Transformation of path information for WCET analysis during compilation

“This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder." “Copyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.”Performing worst-case execution time (WCET) analysis on machine code with program path annotation provided at high-level source code level requires the transformation of path annotations from the source-code level to assembly/object-code level. This path-information transformation can be done outside or integrated into the compiler during code compilation. The first approach is easier to implement but lacks for the support of strong code optimizations performed by the compiler because the external tool would have to make guesses about optimizations. In this paper we present an approach for the program code compilation that integrates the transformation of program path information into the compiler. Path information is transformed through all compiler stages to the adequate path information for the corresponding assembly code level. The WCET analysis tool processes the program at assembly code level with the correctly transformed program-path information to obtain accurate runtime bounds. Several experiments were performed to demonstrate the importance of supporting the transformation of path-information in aggressively optimizing compilers