Re: [Qemu-devel] [PATCH for-2.11 4/6] ppc: replace inter-function cyclic dependency/recurssion with 2 simple lookups

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 25 Aug 2017 14:12:08 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Thu, Aug 24, 2017 at 10:21:49AM +0200, Igor Mammedov wrote:
> > previous patches cleaned up cpu model/alias naming which
> > allows to simplify cpu model/alias to cpu type lookup a bit
> > byt removing recurssion and dependency of ppc_cpu_class_by_name() /
> > ppc_cpu_class_by_alias() on each other.
> > Besides of simplifying code it reduces it by ~15LOC.
> > 
> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>  
> 
> Urm.. I think this is probably good.  But I'm having a little trouble
> convincing myself this really has the same effect as before.
It's hard to wrap brain around current cyclic recursion and
how to 2 simple linear lookups could replace it.

By itself this patch won't work, it depends on 2-3/6 for
normalized cpu type names and recursion-less alias table.

The only change in behavior here is that it does alias
translation first and only then cpu_model to type translation.

> 
> > ---
> >  target/ppc/translate_init.c | 43 +++++++++++++------------------------------
> >  1 file changed, 13 insertions(+), 30 deletions(-)
> > 
> > diff --git a/target/ppc/translate_init.c b/target/ppc/translate_init.c
> > index 0325226..f1a559d 100644
> > --- a/target/ppc/translate_init.c
> > +++ b/target/ppc/translate_init.c
> > @@ -10176,22 +10176,6 @@ PowerPCCPUClass *ppc_cpu_class_by_pvr_mask(uint32_t pvr)
> >      return pcc;
> >  }
> >  
> > -static gint ppc_cpu_compare_class_name(gconstpointer a, gconstpointer b)
> > -{
> > -    ObjectClass *oc = (ObjectClass *)a;
> > -    const char *name = b;
> > -    PowerPCCPUClass *pcc = POWERPC_CPU_CLASS(oc);
> > -
> > -    if (strncasecmp(name, object_class_get_name(oc), strlen(name)) == 0 &&
> > -        ppc_cpu_is_valid(pcc) &&
> > -        strcmp(object_class_get_name(oc) + strlen(name),
> > -               POWERPC_CPU_TYPE_SUFFIX) == 0) {
> > -        return 0;
> > -    }
> > -    return -1;
> > -}
> > -
> > -
> >  static ObjectClass *ppc_cpu_class_by_name(const char *name);
> >  
> >  static ObjectClass *ppc_cpu_class_by_alias(PowerPCCPUAlias *alias)
> > @@ -10216,8 +10200,8 @@ static ObjectClass *ppc_cpu_class_by_alias(PowerPCCPUAlias *alias)
> >  
> >  static ObjectClass *ppc_cpu_class_by_name(const char *name)
> >  {
> > -    GSList *list, *item;
> > -    ObjectClass *ret = NULL;
> > +    char *cpu_model, *typename;
> > +    ObjectClass *oc;
> >      const char *p;
> >      int i, len;
> >  
> > @@ -10238,21 +10222,20 @@ static ObjectClass *ppc_cpu_class_by_name(const char *name)
> >          }
> >      }
> >  
> > -    list = object_class_get_list(TYPE_POWERPC_CPU, false);
> > -    item = g_slist_find_custom(list, name, ppc_cpu_compare_class_name);
> > -    if (item != NULL) {
> > -        ret = OBJECT_CLASS(item->data);
> > +    cpu_model = g_ascii_strup(name, -1);
> > +    p = ppc_cpu_lookup_alias(cpu_model);
> > +    if (p) {
> > +        g_free(cpu_model);
> > +        cpu_model = g_strdup(p);
> >      }
> > -    g_slist_free(list);
> >  
> > -    if (ret) {
> > -        return ret;
> > -    }
> > +    typename = g_strdup_printf("%s" POWERPC_CPU_TYPE_SUFFIX, cpu_model);
> > +    oc = object_class_by_name(typename);
> > +    g_free(typename);
> > +    g_free(cpu_model);
> >  
> > -    for (i = 0; ppc_cpu_aliases[i].alias != NULL; i++) {
> > -        if (strcasecmp(ppc_cpu_aliases[i].alias, name) == 0) {
> > -            return ppc_cpu_class_by_alias(&ppc_cpu_aliases[i]);
> > -        }
> > +    if (oc && ppc_cpu_is_valid(POWERPC_CPU_CLASS(oc))) {
> > +        return oc;
> >      }
> >  
> >      return NULL;  
>