A graphics processing unit (GPU) includes a plurality of programmable processing cores configured to process graphics primitives and corresponding data and a plurality of fixed-function hardware units. The plurality of processing cores and the plurality of fixed-function hardware units are configured to implement a configurable number of virtual pipelines to concurrently process different command flows. Each virtual pipeline includes a configurable number of fragments and an operational state of each virtual pipeline is specified by a different context. The configurable number of virtual pipelines can be modified from a first number to a second number that is different than the first number. An emulation of a fixed-function hardware unit can be instantiated on one or more of the graphics processing cores in response to detection of a bottleneck in a fixed-function hardware unit. One or more of the virtual pipelines can then be reconfigured to utilize the emulation instead of the fixed-function hardware unit.