What are Bifrost, Midgard and Utgard?

Bifrost, Midgard and Utgard are the different types of graphics architecture in Mali GPUs:

Bifrost
Arm’s latest architecture. Features in Mali-G7x and Mali-G5x series GPUs.

Midgard
Previous-generation architecture. Features in Mali-T8xx, Mali-T7xx and Mali-T6xx series GPUs.

Utgard
First-generation architecture. Features in Mali-4xx series GPUs.