[PATCH] D122857: [LoopCacheAnalysis] Enable delinearization of fixed sized arrays

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/Analysis/LoopCacheAnalysis.cpp:335
+  SmallVector<int, 4> SrcSizes;
+  getIndexExpressionsFromGEP(*SE, SrcGEP, SrcSubscripts, SrcSizes);
+
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So, I guess this is something of a pre-existing issue, but this API looks completely broken to me. Deriving information from a GEP source element type is blatantly illegal under IR semantics -- in particular, the array bounds specified therein may be completely arbitrary.

The correct way to derive such information is from SCEV addrec expressions. For example in your first test you have `%arrayidx10` with SCEV `{{(8 + %a)<nuw>,+,8192}<nuw><%for.body>,+,4}<nuw><%for.body4>`, and the steps of those addrecs //are// semantically meaningful.


Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D122857/new/

https://reviews.llvm.org/D122857