FreeBSD ABI?

[Yuri]

Where is it documented?
Are there differences with the linux ABI?

Particularly I am interested in stack alignment requirement. For example 
i386 Solaris, Linux and MacOS have 16 bit stack alignment for procedure 
calls. This is reflected in LLVM sources:

   if (isTargetDarwin() || isTargetLinux() || isTargetSolaris() || Is64Bit)
     stackAlignment = 16;


But FreeBSD is excluded there. Is this a bug in LLVM which magically 
doesn't cause crashes or this is correct and FreeBSD doesn't have 16 bit 
alignment?

Yuri