user: Demonstrate the C code that generates the assembly output below:

```asm
<helper_double_8>:
  endbr64
  push   %rbx
  mov    %rdi,%rax
  lea    0x800(%rdi),%rbx
  mov    %rdi,%rdx
  nopw   0x0(%rax,%rax,1)
L8:
  lea    0x20(%rdx),%rcx
  lea    0x40(%rdx),%rsi
  lea    0x60(%rdx),%rdi
  lea    0x80(%rdx),%r8
  lea    0xa0(%rdx),%r9
  lea    0xc0(%rdx),%r10
  lea    0xe0(%rdx),%r11
  vmovupd (%rdx),%ymm0
  vmovupd (%rcx),%ymm1
  vmovupd (%rsi),%ymm2
  vmovupd (%rdi),%ymm3
  vmovupd (%r8),%ymm4
  vmovupd (%r9),%ymm5
  vmovupd (%r10),%ymm6
  vmovupd (%r11),%ymm7
  vpermilpd $0x0,%ymm0,%ymm8
  vpermilpd $0xf,%ymm0,%ymm9
  vxorpd %ymm10,%ymm10,%ymm10
  vsubpd %ymm9,%ymm10,%ymm11
  vaddsubpd %ymm11,%ymm8,%ymm0
  vpermilpd $0x0,%ymm1,%ymm8
  vpermilpd $0xf,%ymm1,%ymm9
  vxorpd %ymm10,%ymm10,%ymm10
  vsubpd %ymm9,%ymm10,%ymm11
  vaddsubpd %ymm11,%ymm8,%ymm1
  vpermilpd $0x0,%ymm2,%ymm8
  vpermilpd $0xf,%ymm2,%ymm9
  vxorpd %ymm10,%ymm10,%ymm10
  vsubpd %ymm9,%ymm10,%ymm11
  vaddsubpd %ymm11,%ymm8,%ymm2
  vpermilpd $0x0,%ymm3,%ymm8
  vpermilpd $0xf,%ymm3,%ymm9
  vxorpd %ymm10,%ymm10,%ymm10
  vsubpd %ymm9,%ymm10,%ymm11
  vaddsubpd %ymm11,%ymm8,%ymm3
  vpermilpd $0x0,%ymm4,%ymm8
  vpermilpd $0xf,%ymm4,%ymm9
  vxorpd %ymm10,%ymm10,%ymm10
  vsubpd %ymm9,%ymm10,%ymm11
  vaddsubpd %ymm11,%ymm8,%ymm4
  vpermilpd $0x0,%ymm5,%ymm8
  vpermilpd $0xf,%ymm5,%ymm9
  vxorpd %ymm10,%ymm10,%ymm10
  vsubpd %ymm9,%ymm10,%ymm11
  vaddsubpd %ymm11,%ymm8,%ymm5
  vpermilpd $0x0,%ymm6,%ymm8
  vpermilpd $0xf,%ymm6,%ymm9
  vxorpd %ymm10,%ymm10,%ymm10
  vsubpd %ymm9,%ymm10,%ymm11
  vaddsubpd %ymm11,%ymm8,%ymm6
  vpermilpd $0x0,%ymm7,%ymm8
  vpermilpd $0xf,%ymm7,%ymm9
  vxorpd %ymm10,%ymm10,%ymm10
  vsubpd %ymm9,%ymm10,%ymm11
  vaddsubpd %ymm11,%ymm8,%ymm7
  vperm2f128 $0x0,%ymm0,%ymm0,%ymm8
  vxorpd %ymm9,%ymm9,%ymm9
  vsubpd %ymm0,%ymm9,%ymm10
  vperm2f128 $0x31,%ymm10,%ymm0,%ymm11
  vaddpd %ymm11,%ymm8,%ymm0
  vperm2f128 $0x0,%ymm1,%ymm1,%ymm8
  vxorpd %ymm9,%ymm9,%ymm9
  vsubpd %ymm1,%ymm9,%ymm10
  vperm2f128 $0x31,%ymm10,%ymm1,%ymm11
  vaddpd %ymm11,%ymm8,%ymm1
  vperm2f128 $0x0,%ymm2,%ymm2,%ymm8
  vxorpd %ymm9,%ymm9,%ymm9
  vsubpd %ymm2,%ymm9,%ymm10
  vperm2f128 $0x31,%ymm10,%ymm2,%ymm11
  vaddpd %ymm11,%ymm8,%ymm2
  vperm2f128 $0x0,%ymm3,%ymm3,%ymm8
  vxorpd %ymm9,%ymm9,%ymm9
  vsubpd %ymm3,%ymm9,%ymm10
  vperm2f128 $0x31,%ymm10,%ymm3,%ymm11
  vaddpd %ymm11,%ymm8,%ymm3
  vperm2f128 $0x0,%ymm4,%ymm4,%ymm8
  vxorpd %ymm9,%ymm9,%ymm9
  vsubpd %ymm4,%ymm9,%ymm10
  vperm2f128 $0x31,%ymm10,%ymm4,%ymm11
  vaddpd %ymm11,%ymm8,%ymm4
  vperm2f128 $0x0,%ymm5,%ymm5,%ymm8
