Revert "[CFIFixup] Factor logic into helpers and use range-based loops (NFC) (#125137)"
This reverts commit f14f19738916572322c310e84196134545c15c49, which
breaks a number of build bots:
- https://lab.llvm.org/buildbot/#/builders/163/builds/12726
- https://lab.llvm.org/buildbot/#/builders/144/builds/17106
- https://lab.llvm.org/buildbot/#/builders/123/builds/12855
- https://lab.llvm.org/buildbot/#/builders/133/builds/10660
- https://lab.llvm.org/buildbot/#/builders/88/builds/7482
- https://lab.llvm.org/buildbot/#/builders/180/builds/12313
- https://lab.llvm.org/buildbot/#/builders/160/builds/12316