[Bug target/79177] use the register keyword with ymm0 register

[alexander.kjall at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79177

--- Comment #3 from Alexander Kjäll <alexander.kjall at gmail dot com> ---
I wrote a small testcase that reproduced the structure of the error, with just
some dummy asm:

#include <immintrin.h>

int main() {
  __m256 _YMM0;
  register int p1 asm ("r12") = 1;
  //register int p2 asm ("r13") = 2;
  register __m256 p2 asm ("ymm0") = _YMM0;
  register int result asm ("rax");
  asm ("CLI" : "=r" (result) : "0" (p1), "r" (p2));
}