On Sun, 24 Oct 2021 19:28:42 +0000, Gibney, Dave wrote: >Seem that is this case, it would be the responsibility of the new A64 code >(by definition, A64 code is new) to protect itself by saving before the call >and restoring after. > That may not be necessary. If the AMODE 24/31 subroutine is "old", using no Grande instructions, it will not modify top halves and they need not be saved/restored.
One hazard: The STORAGE function modifies some top halves even when called in AMODE 24/31. This is not considered a defect because the conventions do not require preserving R0, R1, R14. or R15 and STORAGE modifies no other registers. >> -----Original Message----- >> From: Binyamin Dissen >> >> Not necessarily. >> >> An A64 routine can step down to call an A31 routine which will not save top >> halves and will only provide an 18 word save area. >> >> On Sun, 24 Oct 2021 17:23:31 +0000 Seymour J Metz wrote: >> :> >> :>If R13 points to an 18-word save area, then there is no top half to save. >> R13 >> must point to an appropriate save area before calling the A64 routine. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
