struct CrlEdge / crl_edge_t

Description

An edge between two basic blocks.

Additional to accessing the slot directly, this class emulates a map structure with the following special attributes:

• "type" :: ValueIdentifier containing type()

• "linear" :: ValueUnsigned containing is_linear()

• "source" :: ValueItem containing source()

• "target" :: ValueItem containing target()

These wrappers are especially implemented for environments where only the CrlStructure interface is available, but not the interface for this special class, particularly in OptLa. If you use the native C/C++ library interface, better use the slot access directly.

Note

Edges' reference counting is interesting, since both ends (source and target) must be != NULL in order in increment the reference counter and prevent deletion. This is because they are stored in hash tables at blocks, indexed by the buddy block.

This leads to potentially dangerous traps: when generating a raw edge with both ends NULL, like:

edge = new Edge;

you must be careful to not set the ends like this without protection:

edge->set_source (source);
edge->set_target (target);  // CRASH!

The reason is that the set_source() invocation will deallocate the edge due to the reference counter being 0.

So protect the above sequence:

CRL_REF (edge);
edge->set_source (source);
edge->set_target (target);  // ok.
CRL_UNREF (edge);

After this requence, the ref_count() of the edge is 2 (if it was 0 before), so the CRL_UNREF() does not delete it.

Alternatively, set the edges upon creation:

edge= new Edge (source, target);

Kinship

Immediate super class: RoutineItem

Type Aliases

Slots

Inherited Slots

Members