ruy::ThreadPool: when there is only 1 task, don't even touch atomic counters. Saves a store-release and a load-acquire (total ~100 cycles) per matmul.
ruy::ThreadPool: when there is only 1 task, don't even touch atomic counters.
Saves a store-release and a load-acquire (total ~100 cycles) per matmul.

PiperOrigin-RevId: 261321407

google/ruy,google/ruy,google/ruy,google/ruy