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

```asm
<ddst>:
  endbr64
  push   %rbp
  push   %rbx
  sub    $0x8,%rsp
  mov    %edi,%ebx
  mov    %rdx,%rbp
  test   %esi,%esi
  js     L115
  cmp    $0x4,%edi
  jle    L80
  mov    %rdx,%rsi
  call   <dstsub@plt>
  mov    %rbp,%rsi
  mov    %ebx,%edi
  call   <bitrv2@plt>
  mov    %rbp,%rsi
  mov    %ebx,%edi
  call   <cftfsub@plt>
  mov    %rbp,%rsi
  mov    %ebx,%edi
  call   <rftfsub@plt>
L30:
  movsd  0x0(%rbp),%xmm0
  movsd  0x8(%rbp),%xmm1
  movapd %xmm0,%xmm4
  subsd  %xmm1,%xmm4
  addsd  %xmm1,%xmm0
  movsd  %xmm0,0x0(%rbp)
L46:
  lea    0x8(%rbp),%rax
  mov    $0x2,%edx
  movq   D4(%rip),%xmm3
L52:
  movsd  0x8(%rax),%xmm0
  movsd  0x10(%rax),%xmm2
  movapd %xmm0,%xmm1
  xorpd  %xmm3,%xmm1
  subsd  %xmm2,%xmm1
  movsd  %xmm1,(%rax)
  subsd  %xmm2,%xmm0
  movsd  %xmm0,0x8(%rax)
  add    $0x2,%edx
  add    $0x10,%rax
  cmp    %edx,%ebx
  jg     L52
L28:
  movslq %ebx,%rbx
  xorpd  D4(%rip),%xmm4
  movsd  %xmm4,-0x8(%rbp,%rbx,8)
L56:
  add    $0x8,%rsp
  pop    %rbx
  pop    %rbp
  ret
L115:
  movslq %edi,%rax
  movsd  -0x8(%rdx,%rax,8),%xmm4
  lea    -0x2(%rdi),%eax
  cmp    $0x1,%eax
  jle    L63
  cltq
  lea    0x0(,%rax,8),%rdx
  lea    0x0(%rbp,%rdx,1),%rax
  lea    -0x10(%rbp,%rdx,1),%rdx
  lea    -0x4(%rdi),%ecx
  shr    %ecx
  mov    %ecx,%ecx
  shl    $0x4,%rcx
  sub    %rcx,%rdx
  movq   D4(%rip),%xmm3
L54:
  movsd  (%rax),%xmm0
  movsd  -0x8(%rax),%xmm2
  movapd %xmm0,%xmm1
  xorpd  %xmm3,%xmm1
  subsd  %xmm2,%xmm1
  movsd  %xmm1,0x8(%rax)
  subsd  %xmm2,%xmm0
  movsd  %xmm0,(%rax)
  sub    $0x10,%rax
  cmp    %rdx,%rax
  jne    L54
L63:
  movsd  0x0(%rbp),%xmm0
  movapd %xmm0,%xmm1
  addsd  %xmm4,%xmm1
  movsd  %xmm1,0x8(%rbp)
  subsd  %xmm4,%xmm0
  movsd  %xmm0,0x0(%rbp)
  cmp    $0x4,%ebx
  jg     L138
  je     L110
L27:
  mov    %rbp,%rsi
  mov    %ebx,%edi
  call   <dstsub4@plt>
  jmp    L56
L138:
  mov    %rbp,%rsi
  mov    %ebx,%edi
  call   <rftbsub@plt>
  mov    %rbp,%rsi
  mov    %ebx,%edi
  call   <bitrv2@plt>
  mov    %rbp,%rsi
  mov    %ebx,%edi
  call   <cftbsub@plt>
  mov    %rbp,%rsi
  mov    %ebx,%edi
  call   <dstsub@plt>
  jmp    L56
L110:
  mov    %rbp,%rsi
  mov    $0x4,%edi
  call   <cftfsub@plt>
  jmp    L27
L32:
  mov    %rbp,%rsi
  mov    $0x4,%edi
  call   <cftfsub@plt>
  jmp    L30
L80:
  mov    %rdx,%rsi
  call   <dstsub4@plt>
  cmp    $0x4,%ebx
  je     L32
  movsd  0x0(%rbp),%xmm0
  movsd  0x8(%rbp),%xmm1
  movapd %xmm0,%xmm4
  subsd  %xmm1,%xmm4
  addsd  %xmm1,%xmm0
  movsd  %xmm0,0x0(%rbp)
  cmp    $0x2,%ebx
  jg     L46
  jmp    L28
```

tool_calls: name: disassemble_data
arguments: tag: D4
type: byte[16]

tool: {"D4": [0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00]}

assistant: ```c
void ddst(int n, int isgn, double *a) {
  void bitrv2(int n, double *a);
  void cftfsub(int n, double *a);
  void cftbsub(int n, double *a);
  void rftfsub(int n, double *a);
  void rftbsub(int n, double *a);
  void dstsub(int n, double *a);
  void dstsub4(int n, double *a);
  int j;
  double xr;
  if (isgn < 0) {
    xr = a[n - 1];
    for (j = n - 2; j >= 2; j -= 2) {
      a[j + 1] = -a[j] - a[j - 1];
      a[j] -= a[j - 1];
    }
    a[1] = a[0] + xr;
    a[0] -= xr;
    if (n > 4) {
      rftbsub(n, a);
      bitrv2(n, a);
      cftbsub(n, a);
    } else if (n == 4) {
      cftfsub(n, a);
    }
  }
  if (n > 4) {
    dstsub(n, a);
  } else {
    dstsub4(n, a);
  }
  if (isgn >= 0) {
    if (n > 4) {
      bitrv2(n, a);
      cftfsub(n, a);
      rftfsub(n, a);
    } else if (n == 4) {
      cftfsub(n, a);
    }
    xr = a[0] - a[1];
    a[0] += a[1];
    for (j = 2; j < n; j += 2) {
      a[j - 1] = -a[j] - a[j + 1];
      a[j] -= a[j + 1];
    }
    a[n - 1] = -xr;
  }
}
```