[llvm] [SCEV] Simplify SCEVExpr for PHI to SCEV for operand if operands are identical (PR #115945)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Compile-time: https://llvm-compile-time-tracker.com/compare.php?from=29062329f3cf0ac8f1ae626e758ca64f82294fbf&to=b49b86076b0cfe3449462cc8e81fd2e450d0088d&stat=instructions%3Au There is a large impact on kimwy.cc, but it also has large code size changes, so probably second order effects.

https://github.com/llvm/llvm-project/pull/115945