> How much do misses on the branch prediction level cost? How much > pipeline interlocks? I don't think those would be _that_ dramatic. Since > today's compilers are said to be optimizing quite well...
It all depends on the code you're running. Certainly branch prediction can have a major effect if the hardware consistently gets it wrong. Even arm hardware has 5/7 stage pipelines that need flushing on a mispredict. Pipeline interlocks are likely to be relatively small, for most Arm hardware at least (ia64 is a completely different story :-). As a compiler author I'd generally expect a few % performance improvement from a good scheduling model. I wouldn't assuming the compiler gets everything right, as it's quite common for systems to be built for the lowest common denominator target. Paul _______________________________________________ Qemu-devel mailing list Qemu-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/qemu-devel
