[ARM] general registers

Name    Number      APCS Role

a1      0           argument 1 / integer result / scratch register
a2      1           argument 2 / scratch register
a3      2           argument 3 / scratch register
a4      3           argument 4 / scratch register

v1      4           register variable
v2      5           register variable
v3      6           register variable
v4      7           register variable
v5      8           register variable

sb/v6   9           static base / register variable
sl/v7   10          stack limit / stack chunk handle / reg. variable
fp      11          frame pointer
ip      12          scratch register / new-sb in inter-link-unit calls
sp      13          lower end of current stack frame
lr      14          link address / scratch register
pc      15          program counter