Register Variables
==================
Register variables have their own stab type, `N_RSYM' (`C_RSYM' for
XCOFF), and their own symbol descriptor, `r'. The stab's value is the
number of the register where the variable data will be stored.
AIX defines a separate symbol descriptor `d' for floating point
registers. This seems unnecessary; why not just just give floating
point registers different register numbers? I have not verified whether
the compiler actually uses `d'.
If the register is explicitly allocated to a global variable, but not
initialized, as in:
register int g_bar asm ("%g5");
then the stab may be emitted at the end of the object file, with the
other bss symbols.