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

```asm
<kernel_dtrmv_u_t_8_lib4>:
  endbr64
  mov    %edi,%eax
  lea    0x0(,%rdx,4),%edi
  push   %r12
  prefetcht0 (%rsi)
  movslq %edi,%rdi
  push   %rbp
  prefetcht0 0x40(%rsi)
  prefetcht0 0x80(%rsi)
  shl    $0x3,%rdi
  push   %rbx
  prefetcht0 0xc0(%rsi)
  lea    0x40(%rdi),%r12
  lea    0x80(%rdi),%rbp
  lea    0xc0(%rdi),%rbx
  cmp    $0x3,%eax
  jle    L50
  lea    -0x4(%rax),%r11d
  pxor   %xmm11,%xmm11
  mov    %rsi,%rdx
  shr    $0x2,%r11d
  movapd %xmm11,%xmm4
  movapd %xmm11,%xmm5
  add    $0x1,%r11d
  movapd %xmm11,%xmm6
  movapd %xmm11,%xmm7
  mov    %r11,%r10
  movapd %xmm11,%xmm8
  movapd %xmm11,%xmm9
  shl    $0x5,%r10
  movapd %xmm11,%xmm10
  add    %rcx,%r10
  nopl   0x0(%rax)
L1:
  mov    %rdx,%rax
  movsd  (%rcx),%xmm2
  movsd  0x8(%rcx),%xmm1
  add    %rdi,%rdx
  movsd  (%rax),%xmm12
  movsd  0x60(%rax),%xmm13
  prefetcht0 (%rdx)
  prefetcht0 (%rax,%rbp,1)
  movsd  0x10(%rcx),%xmm0
  movsd  0x18(%rcx),%xmm3
  prefetcht0 (%rax,%rbx,1)
  add    $0x20,%rcx
  mulsd  %xmm2,%xmm12
  prefetcht0 (%rax,%r12,1)
  mulsd  %xmm2,%xmm13
  addsd  %xmm12,%xmm10
  movsd  0x20(%rax),%xmm12
  addsd  %xmm7,%xmm13
  movsd  0xa0(%rax),%xmm7
  mulsd  %xmm2,%xmm12
  mulsd  %xmm2,%xmm7
  addsd  %xmm12,%xmm9
  movsd  0x40(%rax),%xmm12
  addsd  %xmm5,%xmm7
  movsd  0x68(%rax),%xmm5
  mulsd  %xmm2,%xmm12
  mulsd  %xmm1,%xmm5
  addsd  %xmm8,%xmm12
  movsd  0x80(%rax),%xmm8
  addsd  %xmm13,%xmm5
  movsd  0x10(%rax),%xmm13
  mulsd  %xmm2,%xmm8
  mulsd  %xmm0,%xmm13
  addsd  %xmm6,%xmm8
  movsd  0xc0(%rax),%xmm6
  mulsd  %xmm2,%xmm6
  mulsd  0xe0(%rax),%xmm2
  addsd  %xmm4,%xmm6
  movsd  0x8(%rax),%xmm4
  addsd  %xmm11,%xmm2
  movsd  0x28(%rax),%xmm11
  mulsd  %xmm1,%xmm4
  mulsd  %xmm1,%xmm11
  addsd  %xmm4,%xmm10
  movsd  0x48(%rax),%xmm4
  addsd  %xmm9,%xmm11
  movsd  0xa8(%rax),%xmm9
  mulsd  %xmm1,%xmm4
  mulsd  %xmm1,%xmm9
  addsd  %xmm10,%xmm13
  addsd  %xmm4,%xmm12
  movsd  0x88(%rax),%xmm4
  addsd  %xmm7,%xmm9
  movsd  0x50(%rax),%xmm7
  mulsd  %xmm1,%xmm4
  mulsd  %xmm0,%xmm7
  addsd  %xmm8,%xmm4
  movsd  0xc8(%rax),%xmm8
  addsd  %xmm12,%xmm7
  mulsd  %xmm1,%xmm8