  vxorpd %ymm9,%ymm9,%ymm9
  vsubpd %ymm5,%ymm9,%ymm10
  vperm2f128 $0x31,%ymm10,%ymm5,%ymm11
  vaddpd %ymm11,%ymm8,%ymm5
  vperm2f128 $0x0,%ymm6,%ymm6,%ymm8
  vxorpd %ymm9,%ymm9,%ymm9
  vsubpd %ymm6,%ymm9,%ymm10
  vperm2f128 $0x31,%ymm10,%ymm6,%ymm11
  vaddpd %ymm11,%ymm8,%ymm6
  vperm2f128 $0x0,%ymm7,%ymm7,%ymm8
  vxorpd %ymm9,%ymm9,%ymm9
  vsubpd %ymm7,%ymm9,%ymm10
  vperm2f128 $0x31,%ymm10,%ymm7,%ymm11
  vaddpd %ymm11,%ymm8,%ymm7
  vaddpd %ymm1,%ymm0,%ymm8
  vsubpd %ymm1,%ymm0,%ymm9
  vaddpd %ymm3,%ymm2,%ymm10
  vsubpd %ymm3,%ymm2,%ymm11
  vaddpd %ymm5,%ymm4,%ymm12
  vsubpd %ymm5,%ymm4,%ymm13
  vaddpd %ymm7,%ymm6,%ymm14
  vsubpd %ymm7,%ymm6,%ymm15
  vaddpd %ymm10,%ymm8,%ymm0
  vsubpd %ymm10,%ymm8,%ymm2
  vaddpd %ymm11,%ymm9,%ymm1
  vsubpd %ymm11,%ymm9,%ymm3
  vaddpd %ymm14,%ymm12,%ymm4
  vsubpd %ymm14,%ymm12,%ymm6
  vaddpd %ymm15,%ymm13,%ymm5
  vsubpd %ymm15,%ymm13,%ymm7
  vaddpd %ymm4,%ymm0,%ymm8
  vsubpd %ymm4,%ymm0,%ymm12
  vaddpd %ymm5,%ymm1,%ymm9
  vsubpd %ymm5,%ymm1,%ymm13
  vaddpd %ymm6,%ymm2,%ymm10
  vsubpd %ymm6,%ymm2,%ymm14
  vaddpd %ymm7,%ymm3,%ymm11
  vsubpd %ymm7,%ymm3,%ymm15
  vmovupd %ymm8,(%rdx)
  vmovupd %ymm9,(%rcx)
  vmovupd %ymm10,(%rsi)
  vmovupd %ymm11,(%rdi)
  vmovupd %ymm12,(%r8)
  vmovupd %ymm13,(%r9)
  vmovupd %ymm14,(%r10)
  vmovupd %ymm15,(%r11)
  add    $0x100,%rdx
  cmp    %rdx,%rbx
  jne    L8
  lea    0x100(%rax),%rdx
  mov    %rdx,%r11
  jmp    L17
  nopl   0x0(%rax)
L0:
  lea    0x100(%rax),%rdx
L17:
  lea    0x200(%rax),%rcx
  lea    0x300(%rax),%rsi
  lea    0x400(%rax),%rdi
  lea    0x500(%rax),%r8
  lea    0x600(%rax),%r9
  lea    0x700(%rax),%r10
  vmovupd (%rax),%ymm0
  vmovupd (%rdx),%ymm1
  vmovupd (%rcx),%ymm2
  vmovupd (%rsi),%ymm3
  vmovupd (%rdi),%ymm4
  vmovupd (%r8),%ymm5
  vmovupd (%r9),%ymm6
  vmovupd (%r10),%ymm7
  vaddpd %ymm1,%ymm0,%ymm8
  vsubpd %ymm1,%ymm0,%ymm9
  vaddpd %ymm3,%ymm2,%ymm10
  vsubpd %ymm3,%ymm2,%ymm11
  vaddpd %ymm5,%ymm4,%ymm12
  vsubpd %ymm5,%ymm4,%ymm13
  vaddpd %ymm7,%ymm6,%ymm14
  vsubpd %ymm7,%ymm6,%ymm15
  vaddpd %ymm10,%ymm8,%ymm0
  vsubpd %ymm10,%ymm8,%ymm2
  vaddpd %ymm11,%ymm9,%ymm1
  vsubpd %ymm11,%ymm9,%ymm3
  vaddpd %ymm14,%ymm12,%ymm4
  vsubpd %ymm14,%ymm12,%ymm6
  vaddpd %ymm15,%ymm13,%ymm5
  vsubpd %ymm15,%ymm13,%ymm7
  vaddpd %ymm4,%ymm0,%ymm8
  vsubpd %ymm4,%ymm0,%ymm12
  vaddpd %ymm5,%ymm1,%ymm9
  vsubpd %ymm5,%ymm1,%ymm13
  vaddpd %ymm6,%ymm2,%ymm10
  vsubpd %ymm6,%ymm2,%ymm14
  vaddpd %ymm7,%ymm3,%ymm11
  vsubpd %ymm7,%ymm3,%ymm15
  vmovupd %ymm8,(%rax)
  vmovupd %ymm9,(%rdx)
  vmovupd %ymm10,(%rcx)
  vmovupd %ymm11,(%rsi)
