Unrolling Loops
2 days ago
- #compiler-optimization
- #loop-unrolling
- #cpp
- Giving the compiler more information helps with optimization, such as specifying loop iteration counts ahead of time.
- Using `std::span<int, 8>` allows the compiler to unroll loops, saving instructions and improving performance.
- The compiler uses different strategies for loop unrolling depending on the iteration count, sometimes falling back to regular loops for large counts.
- Partial loop unrolling and speculative unrolling are techniques compilers use when exact counts aren't known.
- Profile-guided optimization (PGO) can help compilers make better guesses about loop counts.
- The post is part of the 'Advent of Compiler Optimisations 2025' series and was written by Matt Godbolt.