The agreement between a caller and a subroutine on argument and result placement, processor register preservation, and call stack organization. Callee-saved registers retain their incoming values across a call; caller-saved registers must be saved by the caller if their values are still needed afterwards.
The saved instruction address at which execution resumes after a function returns. A recursive call must preserve the current return address before another call overwrites the link register.
The 32-bit calling convention for the ARM architecture family. Its base variant passes initial arguments in
r0–r3, returns a word in r0, preserves r4–r8, r10, r11, and sp, and requires eight-byte stack pointer alignment at public calls.[ref]A processor register that a subroutine may overwrite. A caller retaining a live value in such a processor register must preserve it elsewhere before calling. Argument and result processor registers commonly have this role.
A processor register whose incoming value a called subroutine must restore before returning if it modifies it. This lets a caller retain live values across calls, but the caller must in turn preserve its own caller's values when using these processor registers.
