There are basically two types of functions. A function that requires a stack frame is called a frame function. A function that does not require a stack frame is called a leaf function.

A frame function is a function that allocates stack space, calls other functions, saves nonvolatile registers, or uses exception handling. It also requires a function table entry. A frame function requires a prolog and an epilog. A frame function can dynamically allocate stack space and can employ a frame pointer. A frame function has the full capabilities of this calling standard at its disposal.

If a frame function does not call another function then it is not required to align the stack (referenced in Section Stack Allocation).

A leaf function is one that does not require a function table entry. It can't make changes to any nonvolatile registers, including RSP, which means that it can't call any functions or allocate stack space. It is allowed to leave the stack unaligned while it executes.

Stack Usage