LibreOffice now prefers to use LLVM Clang rather than other compilers to build new rendering code. When you fall back to CPU-based software grate, considering that Google’s own emphasis on the Skia engine is Based on Clang, Clang generates much better code performance than other compilers. So when you build the Version of Windows LibreOffice 7.0, there are now hard requirements for using Clang.
Lubo?Lu?k made changes in LibreOffice’s Git code repository to require Skia on Windows to compile with the Clang compiler. Rendering with Skia is the default setting on Windows, and in its CPU-based grating mode, “the performance of compiling with MSVC is much worse” than in Clang.
Ideally, most LibreOffice 7.0 users will use the Vulkan acceleration feature provided by Skia, but CPU-based acceleration is important for users who use older/unsupported drivers or hardware. The following video shows the performance difference between using Clang (top half) and LibreOffice built with Microsoft MSVC.
Video address: https://youtu.be/iSo4wVtGQ2A
Because of this huge performance difference, LibreOffice now requires clang to build on windows platforms. If Skia is only used on other platforms, you might see Clang’s hardware requirements on platforms such as Linux, which is only a recommendation for now — unless Skia code or the GCC compiler is better optimized, it’s not required to deliver better performance without Clang.
Finally, using Skia rendering code and LibreOffice 7.0 with Vulkan support will be released in August.