Summary
In this chapter, we augmented the workspace of the compiler by processing the static source code and capturing the program's runtime behaviors. In the first part of this chapter, we learned how to use the infrastructure provided by LLVM to create a sanitizer – a technique that inserts instrumentation code into the target program for the sake of checking certain runtime properties. By using a sanitizer, software engineers can improve their development quality with ease and with high precision. In the second part of this chapter, we extended the usages of such runtime data to the domain of compiler optimization; PGO is a technique that uses dynamic information, such as the execution frequency of basic blocks or functions, to make more aggressive decisions for optimizing the code. Finally, we learned how to access such data with an LLVM Pass, which enables us to add PGO enhancement to existing optimizations.
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