Abstract: One embodiment of the present invention provides a system that avoids write-after-write (WAW) hazards while speculatively executing instructions. The system starts in a normal execution mode, wherein the system issues instructions for execution in program order. Upon encountering an unresolved data dependency during execution of an instruction, the system generates a checkpoint, defers the instruction, and executes subsequent instructions in an execute-ahead mode. During this execute-ahead mode, instructions that cannot be executed because of unresolved data dependencies are deferred, and other non-deferred instructions are executed in program order. If an unresolved data dependency is resolved during the execute-ahead mode, the system moves into a deferred mode wherein the system executes deferred instructions.

Abstract: One embodiment of the present invention facilitates low-level systems programming in dynamic, “pointer-safe” programming languages, which disallow arbitrary references through pointers. It does so by avoiding the creation of object instances in the traditional fashion. Rather, a large heap is defined to store dynamically allocated data objects, and explicit memory management operations are implemented in order to allocate and deallocate memory from the heap. Traditional object pointers are replaced by indices to the heap. The described technique allows the bypassing of traditional object allocation, thus making object allocation static from the viewpoint of the pointer-safe programming language—with the exception of the large array that is allocated to serve as the heap. Since the new memory system is implemented on top of an existing automatic memory system, varying degrees of automatic and manual memory management are possible.