X32 ABI (x32 application binary interface) is an application binary interface project and one of the interfaces of the Linux kernel. It that allows programs to take advantage of the benefits of x86-64 (larger number of CPU registers, better floating-point performance, faster position-independent code shared libraries, function parameters passed via registers, faster syscall instruction) while using 32-bit pointers and thus avoiding the overhead of 64-bit pointers.

• x32 ABI Development Website
• rpm5 tracker

As of 23 February 2015 x32 is initialized in pld builders and packages can be built.

• valgrind: no support as of 2015-02-02: http://sourceforge.net/p/valgrind/mailman/message/33306917/
• octave: no support, disable octave bcond for x32
• llvm: llvm 3.5.x does not build on x32, llvm 3.6.0 almost does, needs only makefile tweaks
• php: 5.5, and 5.6 built, older versions need backporting
• qt5
  • qt5-qtbase: to compile, need bootstrap with --without qch --without qm --without directfb, but fails with compilation