https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84907
Bug ID: 84907
Summary: [8 Regression] ppc64le gromacs miscompilation since
r256656
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: jakub at gcc dot gnu.org
Target Milestone: ---
typedef float V __attribute__((altivec(vector__)));
struct SimdFloatTag {};
struct SimdFloat
{
SimdFloat () {}
SimdFloat (float f) : simdInternal_(__builtin_vec_splats (f)) {}
SimdFloat (V simd) : simdInternal_(simd) {}
V simdInternal_;
};
template <typename T>
struct SimdTraits {};
template <>
struct SimdTraits <SimdFloat>
{
using type = float;
static constexpr int width = 4;
using tag = SimdFloatTag;
};
static inline SimdFloat
simdLoad (const float *m, SimdFloatTag = {})
{
return { *reinterpret_cast <const V *>(m) };
}
static inline SimdFloat
simdLoadU (const float *m, SimdFloatTag = {})
{
return { *reinterpret_cast <const V *>(m) };
}
static inline void
store (float *m, SimdFloat a)
{
*reinterpret_cast <V *>(m) = a.simdInternal_;
}
template <typename T>
static inline T
load (const typename SimdTraits <T>::type *m)
{
return simdLoad (m, typename SimdTraits <T>::tag ());
}
template <typename T>
static inline T
loadU (const typename SimdTraits <T>::type *m)
{
return simdLoadU (m, typename SimdTraits <T>::tag ());
}
template <typename T, typename TSimd, int simdWidth> void
loadStoreTester (TSimd loadFn (const T *mem), void storeFn (T *mem, TSimd),
const int loadOffset, const int storeOffset)
{
alignas(16) T src[simdWidth * 4];
alignas(16) T dst[simdWidth * 4];
T *pCopySrc = src + simdWidth + loadOffset;
T *pCopyDst = dst + simdWidth + storeOffset;
int i;
for (i = 0; i < simdWidth * 4; i++)
{
src[i] = 1 + i;
dst[i] = -1 - i;
}
storeFn (pCopyDst, loadFn (pCopySrc));
for (i = 0; i < simdWidth; i++)
if (pCopySrc[i] != pCopyDst[i]) __builtin_abort ();
for (i = 0; i < simdWidth*4; i++)
{
if (src[i] != (T) (1 + i)) __builtin_abort ();
if (dst + i < pCopyDst || dst + i >= pCopyDst + simdWidth)
if (dst[i] != (T) (-1 - i)) __builtin_abort ();
}
}
template <typename T, typename TSimd> TSimd
loadWrapper (const T *m) { return load <TSimd> (m); }
template <typename T, typename TSimd> TSimd
loadUWrapper (const T *m) { return loadU <TSimd> (m); }
int
main ()
{
loadStoreTester <float, SimdFloat, 4> (loadWrapper, store, 0, 0);
for (int i = 0; i < 4; i++)
loadStoreTester <float, SimdFloat, 4> (loadUWrapper, store, i, 0);
}
aborts starting with r256656 on powerpc64le-linux with
-O2 -m64 -mcpu=power8 -mtune=power8 -mvsx -std=c++11, reduced from
gromacs-2018/src/gromacs/simd/tests/bootstrap_loadstore.cpp
Not really sure if it isn't a gromacs bug, i.e. whether
gromacs-2018/src/gromacs/simd/impl_ibm_vsx/impl_ibm_vsx_simd_float.h
static inline SimdFloat gmx_simdcall
simdLoadU(const float *m, SimdFloatTag = {})
{
return {
*reinterpret_cast<const __vector float *>(m)
};
}
is actually well defined unaligned load (if aligned to __alignof__(float), but
not __alignof__(__vector float)). If not, the gromacs folks should be told.
