[Bug target/85077] New: V[248][SD]F abs not optimized to

[kretz at kde dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85077

            Bug ID: 85077
           Summary: V[248][SD]F abs not optimized to
           Product: gcc
           Version: 8.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kretz at kde dot org
  Target Milestone: ---

The following test case (also at https://godbolt.org/g/XEPk7M) shows that `x <
0 ? -x : x` is not optimized to an efficient abs implementation. This is not
only the case for SSE, but also for AVX and AVX512 vectors.

The my_abs functions show what I'd expect the result to be.

#include <x86intrin.h>

template <class T, int N> using V [[gnu::vector_size(N)]] = T;

auto abs(V<float, 16> x) { return x < 0 ? -x : x; }
auto my_abs(V<float, 16> x) {
    return _mm_and_ps((__m128)(~V<unsigned, 16>() >> 1), x);
}

auto abs(V<double, 16> x) { return x < 0 ? -x : x; }
auto my_abs(V<double, 16> x) {
    return _mm_and_pd((__m128d)(~V<unsigned long long, 16>() >> 1), x);
}