  vmovupd %ymm12,(%rdi)
  vmovupd %ymm13,(%r8)
  vmovupd %ymm14,(%r9)
  vmovupd %ymm15,(%r10)
  add    $0x20,%rax
  cmp    %rax,%r11
  jne    L0
  pop    %rbx
  ret
```

assistant: ```c
void helper_double_8(double *buf) {
  for (int j = 0; j < 256; j += 32) {
    for (int k = 0; k < 4; k += 4) {
      __asm__ volatile("vmovupd (%0), %%ymm0\n"
                       "vmovupd (%1), %%ymm1\n"
                       "vmovupd (%2), %%ymm2\n"
                       "vmovupd (%3), %%ymm3\n"
                       "vmovupd (%4), %%ymm4\n"
                       "vmovupd (%5), %%ymm5\n"
                       "vmovupd (%6), %%ymm6\n"
                       "vmovupd (%7), %%ymm7\n"
                       "vpermilpd $0, %%ymm0, %%ymm8\n"
                       "vpermilpd $15, %%ymm0, %%ymm9\n"
                       "vxorpd %%ymm10, %%ymm10, %%ymm10\n"
                       "vsubpd %%ymm9, %%ymm10, %%ymm11\n"
                       "vaddsubpd %%ymm11, %%ymm8, %%ymm0\n"
                       "vpermilpd $0, %%ymm1, %%ymm8\n"
                       "vpermilpd $15, %%ymm1, %%ymm9\n"
                       "vxorpd %%ymm10, %%ymm10, %%ymm10\n"
                       "vsubpd %%ymm9, %%ymm10, %%ymm11\n"
                       "vaddsubpd %%ymm11, %%ymm8, %%ymm1\n"
                       "vpermilpd $0, %%ymm2, %%ymm8\n"
                       "vpermilpd $15, %%ymm2, %%ymm9\n"
                       "vxorpd %%ymm10, %%ymm10, %%ymm10\n"
                       "vsubpd %%ymm9, %%ymm10, %%ymm11\n"
                       "vaddsubpd %%ymm11, %%ymm8, %%ymm2\n"
                       "vpermilpd $0, %%ymm3, %%ymm8\n"
                       "vpermilpd $15, %%ymm3, %%ymm9\n"
                       "vxorpd %%ymm10, %%ymm10, %%ymm10\n"
                       "vsubpd %%ymm9, %%ymm10, %%ymm11\n"
                       "vaddsubpd %%ymm11, %%ymm8, %%ymm3\n"
                       "vpermilpd $0, %%ymm4, %%ymm8\n"
                       "vpermilpd $15, %%ymm4, %%ymm9\n"
                       "vxorpd %%ymm10, %%ymm10, %%ymm10\n"
                       "vsubpd %%ymm9, %%ymm10, %%ymm11\n"
                       "vaddsubpd %%ymm11, %%ymm8, %%ymm4\n"
                       "vpermilpd $0, %%ymm5, %%ymm8\n"
                       "vpermilpd $15, %%ymm5, %%ymm9\n"
                       "vxorpd %%ymm10, %%ymm10, %%ymm10\n"
                       "vsubpd %%ymm9, %%ymm10, %%ymm11\n"
                       "vaddsubpd %%ymm11, %%ymm8, %%ymm5\n"
                       "vpermilpd $0, %%ymm6, %%ymm8\n"
                       "vpermilpd $15, %%ymm6, %%ymm9\n"
                       "vxorpd %%ymm10, %%ymm10, %%ymm10\n"
