Cache side-channel attacks pose real threats to computer system security. Prior work called Cloak leverages commodity hardware transactional memory (HTM) to protect sensitive data and code from cache side-channel attacks. However, Cloak requires tedious and error-prone manual modifications to vulnerable software by programmers. This paper presents Cape, a compiler analysis and transformation that soundly and automatically protects programs from cache side-channel attacks using Cloak’s defense. An evaluation shows that Cape provides protection that is as strong as Cloak’s, while performing competitively with Cloak.