CppCon 2018

Optimizing compilers can seem rather fickle: sometimes they do something very sophisticated that surprises us, other times they fail to perform an optimization we assumed they would. By understanding the limits on their knowledge, and the constraints in their output, we can much more reliably predict when certain kinds of optimizations can occur. This, in turn, allows our designs to be informed by being friendly to the optimizer.

This talk will discuss concepts fundamental to understanding optimization such as the role of static types, basic blocks, and correctness of emitted code. It will also go through many examples: where inlining does and doesn't occur and why, const propagation, branch pruning, utilizing inferred information/values, the roles of const and value vs reference semantics, etc. It will also show how to help the compiler: writing code in different ways which encourages different optimization strategies.