                       "vsubpd %%ymm9, %%ymm10, %%ymm11\n"
                       "vaddsubpd %%ymm11, %%ymm8, %%ymm6\n"
                       "vpermilpd $0, %%ymm7, %%ymm8\n"
                       "vpermilpd $15, %%ymm7, %%ymm9\n"
                       "vxorpd %%ymm10, %%ymm10, %%ymm10\n"
                       "vsubpd %%ymm9, %%ymm10, %%ymm11\n"
                       "vaddsubpd %%ymm11, %%ymm8, %%ymm7\n"
                       "vperm2f128 $0, %%ymm0, %%ymm0, %%ymm8\n"
                       "vxorpd %%ymm9, %%ymm9, %%ymm9\n"
                       "vsubpd %%ymm0, %%ymm9, %%ymm10\n"
                       "vperm2f128 $49, %%ymm10, %%ymm0, %%ymm11\n"
                       "vaddpd %%ymm11, %%ymm8, %%ymm0\n"
                       "vperm2f128 $0, %%ymm1, %%ymm1, %%ymm8\n"
                       "vxorpd %%ymm9, %%ymm9, %%ymm9\n"
                       "vsubpd %%ymm1, %%ymm9, %%ymm10\n"
                       "vperm2f128 $49, %%ymm10, %%ymm1, %%ymm11\n"
                       "vaddpd %%ymm11, %%ymm8, %%ymm1\n"
                       "vperm2f128 $0, %%ymm2, %%ymm2, %%ymm8\n"
                       "vxorpd %%ymm9, %%ymm9, %%ymm9\n"
                       "vsubpd %%ymm2, %%ymm9, %%ymm10\n"
                       "vperm2f128 $49, %%ymm10, %%ymm2, %%ymm11\n"
                       "vaddpd %%ymm11, %%ymm8, %%ymm2\n"
                       "vperm2f128 $0, %%ymm3, %%ymm3, %%ymm8\n"
                       "vxorpd %%ymm9, %%ymm9, %%ymm9\n"
                       "vsubpd %%ymm3, %%ymm9, %%ymm10\n"
                       "vperm2f128 $49, %%ymm10, %%ymm3, %%ymm11\n"
                       "vaddpd %%ymm11, %%ymm8, %%ymm3\n"
                       "vperm2f128 $0, %%ymm4, %%ymm4, %%ymm8\n"
                       "vxorpd %%ymm9, %%ymm9, %%ymm9\n"
                       "vsubpd %%ymm4, %%ymm9, %%ymm10\n"
                       "vperm2f128 $49, %%ymm10, %%ymm4, %%ymm11\n"
                       "vaddpd %%ymm11, %%ymm8, %%ymm4\n"
                       "vperm2f128 $0, %%ymm5, %%ymm5, %%ymm8\n"
                       "vxorpd %%ymm9, %%ymm9, %%ymm9\n"
                       "vsubpd %%ymm5, %%ymm9, %%ymm10\n"
                       "vperm2f128 $49, %%ymm10, %%ymm5, %%ymm11\n"
                       "vaddpd %%ymm11, %%ymm8, %%ymm5\n"
                       "vperm2f128 $0, %%ymm6, %%ymm6, %%ymm8\n"
                       "vxorpd %%ymm9, %%ymm9, %%ymm9\n"
                       "vsubpd %%ymm6, %%ymm9, %%ymm10\n"
                       "vperm2f128 $49, %%ymm10, %%ymm6, %%ymm11\n"
                       "vaddpd %%ymm11, %%ymm8, %%ymm6\n"
