You can easily verify this in your specific code base but I believe the compiler prefers not-taken jumps for paths it predicts to be less frequently taken. You

You can easily verify this in your specific code base but I believe the compiler prefers not-taken jumps for paths it predicts to be less frequently taken. You can provide hints that the path is a cold one to ensure the compiler uses the most efficient conditional branch layout. On some architectures the compiler will also provide this hint to the CPU (with a prefix, the instruction it selects, or a flag bit in the instruction) which avoids the perf hit on the first iteration. Both Clang and GCC recognize __builtin_expect which can be wrapped in a macro easily: #define unlikely(x) __builtin_expect(!!(x), 0)