[Bug tree-optimization/16913] [3.5 Regression] restrict does not make a different

["zhangjie at magima dot com dot cn" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From zhangjie at magima dot com dot cn  2004-08-18 03:33 -------
I'm investigating this. It seems that gcc failed to get the correct alias set
for b[j+N/4]. Current get_alias_set () uses find_base_decl () to find the base
pointer that the address pointer expression depends on. But when the pointer
expression has been gimplified, find_base_decl () cannot follow the ud chains to
find the true base pointer. My initial thought is replace find_base_decl with
something that can walk ud chains to find the true base pointer.

And When I looked tts t04.generic dump

foo (a, b, n, j)
{
  unsigned int i.0;
  unsigned int T.1;
  float * restrict T.2;
  float * restrict T.3;
  unsigned int j.4;
  unsigned int T.5;
  float * restrict T.6;
  float * restrict T.7;
  float * restrict T.8;
  float T.9;
  float * restrict T.10;
  float T.11;
  float T.12;
  float T.13;
  int i;

  i = 0;
  goto <D1042>;
  <D1041>:;
  i.0 = (unsigned int)i;
  T.1 = i.0 * 4;
  T.2 = (float * restrict)T.1;
  T.3 = T.2 + a;
  j.4 = (unsigned int)j;
  T.5 = j.4 * 4;
  T.6 = (float * restrict)T.5;
  T.7 = T.6 + b;
  T.8 = T.7 + 200B;
  T.9 = *T.8;
  j.4 = (unsigned int)j;
  T.5 = j.4 * 4;
  T.6 = (float * restrict)T.5;
  T.7 = T.6 + b;
  T.10 = T.7 - 200B;
  T.11 = *T.10;
  T.12 = T.9 + T.11;
  T.13 = T.12 * 5.0e-1;
  *T.3 = T.13;
  i = i + 1;
  <D1042>:;
  if (i < n)
    {
      goto <D1041>;
    }
  else
    {
      goto <D1043>;
    }
  <D1043>:;
}

I found it was rather weird that "T.1" was first cast to (float * restrict)
before it was added with "a". I think it's  better to directly add the index to
"a" without the cast. I asked this on the gcc mailing list with a simpler case
<http://gcc.gnu.org/ml/gcc/2004-08/msg00700.html>.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16913