Re: [Qemu-devel] [4351] Make the paged properties of the tb-jmp-cache hash function work for TARGET_PAGE_BITS ! = 12.

["Edgar E. Iglesias" <edgar.iglesias@axis.com>]

On Tue, May 06, 2008 at 01:31:02PM +0100, Paul Brook wrote:
> >  {
> >      target_ulong tmp;
> >      tmp = pc ^ (pc >> (TARGET_PAGE_BITS - TB_JMP_PAGE_BITS));
> > -    return (tmp >> TB_JMP_PAGE_BITS) & TB_JMP_PAGE_MASK;
> > +    return (tmp >> (TARGET_PAGE_BITS - TB_JMP_PAGE_BITS)) &
> > TB_JMP_PAGE_MASK; }
> 
> 
> I'm not sure what you're trying to achieve here, but this is definitely wrong.
> TARGET_PAGE_BITS may be less than TB_JMP_PAGE_BITS.

Hi Paul,

Thanks for the comment. 

I didn't find any page bits under 10 in the tree. Please note that the constant beeing used is not TB_JMP_CACHE_BITS but TB_JMP_PAGE_BITS. Also that same right shift constant was already used in the initial shift of pc in that same routine.

Before committing I ran tests with target page bits 10, 11, 12, and 13 and the modified hash function behaved ok here. Are there more setups I should test ?

Best regards
-- 
Edgar E. Iglesias
Axis Communications AB