The default compiler in Apple's Xcode developer tools is the LLVM-based Clang. Ars Technica reports that they received a heads-up from a developer who works on low-level ARM assembly coding that the latest version of Clang in Xcode adds support for a quad-core, ARM-based processor from Marvell -- the Armada XP.
Ars confirmed that the source code for portions of Clang includes definitions (highlighted in the source code listing shown above) for an architecture type of "armv7k" and a CPU type of "pj4b." According to Ars, PJ4B is a specialized CPU design used in the Armada XP embedded processors.
So, what does this all mean? The most likely interpretation is that Apple is using the Marvell chip in prototype iOS and MacBook Air devices. As Ars notes, a prototype logic board powered by the Armada XP would let Apple software engineers experiment on optimization of the two operating systems while the hardware design team finishes work on a future quad-core ARM design. Is this the A6, successor to the existing A5 processor? Most feel that the A6 is just a smaller and more efficient dual-core processor, but Ars comments that the smaller design would allow Apple to add more cores if necessary.