user: What is the c source code of the assembly code below?

```asm
<FFT>:
  endbr64
  movslq %esi,%r9
  push   %r15
  mov    %edi,%r15d
  push   %r14
  push   %r13
  push   %r12
  mov    $0x1,%r12d
  push   %rbp
  mov    %rcx,%rbp
  mov    %r9d,%ecx
  push   %rbx
  shl    %cl,%r12d
  mov    %rdx,%rbx
  movslq %r12d,%r13
  mov    %r13,%rsi
  sub    $0x28,%rsp
  sar    %rsi
  mov    %r12d,0xc(%rsp)
  cmp    $0x1,%r13
  jle    L94
  lea    -0x1(%r13),%r8
  xor    %edx,%edx
  xor    %ecx,%ecx
  cs nopw 0x0(%rax,%rax,1)
L34:
  mov    %rsi,%rax
  cmp    %rsi,%rdx
  jl     L190
  nopl   0x0(%rax,%rax,1)
L199:
  sub    %rax,%rdx
  sar    %rax
  cmp    %rax,%rdx
  jge    L199
L190:
  add    $0x1,%rcx
  add    %rax,%rdx
  cmp    %rcx,%r8
  je     L94
  cmp    %rcx,%rdx
  jle    L34
  lea    0x0(,%rdx,8),%rax
  movsd  (%rbx,%rcx,8),%xmm1
  movsd  0x0(%rbp,%rcx,8),%xmm0
  lea    (%rbx,%rax,1),%rdi
  add    %rbp,%rax
  movsd  (%rdi),%xmm2
  movsd  %xmm2,(%rbx,%rcx,8)
  movsd  (%rax),%xmm2
  movsd  %xmm2,0x0(%rbp,%rcx,8)
  movsd  %xmm1,(%rdi)
  movsd  %xmm0,(%rax)
  jmp    L34
L94:
  test   %r9,%r9
  jle    L217
  pxor   %xmm7,%xmm7
  mov    $0x1,%r14d
  xor    %r12d,%r12d
  movsd  D64(%rip),%xmm5
  movsd  D19(%rip),%xmm8
  movapd %xmm7,%xmm6
  movsd  D38(%rip),%xmm9
  movq   D13(%rip),%xmm10
L6:
  mov    %r14,%rdi
  add    %r14,%r14
  test   %rdi,%rdi
  jle    L50
  lea    0x0(,%rdi,8),%rdx
  movapd %xmm7,%xmm4
  movapd %xmm8,%xmm0
  xor    %esi,%esi
  lea    (%rbx,%rdx,1),%rcx
  add    %rbp,%rdx
  nopl   0x0(%rax)
L25:
  mov    %rsi,%rax
  cmp    %rsi,%r13
  jle    L210
  nopl   0x0(%rax,%rax,1)
L211:
  movsd  (%rcx,%rax,8),%xmm3
  movsd  (%rdx,%rax,8),%xmm1
  movapd %xmm3,%xmm2
  movapd %xmm1,%xmm11
  mulsd  %xmm0,%xmm2
  mulsd  %xmm4,%xmm11
  mulsd  %xmm4,%xmm3
  mulsd  %xmm0,%xmm1
  subsd  %xmm11,%xmm2
  addsd  %xmm3,%xmm1
  movsd  (%rbx,%rax,8),%xmm3
  subsd  %xmm2,%xmm3
  movsd  %xmm3,(%rcx,%rax,8)
  movsd  0x0(%rbp,%rax,8),%xmm3
  subsd  %xmm1,%xmm3
  movsd  %xmm3,(%rdx,%rax,8)
  addsd  (%rbx,%rax,8),%xmm2
  movsd  %xmm2,(%rbx,%rax,8)
  addsd  0x0(%rbp,%rax,8),%xmm1
  movsd  %xmm1,0x0(%rbp,%rax,8)
  add    %r14,%rax
  cmp    %rax,%r13
  jg     L211
L210:
  movapd %xmm5,%xmm1
  movapd %xmm6,%xmm2
  add    $0x1,%rsi
  mulsd  %xmm0,%xmm1
  mulsd  %xmm4,%xmm2
  mulsd  %xmm6,%xmm0
  mulsd  %xmm5,%xmm4
  subsd  %xmm2,%xmm1
  addsd  %xmm0,%xmm4
  cmp    %rdi,%rsi
  je     L50
  movapd %xmm1,%xmm0
  jmp    L25
  nopw   0x0(%rax,%rax,1)
L50:
  movapd %xmm8,%xmm6
  subsd  %xmm5,%xmm6
  mulsd  %xmm9,%xmm6
  ucomisd %xmm6,%xmm7
  ja     L136
  sqrtsd %xmm6,%xmm6
L70:
  cmp    $0x1,%r15d
  jne    L24
  xorpd  %xmm10,%xmm6
L24:
  addsd  %xmm8,%xmm5
  mulsd  %xmm9,%xmm5
  ucomisd %xmm5,%xmm7
  ja     L59
  sqrtsd %xmm5,%xmm5
L170:
  add    $0x1,%r12
  cmp    %r9,%r12
  jne    L6
L217:
  cmp    $0x1,%r15d
  je     L111
L66:
  add    $0x28,%rsp
  mov    $0x1,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L111:
  test   %r13,%r13
  jle    L66
  pxor   %xmm1,%xmm1
  xor    %eax,%eax
  cvtsi2sdl 0xc(%rsp),%xmm1
L43:
  movsd  (%rbx,%rax,8),%xmm0
  divsd  %xmm1,%xmm0
  movsd  %xmm0,(%rbx,%rax,8)
  movsd  0x0(%rbp,%rax,8),%xmm0
  divsd  %xmm1,%xmm0
  movsd  %xmm0,0x0(%rbp,%rax,8)
  add    $0x1,%rax
  cmp    %rax,%r13
  jne    L43
  jmp    L66
L59:
  movapd %xmm5,%xmm0
  mov    %r9,0x18(%rsp)
  movsd  %xmm6,0x10(%rsp)
  call   <sqrt@plt>
  mov    D38(%rip),%rax
  mov    0x18(%rsp),%r9
  pxor   %xmm7,%xmm7
  movq   D13(%rip),%xmm10
  movsd  0x10(%rsp),%xmm6
  movapd %xmm0,%xmm5
  movq   %rax,%xmm9
  mov    D19(%rip),%rax
  movq   %rax,%xmm8
  jmp    L170
L136:
  movapd %xmm6,%xmm0
  mov    %r9,0x18(%rsp)
  movsd  %xmm5,0x10(%rsp)
  call   <sqrt@plt>
  mov    D38(%rip),%rax
  mov    0x18(%rsp),%r9
  pxor   %xmm7,%xmm7
  movq   D13(%rip),%xmm10
  movsd  0x10(%rsp),%xmm5
  movapd %xmm0,%xmm6
  movq   %rax,%xmm9
  mov    D19(%rip),%rax
  movq   %rax,%xmm8
  jmp    L70
```

