user: 请将这段汇编代码片段转换成等效的C代码:

```asm
<dfft>:
  endbr64
  push   %r15
  mov    %edx,%eax
  push   %r14
  mov    %rsi,%r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  mov    %rdi,%rbx
  sub    $0x68,%rsp
  cmp    $0x2,%edx
  jle    L7
  movl   $0x1,0x44(%rsp)
  mov    $0x2,%r13d
L173:
  mov    %r13d,%edx
  add    %r13d,%r13d
  addl   $0x1,0x44(%rsp)
  cmp    %r13d,%eax
  jg     L173
  je     L155
  lea    0x0(,%rdx,4),%edi
  mov    %edi,0x48(%rsp)
L106:
  cmp    %eax,%r13d
  jle    L124
  mov    %r13d,%edx
  movslq %eax,%rdi
  sub    %eax,%edx
  lea    -0x1(%rdx),%ecx
  lea    0x1(%rdi),%rdx
  shl    $0x3,%rdi
  lea    (%rdx,%rcx,1),%rax
  lea    (%r14,%rdi,1),%rbp
  add    %rbx,%rdi
  shl    $0x3,%rax
  lea    (%r14,%rax,1),%rsi
  cmp    %rsi,%rdi
  jae    L179
  add    %rbx,%rax
  cmp    %rax,%rbp
  jb     L58
L179:
  lea    0x8(,%rcx,8),%r12
  xor    %esi,%esi
  mov    %r12,%rdx
  call   <memset@plt>
  mov    %r12,%rdx
  xor    %esi,%esi
  mov    %rbp,%rdi
  call   <memset@plt>
L124:
  xor    %eax,%eax
  mov    %r13d,%esi
  lea    D15(%rip),%rdi
  call   <printf@plt>
  cmpl   $0x1,0x44(%rsp)
  je     L6
L231:
  movl   $0x1,0x4c(%rsp)
  movq   D44(%rip),%xmm7
  mov    %r13d,%r15d
L97:
  mov    0x48(%rsp),%eax
  pxor   %xmm0,%xmm0
  movsd  D32(%rip),%xmm5
  mov    %eax,%r10d
  lea    0x7(%rax),%edx
  shr    $0x1f,%r10d
  add    %eax,%r10d
  sar    %r10d
  test   %eax,%eax
  cvtsi2sd %r10d,%xmm0
  cmovns %eax,%edx
  mov    %r10d,0x48(%rsp)
  mov    %edx,%edi
  sar    $0x3,%edi
  divsd  %xmm0,%xmm5
  mov    %edi,0x40(%rsp)
  movsd  %xmm5,0x30(%rsp)
  cmp    $0x7,%eax
  jle    L126
  lea    (%r10,%r10,1),%eax
  movslq %edi,%r11
  pxor   %xmm5,%xmm5
  mov    %r15d,%r8d
  mov    %eax,0x3c(%rsp)
  mov    %r14,%r15
  movapd %xmm5,%xmm3
  lea    0x58(%rsp),%r12
  mov    D30(%rip),%rax
  lea    0x0(,%r11,8),%rbp
  add    %r11,%r11
  mov    $0x1,%r9d
  lea    (%rbx,%rbp,1),%r13
  add    %r14,%rbp
  mov    %rbx,%r14
  mov    %r9d,%ebx
  movq   %rax,%xmm6
  movq   %rax,%xmm4
  nopl   0x0(%rax)
L72:
  pxor   %xmm8,%xmm8
  mov    0x3c(%rsp),%edi
  mov    %ebx,%eax
  cvtsi2sd %ebx,%xmm8
  mulsd  0x30(%rsp),%xmm8
  cmp    %ebx,%r8d
  jle    L185
  nopl   0x0(%rax,%rax,1)
L261:
  cltq
  movslq %edi,%rcx
  lea    (%r11,%rax,1),%rdx
  lea    0x0(,%rcx,8),%rsi
  lea    -0x8(,%rdx,8),%rdx
  nopl   0x0(%rax)
L131:
  movsd  (%r14,%rdx,1),%xmm1
  movsd  -0x8(%r14,%rax,8),%xmm0
  movapd %xmm0,%xmm11
  addsd  %xmm1,%xmm0
  subsd  %xmm1,%xmm11
  movsd  %xmm0,-0x8(%r14,%rax,8)
  movsd  0x0(%r13,%rdx,1),%xmm1
  movsd  -0x8(%r13,%rax,8),%xmm0
  movapd %xmm0,%xmm10
  addsd  %xmm1,%xmm0
  subsd  %xmm1,%xmm10
  movsd  %xmm0,-0x8(%r13,%rax,8)
  movsd  (%r15,%rdx,1),%xmm2
  movsd  -0x8(%r15,%rax,8),%xmm1
  movapd %xmm1,%xmm0
  addsd  %xmm2,%xmm1
  subsd  %xmm2,%xmm0
  movsd  %xmm1,-0x8(%r15,%rax,8)
  movsd  0x0(%rbp,%rdx,1),%xmm9
  movsd  -0x8(%rbp,%rax,8),%xmm1
  movapd %xmm1,%xmm2
  addsd  %xmm9,%xmm1
  subsd  %xmm9,%xmm2
  movapd %xmm11,%xmm9
  movsd  %xmm1,-0x8(%rbp,%rax,8)
  movapd %xmm10,%xmm1
  add    %rcx,%rax
  subsd  %xmm0,%xmm1
  subsd  %xmm2,%xmm9
  addsd  %xmm11,%xmm2
  movapd %xmm3,%xmm11
  addsd  %xmm10,%xmm0
  movapd %xmm4,%xmm10
  mulsd  %xmm1,%xmm11
  xorpd  %xmm7,%xmm1
  mulsd  %xmm2,%xmm10
