[clang] [llvm] [libc] [libcxx] [compiler-rt] [lldb] [flang] [clang-tools-extra] [libunwind] [libcxxabi] [lld] Fix a bug in Smith's algorithm used in complex div. (PR #78330)

[John McCall via cfe-commits]

https://github.com/rjmccall approved this pull request.

LGTM as far as my requests; please wait for approval from the other reviewers.

This is unrelated, but I wonder if we should proactively outline this sequence; it's quite long.

https://github.com/llvm/llvm-project/pull/78330