[Bug target/54703] New: [miscompilation] _mm_sub_pd is incorrectly substituted with vandnps

[kretz at kde dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54703

             Bug #: 54703
           Summary: [miscompilation] _mm_sub_pd is incorrectly substituted
                    with vandnps
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: kretz@kde.org


The following testcase:

#include <xmmintrin.h>
__attribute__((aligned(16))) static const unsigned long long mask[2] = {
0xffffffffff000000ull, 0xffffffffff000000ull };
inline __m128d foo(__m128d v1) {
    const __m128d h1 = _mm_and_pd(v1, _mm_load_pd(reinterpret_cast<const double
*>(&mask)));
    const __m128d l1 = _mm_sub_pd(v1, h1);
    return _mm_mul_pd(h1, l1);
}
__m128d test() {
    __m128d a = _mm_set1_pd(2.);
    return foo(foo(a));
}

compiles to

        .cfi_startproc
        vmovaps _ZL4mask(%rip), %xmm0
        vandps  .LC0(%rip), %xmm0, %xmm2
        vandnps .LC0(%rip), %xmm0, %xmm1
        vmulpd  %xmm1, %xmm2, %xmm1
        vandps  %xmm0, %xmm1, %xmm0
        vsubpd  %xmm0, %xmm1, %xmm1
        vmulpd  %xmm1, %xmm0, %xmm0
        ret
        .cfi_endproc

The second foo call is correct: vandps and vsubpd are used. But the first call
uses vandps and vandnps. This pattern would be correct for integers, but is
obviously wrong for floating point numbers.