I am currently preparing to participate in GSoC. My proposal is Creating a diagnostic to warn when profile data from PGO contradict with user provided data via __builtin_expect, __builtin_unpredictable and others. This can be useful to detect that a profile wasn’t generated with a normal workload and to detect that a hint provided to the complier is inaccurate. Do you think it is a good idea for a GSoC proposal? I didn’t find any implementation of this in clang, is there any existing implementation?