m68k assembly question: jsr vs. bsr

[John Paul Adrian Glaubitz]

Hi!

https://github.com/llvm/llvm-project/issues/60354#issuecomment-1412018845

Adrian

[Geert Uytterhoeven]

Hi Adrian,

On Wed, Feb 1, 2023 at 11:17 PM John Paul Adrian Glaubitz

https://github.com/llvm/llvm-project/issues/60354#issuecomment-1412018845

"jsr" is an absolute jump to a subroutine.
"bsr" is a relative jump (8-bit, 16-bit, or 32-bit signed offset) to a
subroutine,
i.e. typically for calling a nearby function.

There's also "jbsr", which is an assembler macro that picks the most
appropriate: bsr does not need relocation, but bsr.l is 68020+ only.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ***@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

[Andreas Schwab]

Post by Geert Uytterhoeven
Hi Adrian,
On Wed, Feb 1, 2023 at 11:17 PM John Paul Adrian Glaubitz

https://github.com/llvm/llvm-project/issues/60354#issuecomment-1412018845

"jsr" is an absolute jump to a subroutine.
"bsr" is a relative jump (8-bit, 16-bit, or 32-bit signed offset) to a
subroutine,
i.e. typically for calling a nearby function.

jsr/jmp also take pcrel, but bsr/bra with 8-bit disp is shorter.