Fw: Re: [RFC/PATCH] Updated: ppc64: Add mem=X option

[Anton Blanchard]

Hi,

> +unsigned long prom_memparse(const char *ptr, const char **retptr)
> +{
> +	unsigned long ret = prom_strtoul(ptr, retptr);
> +
> +	switch (**retptr) {
> +	case 'G':
> +	case 'g':
> +		ret <<= 10;
> +	case 'M':
> +	case 'm':
> +		ret <<= 10;
> +	case 'K':
> +	case 'k':
> +		ret <<= 10;
> +		(*retptr)++;
> +	default:
> +		break;
> +	}
> +	return ret;
> +}
>
> I get following exception with the above switch statement in place. 

That makes me think gcc is using a particular switch statement
optimisation. You create a table indexed by the switch values (or part of
them). This table contains target addresses for the particular switch
case. You throw it in the count register then do a bctr.

Come to think of it, Im not sure how this optimisation can be safe
before we copy the kernel down.

Anton