[Bug tree-optimization/43433] New: Missed vectorization: "complicated access pattern" for increasing and decreasing data indexing

[Bug tree-optimization/43433] New: Missed vectorization: "complicated access pattern" for increasing and decreasing data indexing

[spop at gcc dot gnu dot org]

Both these loop kernels from FFmpeg fail with:
gcc-4.5 -c vector_fmul_window.c -O3 -ffast-math -ftree-vectorizer-verbose=7
-msse2
[...]
vector_fmul_window.c:7: note: not vectorized: complicated access pattern.

They look similar in the fact that they use both an increasing and a decreasing
induction variables indexing data references.

void vector_fmul_reverse_c(float *dst, const float *src0, const float *src1,
int len){
    int i;
    src1 += len-1;
    for(i=0; i<len; i++)
        dst[i] = src0[i] * src1[-i];
}

void ff_vector_fmul_window_c(float *dst, const float *src0, const float *src1,
const float *win, float add_bias, int len)
{
  int i,j;
  dst += len;
  win += len;
  src0+= len;
  for(i=-len, j=len-1; i<0; i++, j--) {
    float s0 = src0[i];
    float s1 = src1[j];
    float wi = win[i];
    float wj = win[j];
    dst[i] = s0*wj - s1*wi + add_bias;
    dst[j] = s0*wi + s1*wj + add_bias;
  }
}


-- 
           Summary: Missed vectorization: "complicated access pattern" for
                    increasing and decreasing data indexing
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: spop at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43433

[Bug tree-optimization/43433] Missed vectorization: "complicated access pattern" for increasing and decreasing data indexing

[spop at gcc dot gnu dot org]

------- Comment #1 from spop at gcc dot gnu dot org  2010-03-18 21:08 -------
Duplicated of PR43432: pressed "commit bug" twice.

*** This bug has been marked as a duplicate of 43432 ***


-- 

spop at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE
            Summary|Missed vectorization:       |Missed vectorization:
                   |"complicated access pattern"|"complicated access pattern"
                   |for increasing and          |for increasing and
                   |decreasing data indexing    |decreasing data indexing


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43433