user: What would the C source look like for the assembly code provided here:

```asm
<kernel_dtrmv_u_n_2_lib4>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %edi,-0x44(%rbp)
  mov    %rsi,-0x50(%rbp)
  mov    %rdx,-0x58(%rbp)
  mov    %rcx,-0x60(%rbp)
  mov    %r8d,-0x48(%rbp)
  cmpl   $0x0,-0x44(%rbp)
  jle    L45
  mov    -0x50(%rbp),%rax
  prefetcht0 (%rax)
  mov    -0x50(%rbp),%rax
  add    $0x40,%rax
  prefetcht0 (%rax)
  movl   $0x4,-0x34(%rbp)
  pxor   %xmm0,%xmm0
  movsd  %xmm0,-0x30(%rbp)
  pxor   %xmm0,%xmm0
  movsd  %xmm0,-0x28(%rbp)
  mov    -0x34(%rbp),%eax
  shl    $0x2,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  prefetcht0 (%rax)
  mov    -0x34(%rbp),%eax
  shl    $0x2,%eax
  cltq
  add    $0x8,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  prefetcht0 (%rax)
  mov    -0x58(%rbp),%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,-0x20(%rbp)
  mov    -0x58(%rbp),%rax
  movsd  0x8(%rax),%xmm0
  movsd  %xmm0,-0x18(%rbp)
  mov    -0x50(%rbp),%rax
  movsd  (%rax),%xmm0
  mulsd  -0x20(%rbp),%xmm0
  movsd  -0x30(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x30(%rbp)
  mov    -0x34(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x18(%rbp),%xmm0
  movsd  -0x30(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x30(%rbp)
  mov    -0x34(%rbp),%eax
  add    $0x1,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x18(%rbp),%xmm0
  movsd  -0x28(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x28(%rbp)
  mov    -0x34(%rbp),%eax
  add    %eax,%eax
  cltq
  shl    $0x3,%rax
  add    %rax,-0x50(%rbp)
  addq   $0x10,-0x58(%rbp)
  movl   $0x2,-0x38(%rbp)
  jmp    L82
L92:
  mov    -0x34(%rbp),%eax
  shl    $0x2,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  prefetcht0 (%rax)
  mov    -0x34(%rbp),%eax
  shl    $0x2,%eax
  cltq
  add    $0x8,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  prefetcht0 (%rax)
  mov    -0x58(%rbp),%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,-0x20(%rbp)
  mov    -0x58(%rbp),%rax
  movsd  0x8(%rax),%xmm0
  movsd  %xmm0,-0x18(%rbp)
  mov    -0x58(%rbp),%rax
  movsd  0x10(%rax),%xmm0
  movsd  %xmm0,-0x10(%rbp)
  mov    -0x58(%rbp),%rax
  movsd  0x18(%rax),%xmm0
  movsd  %xmm0,-0x8(%rbp)
  mov    -0x50(%rbp),%rax
  movsd  (%rax),%xmm0
  mulsd  -0x20(%rbp),%xmm0
  movsd  -0x30(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x30(%rbp)
  mov    -0x50(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x20(%rbp),%xmm0
  movsd  -0x28(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x28(%rbp)
  mov    -0x34(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x18(%rbp),%xmm0
  movsd  -0x30(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x30(%rbp)
  mov    -0x34(%rbp),%eax
  add    $0x1,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x18(%rbp),%xmm0
  movsd  -0x28(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x28(%rbp)
  mov    -0x34(%rbp),%eax
  add    %eax,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x10(%rbp),%xmm0
  movsd  -0x30(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x30(%rbp)
  mov    -0x34(%rbp),%eax
  add    %eax,%eax
  add    $0x1,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x10(%rbp),%xmm0
  movsd  -0x28(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x28(%rbp)
  mov    -0x34(%rbp),%edx
  mov    %edx,%eax
  add    %eax,%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x8(%rbp),%xmm0
