That's absolutely doable, just... How much is predicted unconditional jump slower/faster than ENDBR64? What's the ratio of virtual/static calls in real-world pr

That's absolutely doable, just... How much is predicted unconditional jump slower/faster than ENDBR64? What's the ratio of virtual/static calls in real-world programs? And while your last proposal ("foo: endbr64; foo_internal: <code>") evades those questions, it raises up questions about maintaining function alignment (16 bytes IIRC? Is this even necessary today?) and restructuring the compiler to distinguish the inner/external symbol addresses. Plus, of course, somebody has to actually sit down and write the code to implement that, as opposed to just adding "if (func->is_escaping) emit_endbr(...);" at the beginning of the code that emits the object code for a function body.