user: 下面的汇编指令对应的C源代码是什么:

```asm
<mean_arrays>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  mov    %rdi,%r13
  mov    %rcx,%rdi
  push   %r12
  mov    %esi,%r12d
  xor    %esi,%esi
  push   %rbp
  mov    %edx,%ebp
  shl    $0x2,%edx
  push   %rbx
  mov    %rcx,%rbx
  sub    $0x8,%rsp
  call   <memset@plt>
  test   %r12d,%r12d
  jle    L0
  test   %ebp,%ebp
  jle    L155
  lea    -0x1(%r12),%eax
  mov    %ebp,%edi
  mov    %ebp,%r8d
  mov    %r13,%rcx
  lea    0x8(%r13,%rax,8),%r9
  mov    %ebp,%eax
  lea    -0x1(%rbp),%r10d
  and    $0xfffffffc,%edi
  shr    $0x2,%eax
  and    $0x3,%r8d
  mov    %ebp,%esi
  lea    -0x1(%rax),%edx
  add    $0x1,%rdx
  shl    $0x4,%rdx
  nopw   0x0(%rax,%rax,1)
L40:
  mov    (%rcx),%r11
  mov    %rbx,%rax
  lea    0x4(%r11),%r13
  sub    %r13,%rax
  cmp    $0x8,%rax
  jbe    L111
  cmp    $0x1,%ebp
  je     L111
  cmp    $0x2,%r10d
  jbe    L95
  xor    %eax,%eax
  nopl   0x0(%rax)
L100:
  movups (%rbx,%rax,1),%xmm0
  movups (%r11,%rax,1),%xmm3
  addps  %xmm3,%xmm0
  movups %xmm0,(%rbx,%rax,1)
  add    $0x10,%rax
  cmp    %rdx,%rax
  jne    L100
  cmp    %edi,%ebp
  je     L164
  mov    %r8d,%r14d
  cmp    $0x1,%r8d
  je     L110
  mov    %edi,%r13d
  mov    %edi,%eax
L211:
  lea    (%rbx,%r13,4),%r15
  movq   (%r11,%r13,4),%xmm0
  mov    %r14d,%r13d
  movq   (%r15),%xmm1
  and    $0xfffffffe,%r13d
  add    %r13d,%eax
  addps  %xmm1,%xmm0
  movlps %xmm0,(%r15)
  cmp    %r13d,%r14d
  je     L164
L105:
  cltq
  lea    (%rbx,%rax,4),%r13
  movss  0x0(%r13),%xmm0
  addss  (%r11,%rax,4),%xmm0
  movss  %xmm0,0x0(%r13)
L164:
  add    $0x8,%rcx
  cmp    %r9,%rcx
  jne    L40
L9:
  pxor   %xmm2,%xmm2
  cvtsi2ss %r12d,%xmm2
  cmp    $0x2,%r10d
  jbe    L90
  mov    %ebp,%edx
  movaps %xmm2,%xmm1
  mov    %rbx,%rax
  shr    $0x2,%edx
  shufps $0x0,%xmm1,%xmm1
  sub    $0x1,%edx
  shl    $0x4,%rdx
  lea    0x10(%rbx,%rdx,1),%rdx
  nopw   0x0(%rax,%rax,1)
L38:
  movups (%rax),%xmm0
  add    $0x10,%rax
  divps  %xmm1,%xmm0
  movups %xmm0,-0x10(%rax)
  cmp    %rdx,%rax
  jne    L38
  mov    %ebp,%eax
  and    $0xfffffffc,%eax
  test   $0x3,%bpl
  je     L155
L218:
  movslq %eax,%rdx
  shl    $0x2,%rdx
  lea    (%rbx,%rdx,1),%rcx
  movss  (%rcx),%xmm0
  divss  %xmm2,%xmm0
  movss  %xmm0,(%rcx)
  lea    0x1(%rax),%ecx
  cmp    %ecx,%ebp
  jle    L155
  lea    0x4(%rbx,%rdx,1),%rcx
  add    $0x2,%eax
  movss  (%rcx),%xmm0
  divss  %xmm2,%xmm0
  movss  %xmm0,(%rcx)
  cmp    %eax,%ebp
  jle    L155
  lea    0x8(%rbx,%rdx,1),%rax
  movss  (%rax),%xmm0
  divss  %xmm2,%xmm0
  movss  %xmm0,(%rax)
L155:
  add    $0x8,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax)
L111:
  xor    %eax,%eax
  nopw   0x0(%rax,%rax,1)
L131:
  movss  (%rbx,%rax,4),%xmm0
  addss  (%r11,%rax,4),%xmm0
  movss  %xmm0,(%rbx,%rax,4)
  add    $0x1,%rax
  cmp    %rsi,%rax
  jne    L131
  jmp    L164
L95:
  mov    %ebp,%r14d
  xor    %r13d,%r13d
  xor    %eax,%eax
  jmp    L211
L110:
  mov    %edi,%eax
  jmp    L105
L0:
  lea    -0x1(%rbp),%r10d
  test   %ebp,%ebp
  jg     L9
  jmp    L155
L90:
  xor    %eax,%eax
  jmp    L218
```

assistant: ```c
void mean_arrays(float **a, int n, int els, float *avg) {
  int i;
  int j;
  memset(avg, 0, els * sizeof(float));
  for (j = 0; j < n; ++j) {
    for (i = 0; i < els; ++i) {
      avg[i] += a[j][i];
    }
  }
  for (i = 0; i < els; ++i) {
    avg[i] /= n;
  }
}
```