The XPLINK stack frame layout

Figure 1 shows the XPLINK stack frame layout.

The XPLINK stack register (general-purpose register (GPR) 4) is "biased," meaning it points to a location 2048 bytes before the stack frame for the currently active routine. It grows from numerically higher storage addresses to numerically lower ones, that is, the stack frame for a called function is normally at a lower address than the calling function. The stack frame is aligned on a 32-byte boundary.

Figure 1. XPLINK stack frame layout

The XPLINNK stack register points to a location 2048 bytes before the stack frame for the currently active routine, and grows from numerically higher storage addresses to numerically lower ones.