To scale ILP, designers build deeper and wider out-of-order superscalar CPUs.However, this approach incurs quadratic scaling complexity, area, and energy costs with each generation.While small loops may benefit from increased instruction-window sizes and large loops may see speedups via thread-level parallelism across cores, there remains unexploited medium-granularity parallelism.We propose LoopFrog to tap into this potential by bringing thread-level speculation schemes into the modern era.LoopFrog runs multiple loop iterations from a single thread in parallel within the microarchitecture.The core can spawn future loop iterations as new microarchitectural threadlets based on compiler-inserted hints, which can leapfrog execution beyond the parent thread's instruction window, exposing a new, medium-grained parallelism, orthogonal to traditional ILP and TLP.LoopFrog monitors data dependencies between executing threadlets, forwards data for true dependencies and squashes speculative threadlets on ordering violations.Using an LLVM-based compiler to insert hints, we achieve a geometric mean loop speedup of 43%, translating to whole-program speedups of 9.2% on SPEC CPU 2006 and 9.5% on SPEC CPU 2017 benchmarks, with only modest area and power overheads.

In the era of Exascale computing, writing efficient parallel programs is indispensable, and, at the same time, writing sound parallel programs is very difficult. Specifying parallelism with frameworks such as OpenMP is relatively easy, but data races in these programs are an important source of bugs. In this article, we propose LLOV, a fast, lightweight, language agnostic, and static data race checker for OpenMP programs based on the LLVM compiler framework. We compare LLOV with other state-of-the-art data race checkers on a variety of well-established benchmarks. We show that the precision, accuracy, and the F1 score of LLOV is comparable to other checkers while being orders of magnitude faster. To the best of our knowledge, LLOV is the only tool among the state-of-the-art data race checkers that can verify a C/C++ or FORTRAN program to be data race free.