Re: [PATCH] m68k: Fix asm register constraints for atomic ops

[Arnd Bergmann]

On Sun, Jul 25, 2021 at 12:46 PM Geert Uytterhoeven
<geert@xxxxxxxxxxxxxx> wrote:
>
> Depending on register assignment by the compiler:
>
>     {standard input}:3084: Error: operands mismatch -- statement `andl %a1,%d1' ignored
>     {standard input}:3145: Error: operands mismatch -- statement `orl %a1,%d1' ignored
>     {standard input}:3195: Error: operands mismatch -- statement `eorl %a1,%d1' ignored
>
> Indeed, the first operand must not be an address register.  Fix this by
> adjusting the register constraint from "g" (general purpose register) to
> "d" (data register).
>
> Fixes: e39d88ea3ce4a471 ("locking/atomic, arch/m68k: Implement atomic_fetch_{add,sub,and,or,xor}()")
> Fixes: d839bae4269aea46 ("locking,arch,m68k: Fold atomic_ops")
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Reported-by: Arnd Bergmann <arnd@xxxxxxxx>
> Reported-by: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> ---
> Personally, I have never seen this failure in an 68020+ build, but I can
> reproduce it on Coldfire with the config provided by lkp (with bogus
> CONFIG_RMW_INSNS=y).

This fixed the problem for me in the 68020 build with all compiler versions.

Tested-by: Arnd Bergmann <arnd@xxxxxxxx>