review (S) for 7032162: assert(flat != TypePtr::BOTTOM) failed: cannot alias-analyze an untyped ptr

[Vladimir Kozlov]

This looks better.

Thanks,
Vladimir

Tom Rodriguez wrote:
> On Apr 6, 2011, at 1:49 PM, Vladimir Kozlov wrote:
> 
>> You replaced 'require_constant' with 'true' to the call make_from_constant() so I was wondering if it may change behavior. Specifically it may produce NULL now
>> if oop_constant->can_be_constant() is 'false':
>>
>>      if (require_constant) {
>>        if (!o->can_be_constant())  return NULL;
> 
> In the !JavaObjectInPerm world Strings should always return true for can_be_constant.  Actually I think it would be better to fix it by changing ciObject::should_be_constant instead of just patching that use. I also included Classes in the test for consistency with the old behaviour.  So I've removed the changes in parse3.cpp and done this instead.
> 
> diff -r 8e77e1f26188 src/share/vm/ci/ciObject.cpp                                                                                                     
> --- a/src/share/vm/ci/ciObject.cpp                                                                                                                   
> +++ b/src/share/vm/ci/ciObject.cpp                                                                                                                   
> @@ -194,6 +194,16 @@ bool ciObject::can_be_constant() {
>  // ciObject::should_be_constant()                                                                                                                   
>  bool ciObject::should_be_constant() {                                                                                                               
>    if (ScavengeRootsInCode >= 2)  return true;  // force everybody to be a constant                                                                   
> +  if (!JavaObjectsInPerm) {                                                                                                                         
> +    // We want Strings and Classes to be embeddable by default since                                                                                 
> +    // they used to be in the perm world.  Not all Strings used to be                                                                               
> +    // embeddable but there's no easy way to distinguish the interned                                                                               
> +    // from the regulars ones so just treat them all that way.                                                                                       
> +    ciEnv* env = CURRENT_ENV;                                                                                                                       
> +    if (klass() == env->String_klass() || klass() == env->Class_klass()) {                                                                           
> +      return true;                                                                                                                                   
> +    }                                                                                                                                               
> +  }                                                                                                                                                 
>    return handle() == NULL || !is_scavengable();                                                                                                     
>  }
> 
> tom
> 
>> Vladimir
>>
>> Tom Rodriguez wrote:
>>> http://cr.openjdk.java.net/~never/7032162
>>> 7032162: assert(flat != TypePtr::BOTTOM) failed: cannot alias-analyze an untyped ptr
>>> Reviewed-by:
>>> This appears to be an existing problem with OptimizeStringConcat where
>>> missing control can allow some loads to be split up to where their
>>> base is NULL which causes addresses that can't be analyzed.  The fix
>>> is to use the appropriate control.  If it's truly unneeded it will be
>>> optimized away.  The bug was exposed by the String not in perm changes
>>> because we were no longer treating some constant strings as embeddable
>>> constants.  This is fixed by handling them specially in push_constant.
>>> Tested with failing test from report and full CTW with string opts.
>