user: Please show me the C implementation that matches the assembly code listed below:

```asm
<dmatvec2>:
  endbr64
  push   %r15
  mov    %rcx,%r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  mov    %edx,%ebx
  mov    0x40(%rsp),%rcx
  mov    %edx,-0x2c(%rsp)
  mov    0x38(%rsp),%rdx
  mov    %edi,-0x10(%rsp)
  mov    %esi,-0x30(%rsp)
  mov    %r8,-0x28(%rsp)
  mov    %r9,-0x20(%rsp)
  cmp    $0x7,%ebx
  jle    L122
  mov    %esi,%ebp
  lea    -0x8(%rbx),%esi
  movslq %edi,%rax
  mov    %r9,%r10
  mov    %esi,%ebx
  lea    0x0(,%rax,8),%r11
  mov    %rax,%rdi
  mov    %r15,%rsi
  shr    $0x3,%ebx
  shl    $0x6,%rdi
  mov    %r11,%r9
  mov    %r15,-0x8(%rsp)
  mov    %ebx,-0xc(%rsp)
  sub    %rax,%r9
  movslq %ebp,%r14
  mov    %rbx,-0x18(%rsp)
  shl    $0x6,%rbx
  lea    (%r15,%r9,8),%r9
  lea    0x40(%r8,%rbx,1),%rbx
  mov    %rdi,-0x50(%rsp)
  mov    %rax,%rdi
  mov    %rbx,-0x40(%rsp)
  mov    %rax,%rbx
  lea    (%rax,%rax,2),%rax
  shl    $0x5,%rdi
  shl    $0x4,%rbx
  shl    $0x3,%rax
  add    %r15,%rdi
  mov    %r11,%r15
  mov    %rbx,-0x48(%rsp)
  mov    %rax,-0x38(%rsp)
  nopw   0x0(%rax,%rax,1)
L67:
  mov    -0x48(%rsp),%rax
  movsd  (%r8),%xmm5
  lea    (%r15,%rdi,1),%r11
  lea    (%r15,%rsi,1),%r13
  movsd  (%r10),%xmm6
  movsd  0x8(%r8),%xmm7
  lea    (%r15,%r11,1),%rbx
  lea    (%rax,%rsi,1),%r12
  mov    -0x38(%rsp),%rax
  movsd  %xmm5,-0x70(%rsp)
  movsd  0x8(%r10),%xmm5
  movsd  %xmm6,-0x68(%rsp)
  movsd  0x10(%r8),%xmm2
  movsd  0x10(%r10),%xmm3
  lea    (%rsi,%rax,1),%rbp
  mov    -0x30(%rsp),%eax
  movsd  %xmm7,-0x60(%rsp)
  movsd  0x18(%r8),%xmm4
  movsd  %xmm5,-0x58(%rsp)
  movsd  0x20(%r8),%xmm6
  movsd  0x18(%r10),%xmm5
  movsd  0x20(%r10),%xmm7
  movsd  0x28(%r8),%xmm8
  movsd  0x28(%r10),%xmm9
  movsd  0x30(%r8),%xmm10
  movsd  0x30(%r10),%xmm11
  movsd  0x38(%r8),%xmm12
  movsd  0x38(%r10),%xmm13
  test   %eax,%eax
  jle    L86
  xor    %eax,%eax
  nopw   0x0(%rax,%rax,1)
L14:
  movsd  0x0(%r13,%rax,8),%xmm1
  movsd  -0x60(%rsp),%xmm14
  movsd  (%rsi,%rax,8),%xmm0
  movsd  -0x70(%rsp),%xmm15
  mulsd  %xmm1,%xmm14
  mulsd  -0x58(%rsp),%xmm1
  mulsd  %xmm0,%xmm15
  mulsd  -0x68(%rsp),%xmm0
  addsd  (%rdx,%rax,8),%xmm15
  addsd  (%rcx,%rax,8),%xmm0
  addsd  %xmm15,%xmm14
  movapd %xmm2,%xmm15
  addsd  %xmm0,%xmm1
