[Bug tree-optimization/87914] New: gcc fails to vectorize bitreverse code

[hoganmeier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87914

            Bug ID: 87914
           Summary: gcc fails to vectorize bitreverse code
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hoganmeier at gmail dot com
  Target Milestone: ---

$ gcc -fopenmp-simd -O3 -march=haswell -fopt-info-vec-omp-optimized-missed

template <typename T>
T reverseBits(T x)
{
        unsigned int s = sizeof(x) * 8;
        T mask = ~T(0);
        while ((s >>= 1) > 0)
        {
                mask ^= (mask << s);
                x = ((x >> s) & mask) | ((x << s) & ~mask); // unsupported use
in stmt
        }
    return x;
}

void test_reverseBits(unsigned* x)
{
    #pragma omp simd aligned(x:32)
    for (int i = 0; i < 16; ++i)
        x[i] = reverseBits(x[i]); // couldn't vectorize loop
}

clang and icc vectorize this:
https://godbolt.org/z/ROJZGZ