UNIX ABI Section

The following section describes command-line options specific to UNIX ABI, for restricting the floating-point register range, and defining the kernel mode calling convention. They must be used in conjuction with the -F ELF64 option.

-M rfp

AS restricts floating-point registers to the range F6 - F11. This results in less register saves and restores when entering and exiting the kernel, thereby reducing system time. Attempts to use other floating-point registers cause an error.
Default: All floating-point registers can be used.
Example: ias -F ELF64 -M rfp my_file.s

-M const_gp

IAS sets the single global pointer (GP) model in the object file. The kernel is then considered a single model, with one GP.
Default: No additional flags are set in the object file.
Example: ias -F ELF64 -M const_gp my_file.s

-M no_plabel

IAS sets the model in the object file to single GP and no function descriptors (plabels). As with the -M const_gp option, the kernel is then considered a single GP and doesn’t use plabels.
Default: No additional flags are set in the object file.
Example: ias -F ELF64 -M no_plabel my_file.s