[Bug tree-optimization/21465] New: autovectorisation conflicts with -ffast-math

["micis at gmx dot de" <gcc-bugzilla at gcc dot gnu dot org>]

Consider the following short function:

    void Tst1(float* __restrict__ SrcP, float* __restrict__ DstP, int Len)
    {
        for (int x=0; x<Len; x++)
        {
            DstP[x] = SrcP[x] * SrcP[x];
        }
    }

If this function is compiled with:
    g++41 -O -S TstPow.cpp -ftree-vectorizer-verbose=5  -ftree-vectorize
it is vectorized, but if you compile with:
    g++41 -O -ffast-math -S TstPow.cpp -ftree-vectorizer-verbose=5
    -ftree-vectorize
it is not with the following output:

note: Vectorizing an unaligned access.
note: Alignment of access forced using peeling.
note: not vectorized: stmt not supported: D.2052_15 = __builtin_powf 
(D.2051_14, 2.0e+0)
note: vectorized 0 loops in function.


Michael Cieslinski

-- 
           Summary: autovectorisation conflicts with -ffast-math
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: micis at gmx dot de
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: x86_64-unknown-linux-gnu
  GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21465