  mulsd  0xe8(%rax),%xmm1
  addsd  %xmm6,%xmm8
  movsd  0x70(%rax),%xmm6
  addsd  %xmm2,%xmm1
  movsd  0x30(%rax),%xmm2
  mulsd  %xmm0,%xmm6
  mulsd  %xmm0,%xmm2
  addsd  %xmm5,%xmm6
  movsd  0x90(%rax),%xmm5
  addsd  %xmm2,%xmm11
  movsd  0xd0(%rax),%xmm2
  mulsd  %xmm0,%xmm5
  mulsd  %xmm0,%xmm2
  addsd  %xmm4,%xmm5
  movsd  0xb0(%rax),%xmm4
  addsd  %xmm8,%xmm2
  mulsd  %xmm0,%xmm4
  mulsd  0xf0(%rax),%xmm0
  movsd  0x18(%rax),%xmm10
  movsd  0x58(%rax),%xmm8
  mulsd  %xmm3,%xmm10
  mulsd  %xmm3,%xmm8
  addsd  %xmm9,%xmm4
  movsd  0x38(%rax),%xmm9
  addsd  %xmm1,%xmm0
  mulsd  %xmm3,%xmm9
  addsd  %xmm13,%xmm10
  addsd  %xmm7,%xmm8
  movsd  0x78(%rax),%xmm7
  mulsd  %xmm3,%xmm7
  addsd  %xmm11,%xmm9
  addsd  %xmm6,%xmm7
  movsd  0x98(%rax),%xmm6
  mulsd  %xmm3,%xmm6
  addsd  %xmm5,%xmm6
  movsd  0xb8(%rax),%xmm5
  mulsd  %xmm3,%xmm5
  addsd  %xmm4,%xmm5
  movsd  0xd8(%rax),%xmm4
  mulsd  %xmm3,%xmm4
  mulsd  0xf8(%rax),%xmm3
  addsd  %xmm2,%xmm4
  addsd  %xmm0,%xmm3
  movapd %xmm3,%xmm11
  cmp    %r10,%rcx
  jne    L1
  imul   %rdi,%r11
  add    %r11,%rsi
L5:
  movsd  (%r10),%xmm0
  movsd  (%rsi),%xmm12
  add    %rsi,%rdi
  prefetcht0 (%rsi,%r12,1)
  movsd  0x8(%r10),%xmm1
  movsd  0x10(%r10),%xmm2
  prefetcht0 (%rdi)
  prefetcht0 (%rsi,%rbp,1)
  mulsd  %xmm0,%xmm12
  movsd  0x18(%r10),%xmm3
  prefetcht0 (%rsi,%rbx,1)
  addsd  %xmm12,%xmm10
  movsd  0x20(%rsi),%xmm12
  mulsd  %xmm0,%xmm12
  addsd  %xmm12,%xmm9
  movsd  0x40(%rsi),%xmm12
  mulsd  %xmm0,%xmm12
  addsd  %xmm12,%xmm8
  movsd  0x60(%rsi),%xmm12
  mulsd  %xmm0,%xmm12
  addsd  %xmm12,%xmm7
  movsd  0x80(%rsi),%xmm12
  mulsd  %xmm0,%xmm12
  addsd  %xmm12,%xmm6
  movsd  0xa0(%rsi),%xmm12
  mulsd  %xmm0,%xmm12
  addsd  %xmm5,%xmm12
  movsd  0xc0(%rsi),%xmm5
  mulsd  %xmm0,%xmm5
  mulsd  0xe0(%rsi),%xmm0
  addsd  %xmm4,%xmm5
  movsd  0x28(%rsi),%xmm4
  addsd  %xmm11,%xmm0
  movsd  0x88(%rsi),%xmm11
  mulsd  %xmm1,%xmm4
  mulsd  %xmm1,%xmm11
  addsd  %xmm9,%xmm4
  movsd  0x48(%rsi),%xmm9
  addsd  %xmm6,%xmm11
  movsd  0xc8(%rsi),%xmm6
  mulsd  %xmm1,%xmm9
  mulsd  %xmm1,%xmm6
  addsd  %xmm9,%xmm8
  movsd  0x68(%rsi),%xmm9
  addsd  %xmm5,%xmm6