  mulsd  %xmm4,%xmm1
  mulsd  %xmm3,%xmm2
  subsd  %xmm11,%xmm10
  subsd  %xmm2,%xmm1
  movapd %xmm5,%xmm2
  movsd  %xmm10,(%r14,%rdx,1)
  mulsd  %xmm0,%xmm2
  mulsd  %xmm6,%xmm0
  movsd  %xmm1,(%r15,%rdx,1)
  movapd %xmm6,%xmm1
  mulsd  %xmm9,%xmm1
  addsd  %xmm2,%xmm1
  movsd  %xmm1,0x0(%r13,%rdx,1)
  movapd %xmm9,%xmm1
  mulsd  %xmm5,%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,0x0(%rbp,%rdx,1)
  add    %rsi,%rdx
  cmp    %eax,%r8d
  jg     L131
  lea    (%rbx,%rdi,2),%eax
  shl    $0x2,%edi
  sub    %r10d,%eax
  cmp    %eax,%r8d
  jg     L261
L185:
  add    $0x1,%ebx
  cmp    %ebx,0x40(%rsp)
  jl     L205
  lea    0x50(%rsp),%rsi
  movapd %xmm8,%xmm0
  mov    %r12,%rdi
  mov    %r11,0x28(%rsp)
  mov    %r10d,0x38(%rsp)
  mov    %r8d,0x24(%rsp)
  mov    %rsi,0x18(%rsp)
  movsd  %xmm8,0x10(%rsp)
  call   <sincos@plt>
  movsd  D12(%rip),%xmm0
  mov    0x18(%rsp),%rsi
  mov    %r12,%rdi
  movsd  0x10(%rsp),%xmm8
  movsd  0x50(%rsp),%xmm4
  movsd  0x58(%rsp),%xmm3
  mulsd  %xmm8,%xmm0
  movsd  %xmm4,0x8(%rsp)
  movsd  %xmm3,(%rsp)
  call   <sincos@plt>
  movsd  0x50(%rsp),%xmm6
  movsd  (%rsp),%xmm3
  movsd  0x58(%rsp),%xmm5
  movsd  0x8(%rsp),%xmm4
  movq   D44(%rip),%xmm7
  mov    0x24(%rsp),%r8d
  mov    0x38(%rsp),%r10d
  mov    0x28(%rsp),%r11
  jmp    L72
L205:
  mov    %r14,%rbx
  mov    %r15,%r14
  mov    %r8d,%r15d
L126:
  addl   $0x1,0x4c(%rsp)
  mov    0x4c(%rsp),%eax
  cmp    %eax,0x44(%rsp)
  jg     L97
  mov    %r15d,%r13d
L6:
  cmp    $0x1,%r13d
  jle    L267
L71:
  mov    $0x4,%ecx
  mov    $0x1,%eax
L108:
  movslq %ecx,%rdx
  cltq
  nopl   0x0(%rax)
L105:
  movsd  (%rbx,%rax,8),%xmm1
  movsd  -0x8(%rbx,%rax,8),%xmm0
  movapd %xmm1,%xmm2
  addsd  %xmm0,%xmm2
  subsd  %xmm1,%xmm0
  movsd  %xmm2,-0x8(%rbx,%rax,8)
  movsd  %xmm0,(%rbx,%rax,8)
  movsd  (%r14,%rax,8),%xmm1
  movsd  -0x8(%r14,%rax,8),%xmm0
  movapd %xmm1,%xmm2
  addsd  %xmm0,%xmm2
  subsd  %xmm1,%xmm0
  movsd  %xmm2,-0x8(%r14,%rax,8)
  movsd  %xmm0,(%r14,%rax,8)
  add    %rdx,%rax
  cmp    %eax,%r13d
  jge    L105
  lea    -0x1(%rcx,%rcx,1),%eax
  shl    $0x2,%ecx
  cmp    %r13d,%eax
  jl     L108
  mov    %r13d,%esi
  mov    %r13d,%r8d
  mov    $0x1,%ecx
  mov    $0x1,%edx
  sar    %esi
L70:
  cmp    %ecx,%edx
  jle    L99
  movslq %edx,%rax
  movsd  -0x8(%rbx,%rcx,8),%xmm1
  lea    -0x8(,%rax,8),%rax
  lea    (%rbx,%rax,1),%rdi
  add    %r14,%rax
  movsd  (%rdi),%xmm0
  movsd  %xmm1,(%rdi)
  movsd  %xmm0,-0x8(%rbx,%rcx,8)
  movsd  (%rax),%xmm0
  movsd  -0x8(%r14,%rcx,8),%xmm1
  movsd  %xmm1,(%rax)
  movsd  %xmm0,-0x8(%r14,%rcx,8)
L99:
  mov    %esi,%eax
  cmp    %edx,%esi
  jge    L186
  nopl   0x0(%rax)
L36:
  sub    %eax,%edx
  sar    %eax
  cmp    %eax,%edx
  jg     L36
L186:
  add    $0x1,%rcx
  add    %eax,%edx
  cmp    %rcx,%r8
  jne    L70
L267:
  add    $0x68,%rsp
  mov    %r13d,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L58:
  movq   $0x0,-0x8(%rbx,%rdx,8)
  movq   $0x0,-0x8(%r14,%rdx,8)
  add    $0x1,%rdx
  cmp    %edx,%r13d
  jge    L58
  jmp    L124
L155:
  lea    0x0(,%rdx,4),%eax
  mov    %eax,0x48(%rsp)
  jmp    L231
L7:
  je     L169
  movl   $0x4,0x48(%rsp)
  mov    $0x2,%r13d
  movl   $0x1,0x44(%rsp)
  jmp    L106
L169:
  mov    $0x2,%r13d
  jmp    L71
```

