Stack layout

Edit online

The stack layout grows from numerically higher storage addresses to numerically lower addresses.

Only one register, referred to as the stack pointer (SP), is used for addressing the stack, and GPR1 is the dedicated stack pointer register. It grows from numerically higher storage addresses to numerically lower addresses.

The Runtime Stack figure illustrates what happens when the sender function calls the catcher function, and how the catcher function requires a stack frame of its own. When a function makes no calls and requires no local storage of its own, no stack frame is required and the SP is not altered.

Note:
  1. To reduce confusion, data being passed from the sender function (the caller) is referred to as arguments, and the same data being received by the catcher function (the callee) is referred to as parameters. The output argument area of sender is the same as the input parameter area of catcher.
  2. The address value in the stack pointer must be quadword-aligned. (The address value must be a multiple of 16.)