Abstract: A blocking system intercepts communications between a software program and an operating system in order to handle blocking and unblocking of event signals. The blocking system intercepts system calls to the operating system requesting the blocking and unblocking of event signals and keeps track of which event signals are blocked and unblocked without delivering the system calls to the operating system. The blocking system also intercepts event signals from the operating system and only allows unblocked event signals to pass to the software program. Blocked event signals received by the blocking system are discarded until the program unblocks the blocked event signals. After unblocking an event signal, the blocking system determines whether a corresponding event signal was previously received and blocked. If so, the blocking system transmits a signal indicating that the event corresponding to the event signal occurred.

Abstract: A compiler facilitates efficient unrolling of loops and enables the elimination of extra branches from the loops, including the elimination of conditional branches from unrolled loops with early exits. Unrolling also enhances other optimizations, such as prefetch, scalar replacement, and instruction scheduling. The unroll factor is calculated to determine the amount of loop expansion and the optimum location to place compensation code to complete the original loop count, i.e. before or after the unrolled loop. The compiler is applicable, for example, to modern RISC architectures, where the latency of memory references and branches is higher than that of integer and floating point arithmetic instructions.