That's very impressive for gcc. IIRC adding restrict to LLVM triiggered major bugs and miscompilations at least for the first two attempts. As they said they need to do a crater run to be sure, but even passing the initial smoke test is an achievement for gcc.

However, I'm surprised the code is “only” 3% faster using restric annotation. IIRC the speed-ups were about 5% for LLVM so maybe there is still some performance to gain on the gcc side?

[–] antoyo@lemmy.world 7 points 1 year ago

To be fair, I heard that some bugs for restrict fixed in LLVM were also fixed in GCC as a result of finding them using the LLVM codegen of rustc.

For the 3%, this is in only one particular benchmark. Since I was curious, I compiled my test program with the LLVM codegen and disabled noalias: there's also a 3% performance improvement.