CppCon 2026

Are you smarter than a branch predictor? In this interactive, game-show-themed session, the audience becomes the branch predictor: participants vote on which of two C++ snippets will run faster before we examine what actually happens on real hardware. The snippets are drawn from real-world production code, and correct answers are rewarded with unique specialty erasers (no two are the same!). Through these examples, we build a practical mental model of how modern CPUs handle control flow and why even small branching decisions can have a significant impact on performance. Using annotated assembly, performance-counter data, and cross-platform comparisons, this talk explores branch prediction, misprediction costs, indirect calls and virtual dispatch, and the trade-offs between branches and conditional moves. We examine how different compilers (GCC, Clang, and MSVC) transform code and highlight non-obvious cases where “branchless” code performs worse or behaves differently across architectures. The examples are intentionally small microbenchmarks, but each exposes patterns that appear in real-world systems when control flow becomes the bottleneck. Whether you're a systems engineer or just curious about what your branch predictor is doing behind your back, this session will give you a concrete mental model of control flow. You'll leave with the tools to profile your code, interpret assembly, and make informed decisions about when to rely on compiler heuristics versus manual optimization.