Doing it with a trampoline is probably slower than if C really had tail calls. On the other hand, adding "real" tail calls to C would probably require changing the ABI (e.g. to "tailcc" or "fastcc -tailcallopt"), and I think there's some reason to think this would probably impose a penalty everywhere (https://llvm.org/docs/CodeGenerator.html#tail-call-optimizat...).
Doing it with a trampoline is probably slower than if C really had tail calls. On the other hand, adding "real" tail calls to C would probably require changing the ABI (e.g. to "tailcc" or "fastcc -tailcallopt"), and I think there's some reason to think this would probably impose a penalty everywhere (https://llvm.org/docs/CodeGenerator.html#tail-call-optimizat...).