Returning Values From Functions

The compiler returns function results in registers A, R0, R2, and Y0:

• 8-bit integer values — Y0.
• 16-bit integer values — Y0.
• 32-bit integer or float values — A.

• 64-bit integer or float values — Upper 32-bit word in B, Lower 32-bit word in A.

• All pointer values — R2.
• Structure results — R0 contains a pointer to a temporary space allocated by the caller. The pointer is a hidden parameter value.

Additionally, the compiler:

• Reserves R5 for the stack frame pointer when a function makes a dynamic allocation. (This is the original stack pointer before allocations.) Otherwise, the compiler saves R5 across function calls.
• Saves registers C10 and D10 across function calls.
• Does not save registers C2 and D2 across function calls.