[Bug tree-optimization/41898] GCC ignores restrict on array

[Bug tree-optimization/41898] GCC ignores restrict on array

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=41898

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Possibly related (implementation-wise) are ideas to handle array element
contents field-sensitive but not elements, thus have for

T p[10];

fields for members of 'T' but re-use the appropriate member for each
array element of 'p'.  This would support doing field-sensitive
analysis for allocated storage and varinfo fields would "wrap around"
the full variables size.  One conservative subfield allocation
strathegy for allocated storage is N pointers aligned to pointer
alignment.

[Bug tree-optimization/41898] GCC ignores restrict on array

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2009-11-01 21:00 -------
It works with

int * __restrict__ a;
int * __restrict__ b;

extern void link_error (void);

int main()
{
  a[0] = 0;
  b[0] = 1;
  if (a[0] != 0)
    link_error ();
  return 0;
}


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41898

[Bug tree-optimization/41898] GCC ignores restrict on array

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2009-11-01 20:59 -------
Without __restrict__ we don't optimize the call to link_error either.  Because
the stores may alias - they are only redundant because of the identical
RHS.  See PR23094 for that missed optimization.

But restrict indeed doesn't help here.  Testcase that can be optimized
only because of restrict:

int * __restrict__ a[1];
int * __restrict__ b[1];

extern void link_error (void);

int main()
{
  a[0][0] = 0;
  b[0][0] = 1;
  if (a[0][0] != 0)
    link_error ();
  return 0;
}


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2009-11-01 20:59:25
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41898