  movsd  0x50(%rsi),%xmm5
  mulsd  %xmm1,%xmm9
  mulsd  %xmm2,%xmm5
  addsd  %xmm9,%xmm7
  movsd  0xa8(%rsi),%xmm9
  addsd  %xmm8,%xmm5
  movsd  0x90(%rsi),%xmm8
  mulsd  %xmm1,%xmm9
  mulsd  0xe8(%rsi),%xmm1
  mulsd  %xmm2,%xmm8
  addsd  %xmm12,%xmm9
  movsd  0x70(%rsi),%xmm12
  addsd  %xmm1,%xmm0
  movsd  0xd0(%rsi),%xmm1
  mulsd  %xmm2,%xmm12
  addsd  %xmm11,%xmm8
  movsd  0xb8(%rsi),%xmm11
  mulsd  %xmm2,%xmm1
  mulsd  %xmm3,%xmm11
  addsd  %xmm7,%xmm12
  movsd  0xb0(%rsi),%xmm7
  addsd  %xmm6,%xmm1
  movsd  0x78(%rsi),%xmm6
  mulsd  %xmm2,%xmm7
  mulsd  0xf0(%rsi),%xmm2
  mulsd  %xmm3,%xmm6
  addsd  %xmm9,%xmm7
  movsd  0x98(%rsi),%xmm9
  addsd  %xmm0,%xmm2
  mulsd  %xmm3,%xmm9
  addsd  %xmm12,%xmm6
  addsd  %xmm7,%xmm11
  addsd  %xmm8,%xmm9
  movsd  0xd8(%rsi),%xmm8
  movsd  0x80(%rdi),%xmm7
  mulsd  %xmm3,%xmm8
  mulsd  0xf8(%rsi),%xmm3
  addsd  %xmm1,%xmm8
  movsd  0x28(%r10),%xmm1
  addsd  %xmm2,%xmm3
  movsd  0x30(%r10),%xmm2
  movapd %xmm3,%xmm0
  movsd  0x20(%r10),%xmm3
  mulsd  %xmm3,%xmm7
  addsd  %xmm9,%xmm7
  movsd  0xa0(%rdi),%xmm9
  mulsd  %xmm3,%xmm9
  addsd  %xmm11,%xmm9
  movsd  0xc0(%rdi),%xmm11
  mulsd  %xmm3,%xmm11
  mulsd  0xe0(%rdi),%xmm3
  addsd  %xmm8,%xmm11
  movsd  0xa8(%rdi),%xmm8
  addsd  %xmm0,%xmm3
  mulsd  %xmm1,%xmm8
  addsd  %xmm9,%xmm8
  movsd  0xc8(%rdi),%xmm9
  mulsd  %xmm1,%xmm9
  mulsd  0xe8(%rdi),%xmm1
  addsd  %xmm11,%xmm9
  movapd %xmm1,%xmm0
  movsd  0xd0(%rdi),%xmm1
  addsd  %xmm3,%xmm0
  mulsd  %xmm2,%xmm1
  mulsd  0xf0(%rdi),%xmm2
  addsd  %xmm9,%xmm1
  addsd  %xmm0,%xmm2
  movsd  0xf8(%rdi),%xmm0
  mulsd  0x38(%r10),%xmm0
  addsd  %xmm2,%xmm0
  test   %r9d,%r9d
  je     L26
  movsd  (%r8),%xmm15
  movsd  0x8(%r8),%xmm14
  movsd  0x10(%r8),%xmm13
  movsd  0x18(%r8),%xmm12
  movsd  0x20(%r8),%xmm11
  movsd  0x28(%r8),%xmm9
  movsd  0x30(%r8),%xmm3
  movsd  0x38(%r8),%xmm2
  cmp    $0x1,%r9d
  je     L44
  subsd  %xmm10,%xmm15
  subsd  %xmm4,%xmm14
  subsd  %xmm5,%xmm13
  subsd  %xmm6,%xmm12
  subsd  %xmm7,%xmm11
  subsd  %xmm8,%xmm9
  subsd  %xmm1,%xmm3
  subsd  %xmm0,%xmm2
  movapd %xmm15,%xmm10
  movapd %xmm14,%xmm4
  movapd %xmm13,%xmm5
  movapd %xmm12,%xmm6
  movapd %xmm11,%xmm7
