See more detailed analysis in https://bugs.llvm.org/show_bug.cgi?id=36311.
isUniform() information is recomputed after LV started transforming the underlying IR and that triggered an assert in SCEV.
From vectorizer's architectural perspective, such information, while still useful in vector code gen, should not be recomputed after the start of transforming the LLVM IR. Instead, we should collect and cache such information during the analysis phase of LV and use the cached info during code gen.
From the symptom perspective, this assert as it stands right now is not very useful. Legality already rejected loops that would trigger the assert. As such, commenting out the assert is NFC from vectorizer's functionality perspective. On top of that, just above the assertion, we check for unit-strided load/store or
gather scatter. Addresses can't be uniform below that check.
From vectorization theory point of view, we don't have to reject all cases of stores to uniform addresses. Eventually, we should support safe/profitable cases.
This patch resolves the issue by removing the useless assertion that is invoking LAA's isUniform() that requires up-to-date DomTree ---- once vector code gen starts modifying CFG, we don't have an up-to-date DomTree.