[Bug target/114676] [12/13/14 Regression] DSE removes assignment that is used later

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114676

--- Comment #13 from Andreas Krebbel <krebbel at gcc dot gnu.org> ---
We will go and fix PyTorch instead. Although it is not clearly documented, the
way PyTorch uses the builtin right now is probably not what was intended. It is
pretty clear that the element type pointer needs to alias vectors of the same
element type, but there is no saying about aliasing everything.

I'm just wondering how to improve the diagnostics in our backend to catch this.
The example below is similar to what PyTorch does today. Casting mem to
(float*) prevents our builtin code from complaining about the type mismatch and
by that opens the door for the much harder to debug TBAA problem.

#include <vecintrin.h>

void __attribute__((noinline)) foo (int *mem)
{
  vec_xst ((vector float){ 1.0f, 2.0f, 3.0f, 4.0f }, 0, (float*)mem);
}

int
main ()
{
  int m[4] = { 0 };
  foo (m);
  if (m[3] == 0)
    __builtin_abort ();
  return 0;
}