On a more high-level, I’d be curious to hear from @axic or @chriseth what they think about this EIP.
Chris wrote above some suggestions which would prevent “walking” into a subroutine or jumping into one. IMO that would be a mistake, but I’m curious to hear why it would be beneficial. As it is now, consider the following code, in pseudo-code;
func formula(a, b int) int{
return add(a * a, b*b)
}
func add(a, b, int) int{
return a + b
}
When translated to the evm, this could be implemented a tail return,
LABEL_FORMULA:
// code to put `a*a` and `b*b` on stack
...
JUMP LABEL_ADD
LABEL_ADD:
BEGINSUB
add
RETSUB
For a perhaps better example, see The Go low-level calling convention on x86-64 · dr knz @ work , where a c compiler generates similar code
Compare how DoCallAdd works in C or C++:
DoCallAdd: movl $3, %edx movl $2, %esi movl $1, %edi jmp FuncAdd
In short, allowing jumps into subroutines enables infinite (tail-) recursion.