashed when building on GitHub
phate
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Feb 10, 2026
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I have some more comments to the map accessor methods.
phate
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Feb 10, 2026
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This PR extends the ScalarEvolution implementation by adding support for computing recurrences for
GetElementPtroperations. It does this by adding a few new cases to theGetOrCreateSCEVForOutput()method, particularly forGetElementPtr,Load,IOBarrierandSExtoperations. The SCEV for the GetElementPtr operation is computed recursively to support an arbitrary number of indexes, and supports both array and struct GEPs. This PR also adds two simple tests for the two types of GEPs.Since the value of a GEP is not directly tied to the update of an induction variable (passes through a load from memory), some changes were needed in the way recurrences are computed. Particularly, we now compute recurrences for all valid SCEVs as opposed to computing the recurrences for just the loop variables. By valid we mean that the dependencies for the RVSDG output the SCEV corresponds to passes the three requirements. These being:
This change means that we end up with a larger amount of chain recurrences at the end of the analysis, some of which can be seen as "junk" or "noise". For the analysis itself this makes no difference, however for measuring the results, we should probably filter most of these out.