user: Demonstrate the C code that generates the assembly output below:

```asm
<decode_dxt1_block>:
  endbr64
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x48,%rsp
  mov    %rdi,%rbp
  mov    %rsi,%rbx
  mov    %fs:0x28,%rax
  mov    %rax,0x38(%rsp)
  xor    %eax,%eax
  mov    (%rdi),%r13d
  mov    0x8(%rdi),%r12d
  lea    0x10(%rsp),%rcx
  lea    0xc(%rsp),%rdx
  lea    0x8(%rsp),%rsi
  mov    %r13d,%edi
  call   <rgb565_le@plt>
  lea    0x1c(%rsp),%rcx
  lea    0x18(%rsp),%rdx
  lea    0x14(%rsp),%rsi
  mov    %r12d,%edi
  call   <rgb565_le@plt>
  movq   $0x0,0x28(%rsp)
  mov    $0xff,%ecx
  mov    0x10(%rsp),%edx
  mov    0xc(%rsp),%esi
  mov    0x8(%rsp),%edi
  call   <color@plt>
  mov    %eax,0x20(%rsp)
  mov    $0xff,%ecx
  mov    0x1c(%rsp),%edx
  mov    0x18(%rsp),%esi
  mov    0x14(%rsp),%edi
  call   <color@plt>
  mov    %eax,0x24(%rsp)
  cmp    %r12d,%r13d
  jle    L12
  mov    0x10(%rsp),%edx
  mov    0x1c(%rsp),%eax
  lea    (%rax,%rdx,2),%eax
  movslq %eax,%rdx
  imul   $0x55555556,%rdx,%rdx
  shr    $0x20,%rdx
  sar    $0x1f,%eax
  sub    %eax,%edx
  mov    0xc(%rsp),%ecx
  mov    0x18(%rsp),%eax
  lea    (%rax,%rcx,2),%eax
  movslq %eax,%rsi
  imul   $0x55555556,%rsi,%rsi
  shr    $0x20,%rsi
  sar    $0x1f,%eax
  sub    %eax,%esi
  mov    0x8(%rsp),%ecx
  mov    0x14(%rsp),%eax
  lea    (%rax,%rcx,2),%eax
  movslq %eax,%rdi
  imul   $0x55555556,%rdi,%rdi
  shr    $0x20,%rdi
  sar    $0x1f,%eax
  sub    %eax,%edi
  mov    $0xff,%ecx
  call   <color@plt>
  mov    %eax,0x28(%rsp)
  mov    0x1c(%rsp),%edx
  mov    0x10(%rsp),%eax
  lea    (%rax,%rdx,2),%eax
  movslq %eax,%rdx
  imul   $0x55555556,%rdx,%rdx
  shr    $0x20,%rdx
  sar    $0x1f,%eax
  sub    %eax,%edx
  mov    0x18(%rsp),%ecx
  mov    0xc(%rsp),%eax
  lea    (%rax,%rcx,2),%eax
  movslq %eax,%rsi
  imul   $0x55555556,%rsi,%rsi
  shr    $0x20,%rsi
  sar    $0x1f,%eax
  sub    %eax,%esi
  mov    0x14(%rsp),%ecx
  mov    0x8(%rsp),%eax
  lea    (%rax,%rcx,2),%eax
  movslq %eax,%rdi
  imul   $0x55555556,%rdi,%rdi
  shr    $0x20,%rdi
  sar    $0x1f,%eax
  sub    %eax,%edi
  mov    $0xff,%ecx
  call   <color@plt>
L14:
  mov    %eax,0x2c(%rsp)
  mov    0x10(%rbp),%edx
  mov    %rbx,%rax
  lea    0x40(%rbx),%rsi
L30:
  mov    %edx,%ecx
  and    $0x3,%ecx
  mov    0x20(%rsp,%rcx,4),%ecx
  mov    %ecx,(%rax)
  sar    $0x2,%edx
  add    $0x4,%rax
  cmp    %rsi,%rax
  jne    L30
  mov    0x38(%rsp),%rax
  sub    %fs:0x28,%rax
  jne    L23
  add    $0x48,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
L12:
  mov    0x1c(%rsp),%eax
  add    0x10(%rsp),%eax
  mov    %eax,%edx
  shr    $0x1f,%edx
  add    %eax,%edx
  sar    %edx
  mov    0x18(%rsp),%eax
  add    0xc(%rsp),%eax
  mov    %eax,%esi
  shr    $0x1f,%esi
  add    %eax,%esi
  sar    %esi
  mov    0x14(%rsp),%eax
  add    0x8(%rsp),%eax
  mov    %eax,%edi
  shr    $0x1f,%edi
  add    %eax,%edi
  sar    %edi
  mov    $0xff,%ecx
  call   <color@plt>
  mov    %eax,0x28(%rsp)
  mov    $0xff,%ecx
  mov    $0x0,%edx
  mov    $0x0,%esi
  mov    $0x0,%edi
  call   <color@plt>
  jmp    L14
L23:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
void decode_dxt1_block(const uint8_t *data, uint32_t *outbuf) {
  uint8_t r0, g0, b0, r1, g1, b1;
  int q0 = *(uint16_t *)(data);
  int q1 = *(uint16_t *)(data + 2);
  rgb565_le(q0, &r0, &g0, &b0);
  rgb565_le(q1, &r1, &g1, &b1);
  uint_fast32_t c[4] = {color(r0, g0, b0, 255), color(r1, g1, b1, 255)};
  if (q0 > q1) {
    c[2] = color((r0 * 2 + r1) / 3, (g0 * 2 + g1) / 3, (b0 * 2 + b1) / 3, 255);
    c[3] = color((r0 + r1 * 2) / 3, (g0 + g1 * 2) / 3, (b0 + b1 * 2) / 3, 255);
  } else {
    c[2] = color((r0 + r1) / 2, (g0 + g1) / 2, (b0 + b1) / 2, 255);
    c[3] = color(0, 0, 0, 255);
  }
  uint_fast32_t d = (*(uint32_t *)(data + 4));
  for (int i = 0; i < 16; i++, d >>= 2)
    outbuf[i] = c[d & 3];
}
```