Ok, it obviously doesn't increase the number of ISA registers. What I am suggesting is something else - imagine a situation in which the compiler understands that the spill over will take place, and therefore rearranges the code such that it reduces the pressure on the registers. It can do that if it can break the data dependencies between the variables for instance. Or it can do that by unrolling the loops or by moving the initialization closer to where the variable is being used, no? I am pretty certain that compilers are already doing these kind of transformations, and in a sense this is taking advantage of register renaming but indirectly.