HLASM - BAS = Branch And Save
The opcode of the BAS instruction is X'4D'.
- Branch to a subroutine in the current CSECT
- Register to receive the return address.
- destination address (index, base, displacement).
- The processor places the address of the byte following the BAS
instruction (which is both the next sequential instruction address and
the expected return address) in the first register.
- It branches to the destination address.
- The condition code does not change.
- Only if the processor is in Amode 31, then the high-order bit
of the 32-bit return address will be set to 1.
- BASR branches to a routine whose address is
contained in a register.
- BCR is the preferred return instruction.
- BASSM branches to another routine that may need
to be called in a different Amode.
- The BAS instruction was introduced with the 370/XA architecture.
- The PSW's Amode setting determines how many bits are used for the return
and destination addresses.
YREGS * Define register names
ENTRY BASR R15,R0 * Obtain routine address
USEBASE USING USEBASE,R15 * Make code addressable
BAS R14,SUBRTN * Call subprogram
SUBRTN DS 0H * Align routine to halfword
... * Subroutine logic goes here
BR R14 * Return to caller
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