Improving processor performance by simplifying and bypassing trivial computations

During the course of a program´s execution, a processor performs mangy trivial computations; that is, computations that can be simplified or where the result is zero, one, or equal to one of the input operands. This paper shows that, despite compiling a program with aggressive optimizations (-O3), approximately 30% of all arithmetic instructions, which account for 12% of all dynamic instructions, are trivial computations. The amount of trivial computation is not heavily dependent on the program´s specific input values. Our results show that eliminating trivial computations dynamically at run-time yields an average speedup of 8% for a typical processor. Even for a very aggressive processor (i.e. one with no functional unit constraints), the average speedup is still 6%. It also is important to note that the area cost (i.e. hardware) required to dynamically detect and eliminate these trivial computations is very low, consisting of only a few comparators and multiplexers.