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

[Tom Rodriguez]

Thanks!

tom

On Apr 6, 2011, at 2:07 PM, Vladimir Kozlov wrote:

> 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.