  movapd %xmm9,%xmm8
  movapd %xmm3,%xmm1
  movapd %xmm2,%xmm0
L26:
  pop    %rbx
  movsd  %xmm10,(%r8)
  pop    %rbp
  movsd  %xmm4,0x8(%r8)
  pop    %r12
  movsd  %xmm5,0x10(%r8)
  movsd  %xmm6,0x18(%r8)
  movsd  %xmm7,0x20(%r8)
  movsd  %xmm8,0x28(%r8)
  movsd  %xmm1,0x30(%r8)
  movsd  %xmm0,0x38(%r8)
  ret
  nopl   0x0(%rax,%rax,1)
L44:
  addsd  %xmm15,%xmm10
  addsd  %xmm14,%xmm4
  addsd  %xmm13,%xmm5
  addsd  %xmm12,%xmm6
  addsd  %xmm11,%xmm7
  addsd  %xmm9,%xmm8
  addsd  %xmm3,%xmm1
  addsd  %xmm2,%xmm0
  jmp    L26
  nopl   0x0(%rax,%rax,1)
L50:
  pxor   %xmm11,%xmm11
  mov    %rcx,%r10
  movapd %xmm11,%xmm4
  movapd %xmm11,%xmm5
  movapd %xmm11,%xmm6
  movapd %xmm11,%xmm7
  movapd %xmm11,%xmm8
  movapd %xmm11,%xmm9
  movapd %xmm11,%xmm10
  jmp    L5
```

assistant: ```c
void kernel_dtrmv_u_t_8_lib4(int kmax, double *A, int sda, double *x, double *y, int alg) {
  __builtin_prefetch(A);
  __builtin_prefetch(A + 8);
  __builtin_prefetch(A + 16);
  __builtin_prefetch(A + 24);
  const int lda = 4;
  const int bs = 4;
  int k;
  double x_0, x_1, x_2, x_3, y_0 = 0, y_1 = 0, y_2 = 0, y_3 = 0, y_4 = 0, y_5 = 0, y_6 = 0, y_7 = 0;
  k = 0;
  for (; k < kmax - 3; k += 4) {
    __builtin_prefetch(A + sda * bs);
    __builtin_prefetch(A + sda * bs + 8);
    __builtin_prefetch(A + sda * bs + 16);
    __builtin_prefetch(A + sda * bs + 24);
    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[0 + lda * 1] * x_0;
    y_2 += A[0 + lda * 2] * x_0;
    y_3 += A[0 + lda * 3] * x_0;
    y_4 += A[0 + lda * 4] * x_0;
    y_5 += A[0 + lda * 5] * x_0;
    y_6 += A[0 + lda * 6] * x_0;
    y_7 += A[0 + lda * 7] * x_0;
    y_0 += A[1 + lda * 0] * x_1;
    y_1 += A[1 + lda * 1] * x_1;
    y_2 += A[1 + lda * 2] * x_1;
    y_3 += A[1 + lda * 3] * x_1;
    y_4 += A[1 + lda * 4] * x_1;
    y_5 += A[1 + lda * 5] * x_1;
    y_6 += A[1 + lda * 6] * x_1;
    y_7 += A[1 + lda * 7] * x_1;
    y_0 += A[2 + lda * 0] * x_2;
    y_1 += A[2 + lda * 1] * x_2;
    y_2 += A[2 + lda * 2] * x_2;
    y_3 += A[2 + lda * 3] * x_2;
    y_4 += A[2 + lda * 4] * x_2;
    y_5 += A[2 + lda * 5] * x_2;
    y_6 += A[2 + lda * 6] * x_2;
