[Bug tree-optimization/18438] New: vectorizer failed for vector matrix multiplication

["giovannibajo at libero dot it" <gcc-bugzilla at gcc dot gnu dot org>]

Vectorizer fails to handle this:


------------------------------------------------------------
#define NUMPOINTS 50000

#define align(x) __attribute__((align(x)))

typedef float align(16) MATRIX[3][3];

static float points[NUMPOINTS][4];
static align(16) float opoints[NUMPOINTS][4];
static bool flags[NUMPOINTS];
static MATRIX gmatrix;


void RotateVectors (void)
{
  int i, r;

  for (r = 0; r < 4; r++)
  {
    for (i = 0; i < NUMPOINTS; i++)
    {
      opoints[i][0] =     gmatrix[0][0] * points[i][0]
                        + gmatrix[0][1] * points[i][1]
                        + gmatrix[0][2] * points[i][2];
      opoints[i][1] =     gmatrix[1][0] * points[i][0]
                        + gmatrix[1][1] * points[i][1]
                        + gmatrix[1][2] * points[i][2];
      opoints[i][2] =     gmatrix[2][0] * points[i][0]
                        + gmatrix[2][1] * points[i][1]
                        + gmatrix[2][2] * points[i][2];
      flags[i] = true;
    }
  }
}
------------------------------------------------------------
loop at bench.cc:52: not vectorized: complicated access pattern.
loop at bench.cc:52: bad data access.

-- 
           Summary: vectorizer failed for vector matrix multiplication
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: giovannibajo at libero dot it
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18438