user: 请将这段汇编代码片段转换成等效的C代码:

```asm
<c_nb_step>:
  endbr64
  test   %edx,%edx
  jle    L24
  push   %r15
  pxor   %xmm8,%xmm8
  movaps %xmm0,%xmm7
  lea    0xc(%rdi),%r15
  push   %r14
  pxor   %xmm5,%xmm5
  mov    %rsi,%r14
  cvtss2sd %xmm0,%xmm8
  push   %r13
  mov    %edx,%r13d
  push   %r12
  xor    %r12d,%r12d
  push   %rbp
  mov    %rdi,%rbp
  push   %rbx
  sub    $0x68,%rsp
  movsd  D13(%rip),%xmm6
  nopl   0x0(%rax,%rax,1)
L48:
  lea    0x0(,%r12,4),%eax
  movapd %xmm5,%xmm4
  movapd %xmm5,%xmm3
  xor    %ebx,%ebx
  cltq
  shl    $0x2,%rax
  lea    0x0(%rbp,%rax,1),%rcx
  lea    0x4(%rax,%rbp,1),%rdx
  lea    0xc(%rax,%rbp,1),%rax
  jmp    L21
  nopl   0x0(%rax)
L14:
  mov    %esi,%ebx
L21:
  cmp    %ebx,%r12d
  je     L56
  lea    0x0(,%rbx,4),%esi
  movss  (%rcx),%xmm2
  movss  (%rdx),%xmm1
  movslq %esi,%rsi
  subss  0x0(%rbp,%rsi,4),%xmm2
  subss  0x4(%rbp,%rsi,4),%xmm1
  lea    0x0(,%rsi,4),%rdi
  cvtss2sd %xmm2,%xmm2
  cvtss2sd %xmm1,%xmm1
  movapd %xmm2,%xmm10
  movapd %xmm1,%xmm0
  mulsd  %xmm2,%xmm10
  mulsd  %xmm1,%xmm0
  addsd  %xmm0,%xmm10
  ucomisd %xmm10,%xmm5
  ja     L51
  movapd %xmm10,%xmm9
  sqrtsd %xmm9,%xmm9
L7:
  movss  0xc(%rbp,%rdi,1),%xmm0
  mulss  (%rax),%xmm0
  divsd  %xmm9,%xmm2
  cvtss2sd %xmm0,%xmm0
  divsd  %xmm10,%xmm0
  divsd  %xmm9,%xmm1
  mulsd  %xmm6,%xmm0
  mulsd  %xmm0,%xmm2
  subsd  %xmm2,%xmm3
  mulsd  %xmm0,%xmm1
  subsd  %xmm1,%xmm4
L56:
  lea    0x1(%rbx),%esi
  cmp    %esi,%r13d
  jne    L14
  pxor   %xmm0,%xmm0
  lea    0x1(%r12),%eax
  add    $0x10,%r14
  add    $0x10,%r15
  cvtss2sd -0x10(%r15),%xmm0
  divsd  %xmm0,%xmm3
  pxor   %xmm0,%xmm0
  cvtss2sd -0x10(%r14),%xmm0
  mulsd  %xmm8,%xmm3
  addsd  %xmm0,%xmm3
  pxor   %xmm0,%xmm0
  cvtsd2ss %xmm3,%xmm3
  movss  %xmm3,-0x10(%r14)
  cvtss2sd -0x10(%r15),%xmm0
  divsd  %xmm0,%xmm4
  pxor   %xmm0,%xmm0
  cvtss2sd -0xc(%r14),%xmm0
  mulsd  %xmm8,%xmm4
  addsd  %xmm0,%xmm4
  movaps %xmm7,%xmm0
  mulss  %xmm3,%xmm0
  cvtsd2ss %xmm4,%xmm4
  movss  %xmm4,-0xc(%r14)
  addss  -0x1c(%r15),%xmm0
  movss  %xmm0,-0x1c(%r15)
  movss  -0xc(%r14),%xmm0
  mulss  %xmm7,%xmm0
  addss  -0x18(%r15),%xmm0
  movss  %xmm0,-0x18(%r15)
  cmp    %ebx,%r12d
  je     L0
  mov    %eax,%r12d
  jmp    L48
  nopl   0x0(%rax,%rax,1)
L0:
  add    $0x68,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L24:
  ret
L51:
  movapd %xmm10,%xmm0
  mov    %rax,0x28(%rsp)
  mov    %rdx,0x20(%rsp)
  mov    %rdi,0x18(%rsp)
  mov    %rcx,0x10(%rsp)
  movsd  %xmm8,0x58(%rsp)
  movss  %xmm7,0x54(%rsp)
  movsd  %xmm1,0x48(%rsp)
  movsd  %xmm2,0x40(%rsp)
  movsd  %xmm4,0x38(%rsp)
  movsd  %xmm3,0x30(%rsp)
  movsd  %xmm10,0x8(%rsp)
  call   <sqrt@plt>
  mov    D13(%rip),%rax
  mov    0x20(%rsp),%rdx
  pxor   %xmm5,%xmm5
  movsd  0x58(%rsp),%xmm8
  movss  0x54(%rsp),%xmm7
  movapd %xmm0,%xmm9
  movq   %rax,%xmm6
  movsd  0x48(%rsp),%xmm1
  movsd  0x40(%rsp),%xmm2
  movsd  0x38(%rsp),%xmm4
  movsd  0x30(%rsp),%xmm3
  mov    0x28(%rsp),%rax
  mov    0x18(%rsp),%rdi
  mov    0x10(%rsp),%rcx
  movsd  0x8(%rsp),%xmm10
  jmp    L7
```

tool_calls: name: retrieve_data
arguments: tag: D13
datatype: byte[8]

tool: {"D13": [0xd1,0x37,0x97,0x65,0x9b,0x58,0xd2,0x3d]}

assistant: ```c
void c_nb_step(unsigned long ipos, unsigned long ivel, float dt, int n_bodies) {
  float *pos = (float *)ipos;
  float *vel = (float *)ivel;
  int i;
  int j;
  for (i = 0; i < n_bodies; i++) {
    double f_x = 0.0;
    double f_y = 0.0;
    for (j = 0; j < n_bodies; j++) {
      double d_x;
      double d_y;
      double dist_tmp;
      double distance;
      double force;
      if (i == j) {
        continue;
      }
      d_x = pos[i * 4] - pos[j * 4];
      d_y = pos[i * 4 + 1] - pos[j * 4 + 1];
      dist_tmp = (d_x * d_x) + (d_y * d_y);
      distance = sqrt(dist_tmp);
      force = 6.67428e-11 * ((pos[i * 4 + 3] * pos[j * 4 + 3]) / dist_tmp);
      f_x -= force * (d_x / distance);
      f_y -= force * (d_y / distance);
    }
    vel[i * 4] += dt * (f_x / pos[i * 4 + 3]);
    vel[i * 4 + 1] += dt * (f_y / pos[i * 4 + 3]);
    pos[i * 4] += dt * vel[i * 4];
    pos[i * 4 + 1] += dt * vel[i * 4 + 1];
  }
}
```