Techniques are disclosed relating to sharing datapath circuitry among multiple SIMD groups. In some embodiments, pipeline circuitry is configured to perform operations specified by instructions of first and second assigned SIMD groups. The pipeline circuitry may include first and second front-end circuitry configured to decode instructions of the respective SIMD groups. The pipeline circuitry may include shared execution circuitry configured to perform operations specified by the first and second assigned SIMD groups and arbitration circuitry configured to select an instruction from among at least the first and second front-end circuitry for assignment to the shared execution circuitry in a current cycle. The arbitration circuitry may select an instruction based on one or more of: stall counts, whether available instructions are being speculatively executed, whether ones of available instructions target a particular portion of the shared execution circuitry, numbers of execution cycles, and SIMD group ages.