  movsd  (%r12,%rax,8),%xmm0
  mulsd  %xmm0,%xmm15
  mulsd  %xmm3,%xmm0
  addsd  %xmm15,%xmm14
  movapd %xmm4,%xmm15
  addsd  %xmm1,%xmm0
  movsd  0x0(%rbp,%rax,8),%xmm1
  mulsd  %xmm1,%xmm15
  mulsd  %xmm5,%xmm1
  addsd  %xmm15,%xmm14
  movapd %xmm6,%xmm15
  addsd  %xmm0,%xmm1
  movsd  (%rdi,%rax,8),%xmm0
  mulsd  %xmm0,%xmm15
  mulsd  %xmm7,%xmm0
  addsd  %xmm15,%xmm14
  movapd %xmm8,%xmm15
  addsd  %xmm1,%xmm0
  movsd  (%r11,%rax,8),%xmm1
  mulsd  %xmm1,%xmm15
  mulsd  %xmm9,%xmm1
  addsd  %xmm14,%xmm15
  movapd %xmm10,%xmm14
  addsd  %xmm1,%xmm0
  movsd  (%rbx,%rax,8),%xmm1
  mulsd  %xmm1,%xmm14
  mulsd  %xmm11,%xmm1
  addsd  %xmm15,%xmm14
  movapd %xmm12,%xmm15
  addsd  %xmm0,%xmm1
  movsd  (%r9,%rax,8),%xmm0
  mulsd  %xmm0,%xmm15
  mulsd  %xmm13,%xmm0
  addsd  %xmm14,%xmm15
  addsd  %xmm1,%xmm0
  movsd  %xmm15,(%rdx,%rax,8)
  movsd  %xmm0,(%rcx,%rax,8)
  add    $0x1,%rax
  cmp    %rax,%r14
  jne    L14
L86:
  mov    -0x50(%rsp),%rax
  add    $0x40,%r8
  add    $0x40,%r10
  add    %rax,%rsi
  add    %rax,%rdi
  add    %rax,%r9
  cmp    %r8,-0x40(%rsp)
  jne    L67
  mov    -0xc(%rsp),%eax
  mov    -0x8(%rsp),%r15
  lea    0x8(,%rax,8),%eax
  mov    %eax,-0x70(%rsp)
  mov    -0x18(%rsp),%rax
  add    $0x1,%rax
  imul   -0x50(%rsp),%rax
  add    %rax,%r15
L36:
  mov    -0x2c(%rsp),%r10d
  mov    -0x70(%rsp),%r9d
  lea    -0x3(%r10),%eax
  cmp    %r9d,%eax
  jle    L113
  movslq -0x10(%rsp),%r12
  movslq %r9d,%rsi
  mov    -0x28(%rsp),%r8
  mov    %r15,-0x58(%rsp)
  lea    0x0(,%rsi,8),%rbx
  lea    (%r12,%r12,2),%rax
  lea    0x0(,%r12,4),%ebp
  lea    (%r15,%rax,8),%rdi
  lea    -0x4(%r10),%eax
  movslq -0x30(%rsp),%r10
  movslq %ebp,%rbp
  sub    %r9d,%eax
  lea    0x0(,%r12,8),%r14
  lea    (%r8,%rbx,1),%r11
  shl    $0x3,%rbp
  shr    $0x2,%eax
  add    -0x20(%rsp),%rbx
  shl    $0x4,%r12
  mov    %eax,-0x60(%rsp)
  mov    %rax,-0x68(%rsp)
  lea    (%rsi,%rax,4),%rax
  mov    %r15,%rsi
  mov    %r10d,%r15d
  lea    0x20(%r8,%rax,8),%r13
  cs nopw 0x0(%rax,%rax,1)
L121:
  movsd  (%r11),%xmm2
  movsd  (%rbx),%xmm3
  lea    (%r14,%rsi,1),%r9
  lea    (%r12,%rsi,1),%r8
  movsd  0x8(%r11),%xmm4
  movsd  0x8(%rbx),%xmm5
  movsd  0x10(%r11),%xmm6
  movsd  0x10(%rbx),%xmm7
  movsd  0x18(%r11),%xmm8
  movsd  0x18(%rbx),%xmm9
  test   %r15d,%r15d
  jle    L5
