Re: [Qemu-devel] [PATCH for-1.5?] target-ppc: Drop unnecessary dynamic cast in ppc_env_get_cpu()

[Anthony Liguori <aliguori@us.ibm.com>]

Andreas Färber <afaerber@suse.de> writes:

> A transition from CPUPPCState to PowerPCCPU can be considered safe,
> just like PowerPCCPU::env access in the opposite direction.
>
> This should slightly improve interrupt performance.
>
> Reported-by: Anthony Liguori <aliguori@us.ibm.com>
> Signed-off-by: Andreas Färber <afaerber@suse.de>

Another option would be to leave it and do something like:

diff --git a/qom/object.c b/qom/object.c
index 75e6aac..cba1d88 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -126,8 +126,13 @@ static TypeImpl *type_register_internal(const TypeInfo *info)
 
 TypeImpl *type_register(const TypeInfo *info)
 {
+    TypeImpl *impl;
+
     assert(info->parent);
-    return type_register_internal(info);
+    impl = type_register_internal(info);
+    g_free(impl->name);
+    impl->name = info->name;
+    return impl;
 }
 
 TypeImpl *type_register_static(const TypeInfo *info)
@@ -449,10 +490,16 @@ Object *object_dynamic_cast_assert(Object *obj, const char *typename)
 ObjectClass *object_class_dynamic_cast(ObjectClass *class,
                                        const char *typename)
 {
-    TypeImpl *target_type = type_get_by_name(typename);
+    TypeImpl *target_type;
     TypeImpl *type = class->type;
     ObjectClass *ret = NULL;
 
+    if (type->name == typename) {
+        return class;
+    }
+
+    target_type = type_get_by_name(typename);
+
     if (!target_type) {
         /* target class type unknown, so fail the cast */
         return NULL;

Which makes casting an object to it's concrete class free.

Regards,

Anthony Liguori

> ---
>  target-ppc/cpu-qom.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target-ppc/cpu-qom.h b/target-ppc/cpu-qom.h
> index eb03a00..f62181f 100644
> --- a/target-ppc/cpu-qom.h
> +++ b/target-ppc/cpu-qom.h
> @@ -91,7 +91,7 @@ typedef struct PowerPCCPU {
>  
>  static inline PowerPCCPU *ppc_env_get_cpu(CPUPPCState *env)
>  {
> -    return POWERPC_CPU(container_of(env, PowerPCCPU, env));
> +    return container_of(env, PowerPCCPU, env);
>  }
>  
>  #define ENV_GET_CPU(e) CPU(ppc_env_get_cpu(e))
> -- 
> 1.8.1.4