[PATCH] D105827: [SLP]Workaround for InsertSubVector cost.

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added a comment.

In D105827#2880704 <https://reviews.llvm.org/D105827#2880704>, @aeubanks wrote:

> This is causing hangs
> `$ clang++ -O2 -c reduced2.ll -o /dev/null`
> F17952182: reduced2.ll <https://reviews.llvm.org/F17952182>

Investigated it, actually hangs in `X86 DAG->DAG Instruction Selection on function (_ZN12SpinningCube6UpdateEv)` even without SLP vectorizer with the attached reproducer (hangs with 12.0.0 and trunk, 11.0.1 does not recognize `poison` but passes if I replace `poison` by `undef`. 12.0.0 and trunk still hangs even in this case). Command to reproduce is `llc reduced.ll -o /dev/null`. Looks like the bug was introduced somewhat between llvm 11 and 12. F17954903: reduced.ll <https://reviews.llvm.org/F17954903>


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