  xor    %eax,%eax
  xchg   %ax,%ax
L11:
  movsd  (%rsi,%rax,8),%xmm0
  movapd %xmm2,%xmm11
  movapd %xmm4,%xmm10
  mulsd  %xmm0,%xmm11
  movapd %xmm0,%xmm1
  movsd  (%r9,%rax,8),%xmm0
  mulsd  %xmm3,%xmm1
  addsd  (%rdx,%rax,8),%xmm11
  mulsd  %xmm0,%xmm10
  addsd  (%rcx,%rax,8),%xmm1
  mulsd  %xmm5,%xmm0
  addsd  %xmm11,%xmm10
  movapd %xmm6,%xmm11
  addsd  %xmm0,%xmm1
  movsd  (%r8,%rax,8),%xmm0
  mulsd  %xmm0,%xmm11
  mulsd  %xmm7,%xmm0
  addsd  %xmm10,%xmm11
  movapd %xmm8,%xmm10
  addsd  %xmm0,%xmm1
  movsd  (%rdi,%rax,8),%xmm0
  mulsd  %xmm0,%xmm10
  mulsd  %xmm9,%xmm0
  addsd  %xmm11,%xmm10
  addsd  %xmm1,%xmm0
  movsd  %xmm10,(%rdx,%rax,8)
  movsd  %xmm0,(%rcx,%rax,8)
  add    $0x1,%rax
  cmp    %rax,%r10
  jne    L11
L5:
  add    $0x20,%r11
  add    %rbp,%rsi
  add    $0x20,%rbx
  add    %rbp,%rdi
  cmp    %r11,%r13
  jne    L121
  mov    -0x70(%rsp),%eax
  mov    -0x60(%rsp),%ebx
  mov    -0x58(%rsp),%r15
  lea    0x4(%rax,%rbx,4),%eax
  mov    %eax,-0x70(%rsp)
  mov    -0x68(%rsp),%rax
  add    $0x1,%rax
  imul   %rbp,%rax
  add    %rax,%r15
L113:
  mov    -0x2c(%rsp),%r10d
  mov    -0x70(%rsp),%eax
  cmp    %eax,%r10d
  jle    L1
  movslq -0x10(%rsp),%r8
  movslq -0x30(%rsp),%rsi
  movslq %eax,%rdi
  mov    -0x28(%rsp),%r11
  mov    -0x20(%rsp),%rbx
  shl    $0x3,%r8
  mov    %rsi,%r9
L107:
  movsd  (%r11,%rdi,8),%xmm3
  movsd  (%rbx,%rdi,8),%xmm4
  test   %r9d,%r9d
  jle    L8
  xor    %eax,%eax
  nopl   0x0(%rax,%rax,1)
L53:
  movsd  (%r15,%rax,8),%xmm0
  movapd %xmm3,%xmm1
  movsd  (%rcx,%rax,8),%xmm2
  mulsd  %xmm0,%xmm1
  mulsd  %xmm4,%xmm0
  addsd  (%rdx,%rax,8),%xmm1
  movsd  %xmm1,(%rdx,%rax,8)
  addsd  %xmm2,%xmm0
  movsd  %xmm0,(%rcx,%rax,8)
  add    $0x1,%rax
  cmp    %rax,%rsi
  jne    L53
L8:
  add    $0x1,%rdi
  add    %r8,%r15
  cmp    %edi,%r10d
  jg     L107
L1:
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L122:
  movl   $0x0,-0x70(%rsp)
  jmp    L36
```

assistant: ```c
void dmatvec2(int lda, int m, int n, double *A, double *x0, double *x1, double *y0, double *y1) {
  register double v00, v10, v20, v30, v40, v50, v60, v70, v01, v11, v21, v31, v41, v51, v61, v71;
  register double t0, t1, t2, t3, t4, t5, t6, t7;
  register double f0, f1;
  double *Mki0, *Mki1, *Mki2, *Mki3, *Mki4, *Mki5, *Mki6, *Mki7;
