Function bevy_render::batching::no_gpu_preprocessing::batch_and_prepare_sorted_render_phase

pub fn batch_and_prepare_sorted_render_phase<I, GBD>(
    batched_instance_buffer: ResMut<'_, BatchedInstanceBuffer<GBD::BufferData>>,
    phases: ResMut<'_, ViewSortedRenderPhases<I>>,
    param: StaticSystemParam<'_, '_, GBD::Param>,
)
where
    I: CachedRenderPipelinePhaseItem + SortedPhaseItem,
    GBD: GetBatchData,

Batch the items in a sorted render phase, when GPU instance buffer building isn’t in use. This means comparing metadata needed to draw each phase item and trying to combine the draws into a batch.