gcc note for modify number of register

in machine.h

FIRST_PSEUDO_REGISTER

FIXED_REGISTERS

CALL_USED_REGISTERS

REG_ALLOC_ORDER

REG_CLASS_NAMES



for arm

arm.c
arm_compute_save_reg0_reg12_mask


arm.h
*_REG_OK_FOR_*

THUMB
HI_REG

arm_dbx_register_number

struct machine_function
rtx call_via[14]; <---