Gallium3D LLVMpipe Isn't Yet Fit For ARM

While OpenGL is becoming a requirement for more of the Linux desktops out there, and ARM open-source graphics drivers aren't yet commonplace, using the Gallium3D LLVMpipe software rasterizer on ARM isn't yet a really viable solution.

LLVMpipe, which allows for running OpenGL on the CPU without the support of GPU and attempts to leverage LLVM for optimizations and taking advantage of multiple processing cores, simply isn't well-optimized yet. With the ARM Cortex-A15 being quite a nice upgrade over the Cortex-A9 ARM SoCs, I decided to build Mesa 9.1-devel Git with LLVM 3.1 on the Samsung Chromebook with its Exynos 5 Dual from Ubuntu 12.10.

While Gallium3D's LLVMpipe driver will run on ARM just as it has in the past, it's not too performant and optimized for this architecture. On x86, LLVMpipe really needs 64-bit support and multiple modern CPU cores (such as those boasting SSE4 and AVX) in order to deliver fairly low performance. On ARM, it just doesn't cut it yet without any ARM-specific optimizations. A modern ARM SoC is fast enough to get a compositing window manager running in software, but not really anything else that's useful.

There's also other use-cases where LLVMpipe just doesn't cut it, as covered in Not All Linux Users Want To Toke On LLVMpipe.