    y_7 += A[2 + lda * 7] * x_2;
    y_0 += A[3 + lda * 0] * x_3;
    y_1 += A[3 + lda * 1] * x_3;
    y_2 += A[3 + lda * 2] * x_3;
    y_3 += A[3 + lda * 3] * x_3;
    y_4 += A[3 + lda * 4] * x_3;
    y_5 += A[3 + lda * 5] * x_3;
    y_6 += A[3 + lda * 6] * x_3;
    y_7 += A[3 + lda * 7] * x_3;
    A += sda * bs;
    x += 4;
  }
  __builtin_prefetch(A + sda * bs);
  __builtin_prefetch(A + sda * bs + 8);
  __builtin_prefetch(A + sda * bs + 16);
  __builtin_prefetch(A + sda * bs + 24);
  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[0 + lda * 1] * x_0;
  y_2 += A[0 + lda * 2] * x_0;
  y_3 += A[0 + lda * 3] * x_0;
  y_4 += A[0 + lda * 4] * x_0;
  y_5 += A[0 + lda * 5] * x_0;
  y_6 += A[0 + lda * 6] * x_0;
  y_7 += A[0 + lda * 7] * x_0;
  y_1 += A[1 + lda * 1] * x_1;
  y_2 += A[1 + lda * 2] * x_1;
  y_3 += A[1 + lda * 3] * x_1;
  y_4 += A[1 + lda * 4] * x_1;
  y_5 += A[1 + lda * 5] * x_1;
  y_6 += A[1 + lda * 6] * x_1;
  y_7 += A[1 + lda * 7] * x_1;
  y_2 += A[2 + lda * 2] * x_2;
  y_3 += A[2 + lda * 3] * x_2;
  y_4 += A[2 + lda * 4] * x_2;
  y_5 += A[2 + lda * 5] * x_2;
  y_6 += A[2 + lda * 6] * x_2;
  y_7 += A[2 + lda * 7] * x_2;
  y_3 += A[3 + lda * 3] * x_3;
  y_4 += A[3 + lda * 4] * x_3;
  y_5 += A[3 + lda * 5] * x_3;
  y_6 += A[3 + lda * 6] * x_3;
  y_7 += A[3 + lda * 7] * x_3;
  A += sda * bs;
  x += 4;
  x_0 = x[0];
  x_1 = x[1];
  x_2 = x[2];
  x_3 = x[3];
  y_4 += A[0 + lda * 4] * x_0;
  y_5 += A[0 + lda * 5] * x_0;
  y_6 += A[0 + lda * 6] * x_0;
  y_7 += A[0 + lda * 7] * x_0;
  y_5 += A[1 + lda * 5] * x_1;
  y_6 += A[1 + lda * 6] * x_1;
  y_7 += A[1 + lda * 7] * x_1;
  y_6 += A[2 + lda * 6] * x_2;
  y_7 += A[2 + lda * 7] * x_2;
  y_7 += A[3 + lda * 7] * x_3;
  if (alg == 0) {
    y[0] = y_0;
    y[1] = y_1;
    y[2] = y_2;
    y[3] = y_3;
    y[4] = y_4;
    y[5] = y_5;
    y[6] = y_6;
    y[7] = y_7;
  } else if (alg == 1) {
    y[0] += y_0;
    y[1] += y_1;
    y[2] += y_2;
    y[3] += y_3;
    y[4] += y_4;
    y[5] += y_5;
    y[6] += y_6;
    y[7] += y_7;
  } else {
    y[0] -= y_0;
    y[1] -= y_1;
    y[2] -= y_2;
    y[3] -= y_3;
    y[4] -= y_4;
    y[5] -= y_5;
    y[6] -= y_6;
    y[7] -= y_7;
  }
}
```