if-else分岐とswitch分岐の違い

if_test.asm

004011a0 <_if_test>:
  4011a0:       55                      push   %ebp
  4011a1:       89 e5                   mov    %esp,%ebp
  4011a3:       83 7d 08 01             cmpl   $0x1,0x8(%ebp)
  4011a7:       75 07                   jne    4011b0 <_if_test+0x10>
  4011a9:       b8 01 00 00 00          mov    $0x1,%eax
  4011ae:       eb 53                   jmp    401203 <_if_test+0x63>
  4011b0:       83 7d 08 02             cmpl   $0x2,0x8(%ebp)
  4011b4:       75 07                   jne    4011bd <_if_test+0x1d>
  4011b6:       b8 02 00 00 00          mov    $0x2,%eax
  4011bb:       eb 46                   jmp    401203 <_if_test+0x63>
  4011bd:       83 7d 08 03             cmpl   $0x3,0x8(%ebp)
  4011c1:       75 07                   jne    4011ca <_if_test+0x2a>
  4011c3:       b8 03 00 00 00          mov    $0x3,%eax
  4011c8:       eb 39                   jmp    401203 <_if_test+0x63>
  4011ca:       83 7d 08 04             cmpl   $0x4,0x8(%ebp)
  4011ce:       75 07                   jne    4011d7 <_if_test+0x37>
  4011d0:       b8 04 00 00 00          mov    $0x4,%eax
  4011d5:       eb 2c                   jmp    401203 <_if_test+0x63>
  4011d7:       83 7d 08 05             cmpl   $0x5,0x8(%ebp)
  4011db:       75 07                   jne    4011e4 <_if_test+0x44>
  4011dd:       b8 05 00 00 00          mov    $0x5,%eax
  4011e2:       eb 1f                   jmp    401203 <_if_test+0x63>
  4011e4:       83 7d 08 06             cmpl   $0x6,0x8(%ebp)
  4011e8:       75 07                   jne    4011f1 <_if_test+0x51>
  4011ea:       b8 06 00 00 00          mov    $0x6,%eax
  4011ef:       eb 12                   jmp    401203 <_if_test+0x63>
  4011f1:       83 7d 08 07             cmpl   $0x7,0x8(%ebp)
  4011f5:       75 07                   jne    4011fe <_if_test+0x5e>
  4011f7:       b8 07 00 00 00          mov    $0x7,%eax
  4011fc:       eb 05                   jmp    401203 <_if_test+0x63>
  4011fe:       b8 08 00 00 00          mov    $0x8,%eax
  401203:       5d                      pop    %ebp
  401204:       c3                      ret

switch_test.asm

00401205 <_switch_test>:
  401205:       55                      push   %ebp
  401206:       89 e5                   mov    %esp,%ebp
  401208:       83 ec 10                sub    $0x10,%esp
  40120b:       c7 45 fc 02 00 00 00    movl   $0x2,-0x4(%ebp)
  401212:       83 7d 08 07             cmpl   $0x7,0x8(%ebp)
  401216:       77 40                   ja     401258 <_switch_test+0x53>
  401218:       8b 45 08                mov    0x8(%ebp),%eax
  40121b:       c1 e0 02                shl    $0x2,%eax
  40121e:       05 60 30 40 00          add    $0x403060,%eax
  401223:       8b 00                   mov    (%eax),%eax
  401225:       ff e0                   jmp    *%eax
  401227:       b8 01 00 00 00          mov    $0x1,%eax
  40122c:       eb 2a                   jmp    401258 <_switch_test+0x53>
  40122e:       b8 02 00 00 00          mov    $0x2,%eax
  401233:       eb 23                   jmp    401258 <_switch_test+0x53>
  401235:       b8 03 00 00 00          mov    $0x3,%eax
  40123a:       eb 1c                   jmp    401258 <_switch_test+0x53>
  40123c:       b8 04 00 00 00          mov    $0x4,%eax
  401241:       eb 15                   jmp    401258 <_switch_test+0x53>
  401243:       b8 05 00 00 00          mov    $0x5,%eax
  401248:       eb 0e                   jmp    401258 <_switch_test+0x53>
  40124a:       b8 06 00 00 00          mov    $0x6,%eax
  40124f:       eb 07                   jmp    401258 <_switch_test+0x53>
  401251:       b8 07 00 00 00          mov    $0x7,%eax
  401256:       eb 00                   jmp    401258 <_switch_test+0x53>
  401258:       c9                      leave
  401259:       c3                      ret

test.c

int if_test(int i) {
  if (i == 1) {
    return 1;
  } else if(i == 2){
    return 2;
  } else if(i == 3){
    return 3;
  } else if(i == 4){
    return 4;
  } else if(i == 5){
    return 5;
  } else if(i == 6){
    return 6;
  } else if(i == 7){
    return 7;
  } else {
    return 8;
  }
}

int switch_test(int i) {
  int j = 2;
  switch (i) {
  case 1:
    return 1;
  case 2:
    return 2;
  case 3:
    return 3;
  case 4:
    return 4;
  case 5:
    return 5;
  case 6:
    return 6;
  case 7:
    return 7;
  defalut:
    return 8;
  }
}

int main(void) {
  int i = 2;
  if_test(i);
  switch_test(i);
  return 0;
}