Have successfully build Firefox 3.6.13 on AIX 5.3TL11 with IBM XLC/C++ 9.0 compiler and bugs in this tracking bug.
Bug# 622258 is for further backporting to AIX 5.1 where IBM XLC8 is the last supported compiler release.
Minimum compiler versions: Branch 1.9.1 compiles with VisualAge6 with some additional trivial patches and with XLC/C++ 7 Jul07 fixpack without additional patches on AIX 5.3 Branch 1.9.2 compiles with --disable-accessibility and the patch from bug# 622258 with IBM XLC/C++8 Jul07 fixpack or needs XLC/C++ 9. Branch 2.0 will need XLC/C++ 9 or newer, not ready yet.
branch 1.9.2 will also build AIX 64bit when updating the bundled libffi to version 3.0.10. No other patches are needed when using XLC/C++ 9.0 or newer