user: Converte this assembly snippet into its equivalent C code:

```asm
<lmuller>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  movslq %ecx,%r13
  push   %r12
  mov    %r13d,%eax
  mov    %r8d,%r12d
  push   %rbp
  mov    %rsi,%rbp
  push   %rbx
  mov    %rdi,%rbx
  mov    %rdx,%rdi
  sub    $0x28,%rsp
  add    %r8d,%eax
  mov    %r9,0x10(%rsp)
  mov    %eax,0xc(%rsp)
  js     L170
  movslq 0xc(%rsp),%rax
  xor    %esi,%esi
  lea    0x4(,%rax,4),%rdx
  call   <memset@plt>
  mov    %rax,%rdi
L170:
  test   %r13d,%r13d
  jle    L94
  test   %r12d,%r12d
  jle    L94
  mov    %r12d,%r10d
  mov    %r12d,%edx
  lea    (%rbx,%r13,4),%r15
  movslq %r12d,%r13
  and    $0xfffffffc,%r10d
  shr    $0x2,%edx
  mov    %rdi,0x18(%rsp)
  mov    %rdi,%rax
  lea    0x2(%r10),%ecx
  lea    -0x1(%rdx),%esi
  mov    %r10d,%r11d
  shl    $0x2,%r13
  mov    %ecx,0x4(%rsp)
  lea    0x3(%r10),%ecx
  add    $0x1,%rsi
  shl    $0x2,%r11
  mov    %ecx,0x8(%rsp)
  lea    -0x1(%r12),%ecx
  shl    $0x4,%rsi
  mov    %r12d,%r8d
  lea    0x0(%rbp,%r11,1),%r9
  lea    0x4(%rbp),%r14
  mov    %ecx,%edi
L93:
  mov    %rax,%rdx
  add    $0x4,%rbx
  sub    %r14,%rdx
  cmp    $0x8,%rdx
  seta   %cl
  cmp    $0x2,%edi
  seta   %dl
  test   %dl,%cl
  je     L123
  lea    -0x4(%rbx),%rcx
  lea    (%rax,%r13,1),%rdx
  cmp    %rdx,%rcx
  setae  %cl
  cmp    %rbx,%rax
  setae  %dl
  or     %cl,%dl
  je     L123
  movd   -0x4(%rbx),%xmm4
  xor    %edx,%edx
  pshufd $0x0,%xmm4,%xmm2
  movdqa %xmm2,%xmm3
  psrlq  $0x20,%xmm3
L0:
  movdqu 0x0(%rbp,%rdx,1),%xmm0
  movdqu 0x0(%rbp,%rdx,1),%xmm1
  psrlq  $0x20,%xmm0
  pmuludq %xmm2,%xmm1
  pmuludq %xmm3,%xmm0
  pshufd $0x8,%xmm1,%xmm1
  pshufd $0x8,%xmm0,%xmm0
  punpckldq %xmm0,%xmm1
  movdqu (%rax,%rdx,1),%xmm0
  paddd  %xmm1,%xmm0
  movups %xmm0,(%rax,%rdx,1)
  add    $0x10,%rdx
  cmp    %rsi,%rdx
  jne    L0
  lea    (%rax,%r11,1),%rdx
  cmp    %r10d,%r12d
  je     L37
  mov    -0x4(%rbx),%ecx
  imul   (%r9),%ecx
  add    %ecx,(%rdx)
  cmp    0x4(%rsp),%r12d
  jl     L37
  mov    -0x4(%rbx),%ecx
  imul   0x4(%r9),%ecx
  add    %ecx,0x4(%rdx)
  cmp    0x8(%rsp),%r12d
  jl     L37
  mov    0x8(%r9),%ecx
  imul   -0x4(%rbx),%ecx
  add    %ecx,0x8(%rdx)
L37:
  add    $0x4,%rax
  cmp    %r15,%rbx
  jne    L93
  mov    0x18(%rsp),%rdi
L94:
  mov    0xc(%rsp),%esi
  test   %esi,%esi
  jle    L174
  movslq 0xc(%rsp),%rax
  mov    %rdi,%rdx
  xor    %esi,%esi
  lea    (%rdi,%rax,4),%r8
  nop
L119:
  add    (%rdx),%esi
  add    $0x4,%rdx
  mov    %esi,%ecx
  shr    $0xc,%esi
  and    $0xfff,%ecx
  mov    %ecx,-0x4(%rdx)
  cmp    %r8,%rdx
  jne    L119
  mov    (%rdi,%rax,4),%ecx
  mov    %eax,%edx
  test   %ecx,%ecx
  jne    L112
  nopw   0x0(%rax,%rax,1)
L165:
  sub    $0x1,%rax
  test   %eax,%eax
  js     L122
L161:
  mov    (%rdi,%rax,4),%ecx
  mov    %eax,%edx
  test   %ecx,%ecx
  je     L165
L112:
  add    $0x1,%edx
L122:
  mov    0x10(%rsp),%rax
  mov    %edx,(%rax)
  add    $0x28,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopw   0x0(%rax,%rax,1)
L123:
  xor    %edx,%edx
  nopw   0x0(%rax,%rax,1)
L30:
  mov    0x0(%rbp,%rdx,4),%ecx
  imul   -0x4(%rbx),%ecx
  add    %ecx,(%rax,%rdx,4)
  add    $0x1,%rdx
  cmp    %rdx,%r8
  jne    L30
  jmp    L37
L174:
  mov    $0x0,%eax
  je     L161
  mov    0xc(%rsp),%edx
  add    $0x1,%edx
  jmp    L122
```

assistant: ```c
void lmuller(unsigned *pa, unsigned *pb, unsigned *erg, int alen, int blen, int *erglen) {
  int i, j, clen;
  unsigned *perg, *ppb;
  int c;
  clen = alen + blen;
  for (i = 0; i <= clen; i++)
    erg[i] = 0;
  for (i = 0; i < alen; i++) {
    perg = erg + i;
    ppb = pb;
    for (j = 1; j <= blen; j++) {
      *perg += (*pa) * (*ppb);
      perg++;
      ppb++;
    }
    pa++;
  }
  perg = erg;
  c = 0;
  for (i = 1; i <= clen; i++) {
    *perg += c;
    c = (*perg) >> 12;
    *perg = (*perg) & 4095;
    perg++;
  }
  while ((clen >= 0) && (erg[clen] == 0))
    clen--;
  *erglen = clen + 1;
}
```