[llvm] feat: Scev predicated overflow btc and testing (PR #208581)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

Please fix the formatting of the patch, as detected by the bot.

Please fix the regression test failures (https://github.com/llvm/llvm-project/actions/runs/29055790545?pr=208581).  You might just need to update the tests for the new output.

https://github.com/llvm/llvm-project/pull/208581