On this page, information is collected that could help solving graphics issues in Replicant (see #1539). Besides evaluating free implementations that are relevant to currently supported devices, other implementations should also be listed if they are useful for potential future target devices.
Software rendering uses the CPU and not a dedicated graphics processor for graphics rendering. It is slower than per-GPU implementations and is usually used when it is not possible to make use of the GPU. An advantage is that the same software renderer can work across many different types of hardware, so working on improving a software renderer benefits many different devices, regardless of the SOC that is used. Furthermore, a software renderer doesn't require a kernel driver which makes it easier to work on mainline Linux kernel support for a device.
source code: https://git.replicant.us/replicant/frameworks_native/tree/replicant-6.0/opengl/libagl
The Android software renderer is currently used on all Replicant-supported devices and it is the fastest software renderer that is available for Replicant devices. It is a software renderer that was developed specifically for Android and it is part of the AOSP source code. The renderer includes optimizations for ARM. Development ceased in 2013 and no work was done to support newer GLES versions (which causes #705).
Until ca. 2011 (Android 4.0), another library with the name libagl2 existed and surfaceflinger2 was developed based on Mesa. The source code was later removed and no further development is known. At the time, the work was done to support a newer GLES version for the software renderer, but it was abandoned later. It is questionable if it is worth it to port the old libagl2 library to a recent Replicant version, also given that we would be the only ones using and maintaining the code.
supported devices that use Mali 400: Galaxy S 2, Galaxy S 3, Galaxy S 3 4G, Galaxy Note, Galaxy Note 2
supported devices that use PowerVR SGX540: Nexus S, Galaxy S, Galaxy Nexus, Galaxy Tab 2 7.0, Galaxy Tab 2 10.1