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

```asm
<quicksort>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x78,%rsp
  mov    %esi,0x18(%rsp)
  cmp    $0x1,%esi
  jle    L60
  mov    %rdi,%r10
L31:
  mov    0x18(%rsp),%ebx
  mov    %r10,%r8
  xor    %edx,%edx
  mov    %ebx,%eax
  sar    %eax
  cltq
  mov    (%r10,%rax,4),%edi
  lea    -0x1(%rbx),%eax
  movslq %eax,%rsi
L76:
  mov    (%r8),%r11d
  lea    (%r10,%rsi,4),%r9
  mov    %edx,0x1c(%rsp)
  mov    (%r9),%ecx
  cmp    %edi,%r11d
  jl     L469
  cmp    %ecx,%edi
  jge    L38
  lea    -0x4(%r10,%rsi,4),%rsi
L349:
  mov    %rsi,%r9
  mov    (%rsi),%ecx
  sub    $0x4,%rsi
  sub    $0x1,%eax
  cmp    %edi,%ecx
  jg     L349
L38:
  cmp    %edx,%eax
  jle    L449
  mov    %ecx,(%r8)
  sub    $0x1,%eax
  mov    %r11d,(%r9)
  movslq %eax,%rsi
L469:
  add    $0x1,%rdx
  add    $0x4,%r8
  jmp    L76
L60:
  add    $0x78,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L449:
  mov    0x1c(%rsp),%eax
  mov    %r8,0x38(%rsp)
  mov    %eax,(%rsp)
  cmp    $0x1,%eax
  jle    L480
L660:
  mov    (%rsp),%ebx
  mov    %r10,%r8
  xor    %edx,%edx
  mov    %ebx,%eax
  sar    %eax
  cltq
  mov    (%r10,%rax,4),%edi
  lea    -0x1(%rbx),%eax
  movslq %eax,%rsi
L687:
  mov    (%r8),%r11d
  lea    (%r10,%rsi,4),%r9
  mov    %edx,0x20(%rsp)
  mov    (%r9),%ecx
  cmp    %r11d,%edi
  jg     L240
  cmp    %ecx,%edi
  jge    L79
  lea    -0x4(%r10,%rsi,4),%rsi
L396:
  mov    %rsi,%r9
  mov    (%rsi),%ecx
  sub    $0x4,%rsi
  sub    $0x1,%eax
  cmp    %ecx,%edi
  jl     L396
L79:
  cmp    %edx,%eax
  jle    L378
  mov    %ecx,(%r8)
  sub    $0x1,%eax
  mov    %r11d,(%r9)
  movslq %eax,%rsi
L240:
  add    $0x1,%rdx
  add    $0x4,%r8
  jmp    L687
L480:
  mov    0x1c(%rsp),%ebx
  sub    %ebx,0x18(%rsp)
  mov    0x18(%rsp),%eax
  cmp    $0x1,%eax
  jle    L60
  mov    0x38(%rsp),%r10
  jmp    L31
L378:
  mov    0x20(%rsp),%eax
  mov    %r8,0x40(%rsp)
  mov    %eax,0x4(%rsp)
  cmp    $0x1,%eax
  jle    L212
L169:
  mov    0x4(%rsp),%ebx
  mov    %r10,%r8
  xor    %edx,%edx
  mov    %ebx,%eax
  sar    %eax
  cltq
  mov    (%r10,%rax,4),%edi
  lea    -0x1(%rbx),%eax
  movslq %eax,%rsi
L277:
  mov    (%r8),%r11d
  lea    (%r10,%rsi,4),%r9
  mov    %edx,0x24(%rsp)
  mov    (%r9),%ecx
  cmp    %r11d,%edi
  jg     L582
  cmp    %ecx,%edi
  jge    L495
  lea    -0x4(%r10,%rsi,4),%rsi
L191:
  mov    %rsi,%r9
  mov    (%rsi),%ecx
  sub    $0x4,%rsi
  sub    $0x1,%eax
  cmp    %ecx,%edi
  jl     L191
L495:
  cmp    %edx,%eax
  jle    L130
  mov    %ecx,(%r8)
  sub    $0x1,%eax
  mov    %r11d,(%r9)
  movslq %eax,%rsi
L582:
  add    $0x1,%rdx
  add    $0x4,%r8
  jmp    L277
L212:
  mov    0x20(%rsp),%ebx
  sub    %ebx,(%rsp)
  mov    (%rsp),%eax
  cmp    $0x1,%eax
  jle    L480
  mov    0x40(%rsp),%r10
  jmp    L660
L130:
  mov    0x24(%rsp),%eax
  mov    %r8,0x48(%rsp)
  mov    %eax,0x8(%rsp)
  cmp    $0x1,%eax
  jle    L48
L411:
  mov    0x8(%rsp),%ebx
  mov    %r10,%r8
  xor    %edx,%edx
  mov    %ebx,%eax
  sar    %eax
  cltq
