WB Games announces updated minimum system specifications for the PC edition of Batman: Arkham Knight in a post from yesterday, just a two of days before tomorrow's planned release (thanks DSOGaming). The post adds the AMD Radeon HD 7950 to the spec and also notes that they are working with AMD on performance issues:

The minimum specs for Batman: Arkham Knight for PC have been adjusted and are listed below.

We also want to note that there are some known issues with the performance of Batman: Arkham Knight for PC owners using AMD graphics cards. We are working closely with AMD to rectify these issues as quickly as possible and will provide updates here as they become available. We thank you for your patience in this matter.

MINIMUM:
OS: Win 7 SP1, Win 8.1 (64-bit Operating System Required)
Processor: Intel Core i5-750, 2.67 GHz | AMD Phenom II X4 965, 3.4 GHz
Memory: 6 GB RAM
Graphics: NVIDIA GeForce GTX 660 (2 GB Memory Minimum) | AMD Radeon HD 7950 (3 GB Memory Minimum)
DirectX: Version 11
Network: Broadband Internet connection required
Hard Drive: 45 GB available space