Object oriented apparatus and method for allocating objects on an invocation stack in a partial compilation environment

An apparatus comprising:

• at least one processor;
• a memory coupled to the at least one processor;
• a first compilation unit residing in the memory, the first compilation unit comprising a plurality of object oriented classes that are part of an object oriented program, wherein the object oriented program is defined by the combination of the first compilation unit and at least one other compilation unit;
• and
• a compiler residing in the memory and executed by the at least one processor, the compiler comprising:
• an escape analysis mechanism that marks each instruction in the first compilation unit that allocates a new object as one of global escape, no escape, and arg escape based on information available from classes visible in the first compilation unit and from classes that are outside the first compilation unit that are visible in a specified classpath;
• an object allocation mechanism that allocates at least one object that is created by an instruction marked as no escape by the escape analysis mechanism to an invocation stack frame for a method that allocates the object;
• a code generator that creates two versions of code for a selected object method, a first version using stack allocation of objects and a second version using heap allocation of objects;
• and
• a run time code selector that selects one of the first and second versions to execute at run time based on a determination of whether classes seen at run time match expected classes within predetermined limits.

In an object oriented computer program that comprises a first compilation unit and at least one other compilation unit, a method for allocating objects in the first compilation unit to memory, the method comprising the steps of:

• marking each instruction that allocates a new object as one of global escape, no escape, and arg escape based on information available from classes in the first compilation unit and from classes that are outside the first compilation unit that are visible in a specified classpath;
• creating two versions of code for a selected object method, a first version using stack allocation of objects and a second version using heap allocation of objects;
• and
• selecting at run time one of the first and second versions to execute at run time based on a determination of whether classes seen at run time match expected classes within predetermined limits.

A program product comprising:

• (A) a compiler that compiles a first compilation unit comprising a plurality of object oriented classes that are part of an object oriented program, wherein the object oriented program is defined by the combination of the first compilation unit and at least one other compilation unit, the compiler comprising:
• (A1) an escape analysis mechanism that marks each instruction that allocates a new object as one of global escape, no escape, and arg escape based on information available from classes in the first compilation unit and from classes that are outside the first compilation unit that are visible in a specified classpath;
• (A2) an object allocation mechanism that allocates at least one object that is created by an instruction marked as no escape by the escape analysis mechanism to an invocation stack frame for a method that allocates the object;
• (A3) a code generator that creates two versions of code for a selected object method, a first version using stack allocation of objects and a second version using heap allocation of objects;
• and
• (A4) a run time code selector that selects one of the first and second versions to execute at run time based on a determination of whether classes seen at run time match expected classes within predetermined limits;
• and
• (B) signal bearing media bearing the compiler.