[PATCH] D87827: [SCEVExpander] Support expanding nonintegral pointers with constant base.

[Florian Hahn via Phabricator via llvm-commits]

fhahn added inline comments.


================
Comment at: llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp:134
+  // the reminder of the division will be stripped.
+  if (Op == Instruction::IntToPtr && DL.isNonIntegralPointerType(PtrTy)) {
+    auto *Idx = Builder.CreateUDiv(
----------------
arsenm wrote:
> It seems broken that getCastOpcode would return IntToPtr in a situation where it's illegal
Yes, that seems a rather big hole in getCastOpcode unfortunately and should probably also be changed.

But I think the key question is how to best deal with the problem during SCEV expansion here, because AFAIK we do not have a way to indicate that we failed to expand an expression in the expander.

Is it enough to emit a `GEP` with a computed index? Or should we better try to get a type with an alloc size of 1 byte and use that? I guess there could be configurations which do not have such a type, not sure what to do then.


Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D87827/new/

https://reviews.llvm.org/D87827