review for 7121073: secondary_super_cache memory slice has incorrect bounds in flatten_alias_type

[Tom Rodriguez]

On Dec 15, 2011, at 12:44 PM, Vladimir Kozlov wrote:

> Tom,
> 
> Can you updated related comments? Otherwise looks good.

How about this:

    // If we are referencing a field within a Klass, we need
    // to assume the worst case of an Object.  Both exact and
    // inexact types must flatten to the same alias class so
    // use NotNull as the PTR.

tom

> 
> Thanks,
> Vladimir
> 
> Tom Rodriguez wrote:
>> http://cr.openjdk.java.net/~never/7121073
>> 7 lines changed: 2 ins; 0 del; 5 mod; 3239 unchg
>> 7121073: secondary_super_cache memory slice has incorrect bounds in flatten_alias_type
>> Reviewed-by:
>> To ensure that memory operations for type checks are properly ordered,
>> several fields are smeared together into the same alias slice.  The
>> existing logic is sloppy and includes a slightly larger chunk of
>> memory than intended.  Currently this is fine but changes to the shape
>> of Klass can invalidate it.  The fix is to properly test the
>> boundaries.  Additionally I changed the logic for setting the PTR to
>> use NotNull instead of Constant to be consisten with all the following
>> logic which uses NotNull.  Tested with full CTW.