                       "vperm2f128 $0, %%ymm7, %%ymm7, %%ymm8\n"
                       "vxorpd %%ymm9, %%ymm9, %%ymm9\n"
                       "vsubpd %%ymm7, %%ymm9, %%ymm10\n"
                       "vperm2f128 $49, %%ymm10, %%ymm7, %%ymm11\n"
                       "vaddpd %%ymm11, %%ymm8, %%ymm7\n"
                       "vaddpd %%ymm1, %%ymm0, %%ymm8\n"
                       "vsubpd %%ymm1, %%ymm0, %%ymm9\n"
                       "vaddpd %%ymm3, %%ymm2, %%ymm10\n"
                       "vsubpd %%ymm3, %%ymm2, %%ymm11\n"
                       "vaddpd %%ymm5, %%ymm4, %%ymm12\n"
                       "vsubpd %%ymm5, %%ymm4, %%ymm13\n"
                       "vaddpd %%ymm7, %%ymm6, %%ymm14\n"
                       "vsubpd %%ymm7, %%ymm6, %%ymm15\n"
                       "vaddpd %%ymm10, %%ymm8, %%ymm0\n"
                       "vsubpd %%ymm10, %%ymm8, %%ymm2\n"
                       "vaddpd %%ymm11, %%ymm9, %%ymm1\n"
                       "vsubpd %%ymm11, %%ymm9, %%ymm3\n"
                       "vaddpd %%ymm14, %%ymm12, %%ymm4\n"
                       "vsubpd %%ymm14, %%ymm12, %%ymm6\n"
                       "vaddpd %%ymm15, %%ymm13, %%ymm5\n"
                       "vsubpd %%ymm15, %%ymm13, %%ymm7\n"
                       "vaddpd %%ymm4, %%ymm0, %%ymm8\n"
                       "vsubpd %%ymm4, %%ymm0, %%ymm12\n"
                       "vaddpd %%ymm5, %%ymm1, %%ymm9\n"
                       "vsubpd %%ymm5, %%ymm1, %%ymm13\n"
                       "vaddpd %%ymm6, %%ymm2, %%ymm10\n"
                       "vsubpd %%ymm6, %%ymm2, %%ymm14\n"
                       "vaddpd %%ymm7, %%ymm3, %%ymm11\n"
                       "vsubpd %%ymm7, %%ymm3, %%ymm15\n"
                       "vmovupd %%ymm8, (%0)\n"
                       "vmovupd %%ymm9, (%1)\n"
                       "vmovupd %%ymm10, (%2)\n"
                       "vmovupd %%ymm11, (%3)\n"
                       "vmovupd %%ymm12, (%4)\n"
                       "vmovupd %%ymm13, (%5)\n"
                       "vmovupd %%ymm14, (%6)\n"
                       "vmovupd %%ymm15, (%7)\n" ::"r"(buf + j + k + 0),
                       "r"(buf + j + k + 4), "r"(buf + j + k + 8), "r"(buf + j + k + 12), "r"(buf + j + k + 16), "r"(buf + j + k + 20), "r"(buf + j + k + 24), "r"(buf + j + k + 28)
                       : "%ymm0", "%ymm1", "%ymm2", "%ymm3", "%ymm4", "%ymm5", "%ymm6", "%ymm7", "%ymm8", "%ymm9", "%ymm10", "%ymm11", "%ymm12", "%ymm13", "%ymm14", "%ymm15", "memory");
    }
  }
  for (int j = 0; j < 256; j += 256) {
    for (int k = 0; k < 32; k += 4) {