tool_calls: name: parse_data
arguments: label: D64
datatype: f32[2]
name: parse_data
arguments: label: D19
datatype: f64
name: parse_data
arguments: label: D38
datatype: f32[2]
name: parse_data
arguments: label: D13
datatype: f32[2]

tool: {"D64": [0.0,-1.875]}

tool: D19: 1

tool: {"D38": [0.0,1.75]}

tool: {"D13": [0.0,-0.0]}

assistant: ```c
int FFT(int dir, int m, double *x, double *y) {
  long nn, i, i1, j, k, i2, l, l1, l2;
  double c1, c2, tx, ty, t1, t2, u1, u2, z;
  nn = 1 << m;
  i2 = nn >> 1;
  j = 0;
  for (i = 0; i < nn - 1; i++) {
    if (i < j) {
      tx = x[i];
      ty = y[i];
      x[i] = x[j];
      y[i] = y[j];
      x[j] = tx;
      y[j] = ty;
    }
    k = i2;
    while (k <= j) {
      j -= k;
      k >>= 1;
    }
    j += k;
  }
  c1 = -1.0;
  c2 = 0.0;
  l2 = 1;
  for (l = 0; l < m; l++) {
    l1 = l2;
    l2 <<= 1;
    u1 = 1.0;
    u2 = 0.0;
    for (j = 0; j < l1; j++) {
      for (i = j; i < nn; i += l2) {
        i1 = i + l1;
        t1 = u1 * x[i1] - u2 * y[i1];
        t2 = u1 * y[i1] + u2 * x[i1];
        x[i1] = x[i] - t1;
        y[i1] = y[i] - t2;
        x[i] += t1;
        y[i] += t2;
      }
      z = u1 * c1 - u2 * c2;
      u2 = u1 * c2 + u2 * c1;
      u1 = z;
    }
    c2 = sqrt((1.0 - c1) / 2.0);
    if (dir == 1)
      c2 = -c2;
    c1 = sqrt((1.0 + c1) / 2.0);
  }
  if (dir == 1) {
    for (i = 0; i < nn; i++) {
      x[i] /= (double)nn;
      y[i] /= (double)nn;
    }
  }
  return (1);
}
```