user: 请显示与下面列出的汇编代码相匹配的C语言实现:

```asm
<backcol>:
  endbr64
  push   %r15
  mov    %rsi,%r15
  push   %r14
  push   %r13
  mov    %edi,%r13d
  push   %r12
  lea    -0x1(%rdi),%r12d
  push   %rbp
  mov    %rdx,%rbp
  push   %rbx
  sub    $0x18,%rsp
  test   %ecx,%ecx
  jne    L167
  test   %r12d,%r12d
  js     L159
  movslq %r12d,%rax
  sub    $0x3,%r13d
  imul   $0x1908,%rax,%rdx
  lea    -0x8(,%rax,8),%rbx
  lea    -0x10(%rbp,%rbx,1),%r14
  lea    -0x3200(%rsi,%rdx,1),%rdx
  nopl   0x0(%rax,%rax,1)
L50:
  movsd  0x3200(%rdx),%xmm0
  mov    %rdx,0x8(%rsp)
  call   <is_zero@plt>
  mov    0x8(%rsp),%rdx
  test   %rax,%rax
  jne    L23
  movsd  0x18(%r14),%xmm2
  lea    -0x1(%r12),%esi
  divsd  0x3200(%rdx),%xmm2
  movsd  %xmm2,0x18(%r14)
  test   %r12d,%r12d
  je     L159
  movsd  0x1900(%rdx),%xmm1
  movsd  0x10(%r14),%xmm0
  mulsd  %xmm2,%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,0x10(%r14)
  cmp    $0xffffffff,%r13d
  je     L69
  movslq %esi,%r8
  mov    %r8,%rax
  imul   $0xffffffffffffe700,%r8,%r8
  neg    %rax
  lea    (%rbx,%rax,8),%rdi
  mov    $0x1900,%eax
  sub    %r15,%rax
  lea    0x0(%rbp,%rdi,1),%r9
  add    %rdx,%rax
  add    %r8,%rax
  lea    0x10(%r14),%r8
  add    %r15,%rax
  cmp    %r8,%rax
  lea    0x8(%rdx),%rax
  setae  %r8b
  cmp    %rax,%r9
  lea    0x10(%rbx),%r9
  setae  %al
  or     %eax,%r8d
  lea    0x8(%rbx),%rax
  cmp    %rbx,%rax
  setge  %al
  cmp    %rdi,%r9
  setle  %dil
  or     %edi,%eax
  test   %al,%r8b
  je     L9
  cmp    $0x1,%r13d
  jbe    L9
  mov    %esi,%eax
  lea    -0x10(%r14),%r8
  unpcklpd %xmm2,%xmm2
  mov    %rdx,%rdi
  shr    %eax
  sub    $0x1,%eax
  shl    $0x4,%rax
  sub    %rax,%r8
  mov    %r14,%rax
  nopl   0x0(%rax,%rax,1)
L15:
  movsd  (%rdi),%xmm1
  movupd (%rax),%xmm0
  sub    $0x10,%rax
  sub    $0x3200,%rdi
  movhpd 0x1900(%rdi),%xmm1
  shufpd $0x1,%xmm0,%xmm0
  mulpd  %xmm2,%xmm1
  subpd  %xmm1,%xmm0
  shufpd $0x1,%xmm0,%xmm0
  movups %xmm0,0x10(%rax)
  cmp    %r8,%rax
  jne    L15
  mov    %esi,%edi
  mov    %r13d,%eax
  and    $0xfffffffe,%edi
  sub    %edi,%eax
  cmp    %esi,%edi
  je     L69
  cltq
  movslq %r12d,%r12
  lea    0x0(%rbp,%rax,8),%rdi
  lea    (%rax,%rax,4),%rax
  lea    (%rax,%rax,4),%rax
  movsd  (%rdi),%xmm0
  shl    $0x8,%rax
  add    %r15,%rax
  movsd  (%rax,%r12,8),%xmm1
  mulsd  0x18(%r14),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,(%rdi)
L69:
  sub    $0x1,%r13d
  sub    $0x8,%rbx
  sub    $0x8,%r14
  mov    %esi,%r12d
  sub    $0x1908,%rdx
  jmp    L50
L167:
  test   %r12d,%r12d
  js     L159
  movslq %r12d,%r12
  mov    %edi,%r14d
  lea    (%rdx,%r12,8),%rbx
  imul   $0x1908,%r12,%r12
  lea    0x1900(%rsi,%r12,1),%r12
  nopw   0x0(%rax,%rax,1)
L128:
  cmp    %r14d,%r13d
  jle    L70
  movsd  (%rbx),%xmm1
  movslq %r14d,%rax
  mov    %r12,%rdx
  nopw   0x0(%rax,%rax,1)
L46:
  movsd  (%rdx),%xmm0
  mulsd  0x0(%rbp,%rax,8),%xmm0
  add    $0x1,%rax
  add    $0x1900,%rdx
  subsd  %xmm0,%xmm1
  movsd  %xmm1,(%rbx)
  cmp    %eax,%r13d
  jg     L46
L70:
  movsd  -0x1900(%r12),%xmm0
  call   <is_zero@plt>
  test   %rax,%rax
  jne    L23
  movsd  (%rbx),%xmm0
  sub    $0x1908,%r12
  sub    $0x8,%rbx
  divsd  0x8(%r12),%xmm0
  movsd  %xmm0,0x8(%rbx)
  sub    $0x1,%r14d
  jne    L128
L159:
  add    $0x18,%rsp
  xor    %eax,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax,%rax,1)
L9:
  movslq %r13d,%rax
  mov    %rdx,%rdi
  cs nopw 0x0(%rax,%rax,1)
L10:
  movsd  0x18(%r14),%xmm1
  mulsd  (%rdi),%xmm1
  sub    $0x1900,%rdi
  movsd  0x0(%rbp,%rax,8),%xmm0
  subsd  %xmm1,%xmm0
  movsd  %xmm0,0x0(%rbp,%rax,8)
  sub    $0x1,%rax
  cmp    $0xffffffff,%eax
  jne    L10
  jmp    L69
  nop
L23:
  add    $0x18,%rsp
  mov    $0xffffffff,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
int backcol(int n, double A[][800], double b[], int trans) {
  int i, j;
  if (trans == 0) {
    for (j = n - 1; j >= 0; j--) {
      if (is_zero(A[j][j]))
        return -1;
      b[j] /= A[j][j];
      for (i = j - 1; i >= 0; i--) {
        b[i] -= A[i][j] * b[j];
      }
    }
  } else {
    for (j = n - 1; j >= 0; j--) {
      for (i = j + 1; i < n; i++) {
        b[j] -= A[i][j] * b[i];
      }
      if (is_zero(A[j][j]))
        return -1;
      b[j] /= A[j][j];
    }
  }
  return 0;
}
```