nona42

For games, most performance critical code probably does not run on the CPU but on the GPU. I believe they use pretty standard open source CPU compilers and Sony e.g. do contribute to LLVM.

For Armv8.M and MVE, I expect that Clang and Arm Compiler for Embedded, which is Clang/LLVM based, generates much better code than GCC or IAR.

Regarding code size: the common pitfall is -Os for GCC and -Oz for Clang based compilers to optimise for minimum code size.