#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>

static inline bool
is_zero_add(const uint8_t * addr)
{
        return ((addr[0] + addr[1] + addr[2] + addr[3] + addr[4] + addr[5]) == 0);
}

static inline bool
is_bcast_add(const uint8_t * addr)
{
        return ((addr[0] + addr[1] + addr[2] + addr[3] + addr[4] + addr[5]) == (6*0xff));
}

extern int foo(const uint8_t addr[static 6]);

int
foo(const uint8_t addr[static 6])
{
        int res;

        // Prevent compiler from wholly obviating the computation
        res = 0;
        res += (int)is_zero_add(addr);
        res += (int)is_bcast_add(addr);
        return (res);
}

===========================================================================================

(gdb) disas /m foo
Dump of assembler code for function foo:
22              return ((addr[0] + addr[1] + addr[2] + addr[3] + addr[4] + addr[5]) == 0);
   0x0000000000000004 <+4>:     movzbl (%rdi),%eax
   0x0000000000000007 <+7>:     movzbl 0x1(%rdi),%ecx
   0x000000000000000b <+11>:    add    %eax,%ecx
   0x000000000000000d <+13>:    movzbl 0x2(%rdi),%eax
   0x0000000000000011 <+17>:    add    %ecx,%eax
   0x0000000000000013 <+19>:    movzbl 0x3(%rdi),%ecx
   0x0000000000000017 <+23>:    add    %eax,%ecx
   0x0000000000000019 <+25>:    movzbl 0x4(%rdi),%eax
   0x000000000000001d <+29>:    add    %ecx,%eax
   0x000000000000001f <+31>:    movzbl 0x5(%rdi),%ecx
   0x0000000000000023 <+35>:    add    %eax,%ecx


// Clang just emits ordinary 2-argument adds.


23      }
25      static inline bool
26      is_bcast_add(const uint8_t * addr)
27      {
28              return ((addr[0] + addr[1] + addr[2] + addr[3] + addr[4] + addr[5]) == (6*0xff));
   0x0000000000000025 <+37>:    xor    %eax,%eax
   0x0000000000000027 <+39>:    cmp    $0x5fa,%ecx
   0x000000000000002d <+45>:    sete   %al


// The broadcast check can reuse the addition result