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

bool
is_zero_or(const uint8_t * addr)
{
        return ((addr[0] | addr[1] | addr[2] | addr[3] | addr[4] | addr[5]) == 0);
}

bool
is_bcast_and(const uint8_t * addr)
{
        return ((addr[0] & addr[1] & addr[2] & addr[3] & addr[4] & addr[5]) == 0xff);
}

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

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

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

Clang 8.0.0, -O3:

// Add variants are much the same as the inline versions, but OR/AND get SIMD'd (obviously unhelpful for kernel)

0000000000000000 <is_zero_or>:
   0:   55                      push   %rbp
   1:   48 89 e5                mov    %rsp,%rbp
   4:   66 0f 6e 07             movd   (%rdi),%xmm0
   8:   66 0f 60 c0             punpcklbw %xmm0,%xmm0
   c:   66 0f 61 c0             punpcklwd %xmm0,%xmm0
  10:   66 0f 70 c8 4e          pshufd $0x4e,%xmm0,%xmm1
  15:   66 0f eb c8             por    %xmm0,%xmm1
  19:   66 0f 70 c1 e5          pshufd $0xe5,%xmm1,%xmm0
  1e:   66 0f eb c1             por    %xmm1,%xmm0
  22:   66 0f 7e c0             movd   %xmm0,%eax
  26:   0a 47 04                or     0x4(%rdi),%al
  29:   0a 47 05                or     0x5(%rdi),%al
  2c:   0f 94 c0                sete   %al
  2f:   5d                      pop    %rbp
  30:   c3                      retq

0000000000000040 <is_bcast_and>:
  40:   55                      push   %rbp
  41:   48 89 e5                mov    %rsp,%rbp
  44:   66 0f 6e 07             movd   (%rdi),%xmm0
  48:   66 0f 60 c0             punpcklbw %xmm0,%xmm0
  4c:   66 0f 61 c0             punpcklwd %xmm0,%xmm0
  50:   66 0f 70 c8 4e          pshufd $0x4e,%xmm0,%xmm1
  55:   66 0f db c8             pand   %xmm0,%xmm1
  59:   66 0f 70 c1 e5          pshufd $0xe5,%xmm1,%xmm0
  5e:   66 0f db c1             pand   %xmm1,%xmm0
  62:   66 0f 7e c0             movd   %xmm0,%eax
  66:   22 47 04                and    0x4(%rdi),%al
  69:   22 47 05                and    0x5(%rdi),%al
  6c:   3c ff                   cmp    $0xff,%al
  6e:   0f 94 c0                sete   %al
  71:   5d                      pop    %rbp
  72:   c3                      retq

0000000000000080 <is_zero_add>:
  80:   55                      push   %rbp
  81:   48 89 e5                mov    %rsp,%rbp
  84:   0f b6 07                movzbl (%rdi),%eax
  87:   0f b6 4f 01             movzbl 0x1(%rdi),%ecx
  8b:   01 c1                   add    %eax,%ecx
  8d:   0f b6 47 02             movzbl 0x2(%rdi),%eax
  91:   01 c8                   add    %ecx,%eax
  93:   0f b6 4f 03             movzbl 0x3(%rdi),%ecx
  97:   01 c1                   add    %eax,%ecx
  99:   0f b6 47 04             movzbl 0x4(%rdi),%eax
  9d:   01 c8                   add    %ecx,%eax
  9f:   0f b6 4f 05             movzbl 0x5(%rdi),%ecx
  a3:   01 c1                   add    %eax,%ecx
  a5:   0f 94 c0                sete   %al
  a8:   5d                      pop    %rbp
  a9:   c3                      retq

00000000000000b0 <is_bcast_add>:
  b0:   55                      push   %rbp
  b1:   48 89 e5                mov    %rsp,%rbp
  b4:   0f b6 07                movzbl (%rdi),%eax
  b7:   0f b6 4f 01             movzbl 0x1(%rdi),%ecx
  bb:   01 c1                   add    %eax,%ecx
  bd:   0f b6 47 02             movzbl 0x2(%rdi),%eax
  c1:   01 c8                   add    %ecx,%eax
  c3:   0f b6 4f 03             movzbl 0x3(%rdi),%ecx
  c7:   01 c1                   add    %eax,%ecx
  c9:   0f b6 47 04             movzbl 0x4(%rdi),%eax
  cd:   01 c8                   add    %ecx,%eax
  cf:   0f b6 4f 05             movzbl 0x5(%rdi),%ecx
  d3:   01 c1                   add    %eax,%ecx
  d5:   81 f9 fa 05 00 00       cmp    $0x5fa,%ecx
  db:   0f 94 c0                sete   %al
  de:   5d                      pop    %rbp
  df:   c3                      retq

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

GCC 8.3.0, -O3:

// Add variants are the same, but AND/OR variants generate shorter code by fusing load + and/or into a single OP.

0000000000000000 <is_zero_or>:
   0:   0f b6 07                movzbl (%rdi),%eax
   3:   0a 47 01                or     0x1(%rdi),%al
   6:   0a 47 02                or     0x2(%rdi),%al
   9:   0a 47 03                or     0x3(%rdi),%al
   c:   0a 47 04                or     0x4(%rdi),%al
   f:   0a 47 05                or     0x5(%rdi),%al
  12:   0f 94 c0                sete   %al
  15:   c3                      retq

0000000000000020 <is_bcast_and>:
  20:   0f b6 07                movzbl (%rdi),%eax
  23:   22 47 01                and    0x1(%rdi),%al
  26:   22 47 02                and    0x2(%rdi),%al
  29:   22 47 03                and    0x3(%rdi),%al
  2c:   22 47 04                and    0x4(%rdi),%al
  2f:   22 47 05                and    0x5(%rdi),%al
  32:   3c ff                   cmp    $0xff,%al
  34:   0f 94 c0                sete   %al
  37:   c3                      retq