[llvm] [SLP]Improve/fix subvectors in gather/buildvector nodes handling (PR #104144)

[Alexey Bataev via llvm-commits]

alexey-bataev wrote:

> Unfortunately it's in a very large generated block and we were not able to isolate it to an external repro yet.
> 
> One pointer is, dropping lines 12657-12667 from [SLPVectorizer.cpp](https://github.com/llvm/llvm-project/commit/f3d2609af3031ddb54030548e86335f295cf49ca#diff-e3b933e8c46156c0eaf7cbb67866b712f69a8484bc941d10acec9d4d17b9f061) fixes our test. Could you take a look if the ranges here, and the values set look correct?

Could you provide full stack trace? Also, large code is not a problem, attach it, I will reduce it myself

https://github.com/llvm/llvm-project/pull/104144