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

```asm
<ddst>:
  endbr64
  movslq %edi,%rax
  push   %r12
  mov    %rax,%r12
  push   %rbp
  mov    %rdx,%rbp
  push   %rbx
  lea    -0x8(%rdx,%rax,8),%rbx
  test   %esi,%esi
  js     L12
  cmp    $0x4,%eax
  jle    L25
  mov    %rdx,%rsi
  mov    %eax,%edi
  call   <dstsub@plt>
  mov    %rbp,%rsi
  mov    %r12d,%edi
  call   <cftfsub@plt>
  mov    %rbp,%rsi
  mov    %r12d,%edi
  call   <rftfsub@plt>
  movsd  0x0(%rbp),%xmm1
  movsd  0x8(%rbp),%xmm0
  mov    $0x2,%eax
  movq   D31(%rip),%xmm3
  movapd %xmm1,%xmm4
  subsd  %xmm0,%xmm4
  addsd  %xmm1,%xmm0
  movsd  %xmm0,0x0(%rbp)
  nop
L97:
  movsd  0x0(%rbp,%rax,8),%xmm1
  movsd  0x8(%rbp,%rax,8),%xmm2
  movapd %xmm1,%xmm0
  subsd  %xmm2,%xmm1
  xorpd  %xmm3,%xmm0
  subsd  %xmm2,%xmm0
  unpcklpd %xmm1,%xmm0
  movups %xmm0,-0x8(%rbp,%rax,8)
  add    $0x2,%rax
  cmp    %eax,%r12d
  jg     L97
  xorpd  %xmm4,%xmm3
  movsd  %xmm3,(%rbx)
  pop    %rbx
  pop    %rbp
  pop    %r12
  ret
  nopl   0x0(%rax,%rax,1)
L25:
  mov    %rdx,%rsi
  mov    %eax,%edi
  call   <dstsub4@plt>
  cmp    $0x4,%r12d
  je     L42
  movsd  0x0(%rbp),%xmm0
  movsd  0x8(%rbp),%xmm1
  movq   D31(%rip),%xmm3
  movapd %xmm0,%xmm4
  addsd  %xmm1,%xmm0
  subsd  %xmm1,%xmm4
  movsd  %xmm0,0x0(%rbp)
  cmp    $0x3,%r12d
  jne    L46
L61:
  movsd  0x10(%rbp),%xmm1
  movq   D31(%rip),%xmm3
  movsd  0x18(%rbp),%xmm2
  movapd %xmm1,%xmm0
  xorpd  %xmm3,%xmm0
  subsd  %xmm2,%xmm1
  subsd  %xmm2,%xmm0
  unpcklpd %xmm1,%xmm0
  movups %xmm0,0x8(%rbp)
L46:
  xorpd  %xmm4,%xmm3
  movsd  %xmm3,(%rbx)
  pop    %rbx
  pop    %rbp
  pop    %r12
  ret
  nopl   0x0(%rax)
L12:
  lea    -0x2(%rax),%eax
  movsd  (%rbx),%xmm4
  cmp    $0x1,%eax
  jle    L52
  cltq
  lea    -0x4(%r12),%ecx
  movq   D31(%rip),%xmm3
  lea    0x0(,%rax,8),%rdx
  shr    %ecx
  lea    0x0(%rbp,%rdx,1),%rax
  shl    $0x4,%rcx
  lea    -0x10(%rbp,%rdx,1),%rdx
  sub    %rcx,%rdx
  xchg   %ax,%ax
L56:
  movsd  (%rax),%xmm0
  movsd  -0x8(%rax),%xmm2
  sub    $0x10,%rax
  movapd %xmm0,%xmm1
  xorpd  %xmm3,%xmm0
  subsd  %xmm2,%xmm1
  subsd  %xmm2,%xmm0
  unpcklpd %xmm0,%xmm1
  movups %xmm1,0x10(%rax)
  cmp    %rax,%rdx
  jne    L56
L52:
  movsd  0x0(%rbp),%xmm0
  movapd %xmm0,%xmm1
  addsd  %xmm4,%xmm0
  subsd  %xmm4,%xmm1
  unpcklpd %xmm0,%xmm1
  movups %xmm1,0x0(%rbp)
  cmp    $0x4,%r12d
  jg     L76
  je     L106
L47:
  pop    %rbx
  mov    %rbp,%rsi
  mov    %r12d,%edi
  pop    %rbp
  pop    %r12
  jmp    10a0 <dstsub4@plt>
  nopw   0x0(%rax,%rax,1)
L76:
  mov    %rbp,%rsi
  mov    %r12d,%edi
  call   <rftbsub@plt>
  mov    %rbp,%rsi
  mov    %r12d,%edi
  call   <cftbsub@plt>
  pop    %rbx
  mov    %rbp,%rsi
  mov    %r12d,%edi
  pop    %rbp
  pop    %r12
  jmp    10e0 <dstsub@plt>
  nopl   (%rax)
L42:
  mov    %rbp,%rsi
  mov    $0x4,%edi
  call   <cftfsub@plt>
  movsd  0x0(%rbp),%xmm0
  movsd  0x8(%rbp),%xmm1
  movapd %xmm0,%xmm4
  addsd  %xmm1,%xmm0
  subsd  %xmm1,%xmm4
  movsd  %xmm0,0x0(%rbp)
  jmp    L61
  nopl   (%rax)
L106:
  mov    %rbp,%rsi
  mov    $0x4,%edi
  call   <cftbsub@plt>
  jmp    L47
```

tool_calls: name: retrieve_data
arguments: data_label: D31
data_type: byte[8]

tool: {"D31": [0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x80]}

assistant: ```c
void ddst(int n, int isgn, 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);
      cftbsub(n, a);
    } else if (n == 4) {
      cftbsub(n, a);
    }
  }
  if (n > 4) {
    dstsub(n, a);
  } else {
    dstsub4(n, a);
  }
  if (isgn >= 0) {
    if (n > 4) {
      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;
  }
}
```