Specializing write-barriers for objects in a garbage collected heap

A computer system for controlling the execution of write-barrier program code when a mutator program calls a reference-modifying method of a receiver object via a class pointer field, the system comprising:

• a processor;
• and
• a computer-readable memory that stores program instructions executable by the processor for
• A) including in the receiver object, both a first method version with first write-barrier code and a second method version with second write-barrier code that differs from the first write-barrier code;
• B) before a predetermined condition is met, storing a first pointer in the class pointer field so that a subsequent call to the receiver object method follows the first pointer and executes the first method version;
• and
• C) after the predetermined condition is met, storing a second pointer in the class pointer field so that a subsequent call to the receiver object method follows the second pointer and executes the second method version.

An apparatus operable in a computer system having a memory for controlling the execution of write-barrier program code when a mutator program executing in the memory calls a reference-modifying method of a receiver object via a class pointer field, the apparatus comprising:

• means for inserting a first method version into the receiver object with first write-barrier code and for inserting a second method version into the receiver object with second write-barrier code that differs from the first write-barrier code;
• means, operable before a predetermined condition is met, for storing a first pointer in the class pointer field so that a subsequent call to the receiver object method follows the first pointer and executes the first method version;
• and
• means, operable after the predetermined condition is met, for storing a second pointer in the class pointer field so that a subsequent call to the receiver object method follows the second pointer and executes the second method version.