llvm-project

f91b6a03 - PowerPC: Fix VSX swap removal crash on an undef register (#216714)

PowerPC: Fix VSX swap removal crash on an undef register (#216714) formWebs walks each vector-register use and unions its equivalence class with that of its defining instruction, which it requires to be present in the swap map. A use of an undef register has no defining instruction, so the web formation crashed. Treat it like a physical-register mention so the web is conservatively rejected. Found by AI while working on something else. Co-authored-by: Claude (Opus 4.8) <noreply@anthropic.com>