  mov    (%r10,%rax,4),%edi
  lea    -0x1(%rbx),%eax
  movslq %eax,%rsi
L204:
  mov    (%r8),%r11d
  lea    (%r10,%rsi,4),%r9
  mov    %edx,0x28(%rsp)
  mov    (%r9),%ecx
  cmp    %r11d,%edi
  jg     L511
  cmp    %ecx,%edi
  jge    L321
  lea    -0x4(%r10,%rsi,4),%rsi
L682:
  mov    %rsi,%r9
  mov    (%rsi),%ecx
  sub    $0x4,%rsi
  sub    $0x1,%eax
  cmp    %ecx,%edi
  jl     L682
L321:
  cmp    %edx,%eax
  jle    L555
  mov    %ecx,(%r8)
  sub    $0x1,%eax
  mov    %r11d,(%r9)
  movslq %eax,%rsi
L511:
  add    $0x1,%rdx
  add    $0x4,%r8
  jmp    L204
L48:
  mov    0x24(%rsp),%ebx
  sub    %ebx,0x4(%rsp)
  mov    0x4(%rsp),%eax
  cmp    $0x1,%eax
  jle    L212
  mov    0x48(%rsp),%r10
  jmp    L169
L555:
  mov    0x28(%rsp),%eax
  mov    %r8,0x50(%rsp)
  mov    %eax,0xc(%rsp)
  cmp    $0x1,%eax
  jle    L447
L573:
  mov    0xc(%rsp),%ebx
  mov    %r10,%r8
  xor    %edx,%edx
  mov    %ebx,%eax
  sar    %eax
  cltq
  mov    (%r10,%rax,4),%edi
  lea    -0x1(%rbx),%eax
  movslq %eax,%rsi
L91:
  mov    (%r8),%r11d
  lea    (%r10,%rsi,4),%r9
  mov    %edx,0x2c(%rsp)
  mov    (%r9),%ecx
  cmp    %r11d,%edi
  jg     L607
  cmp    %ecx,%edi
  jge    L189
  lea    -0x4(%r10,%rsi,4),%rsi
L436:
  mov    %rsi,%r9
  mov    (%rsi),%ecx
  sub    $0x4,%rsi
  sub    $0x1,%eax
  cmp    %ecx,%edi
  jl     L436
L189:
  cmp    %edx,%eax
  jle    L605
  mov    %ecx,(%r8)
  sub    $0x1,%eax
  mov    %r11d,(%r9)
  movslq %eax,%rsi
L607:
  add    $0x1,%rdx
  add    $0x4,%r8
  jmp    L91
L605:
  mov    0x2c(%rsp),%eax
  mov    %r8,0x58(%rsp)
  mov    %r10,%r15
  mov    %eax,0x10(%rsp)
  mov    %eax,%ebx
  cmp    $0x1,%eax
  jle    L446
L249:
  mov    %ebx,%eax
  mov    %r15,%r14
  xor    %esi,%esi
  sar    %eax
  cltq
  mov    (%r15,%rax,4),%r8d
  lea    -0x1(%rbx),%eax
  movslq %eax,%rdx
L649:
  mov    (%r14),%r9d
  lea    (%r15,%rdx,4),%rdi
  mov    %esi,%r10d
  mov    (%rdi),%ecx
  cmp    %r9d,%r8d
  jg     L86
  cmp    %ecx,%r8d
  jge    L254
  lea    -0x4(%r15,%rdx,4),%rdx
  nopl   0x0(%rax,%rax,1)
L612:
  mov    %rdx,%rdi
  mov    (%rdx),%ecx
  sub    $0x4,%rdx
  sub    $0x1,%eax
  cmp    %ecx,%r8d
  jl     L612
L254:
  cmp    %esi,%eax
  jle    L693
  mov    %ecx,(%r14)
  sub    $0x1,%eax
  mov    %r9d,(%rdi)
  movslq %eax,%rdx
L86:
  add    $0x1,%rsi
  add    $0x4,%r14
  jmp    L649
L693:
  mov    %r10d,0x30(%rsp)
  mov    %r10d,0x14(%rsp)
  cmp    $0x1,%r10d
  jle    L440
  mov    %r14,0x60(%rsp)
  mov    %r10d,%ebx
L103:
  mov    %ebx,%eax
  mov    %r15,%r14
  xor    %r8d,%r8d
  sar    %eax
  cltq
  mov    (%r15,%rax,4),%esi
  lea    -0x1(%rbx),%eax
  movslq %eax,%rdx
  nopl   (%rax)
L658:
  mov    (%r14),%r9d
  lea    (%r15,%rdx,4),%rdi
  mov    %r8d,%r10d
  mov    (%rdi),%ecx
  cmp    %r9d,%esi
  jg     L512
  cmp    %ecx,%esi
  jge    L1
  lea    -0x4(%r15,%rdx,4),%rdx
  nopw   0x0(%rax,%rax,1)
L568:
  mov    %rdx,%rdi
  mov    (%rdx),%ecx
  sub    $0x4,%rdx
  sub    $0x1,%eax
  cmp    %ecx,%esi
  jl     L568
L1:
  cmp    %r8d,%eax
  jle    L116
  mov    %ecx,(%r14)
  sub    $0x1,%eax
