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

```asm
<squarev>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbx
  sub    $0x38,%rsp
  mov    %rdi,-0x48(%rbp)
  mov    %rsi,-0x50(%rbp)
  mov    %edx,-0x54(%rbp)
  mov    -0x54(%rbp),%eax
  add    $0x2,%eax
  mov    %eax,-0x34(%rbp)
  mov    -0x50(%rbp),%rax
  lea    0x4(%rax),%r12
L129:
  mov    %r12,%rax
  lea    0x2(%rax),%r12
  movw   $0x0,(%rax)
  subl   $0x1,-0x34(%rbp)
  cmpl   $0x0,-0x34(%rbp)
  jne    L129
  mov    -0x54(%rbp),%eax
  cltq
  add    $0x3,%rax
  lea    (%rax,%rax,1),%rdx
  mov    -0x50(%rbp),%rax
  lea    (%rdx,%rax,1),%rbx
  mov    -0x54(%rbp),%eax
  add    $0x2,%eax
  mov    %eax,-0x34(%rbp)
  jmp    L50
L2:
  mov    -0x48(%rbp),%rax
  lea    0x6(%rax),%r13
  mov    -0x34(%rbp),%eax
  cltq
  lea    (%rax,%rax,1),%rdx
  mov    -0x48(%rbp),%rax
  lea    (%rdx,%rax,1),%r12
  jmp    L37
L96:
  movzwl (%r12),%eax
  test   %ax,%ax
  je     L39
  movzwl 0x0(%r13),%eax
  test   %ax,%ax
  jne    L59
L39:
  sub    $0x2,%r12
  add    $0x2,%r13
  jmp    L37
L59:
  movzwl (%r12),%eax
  movzwl %ax,%edx
  movzwl 0x0(%r13),%eax
  movzwl %ax,%eax
  imul   %rax,%rdx
  mov    %rdx,%r14
  cmp    %r13,%r12
  je     L66
  mov    %r14,%rax
  and    $0x80000000,%eax
  test   %rax,%rax
  je     L49
  lea    -0x4(%rbx),%rax
  movzwl (%rax),%edx
  lea    -0x4(%rbx),%rax
  add    $0x1,%edx
  mov    %dx,(%rax)
L49:
  add    %r14,%r14
L66:
  sub    $0x2,%r12
  add    $0x2,%r13
  movzwl (%rbx),%eax
  movzwl %ax,%edx
  movzwl %r14w,%eax
  lea    (%rdx,%rax,1),%r15
  mov    %r15,%rax
  and    $0x10000,%eax
  test   %rax,%rax
  je     L38
  movw   $0x1,-0x36(%rbp)
  jmp    L103
L38:
  movw   $0x0,-0x36(%rbp)
L103:
  mov    %rbx,%rax
  lea    -0x2(%rax),%rbx
  mov    %r15d,%edx
  mov    %dx,(%rax)
  movzwl (%rbx),%eax
  movzwl %ax,%edx
  mov    %r14,%rax
  shr    $0x10,%rax
  movzwl %ax,%eax
  add    %rax,%rdx
  movzwl -0x36(%rbp),%eax
  lea    (%rdx,%rax,1),%r15
  mov    %rbx,%rax
  lea    -0x2(%rax),%rbx
  mov    %r15d,%edx
  mov    %dx,(%rax)
  mov    %r15,%rax
  and    $0x10000,%eax
  test   %rax,%rax
  je     L121
  movzwl (%rbx),%eax
  add    $0x1,%eax
  mov    %ax,(%rbx)
L121:
  add    $0x4,%rbx
L37:
  cmp    %r13,%r12
  jae    L96
  sub    $0x2,%rbx
  subl   $0x1,-0x34(%rbp)
L50:
  cmpl   $0x2,-0x34(%rbp)
  jg     L2
  mov    -0x50(%rbp),%rax
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <shup1@plt>
  mov    $0x0,%eax
  add    $0x38,%rsp
  pop    %rbx
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  pop    %rbp
  ret
```

assistant: ```c
int squarev(a, b, prec)
unsigned short a[], b[];
int prec;
{
  register unsigned short *p, *q, *r;
  register unsigned long u, lp;
  unsigned short carry;
  int k;
  k = prec + 2;
  p = &b[2];
  do
    *p++ = 0;
  while (--k);
  r = &b[prec + 3];
  for (k = prec + 2; k >= 3; k--) {
    q = &a[3];
    p = &a[k];
    while (p >= q) {
      if ((*p == 0) || (*q == 0)) {
        --p;
        ++q;
        continue;
      }
      lp = (unsigned long)(*p) * (unsigned long)(*q);
      if (p != q) {
        if (lp & 0x80000000)
          *(r - 2) += 1;
        lp <<= 1;
      }
      --p;
      ++q;
      u = (unsigned long)(*r) + (lp & 0xffff);
      if (u & 0x10000)
        carry = 1;
      else
        carry = 0;
      *r-- = u;
      u = (unsigned long)(*r) + ((lp >> 16) & 0xffff) + carry;
      *r-- = u;
      if (u & 0x10000)
        *r += 1;
      r += 2;
    }
    --r;
  }
  shup1(b);
  return 0;
}
```