  movsd  -0x30(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x30(%rbp)
  mov    -0x34(%rbp),%edx
  mov    %edx,%eax
  add    %eax,%eax
  add    %edx,%eax
  add    $0x1,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x8(%rbp),%xmm0
  movsd  -0x28(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x28(%rbp)
  mov    -0x34(%rbp),%eax
  shl    $0x2,%eax
  cltq
  shl    $0x3,%rax
  add    %rax,-0x50(%rbp)
  addq   $0x20,-0x58(%rbp)
  addl   $0x4,-0x38(%rbp)
L82:
  mov    -0x44(%rbp),%eax
  sub    $0x3,%eax
  cmp    %eax,-0x38(%rbp)
  jl     L92
  jmp    L47
L12:
  mov    -0x58(%rbp),%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,-0x20(%rbp)
  mov    -0x50(%rbp),%rax
  movsd  (%rax),%xmm0
  mulsd  -0x20(%rbp),%xmm0
  movsd  -0x30(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x30(%rbp)
  mov    -0x50(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x20(%rbp),%xmm0
  movsd  -0x28(%rbp),%xmm1
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x28(%rbp)
  mov    -0x34(%rbp),%eax
  cltq
  shl    $0x3,%rax
  add    %rax,-0x50(%rbp)
  addq   $0x8,-0x58(%rbp)
  addl   $0x1,-0x38(%rbp)
L47:
  mov    -0x38(%rbp),%eax
  cmp    -0x44(%rbp),%eax
  jl     L12
  cmpl   $0x0,-0x48(%rbp)
  jne    L27
  mov    -0x60(%rbp),%rax
  movsd  -0x30(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x60(%rbp),%rax
  add    $0x8,%rax
  movsd  -0x28(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  jmp    L17
L27:
  cmpl   $0x1,-0x48(%rbp)
  jne    L95
  mov    -0x60(%rbp),%rax
  movsd  (%rax),%xmm0
  addsd  -0x30(%rbp),%xmm0
  mov    -0x60(%rbp),%rax
  movsd  %xmm0,(%rax)
  mov    -0x60(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm0
  mov    -0x60(%rbp),%rax
  add    $0x8,%rax
  addsd  -0x28(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  jmp    L17
L95:
  mov    -0x60(%rbp),%rax
  movsd  (%rax),%xmm0
  subsd  -0x30(%rbp),%xmm0
  mov    -0x60(%rbp),%rax
  movsd  %xmm0,(%rax)
  mov    -0x60(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm0
  mov    -0x60(%rbp),%rax
  add    $0x8,%rax
  subsd  -0x28(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  jmp    L17
L45:
  nop
L17:
  pop    %rbp
  ret
```

assistant: ```c
void kernel_dtrmv_u_n_2_lib4(int kmax, double *A, double *x, double *y, int alg) {
  if (kmax <= 0)
    return;
  __builtin_prefetch(A);
  __builtin_prefetch(A + 8);
  const int lda = 4;
  int k;
  double x_0, x_1, x_2, x_3, y_0 = 0, y_1 = 0;
  __builtin_prefetch(A + 4 * lda);
  __builtin_prefetch(A + 4 * lda + 8);
  x_0 = x[0];
  x_1 = x[1];
  y_0 += A[0 + lda * 0] * x_0;
  y_0 += A[0 + lda * 1] * x_1;
  y_1 += A[1 + lda * 1] * x_1;
  A += 2 * lda;
  x += 2;
  k = 2;
  for (; k < kmax - 3; k += 4) {
    __builtin_prefetch(A + 4 * lda);
    __builtin_prefetch(A + 4 * lda + 8);
    x_0 = x[0];
    x_1 = x[1];
    x_2 = x[2];
    x_3 = x[3];
    y_0 += A[0 + lda * 0] * x_0;
    y_1 += A[1 + lda * 0] * x_0;
    y_0 += A[0 + lda * 1] * x_1;
    y_1 += A[1 + lda * 1] * x_1;
    y_0 += A[0 + lda * 2] * x_2;
    y_1 += A[1 + lda * 2] * x_2;
    y_0 += A[0 + lda * 3] * x_3;
    y_1 += A[1 + lda * 3] * x_3;
    A += 4 * lda;
    x += 4;
  }
  for (; k < kmax; k++) {
    x_0 = x[0];
    y_0 += A[0 + lda * 0] * x_0;
    y_1 += A[1 + lda * 0] * x_0;
    A += 1 * lda;
    x += 1;
  }
  if (alg == 0) {
    y[0] = y_0;
    y[1] = y_1;
  } else if (alg == 1) {
    y[0] += y_0;
    y[1] += y_1;
  } else {
    y[0] -= y_0;
    y[1] -= y_1;
  }
}
```