uops.info is also very handy for x86 ( https://uops.info/table_overview.html ).
But if you are just starting, those may be a bit overwhelming. In that case, check out the official intrinsics guides for x86 from Intel ( https://software.intel.com/sites/landingpage/IntrinsicsGuide... ) and a separate one for Arm ( https://developer.arm.com/architectures/instruction-sets/int... )