user: Please show me the C implementation that matches the assembly code listed below:

```asm
<fftixb>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  mov    %ecx,%r13d
  push   %r12
  mov    %rsi,%r12
  push   %rbp
  mov    %rdi,%rbp
  push   %rbx
  sub    $0x8,%rsp
  cmp    %edx,%ecx
  jg     L17
L311:
  mov    %rbp,%rdi
  lea    0x0(,%r13,8),%edx
  xor    %esi,%esi
  movslq %r13d,%rbx
  call   <memset@plt>
  lea    0x0(%r13,%r13,1),%edi
  lea    -0x1(%rdi),%ecx
  test   %r13d,%r13d
  jle    L276
  lea    0x0(,%rbx,8),%rax
  cmp    $0x1,%r13d
  lea    0x0(,%rbx,4),%rdx
  mov    %r13d,%r14d
  lea    -0x8(%rax),%r8
  lea    -0x4(%r12,%rax,1),%rsi
  setne  %r15b
  mov    %rax,%r9
  lea    0x0(%rbp,%r8,1),%r10
  sub    %rdx,%r9
  sub    %r10,%rsi
  add    $0x8,%rsi
  cmp    $0x8,%rsi
  seta   %sil
  cmp    %r9,%rdx
  setle  %r10b
  test   %rax,%rax
  setle  %r11b
  or     %r11d,%r10d
  lea    0x0(%rbp,%rdx,1),%r11
  and    %r10d,%esi
  lea    (%r12,%r9,1),%r10
  and    %r15d,%esi
  cmp    %r10,%r11
  lea    (%r12,%rax,1),%r11
  setbe  %r10b
  cmp    %r11,%rbp
  setae  %r11b
  or     %r11d,%r10d
  test   %r10b,%sil
  je     L2
  add    %r12,%rdx
  add    %rbp,%r9
  lea    0x0(%rbp,%rax,1),%rsi
  cmp    %r9,%rdx
  setbe  %dl
  cmp    %rsi,%r12
  setae  %sil
  or     %sil,%dl
  je     L2
  lea    -0x1(%r13),%edx
  cmp    $0x2,%edx
  jbe    L325
  mov    %r13d,%r9d
  sub    $0x10,%rax
  movaps D28(%rip),%xmm1
  xor    %edx,%edx
  shr    $0x2,%r9d
  lea    0x0(%rbp,%rax,1),%r10
  lea    (%r12,%rax,1),%rsi
  xor    %eax,%eax
  shl    $0x4,%r9
  cs nopw 0x0(%rax,%rax,1)
L248:
  movups 0x0(%rbp,%rax,1),%xmm0
  shufps $0x1b,%xmm0,%xmm0
  movups %xmm0,(%r10,%rdx,1)
  movups (%r12,%rax,1),%xmm0
  add    $0x10,%rax
  xorps  %xmm1,%xmm0
  shufps $0x1b,%xmm0,%xmm0
  movups %xmm0,(%rsi,%rdx,1)
  sub    $0x10,%rdx
  cmp    %r9,%rax
  jne    L248
  mov    %r13d,%eax
  and    $0xfffffffc,%eax
  mov    %eax,%esi
  cmp    %eax,%r13d
  je     L307
L308:
  mov    %r13d,%edx
  sub    %eax,%edx
  cmp    $0x1,%edx
  je     L32
  movq   0x0(%rbp,%rax,4),%xmm0
  lea    0x0(,%rax,4),%r9
  movq   D28(%rip),%xmm6
  sub    %r9,%r8
  shufps $0xe1,%xmm0,%xmm0
  movlps %xmm0,0x0(%rbp,%r8,1)
  movq   (%r12,%rax,4),%xmm0
  mov    %edx,%eax
  and    $0xfffffffe,%eax
  xorps  %xmm6,%xmm0
  add    %eax,%esi
  shufps $0xe1,%xmm0,%xmm0
  movlps %xmm0,(%r12,%r8,1)
  cmp    %eax,%edx
  je     L307
L32:
  movslq %esi,%rdx
  mov    %ecx,%eax
  movss  0x0(%rbp,%rdx,4),%xmm0
  sub    %esi,%eax
  cltq
  movss  %xmm0,0x0(%rbp,%rax,4)
  movss  (%r12,%rdx,4),%xmm0
  xorps  D37(%rip),%xmm0
  movss  %xmm0,(%r12,%rax,4)
L307:
  movsd  D61(%rip),%xmm0
  mov    %r12,%rdx
  mov    %rbp,%rsi
  call   <fft@plt>
  lea    0x10(%rbp),%rcx
  lea    0x4(%rbp),%r8
  lea    0x4(,%rbx,4),%rdi
  lea    0x0(,%rbx,4),%rsi
  lea    0xc(%r12,%rdi,1),%rax
  lea    (%r12,%rsi,1),%rdx
  cmp    %rax,%rbp
  setae  %al
  cmp    %rcx,%rdx
  setae  %cl
  or     %ecx,%eax
  mov    %r12,%rcx
  sub    %r8,%rcx
  cmp    $0x8,%rcx
  seta   %cl
  and    %r15d,%ecx
  and    %ecx,%eax
  mov    %rdi,%rcx
  neg    %rcx
  cmp    $0x8,%rcx
  seta   %cl
  test   %cl,%al
  je     L76
  lea    0x0(%rbp,%rdi,1),%rax
  mov    %r12,%rcx
  sub    %rax,%rcx
  cmp    $0x8,%rcx
  jbe    L76
  lea    -0x1(%r13),%eax
  cmp    $0x2,%eax
  jbe    L0
  mov    %r13d,%ecx
  add    %rbp,%rsi
  xor    %eax,%eax
  shr    $0x2,%ecx
  shl    $0x4,%rcx
  nopl   0x0(%rax)
L224:
  movups (%rsi,%rax,1),%xmm4
  movups %xmm4,0x0(%rbp,%rax,1)
  movups (%rdx,%rax,1),%xmm5
