SCEV expression for ICmpInst

Be careful about oversimplifying signed integer comparisons -- integer arithmetic can easily overflow, so you cannot transform A > B to A - B > 0. The compare instructions in most processors do not simply subtract and test the most significant bit; they compute what the sign of the difference would be in extended precision.

hi Jud,

thanks very much for this. i completely forgot the overflow stuff … so turn the compare instruction to subtract is a bad idea.

–best regards