[Bug tree-optimization/98856] [11 Regression] botan AES-128/XTS is slower by ~17% since r11-6649-g285fa338b06b804e72997c4d876ecf08a9c083af

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98856

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
The following testcase reproduces the assembly:

typedef __UINT64_TYPE__ uint64_t;
void poly_double_le2 (unsigned char *out, const unsigned char *in)
{
  uint64_t W[2];

  __builtin_memcpy (&W, in, 16);
  uint64_t carry = (W[1] >> 63) * 135;
  W[1] = (W[1] << 1) ^ (W[0] >> 63);
  W[0] = (W[0] << 1) ^ carry;
  __builtin_memcpy (out, &W[0], 8);
  __builtin_memcpy (out + 8, &W[1], 8);
}