Automatic Inverse Operation Detection and its Impact in High-level Synthesis

The inverse operations are defined as a set of operations when performed on a variable inside a loop body, the value of the variable remains same after the execution of the loop. Naive programmers may introduce this type of operations in their code. Automatic code generation tool may also employ such operations to undo the effects of some speculatively executed operations. Detection of inverse operation during of high-level synthesis (HLS) will improve its synthesis results. This work proposes a method of finding inverse operations in C program without unrolling the loop. The method uses normalization, symbolic simulation and integer set library to detect inverse operations. Run time of the proposed method is significantly low as it does not unroll the loop. Experiments with an existing HLS tool show the usefulness of the method.