user: 提供的汇编代码用C语言表示会是什么样子：

```asm
<pad>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x28,%rsp
  mov    %edx,0x8(%rsp)
  test   %edx,%edx
  jle    L173
  mov    %ecx,%eax
  mov    %rdi,%rbx
  mov    %rsi,%rdi
  sub    %ecx,%r8d
  shr    $0x4,%eax
  mov    %ecx,%r13d
  lea    -0x1(%rcx),%r15d
  xor    %r12d,%r12d
  lea    -0x1(%rax),%r14d
  mov    %ecx,%eax
  mov    %r8d,%ebp
  and    $0xfffffff0,%eax
  add    $0x1,%r14
  mov    %eax,%esi
  mov    %eax,0xc(%rsp)
  shl    $0x4,%r14
  mov    %rsi,0x10(%rsp)
  mov    %ecx,%esi
  sub    %eax,%esi
  lea    -0x1(%rsi),%eax
  mov    %esi,0x18(%rsp)
  mov    %eax,0x1c(%rsp)
  nopl   0x0(%rax)
L207:
  test   %r13d,%r13d
  jle    L91
  lea    0x1(%rbx),%rdx
  mov    %rdi,%rax
  sub    %rdx,%rax
  cmp    $0xe,%rax
  jbe    L195
  cmp    $0x6,%r15d
  jbe    L195
  cmp    $0xe,%r15d
  jbe    L141
  xor    %eax,%eax
  nopl   0x0(%rax,%rax,1)
L137:
  movdqu (%rbx,%rax,1),%xmm0
  movups %xmm0,(%rdi,%rax,1)
  add    $0x10,%rax
  cmp    %r14,%rax
  jne    L137
  mov    0x10(%rsp),%rax
  mov    0xc(%rsp),%ecx
  lea    (%rbx,%rax,1),%r9
  lea    (%rdi,%rax,1),%rsi
  mov    %r15d,%eax
  cmp    %ecx,%r13d
  je     L94
  cmpl   $0x6,0x1c(%rsp)
  mov    0x18(%rsp),%r11d
  jbe    L193
  mov    %ecx,%eax
  mov    %ecx,%edx
L208:
  mov    (%rbx,%rax,1),%r10
  mov    %r10,(%rdi,%rax,1)
  mov    %r11d,%r10d
  and    $0xfffffff8,%r10d
  mov    %r10d,%eax
  add    %r10d,%edx
  add    %rax,%r9
  add    %rax,%rsi
  mov    %r15d,%eax
  cmp    %r10d,%r11d
  je     L94
L42:
  movzbl (%r9),%eax
  lea    0x1(%rdx),%r10d
  mov    %al,(%rsi)
  mov    %r15d,%eax
  cmp    %r10d,%r13d
  jle    L94
  movzbl 0x1(%r9),%r10d
  mov    %r10b,0x1(%rsi)
  lea    0x2(%rdx),%r10d
  cmp    %r10d,%r13d
  jle    L94
  movzbl 0x2(%r9),%r10d
  mov    %r10b,0x2(%rsi)
  lea    0x3(%rdx),%r10d
  cmp    %r10d,%r13d
  jle    L94
  movzbl 0x3(%r9),%r10d
  mov    %r10b,0x3(%rsi)
  lea    0x4(%rdx),%r10d
  cmp    %r10d,%r13d
  jle    L94
  movzbl 0x4(%r9),%r10d
  mov    %r10b,0x4(%rsi)
  lea    0x5(%rdx),%r10d
  cmp    %r10d,%r13d
  jle    L94
  movzbl 0x5(%r9),%r10d
  add    $0x6,%edx
  mov    %r10b,0x5(%rsi)
  cmp    %edx,%r13d
  jle    L94
  movzbl 0x6(%r9),%edx
  mov    %dl,0x6(%rsi)
L94:
  add    $0x1,%rax
  add    %rax,%rbx
  add    %rax,%rdi
L91:
  test   %ebp,%ebp
  jle    L34
  mov    %ebp,%edx
  xor    %esi,%esi
  mov    %rdx,(%rsp)
  call   <memset@plt>
  mov    (%rsp),%rdx
  mov    %rax,%rdi
  add    %rdx,%rdi
L34:
  add    $0x1,%r12d
  cmp    %r12d,0x8(%rsp)
  jne    L207
L173:
  add    $0x28,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax)
L195:
  mov    %r15d,%eax
  xor    %edx,%edx
  nopl   (%rax)
L194:
  movzbl (%rbx,%rdx,1),%ecx
  mov    %cl,(%rdi,%rdx,1)
  mov    %rdx,%rcx
  add    $0x1,%rdx
  cmp    %rax,%rcx
  jne    L194
  jmp    L94
L141:
  mov    %r13d,%r11d
  mov    %rdi,%rsi
  mov    %rbx,%r9
  xor    %eax,%eax
  xor    %edx,%edx
  jmp    L208
L193:
  mov    %ecx,%edx
  jmp    L42
```

assistant: ```c
void pad(char *a, char *b, int w, int c1, int c2) {
  for (int i = 0; i < w; i++) {
    for (int j = 0; j < c1; j++)
      *b++ = *a++;
    for (int j = 0; j < c2 - c1; j++)
      *b++ = 0;
  }
}
```