Why Sony Is Using LLVM/Clang On The PlayStation 4
Sony is using LLVM/Clang as its CPU compiler as part of the development kit for targeting the PlayStation 4. Here's some more information on their reasoning for doing so and other details.
The slides and videos from last month's LLVM 2013-11 developer meeting are finally available so there will be a couple more LLVM-related posts in the next day or two. One of the topics that was interesting from last month's compiler meeting was about Sony using LLVM/Clang for their next-gen console.
Sony is using LLVM Clang as its PlayStation 4 CPU compiler due to its highly conformant C and C++ front-ends, great C++11 support, excellent diagnostic messages, fast compilation times, and excellent code generation. There wasn't any messages about using LLVM Clang for its more liberal licensing than GCC or other alternatives.
Sony also switched to Clang since one of the previously used compilers (SNC) could not target x86 architectures. The PlayStation 4 is based upon an AMD Jaguar APU compared to the PlayStation 3 being Cell-based. When evaluating GCC, LLVM-GCC, and other compiler options, Clang did not initially come out as the clear winner but they felt it was on a trajectory with the LLVM community being more nimble than GCC, and LLVM with Clang being joined together to make for easier updating and maintenance of their entire compiler stack.
Developers working on the PlayStation 4 development kit also made changes to LLVM Clang, including the default compiler tags, optimizations for cross-compiling, pragmas for custom features, better Windows support, and other back-end tweaks. Now that the Sony PlayStation 4 has launched, the developers can work better with upstreaming the relevant LLVM patches, but as of last month there was still a lot of backlog that the developers had to work through cleaning and sending out. The developers hope to eventually live off the latest upstream LLVM/Clang trunk code-base.
According to Sony, game developers are loving the compiler toolchain except when it comes to the area of debugging. Developers would love for Clang to be able to unoptimize only certain functions, more hooks for developer support, and other improvements in the area of profiling, sanitizing, and static analysis. Improved compiler debugging in general (especially on Linux platforms) has been one of the areas most sought after by game developers on open-source solutions, which is why Valve is working on LLVM's LLDB and its own Linux game debugger software.
For those wanting more details on the PlayStation 4 Clang compiler, see the PDF slides and MOV video recording.
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