  movups %xmm5,(%r12,%rax,1)
  add    $0x10,%rax
  cmp    %rcx,%rax
  jne    L224
  mov    %r13d,%edx
  and    $0xfffffffc,%edx
  mov    %edx,%eax
  cmp    %r13d,%edx
  je     L297
L61:
  mov    %r13d,%ecx
  sub    %edx,%ecx
  cmp    $0x1,%ecx
  je     L134
  lea    (%rbx,%rdx,1),%rsi
  mov    0x0(%rbp,%rsi,4),%rdi
  mov    %rdi,0x0(%rbp,%rdx,4)
  mov    (%r12,%rsi,4),%rsi
  mov    %rsi,(%r12,%rdx,4)
  mov    %ecx,%edx
  and    $0xfffffffe,%edx
  add    %edx,%eax
  cmp    %edx,%ecx
  je     L297
L134:
  lea    0x0(%r13,%rax,1),%edx
  cltq
  movslq %edx,%rdx
  movss  0x0(%rbp,%rdx,4),%xmm0
  movss  %xmm0,0x0(%rbp,%rax,4)
  movss  (%r12,%rdx,4),%xmm0
  movss  %xmm0,(%r12,%rax,4)
L297:
  pxor   %xmm1,%xmm1
  movsd  D20(%rip),%xmm0
  lea    0xf(%r12),%rax
  cvtsi2sd %r13d,%xmm1
  sub    %rbp,%rax
  divsd  %xmm1,%xmm0
  cvtsd2ss %xmm0,%xmm0
  cmp    $0x1e,%rax
  jbe    L93
  test   %r15b,%r15b
  je     L93
  lea    -0x1(%r13),%eax
  cmp    $0x2,%eax
  jbe    L304
  mov    %r13d,%edx
  movaps %xmm0,%xmm2
  xor    %eax,%eax
  shr    $0x2,%edx
  shufps $0x0,%xmm2,%xmm2
  shl    $0x4,%rdx
  nopl   0x0(%rax)
L337:
  movups 0x0(%rbp,%rax,1),%xmm1
  mulps  %xmm2,%xmm1
  movups %xmm1,0x0(%rbp,%rax,1)
  movups (%r12,%rax,1),%xmm1
  mulps  %xmm2,%xmm1
  movups %xmm1,(%r12,%rax,1)
  add    $0x10,%rax
  cmp    %rdx,%rax
  jne    L337
  mov    %r13d,%edx
  and    $0xfffffffc,%edx
  mov    %edx,%eax
  cmp    %r13d,%edx
  je     L252
  mov    %r13d,%r14d
  sub    %edx,%r14d
  cmp    $0x1,%r14d
  je     L166
L164:
  shl    $0x2,%rdx
  movaps %xmm0,%xmm1
  lea    0x0(%rbp,%rdx,1),%rcx
  shufps $0xe0,%xmm1,%xmm1
  add    %r12,%rdx
  movq   (%rcx),%xmm2
  mulps  %xmm1,%xmm2
  movlps %xmm2,(%rcx)
  movq   (%rdx),%xmm2
  mulps  %xmm1,%xmm2
  movlps %xmm2,(%rdx)
  mov    %r14d,%edx
  and    $0xfffffffe,%edx
  add    %edx,%eax
  cmp    %r14d,%edx
  je     L252
L166:
  cltq
  shl    $0x2,%rax
  add    %rax,%rbp
  add    %r12,%rax
  movss  0x0(%rbp),%xmm1
  mulss  %xmm0,%xmm1
  movss  %xmm1,0x0(%rbp)
  mulss  (%rax),%xmm0
  movss  %xmm0,(%rax)
L252:
  add    $0x8,%rsp
  mov    %r13d,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax)
L17:
  mov    %ecx,%r8d
  sub    %edx,%r8d
  movslq %edx,%rdx
  shl    $0x2,%r8d
  lea    (%rsi,%rdx,4),%rdi
  xor    %esi,%esi
  mov    %r8d,%edx
  call   <memset@plt>
  jmp    L311
L2:
  movslq %ecx,%rax
  xor    %edx,%edx
  movss  D37(%rip),%xmm1
  shl    $0x2,%rax
  nopl   0x0(%rax)
L254:
  movss  0x0(%rbp,%rdx,4),%xmm0
  movss  %xmm0,0x0(%rbp,%rax,1)
  movss  (%r12,%rdx,4),%xmm0
  add    $0x1,%rdx
  xorps  %xmm1,%xmm0
  movss  %xmm0,(%r12,%rax,1)
  sub    $0x4,%rax
  cmp    %rbx,%rdx
  jne    L254
  jmp    L307
  nopl   (%rax)
L76:
  add    %rbp,%rsi
  xor    %eax,%eax
  nopl   (%rax)
L255:
  movss  (%rsi,%rax,4),%xmm0
  movss  %xmm0,0x0(%rbp,%rax,4)
  movss  (%rdx,%rax,4),%xmm0
  movss  %xmm0,(%r12,%rax,4)
  add    $0x1,%rax
  cmp    %rbx,%rax
  jne    L255
  jmp    L297
  nopl   0x0(%rax)
L93:
  xor    %eax,%eax
  nopw   0x0(%rax,%rax,1)
L251:
  movss  0x0(%rbp,%rax,4),%xmm1
  mulss  %xmm0,%xmm1
  movss  %xmm1,0x0(%rbp,%rax,4)
  movss  (%r12,%rax,4),%xmm1
  mulss  %xmm0,%xmm1
  movss  %xmm1,(%r12,%rax,4)
  add    $0x1,%rax
  cmp    %rax,%rbx
  jne    L251
  jmp    L252
  xchg   %ax,%ax
L276:
  movsd  D61(%rip),%xmm0
  mov    %r12,%rdx
  mov    %rbp,%rsi
  call   <fft@plt>
  jmp    L252
L325:
  xor    %eax,%eax
  xor    %esi,%esi
  jmp    L308
L0:
  xor    %edx,%edx
  xor    %eax,%eax
  jmp    L61
L304:
  xor    %edx,%edx
  xor    %eax,%eax
  jmp    L164
```

