3.6.1.3 Call-prologues Option

The -mcall-prologues option changes how functions save registers on entry and how those registers are restored on function exit.

If this option is not specified or the -mno-call-prologues options is used, the registers that need to be preserved by each function will be saved and restored by code inside those functions. If the -mcall-prologues option is used, this preservation code is extracted as subroutines that are called at the appropriate points in the function.

Use of this option can reduce code size, but can increase the code’s execution time.