Re: [PATCH] m68k: use conventional function parameters for do_sigreturn

[Greg Ungerer <gerg@uclinux.org>]

Hi Andreas,

On 09/02/16 09:31, Andreas Schwab wrote:
> Greg Ungerer <gerg@uclinux.org> writes:
>> Attached is a test case - derived from the original signal.c code.
> 
> It looks like with all those trivial functions in the non-MMU case the
> compiler sees enough to consider the writes to the (pseudo) function
> arguments dead.
> 
> How about this:
> 
> diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c
> index af1c4f3..3cc9eaa 100644
> --- a/arch/m68k/kernel/signal.c
> +++ b/arch/m68k/kernel/signal.c
> @@ -757,6 +757,11 @@ asmlinkage int do_sigreturn(unsigned long __unused)
>  
>  	if (restore_sigcontext(regs, &frame->sc, frame + 1))
>  		goto badframe;
> +	/*
> +	 * Force a barrier so that the compiler does not consider writes
> +	 * to *sw and *regs as dead.
> +	 */
> +	barrier();
>  	return regs->d0;
>  
>  badframe:
> @@ -781,6 +786,11 @@ asmlinkage int do_rt_sigreturn(unsigned long __unused)
>  
>  	if (rt_restore_ucontext(regs, sw, &frame->uc))
>  		goto badframe;
> +	/*
> +	 * Force a barrier so that the compiler does not consider writes
> +	 * to *sw and *regs as dead.
> +	 */
> +	barrier();
>  	return regs->d0;
>  
>  badframe:

Yes that works too. It forces generation of correct code.

So what is the best path forward here?
Should I submit a gcc bug report?

Regards
Greg