[PATCH] D29641: [SLP] Fix for PR31847: Assertion failed: (isLoopInvariant(Operands[i], L) && "SCEVAddRecExpr operand is not loop-invariant!")

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added a comment.

In https://reviews.llvm.org/D29641#675860, @mkuper wrote:

> So, do we know what exactly is going wrong here? Which disposition we're changing and why?


We're not changing the disposition but seems to me some of the SCEV nodes are returned to cache but without clearing of their dispositions. After that, during some SCEV internal optimizations, SCEV tries to simplify some of SCEV nodes, which are LoopInvariant. During this reassociation, it creates a new SCEV node, which is not actually created but is taken from the cache of previously used SCEV nodes. But this new SCEV node for some reasons has the disposition LoopVariant (it was used before, then freed, but not tracked that the disposition for this node should be cleared). And we have a situation where from 2 LoopInvariant nodes we're getting 1 LoopVariant node, while the code expects only LoopInvariants, of course.


https://reviews.llvm.org/D29641