com.oracle.svm.core.annotate

Annotation Type Hybrid

@Retention(value=RUNTIME)
 @Target(value=TYPE)
public @interface Hybrid

Defines that the annotated class should have a Hybrid layout. Hybrid layouts are hybrids between instance layouts and array layouts. The contents of a specified member array and (optional) member type id slots are directly placed within the class layout. This saves one indirection when accessing the array or type id slots.

The array length is located directly after the HUB pointer, like in regular array. Then (if present) the type id slots follow. Then the instance fields are placed. Then, with the default GC, there is an optional identity hashcode. At the end of the layout, the array elements are located.

    +--------------------------------+
    | pointer to DynamicHub          |
    +--------------------------------+
    | identity hashcode              |
    +--------------------------------+
    | array length                   |
    +--------------------------------+
    | type id slots (optional)       |
    |     ...                        |
    +--------------------------------+
    | instance fields                |
    |     ...                        |
    +--------------------------------+
    | array elements                 |
    :     ...                        :
 

Currently only the DynamicHub class has a hybrid layout.

Required Element Summary

Required Elements

Modifier and Type	Required Element and Description
boolean	canHybridFieldsBeDuplicated If true, we expect that the data in the hybrid fields can be duplicated between the hybrid object and a separate object for the array or bitset.

Element Detail

canHybridFieldsBeDuplicated

public abstract boolean canHybridFieldsBeDuplicated

If true, we expect that the data in the hybrid fields can be duplicated between the hybrid object and a separate object for the array or bitset. For most objects, a duplication could occur if inlining and constant folding result in the internal reference to a hybrid field being constant folded to a constant value, which must be written into the image heap separately from the hybrid object. If false, we expect that this duplication of the hybrid fields can never happen.