[llvm] [SandboxVec][BottomUpVec] Add cost estimation and tr-accept-or-revert pass (PR #126325)

[Jorge Gorbe Moya via llvm-commits]

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+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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slackito wrote:

Do we have a test case where vectorization is rejected due to the cost threshold?

https://github.com/llvm/llvm-project/pull/126325