`callj'
.......
You can write `callj' to have the assembler or the linker determine
the most appropriate form of subroutine call: `call', `bal', or
`calls'. If the assembly source contains enough information--a
`.leafproc' or `.sysproc' directive defining the operand--then `as'
translates the `callj'; if not, it simply emits the `callj', leaving it
for the linker to resolve.