[llvm-branch-commits] [clang] release/23.x: [clang][lex] Cache stat failures in `-Wshadow-header` (#215962) (PR #216116)

[Jan Svoboda via llvm-branch-commits]

jansvoboda11 wrote:

Yes, it's technically an optimization - this is minimizing the perf regression Clang 23 introduces with the new `-Wshadow-header` warning (which also gets enabled through `-Weverything`). We've observed this in real projects internally, so I'd prefer to not release such regression in the first place, rather than fix it later in Clang 24.

If you decide not to merge, that's fine, I'll just cherry-pick this into Apple's 23-aligned release downstream.

https://github.com/llvm/llvm-project/pull/216116