user: What would the C source look like for the assembly code provided here:

```asm
<neuralops_omp_caffe_maxpool2d_bwd>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  mov    %rdi,%rbx
  mov    %rdi,-0x20(%rsp)
  mov    %rdx,%rax
  mov    %rcx,%r13
  mov    %r8,%rdi
  mov    %r9,%r10
  mov    0x48(%rsp),%rcx
  mov    %rsi,%r9
  imul   %rdx,%r9
  imul   %r13,%rbx
  mov    %rbx,%rdx
  imul   %r9,%rdx
  test   %rdx,%rdx
  je     L41
  mov    %rcx,%r8
  lea    (%rcx,%rdx,4),%rdx
L21:
  movl   $0x0,(%r8)
  add    $0x4,%r8
  cmp    %rdx,%r8
  jne    L21
L41:
  cmpq   $0x0,-0x20(%rsp)
  je     L44
  mov    %rdi,%r8
  imul   %r10,%r8
  mov    %r13,%rdx
  imul   %r8,%rdx
  lea    0x0(,%r9,4),%rbx
  mov    %rbx,-0x50(%rsp)
  lea    0x0(,%r8,8),%r15
  lea    0x0(,%r8,4),%rbx
  mov    %rbx,-0x48(%rsp)
  imul   %r13,%rax
  imul   %rsi,%rax
  shl    $0x2,%rax
  mov    %rax,-0x18(%rsp)
  mov    %rcx,-0x30(%rsp)
  lea    0x0(,%rdx,8),%rax
  mov    %rax,-0x10(%rsp)
  mov    0x38(%rsp),%rax
  mov    %rax,-0x28(%rsp)
  lea    0x0(,%rdx,4),%rax
  mov    %rax,-0x8(%rsp)
  mov    0x40(%rsp),%rax
  mov    %rax,-0x38(%rsp)
  lea    0x0(,%rdi,8),%rbx
  lea    0x0(,%rdi,4),%r11
  movq   $0x0,-0x40(%rsp)
  jmp    L100
L42:
  mov    (%rsi,%rax,8),%rdx
  lea    (%r8,%rdx,4),%rdx
  movss  (%rdx),%xmm0
  addss  (%rcx,%rax,4),%xmm0
  movss  %xmm0,(%rdx)
  add    $0x1,%rax
  cmp    %rax,%rdi
  jne    L42
L49:
  add    $0x1,%r9
  add    %rbx,%rsi
  add    %r11,%rcx
  cmp    %r9,%r10
  je     L127
L138:
  mov    $0x0,%eax
  test   %rdi,%rdi
  jne    L42
  jmp    L49
L127:
  add    -0x50(%rsp),%r8
  add    %r15,%r14
  add    -0x48(%rsp),%r12
  add    $0x1,%rbp
  cmp    %rbp,%r13
  je     L120
L12:
  test   %r10,%r10
  je     L127
  mov    %r14,%rsi
  mov    %r12,%rcx
  mov    $0x0,%r9d
  jmp    L138
L120:
  addq   $0x1,-0x40(%rsp)
  mov    -0x40(%rsp),%rax
  mov    -0x18(%rsp),%rcx
  add    %rcx,-0x30(%rsp)
  mov    -0x10(%rsp),%rsi
  add    %rsi,-0x28(%rsp)
  mov    -0x8(%rsp),%rcx
  add    %rcx,-0x38(%rsp)
  cmp    %rax,-0x20(%rsp)
  je     L44
L100:
  mov    -0x30(%rsp),%r8
  mov    -0x28(%rsp),%r14
  mov    -0x38(%rsp),%r12
  mov    $0x0,%ebp
  test   %r13,%r13
  jne    L12
  jmp    L120
L44:
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
void neuralops_omp_caffe_maxpool2d_bwd(size_t batch_sz, size_t in_width, size_t in_height, size_t chan, size_t out_width, size_t out_height, const uint32_t *mask_buf, const float *out_grad, float *in_grad, size_t kernel_w_, size_t kernel_h_, size_t stride_w_, size_t stride_h_, size_t pad_w_, size_t pad_h_) {
  size_t bottom_count = in_width * in_height * chan * batch_sz;
#pragma omp parallel for
  for (size_t i = 0; i < bottom_count; i++) {
    in_grad[i] = 0.0f;
  }
#pragma omp parallel for private(in_grad)
  for (size_t n = 0; n < batch_sz; n++) {
    float *bottom_diff = in_grad + n * in_width * in_height * chan;
    const uint32_t *top_mask = mask_buf + n * out_width * out_height * chan;
    const float *top_diff = out_grad + n * out_width * out_height * chan;
    for (size_t c = 0; c < chan; ++c) {
      for (size_t ph = 0; ph < out_height; ++ph) {
        for (size_t pw = 0; pw < out_width; ++pw) {
          size_t index = ph * out_width + pw;
          uint32_t bottom_index = top_mask[index];
          bottom_diff[bottom_index] += top_diff[index];
        }
      }
      bottom_diff += in_width * in_height;
      top_mask += out_width * out_height;
      top_diff += out_width * out_height;
    }
  }
}
```