[Bug tree-optimization/18412] New: missed vectorization opportunity

["senor_fjord at yahoo dot com" <gcc-bugzilla at gcc dot gnu dot org>]

I'm not sure if this is a missed case or is just not yet implemented.  I'm using
gcc 4.0.0 20041108 with -O3 -ftree-vectorize -fdump-tree-vect-stats
-march=pentium4 -g -ggdb:

the following *is* vectorizable:
#include <stdio.h>
#include <malloc.h>

void foo(int n, int *x) {
  for (int i = 0; i < n; i++)
    x[i] = 7;
}

int main() {
  int size;
  int *x;
  scanf("%d", &size);
  x = (int *)malloc(sizeof(int) * size);
  foo(size, x); 
  return 0;
}

If I manually inline foo as follows, it is *not* vectorized (number of
iterations cannot be computed).

#include <stdio.h>
#include <malloc.h>

int main() {
  int size;
  int *x;
  scanf("%d", &size);
  x = (int *)malloc(sizeof(int) * size);
  for (int i = 0; i < size; i++)
    x[i] = 7;
  return 0;
}

I'm assuming this is because size has its address taken and throws it off. It
just seems like non-intuitive behavior, particularly since gcc ends up inlining
the vectorized function for the first code fragment anyhow.

-- 
           Summary: missed vectorization opportunity
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: senor_fjord at yahoo dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18412