Leaf function example

leaf.cxx

// Compile with: gcc -O2 leaf.c -o leaf
// Proof: https://godbolt.org/z/vg1FSS
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

// Not actually tweaking the stack (except for ret)
int leaf_me_alone(int a, int b)
{
	return a*a + b*b / 2;
}

int main(int argc, const char *argv[])
{
	const char *as, *bs;
	as = bs = NULL;
	
	if ((as = argv[1])) {
		bs = argv[2];
	} 

	if (!as || !bs) {
		return 1;
	}

	int a = atoi(as);
	int b = atoi(bs);
			
	printf("%d\n", leaf_me_alone(a, b));
	printf("%d\n", leaf_me_alone(b, a));
	return 0;
}

leaf.s

leaf_me_alone(int, int):
        imul    esi, esi
        imul    edi, edi
        sar     esi
        lea     eax, [rsi+rdi]
        ret
.LC0:
        .string "%d\n"
main:
        mov     rdi, QWORD PTR [rsi+8]
        mov     eax, 1
        test    rdi, rdi
        je      .L10
        push    rbp
        push    rbx
        sub     rsp, 8
        mov     rbp, QWORD PTR [rsi+16]
        test    rbp, rbp
        je      .L3
        mov     edx, 10
        xor     esi, esi
        call    strtol
        mov     edx, 10
        mov     rdi, rbp
        xor     esi, esi
        mov     rbx, rax
        call    strtol
        imul    ebx, ebx
        mov     edi, OFFSET FLAT:.LC0
        mov     rbp, rax
        imul    ebp, eax
        xor     eax, eax
        mov     esi, ebp
        sar     esi
        add     esi, ebx
        sar     ebx
        call    printf
        lea     esi, [rbx+rbp]
        mov     edi, OFFSET FLAT:.LC0
        xor     eax, eax
        call    printf
        xor     eax, eax
.L3:
        add     rsp, 8
        pop     rbx
        pop     rbp
        ret
.L10:
        ret