5.7.12.2 Call-saved-reg Option

The -fcall-saved-reg option will have the compiler treat the register named reg as an allocatable register that is saved by functions. Functions compiled with this option in effect save and restore the specified register if they use it.

The register specified in this option might be allocated for objects or temporary objects whose duration extends over a function call.

It is an error to specify the Frame Pointer or Stack Pointer registers with this option. Use of this option to specify other registers that have fixed pervasive roles in the machine’s execution model might result in code failure. The same is also true if this option specifies a register in which function values are returned.

This option should be used consistently with all project modules.