  register int firstcol = 0;
  double *M0;
  int k;
  M0 = &A[0];
  while (firstcol < n - 7) {
    Mki0 = M0;
    Mki1 = Mki0 + lda;
    Mki2 = Mki1 + lda;
    Mki3 = Mki2 + lda;
    Mki4 = Mki3 + lda;
    Mki5 = Mki4 + lda;
    Mki6 = Mki5 + lda;
    Mki7 = Mki6 + lda;
    v00 = x0[firstcol];
    v01 = x1[firstcol++];
    v10 = x0[firstcol];
    v11 = x1[firstcol++];
    v20 = x0[firstcol];
    v21 = x1[firstcol++];
    v30 = x0[firstcol];
    v31 = x1[firstcol++];
    v40 = x0[firstcol];
    v41 = x1[firstcol++];
    v50 = x0[firstcol];
    v51 = x1[firstcol++];
    v60 = x0[firstcol];
    v61 = x1[firstcol++];
    v70 = x0[firstcol];
    v71 = x1[firstcol++];
    for (k = 0; k < m; k++) {
      f0 = y0[k];
      f1 = y1[k];
      t0 = Mki0[k];
      f0 += v00 * t0;
      f1 += v01 * t0;
      t1 = Mki1[k];
      f0 += v10 * t1;
      f1 += v11 * t1;
      t2 = Mki2[k];
      f0 += v20 * t2;
      f1 += v21 * t2;
      t3 = Mki3[k];
      f0 += v30 * t3;
      f1 += v31 * t3;
      t4 = Mki4[k];
      f0 += v40 * t4;
      f1 += v41 * t4;
      t5 = Mki5[k];
      f0 += v50 * t5;
      f1 += v51 * t5;
      t6 = Mki6[k];
      f0 += v60 * t6;
      f1 += v61 * t6;
      t7 = Mki7[k];
      f0 += v70 * t7;
      f1 += v71 * t7;
      y0[k] = f0;
      y1[k] = f1;
    }
    M0 += 8 * lda;
  }
  while (firstcol < n - 3) {
    Mki0 = M0;
    Mki1 = Mki0 + lda;
    Mki2 = Mki1 + lda;
    Mki3 = Mki2 + lda;
    v00 = x0[firstcol];
    v01 = x1[firstcol++];
    v10 = x0[firstcol];
    v11 = x1[firstcol++];
    v20 = x0[firstcol];
    v21 = x1[firstcol++];
    v30 = x0[firstcol];
    v31 = x1[firstcol++];
    for (k = 0; k < m; k++) {
      f0 = y0[k];
      f1 = y1[k];
      t0 = Mki0[k];
      f0 += v00 * t0;
      f1 += v01 * t0;
      t1 = Mki1[k];
      f0 += v10 * t1;
      f1 += v11 * t1;
      t2 = Mki2[k];
      f0 += v20 * t2;
      f1 += v21 * t2;
      t3 = Mki3[k];
      f0 += v30 * t3;
      f1 += v31 * t3;
      y0[k] = f0;
      y1[k] = f1;
    }
    M0 += 4 * lda;
  }
  while (firstcol < n) {
    Mki0 = M0;
    v00 = x0[firstcol];
    v01 = x1[firstcol++];
    for (k = 0; k < m; k++) {
      f0 = y0[k];
      f1 = y1[k];
      t0 = Mki0[k];
      f0 += v00 * t0;
      f1 += v01 * t0;
      y0[k] = f0;
      y1[k] = f1;
    }
    M0 += lda;
  }
}
```