Instead of looking through all the vectorizable tree to find the operand
entry, better to store it in a separate map and perform quick lookup,
basing on user tree entry and operand index.
It allows to remove lots of duplicated code, simplify processing and fix
potential future issues with the analysis, affected by the codegen.
Also, improves compile time.
Reviewers: HanKuanChen, RKSimon, hiraditya
Reviewed By: hiraditya
Pull Request: https://github.com/llvm/llvm-project/pull/140549
30ebcf6280