  mov    %r9d,(%rdi)
  movslq %eax,%rdx
L512:
  add    $0x1,%r8
  add    $0x4,%r14
  jmp    L658
L116:
  mov    %r10d,0x34(%rsp)
  mov    %r10d,%ebx
  cmp    $0x1,%r10d
  jle    L642
L156:
  mov    %ebx,%eax
  mov    %r15,%r12
  xor    %esi,%esi
  sar    %eax
  cltq
  mov    (%r15,%rax,4),%edi
  lea    -0x1(%rbx),%eax
  movslq %eax,%rdx
  nopw   0x0(%rax,%rax,1)
L179:
  mov    (%r12),%r9d
  lea    (%r15,%rdx,4),%r8
  mov    %esi,%r13d
  mov    (%r8),%ecx
  cmp    %r9d,%edi
  jg     L102
  cmp    %ecx,%edi
  jge    L419
  lea    -0x4(%r15,%rdx,4),%rdx
  nopl   0x0(%rax)
L162:
  mov    %rdx,%r8
  mov    (%rdx),%ecx
  sub    $0x4,%rdx
  sub    $0x1,%eax
  cmp    %ecx,%edi
  jl     L162
L419:
  cmp    %esi,%eax
  jle    L417
  mov    %ecx,(%r12)
  sub    $0x1,%eax
  mov    %r9d,(%r8)
  movslq %eax,%rdx
L102:
  add    $0x1,%rsi
  add    $0x4,%r12
  jmp    L179
L417:
  mov    %r13d,%r8d
  cmp    $0x1,%r13d
  jle    L16
L127:
  mov    %r8d,%eax
  lea    -0x1(%r8),%ecx
  mov    %r15,%rbp
  sar    %eax
  movslq %ecx,%r11
  cltq
  mov    (%r15,%rax,4),%r9d
  xor    %eax,%eax
  nopl   0x0(%rax,%rax,1)
L676:
  mov    0x0(%rbp),%esi
  lea    (%r15,%r11,4),%rdx
  mov    %eax,%r10d
  mov    (%rdx),%edi
  cmp    %esi,%r9d
  jg     L680
  cmp    %edi,%r9d
  jge    L145
  lea    -0x4(%r15,%r11,4),%r11
  nopl   0x0(%rax,%rax,1)
L20:
  mov    %r11,%rdx
  mov    (%r11),%edi
  sub    $0x4,%r11
  sub    $0x1,%ecx
  cmp    %edi,%r9d
  jl     L20
L145:
  cmp    %eax,%ecx
  jle    L577
  mov    %edi,0x0(%rbp)
  sub    $0x1,%ecx
  mov    %esi,(%rdx)
  movslq %ecx,%r11
L680:
  add    $0x1,%rax
  add    $0x4,%rbp
  jmp    L676
L16:
  sub    %r13d,%ebx
  cmp    $0x1,%ebx
  jle    L642
  mov    %r12,%r15
  jmp    L156
  nopl   0x0(%rax,%rax,1)
L577:
  mov    %r10d,%esi
  mov    %r15,%rdi
  mov    %r8d,0x6c(%rsp)
  mov    %r10d,0x68(%rsp)
  call   <quicksort>
  mov    0x68(%rsp),%r10d
  mov    0x6c(%rsp),%r8d
  sub    %r10d,%r8d
  cmp    $0x1,%r8d
  jle    L16
  mov    %rbp,%r15
  jmp    L127
L642:
  mov    0x34(%rsp),%ebx
  sub    %ebx,0x14(%rsp)
  mov    0x14(%rsp),%eax
  cmp    $0x1,%eax
  jle    L158
  mov    %r14,%r15
  mov    %eax,%ebx
  jmp    L103
L158:
  mov    0x60(%rsp),%r14
L440:
  mov    0x30(%rsp),%ebx
  sub    %ebx,0x10(%rsp)
  mov    0x10(%rsp),%eax
  cmp    $0x1,%eax
  jle    L446
  mov    %r14,%r15
  mov    %eax,%ebx
  jmp    L249
L446:
  mov    0x2c(%rsp),%ebx
  sub    %ebx,0xc(%rsp)
  mov    0xc(%rsp),%eax
  cmp    $0x1,%eax
  jle    L447
  mov    0x58(%rsp),%r10
  jmp    L573
L447:
  mov    0x28(%rsp),%ebx
  sub    %ebx,0x8(%rsp)
  mov    0x8(%rsp),%eax
  cmp    $0x1,%eax
  jle    L48
  mov    0x50(%rsp),%r10
  jmp    L411
```

assistant: ```c
void quicksort(int *A, int len) {
  if (len < 2)
    return;
  int pivot = A[len / 2];
  int i, j;
  for (i = 0, j = len - 1;; i++, j--) {
    while (A[i] < pivot)
      i++;
    while (A[j] > pivot)
      j--;
    if (i >= j)
      break;
    int temp = A[i];
    A[i] = A[j];
    A[j] = temp;
  }
  quicksort(A, i);
  quicksort(A + i, len - i);
}
```