tool_calls: name: parse_data
arguments: data_tag: D28
datatype: byte[16]
name: parse_data
arguments: data_tag: D37
datatype: byte[16]
name: parse_data
arguments: data_tag: D61
datatype: byte[8]
name: parse_data
arguments: data_tag: D20
datatype: f64

tool: {"D28": [0x00,0x00,0x00,0x80,0x00,0x00,0x00,0x80,0x00,0x00,0x00,0x80,0x00,0x00,0x00,0x80]}

tool: {"D37": [0x00,0x00,0x00,0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00]}

tool: {"D61": [0x00,0x00,0x00,0x00,0x00,0x00,0xf0,0xbf]}

tool: D20: 1

assistant: ```c
int fftixb(float *xrr, float *xri, int isize, int ntot) {
  int i, ntotp1;
  float scale;
  if (ntot > isize)
    memset(xri + isize, 0, sizeof(float) * (ntot - isize));
  memset(xrr, 0, sizeof(float) * ntot * 2);
  ntotp1 = 2 * ntot - 1;
  for (i = 0; i < ntot; i++) {
    xrr[ntotp1 - i] = xrr[i];
    xri[ntotp1 - i] = -xri[i];
  }
  fft(-1.0, ntot * 2, xrr, xri);
  for (i = 0; i < ntot; i++) {
    xrr[i] = xrr[i + ntot];
    xri[i] = xri[i + ntot];
  }
  scale = 1.0 / ntot;
  for (i = 0; i < ntot; i++) {
    xrr[i] *= scale;
    xri[i] *= scale;
  }
  return ntot;
}
```