Why there is no `leave` instruction at function epilog on x64? [duplicate] - c++

Question

This question already has answers here:
Why does the x86-64 GCC function prologue allocate less stack than the local variables?
(1 answer)
Why is there no "sub rsp" instruction in this function prologue and why are function parameters stored at negative rbp offsets?
(2 answers)
Closed 4 years ago.
I'm on the way to get idea how the stack works on x86 and x64 machines. What I observed however is that when I manually write a code and disassembly it, it differs from what I see in the code people provide (eg. in their questions and tutorials). Here is little example:
Source
int add(int a, int b) {
int c = 16;
return a + b + c;
}
int main () {
add(3,4);
return 0;
}
x86
add(int, int):
push ebp
mov ebp, esp
sub esp, 16
mov DWORD PTR [ebp-4], 16
mov edx, DWORD PTR [ebp+8]
mov eax, DWORD PTR [ebp+12]
add edx, eax
mov eax, DWORD PTR [ebp-4]
add eax, edx
leave (!)
ret
main:
push ebp
mov ebp, esp
push 4
push 3
call add(int, int)
add esp, 8
mov eax, 0
leave (!)
ret
Now goes x64
add(int, int):
push rbp
mov rbp, rsp
(?) where is `sub rsp, X`?
mov DWORD PTR [rbp-20], edi
mov DWORD PTR [rbp-24], esi
mov DWORD PTR [rbp-4], 16
mov edx, DWORD PTR [rbp-20]
mov eax, DWORD PTR [rbp-24]
add edx, eax
mov eax, DWORD PTR [rbp-4]
add eax, edx
(?) where is `mov rsp, rbp` before popping rbp?
pop rbp
ret
main:
push rbp
mov rbp, rsp
mov esi, 4
mov edi, 3
call add(int, int)
mov eax, 0
(?) where is `mov rsp, rbp` before popping rbp?
pop rbp
ret
As you can see, my main confusion is that when I compile against x86 - I see what I expect. When it's x64 - I miss leave instruction or exact following sequence: mov rsp, rbp then pop rbp. What's worng?
UPDATE
It seems like leave is missing, just because it wasn't altered previously. But then, goes another question - why there is no allocation for local vars in the frame?
To this question #melpomene gives pretty straightforward answer - because of "red zone". Which basically means the function that calls no further functions (leaf) can use the first 128 bytes below the stack without allocating space. So if I insert a call inside an add() to any other dumb function - sub rsp, X and add rsp, X will be added to prologue and epilogue respectively.