tool_calls: name: read_data
arguments: data_tag: D15
type_guessed: string
name: read_data
arguments: data_tag: D44
type_guessed: f32[2]
name: read_data
arguments: data_tag: D32
type_guessed: byte[8]
name: read_data
arguments: data_tag: D30
type_guessed: f32[2]
name: read_data
arguments: data_tag: D12
type_guessed: f64

tool: D15: 
use %d point fft

tool: {"D44": [0.0,-0.0]}

tool: {"D32": [0x18,0x2d,0x44,0x54,0xfb,0x21,0x19,0x40]}

tool: {"D30": [0.0,1.875]}

tool: D12: 3

assistant: ```c
int dfft(double x[], double y[], int np) {
  double *px, *py;
  int i, j, k, m, n, i0, i1, i2, i3, is, id, n1, n2, n4;
  double a, e, a3, cc1, ss1, cc3, ss3, r1, r2, s1, s2, s3, xt, tpi;
  px = x - 1;
  py = y - 1;
  i = 2;
  m = 1;
  while (i < np) {
    i = i + i;
    m = m + 1;
  }
  n = i;
  if (n != np) {
    for (i = np + 1; i <= n; i++) {
      px[i] = 0.0;
      py[i] = 0.0;
    }
    printf("\nuse %d point fft", n);
  }
  n2 = n + n;
  tpi = 2.0 * 3.14159265358979323846;
  for (k = 1; k <= m - 1; k++) {
    n2 = n2 / 2;
    n4 = n2 / 4;
    e = tpi / (double)n2;
    a = 0.0;
    for (j = 1; j <= n4; j++) {
      a3 = 3.0 * a;
      cc1 = cos(a);
      ss1 = sin(a);
      cc3 = cos(a3);
      ss3 = sin(a3);
      a = e * (double)j;
      is = j;
      id = 2 * n2;
      while (is < n) {
        for (i0 = is; i0 <= n - 1; i0 = i0 + id) {
          i1 = i0 + n4;
          i2 = i1 + n4;
          i3 = i2 + n4;
          r1 = px[i0] - px[i2];
          px[i0] = px[i0] + px[i2];
          r2 = px[i1] - px[i3];
          px[i1] = px[i1] + px[i3];
          s1 = py[i0] - py[i2];
          py[i0] = py[i0] + py[i2];
          s2 = py[i1] - py[i3];
          py[i1] = py[i1] + py[i3];
          s3 = r1 - s2;
          r1 = r1 + s2;
          s2 = r2 - s1;
          r2 = r2 + s1;
          px[i2] = r1 * cc1 - s2 * ss1;
          py[i2] = -s2 * cc1 - r1 * ss1;
          px[i3] = s3 * cc3 + r2 * ss3;
          py[i3] = r2 * cc3 - s3 * ss3;
        }
        is = 2 * id - n2 + j;
        id = 4 * id;
      }
    }
  }
  is = 1;
  id = 4;
  while (is < n) {
    for (i0 = is; i0 <= n; i0 = i0 + id) {
      i1 = i0 + 1;
      r1 = px[i0];
      px[i0] = r1 + px[i1];
      px[i1] = r1 - px[i1];
      r1 = py[i0];
      py[i0] = r1 + py[i1];
      py[i1] = r1 - py[i1];
    }
    is = 2 * id - 1;
    id = 4 * id;
  }
  j = 1;
  n1 = n - 1;
  for (i = 1; i <= n1; i++) {
    if (i < j) {
      xt = px[j];
      px[j] = px[i];
      px[i] = xt;
      xt = py[j];
      py[j] = py[i];
      py[i] = xt;
    }
    k = n / 2;
    while (k < j) {
      j = j - k;
      k = k / 2;
    }
    j = j + k;
  }
  return (n);
}
```