user: What is the c source code of the assembly code below?

```asm
<unir_cuatro_imagenes>:
  endbr64
  push   %r15
  lea    (%r8,%r8,1),%eax
  mov    %r8d,%r15d
  push   %r14
  mov    %rdx,%r14
  push   %r13
  movslq %eax,%r13
  push   %r12
  mov    %rsi,%r12
  push   %rbp
  mov    %rcx,%rbp
  push   %rbx
  mov    %r9d,%ebx
  sub    $0x18,%rsp
  mov    %rdi,0x8(%rsp)
  lea    (%r9,%r9,1),%edi
  imul   %eax,%edi
  shl    $0x2,%edi
  call   <malloc@plt>
  mov    %rax,%r9
  mov    %r15d,%eax
  imul   %ebx,%eax
  mov    %eax,0x4(%rsp)
  test   %r15d,%r15d
  jle    L5
  test   %ebx,%ebx
  jle    L5
  movslq %r15d,%r10
  mov    %r9,%r11
  lea    0x0(,%r13,4),%rsi
  xor    %r8d,%r8d
  lea    0x0(,%r10,4),%rdi
  sub    %r14,%r11
  cs nopw 0x0(%rax,%rax,1)
L73:
  lea    (%r11,%r14,1),%rcx
  mov    %r14,%rdx
  xor    %eax,%eax
  nopl   0x0(%rax)
L51:
  movss  (%rdx),%xmm0
  add    $0x1,%eax
  add    %rdi,%rdx
  movss  %xmm0,(%rcx)
  add    %rsi,%rcx
  cmp    %eax,%ebx
  jne    L51
  add    $0x1,%r8d
  add    $0x4,%r14
  cmp    %r8d,%r15d
  jne    L73
  lea    0x0(,%r10,4),%rsi
  lea    0x0(,%r13,4),%rdi
  xor    %r8d,%r8d
  mov    %rsi,%r11
  sub    %rbp,%r11
  add    %r9,%r11
  xchg   %ax,%ax
L58:
  lea    (%r11,%rbp,1),%rcx
  mov    %rbp,%rdx
  xor    %eax,%eax
  nopl   0x0(%rax)
L61:
  movss  (%rdx),%xmm0
  add    $0x1,%eax
  add    %rsi,%rdx
  movss  %xmm0,(%rcx)
  add    %rdi,%rcx
  cmp    %eax,%ebx
  jne    L61
  add    $0x1,%r8d
  add    $0x4,%rbp
  cmp    %r8d,%r15d
  jne    L58
  movslq 0x4(%rsp),%r11
  mov    0x8(%rsp),%r8
  xor    %ebp,%ebp
  lea    0x0(,%r10,4),%rdi
  lea    0x0(,%r13,4),%rsi
  lea    (%r9,%r11,8),%r14
  sub    %r8,%r14
  nopl   (%rax)
L78:
  lea    (%r14,%r8,1),%rcx
  mov    %r8,%rdx
  xor    %eax,%eax
  nopl   0x0(%rax)
L48:
  movss  (%rdx),%xmm0
  add    $0x1,%eax
  add    %rdi,%rdx
  movss  %xmm0,(%rcx)
  add    %rsi,%rcx
  cmp    %eax,%ebx
  jne    L48
  add    $0x1,%ebp
  add    $0x4,%r8
  cmp    %ebp,%r15d
  jne    L78
  lea    (%r10,%r11,2),%rax
  lea    0x0(,%r10,4),%rsi
  shl    $0x2,%r13
  xor    %edi,%edi
  lea    (%r9,%rax,4),%r8
  sub    %r12,%r8
  nopw   0x0(%rax,%rax,1)
L57:
  lea    (%r12,%r8,1),%rcx
  mov    %r12,%rdx
  xor    %eax,%eax
  nopl   0x0(%rax)
L25:
  movss  (%rdx),%xmm0
  add    $0x1,%eax
  add    %rsi,%rdx
  movss  %xmm0,(%rcx)
  add    %r13,%rcx
  cmp    %eax,%ebx
  jne    L25
  add    $0x1,%edi
  add    $0x4,%r12
  cmp    %edi,%r15d
  jne    L57
L5:
  add    $0x18,%rsp
  mov    %r9,%rax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
float *unir_cuatro_imagenes(float *a, float *b, float *c, float *d, int width, int height) {
  int i, j;
  float *output = (float *)malloc(sizeof(float) * (width * 2) * (height * 2));
  float *tmp = output + (width * 2) * height;
  for (i = 0; i < width; i++) {
    for (j = 0; j < height; j++) {
      int index = (width * 2) * j + i;
      output[index] = c[width * j + i];
    }
  }
  for (i = 0; i < width; i++) {
    for (j = 0; j < height; j++) {
      int index = (width * 2) * j + i + width;
      output[index] = d[width * j + i];
    }
  }
  for (i = 0; i < width; i++) {
    for (j = 0; j < height; j++) {
      int index = (height * width * 2) + (width * 2) * j + i;
      output[index] = a[width * j + i];
    }
  }
  for (i = 0; i < width; i++) {
    for (j = 0; j < height; j++) {
      int index = (height * width * 2) + (width * 2) * j + i + width;
      output[index] = b[width * j + i];
    }
  }
  return output;
}
```