      __asm__ volatile("vmovupd (%0), %%ymm0\n"
                       "vmovupd (%1), %%ymm1\n"
                       "vmovupd (%2), %%ymm2\n"
                       "vmovupd (%3), %%ymm3\n"
                       "vmovupd (%4), %%ymm4\n"
                       "vmovupd (%5), %%ymm5\n"
                       "vmovupd (%6), %%ymm6\n"
                       "vmovupd (%7), %%ymm7\n"
                       "vaddpd %%ymm1, %%ymm0, %%ymm8\n"
                       "vsubpd %%ymm1, %%ymm0, %%ymm9\n"
                       "vaddpd %%ymm3, %%ymm2, %%ymm10\n"
                       "vsubpd %%ymm3, %%ymm2, %%ymm11\n"
                       "vaddpd %%ymm5, %%ymm4, %%ymm12\n"
                       "vsubpd %%ymm5, %%ymm4, %%ymm13\n"
                       "vaddpd %%ymm7, %%ymm6, %%ymm14\n"
                       "vsubpd %%ymm7, %%ymm6, %%ymm15\n"
                       "vaddpd %%ymm10, %%ymm8, %%ymm0\n"
                       "vsubpd %%ymm10, %%ymm8, %%ymm2\n"
                       "vaddpd %%ymm11, %%ymm9, %%ymm1\n"
                       "vsubpd %%ymm11, %%ymm9, %%ymm3\n"
                       "vaddpd %%ymm14, %%ymm12, %%ymm4\n"
                       "vsubpd %%ymm14, %%ymm12, %%ymm6\n"
                       "vaddpd %%ymm15, %%ymm13, %%ymm5\n"
                       "vsubpd %%ymm15, %%ymm13, %%ymm7\n"
                       "vaddpd %%ymm4, %%ymm0, %%ymm8\n"
                       "vsubpd %%ymm4, %%ymm0, %%ymm12\n"
                       "vaddpd %%ymm5, %%ymm1, %%ymm9\n"
                       "vsubpd %%ymm5, %%ymm1, %%ymm13\n"
                       "vaddpd %%ymm6, %%ymm2, %%ymm10\n"
                       "vsubpd %%ymm6, %%ymm2, %%ymm14\n"
                       "vaddpd %%ymm7, %%ymm3, %%ymm11\n"
                       "vsubpd %%ymm7, %%ymm3, %%ymm15\n"
                       "vmovupd %%ymm8, (%0)\n"
                       "vmovupd %%ymm9, (%1)\n"
                       "vmovupd %%ymm10, (%2)\n"
                       "vmovupd %%ymm11, (%3)\n"
                       "vmovupd %%ymm12, (%4)\n"
                       "vmovupd %%ymm13, (%5)\n"
                       "vmovupd %%ymm14, (%6)\n"
                       "vmovupd %%ymm15, (%7)\n" ::"r"(buf + j + k + 0),
                       "r"(buf + j + k + 32), "r"(buf + j + k + 64), "r"(buf + j + k + 96), "r"(buf + j + k + 128), "r"(buf + j + k + 160), "r"(buf + j + k + 192), "r"(buf + j + k + 224)
                       : "%ymm0", "%ymm1", "%ymm2", "%ymm3", "%ymm4", "%ymm5", "%ymm6", "%ymm7", "%ymm8", "%ymm9", "%ymm10", "%ymm11", "%ymm12", "%ymm13", "%ymm14", "%ymm15", "memory");
    }
  }
}
```