user: Converte this assembly snippet into its equivalent C code:

```asm
<main>:
  endbr64
  push   %rbx
  xor    %edi,%edi
  mov    $0x1,%esi
  call   <test_significant_bits@plt>
  mov    $0x1,%esi
  mov    $0xffffffff,%edi
  call   <test_significant_bits@plt>
  mov    $0x2,%esi
  mov    $0xfffffffe,%edi
  call   <test_significant_bits@plt>
  mov    $0x3,%esi
  mov    $0xfffffffd,%edi
  call   <test_significant_bits@plt>
  mov    $0x3,%esi
  mov    $0xfffffffc,%edi
  call   <test_significant_bits@plt>
  mov    $0x4,%esi
  mov    $0xfffffffb,%edi
  call   <test_significant_bits@plt>
  mov    $0x4,%esi
  mov    $0xfffffffa,%edi
  call   <test_significant_bits@plt>
  mov    $0x2,%esi
  mov    $0x1,%edi
  call   <test_significant_bits@plt>
  mov    $0x3,%esi
  mov    $0x2,%edi
  call   <test_significant_bits@plt>
  mov    $0x3,%esi
  mov    $0x3,%edi
  call   <test_significant_bits@plt>
  mov    $0x4,%esi
  mov    $0x4,%edi
  call   <test_significant_bits@plt>
  mov    $0x4,%esi
  mov    $0x5,%edi
  call   <test_significant_bits@plt>
  mov    $0x4,%esi
  mov    $0x6,%edi
  call   <test_significant_bits@plt>
  mov    D12(%rip),%rbx
  mov    $0x40,%esi
  mov    (%rbx),%edi
  call   <test_significant_bits@plt>
  mov    D1(%rip),%rax
  mov    $0x40,%esi
  mov    (%rax),%edi
  call   <test_significant_bits@plt>
  mov    (%rbx),%eax
  mov    $0x3f,%esi
  mov    %eax,%edi
  shr    $0x1f,%edi
  add    %eax,%edi
  sar    %edi
  call   <test_significant_bits@plt>
  mov    (%rbx),%eax
  mov    $0x40,%esi
  mov    %eax,%edi
  shr    $0x1f,%edi
  add    %eax,%edi
  sar    %edi
  neg    %edi
  call   <test_significant_bits@plt>
  mov    $0x20,%esi
  mov    $0x55555555,%edi
  call   <test_significant_bits@plt>
  mov    $0x20,%esi
  mov    $0xaaaaaaab,%edi
  call   <test_significant_bits@plt>
  mov    $0x19,%esi
  mov    $0x800000,%edi
  call   <test_significant_bits@plt>
  mov    $0x15,%esi
  mov    $0x80000,%edi
  call   <test_significant_bits@plt>
  mov    $0x11,%esi
  mov    $0x8000,%edi
  call   <test_significant_bits@plt>
  mov    $0xd,%esi
  mov    $0x800,%edi
  call   <test_significant_bits@plt>
  mov    $0x9,%esi
  mov    $0x80,%edi
  call   <test_significant_bits@plt>
  mov    $0x5,%esi
  mov    $0x8,%edi
  call   <test_significant_bits@plt>
  mov    $0x18,%esi
  mov    $0xff800000,%edi
  call   <test_significant_bits@plt>
  mov    $0x14,%esi
  mov    $0xfff80000,%edi
  call   <test_significant_bits@plt>
  mov    $0x10,%esi
  mov    $0xffff8000,%edi
  call   <test_significant_bits@plt>
  mov    $0xc,%esi
  mov    $0xfffff800,%edi
  call   <test_significant_bits@plt>
  mov    $0x8,%esi
  mov    $0xffffff80,%edi
  call   <test_significant_bits@plt>
  mov    $0x4,%esi
  mov    $0xfffffff8,%edi
  call   <test_significant_bits@plt>
  mov    $0x18,%esi
  mov    $0x7fffff,%edi
  call   <test_significant_bits@plt>
  mov    $0x14,%esi
  mov    $0x7ffff,%edi
  call   <test_significant_bits@plt>
  mov    $0x10,%esi
  mov    $0x7fff,%edi
  call   <test_significant_bits@plt>
  mov    $0xc,%esi
  mov    $0x7ff,%edi
  call   <test_significant_bits@plt>
  mov    $0x8,%esi
  mov    $0x7f,%edi
  call   <test_significant_bits@plt>
  mov    $0x4,%esi
  mov    $0x7,%edi
  call   <test_significant_bits@plt>
  xor    %eax,%eax
  pop    %rbx
  ret
```

assistant: ```c
int main(void) {
  test_significant_bits(0, 1);
  test_significant_bits(-1, 1);
  test_significant_bits(-2, 2);
  test_significant_bits(-3, 3);
  test_significant_bits(-4, 3);
  test_significant_bits(-5, 4);
  test_significant_bits(-6, 4);
  test_significant_bits(1, 2);
  test_significant_bits(2, 3);
  test_significant_bits(3, 3);
  test_significant_bits(4, 4);
  test_significant_bits(5, 4);
  test_significant_bits(6, 4);
  test_significant_bits(INT64_MIN, 64);
  test_significant_bits(INT64_MAX, 64);
  test_significant_bits(INT64_MIN / 2, 63);
  test_significant_bits(-(INT64_MIN / 2), 64);
  test_significant_bits(0x55555555, 32);
  test_significant_bits(-0x55555555, 32);
  test_significant_bits(0x800000, 25);
  test_significant_bits(0x80000, 21);
  test_significant_bits(0x8000, 17);
  test_significant_bits(0x800, 13);
  test_significant_bits(0x80, 9);
  test_significant_bits(0x8, 5);
  test_significant_bits(-0x800000, 24);
  test_significant_bits(-0x80000, 20);
  test_significant_bits(-0x8000, 16);
  test_significant_bits(-0x800, 12);
  test_significant_bits(-0x80, 8);
  test_significant_bits(-0x8, 4);
  test_significant_bits(0x7FFFFF, 24);
  test_significant_bits(0x7FFFF, 20);
  test_significant_bits(0x7FFF, 16);
  test_significant_bits(0x7FF, 12);
  test_significant_bits(0x7F, 8);
  test_significant_bits(0x7, 4);
  return 0;
}
```