The RAS assumption is that your don’t override the return value, which we verify at execution. As long as you don’t, your code will run fast. If you do, then

The RAS assumption is that your don’t override the return value, which we verify at execution. As long as you don’t, your code will run fast. If you do, then you’ll take some very expensive pipeline restarts. But you are right that x86 processors can (they all do?) track stack pointer movement in the frontend. For RISC you can track affine transformations of registers or even just the ABI designated stack pointer but it’s usually not worth the high cost.