http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57156
Bug #: 57156
Summary: miscompilation of call to _mm_cmpeq_epi8(a, a) or
_mm_comtrue_epu8(a, a) with uninitialized a
Classification: Unclassified
Product: gcc
Version: 4.8.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: [email protected]
ReportedBy: [email protected]
Testcase:
#include <x86intrin.h>
static inline __m128 allone() {
__m128i a;
#ifdef __XOP__
return _mm_castsi128_ps(_mm_comtrue_epu8(a, a));
#else
return _mm_castsi128_ps(_mm_cmpeq_epi8(a, a));
#endif
}
struct X {
explicit X() : k(allone()) {}
explicit X(bool b) : k(b ? allone() : _mm_setzero_ps()) {}
bool operator!=(const X &rhs) const { return _mm_movemask_ps(k) !=
_mm_movemask_ps(rhs.k); }
__m128 k;
};
int main() {
if (X() != X(true)) {
__builtin_abort();
}
return 0;
}
Compile with "g++ -O1 -msse2" or "g++ -O1 -mxop". If you initialize 'a' with
_mm_setzero_si128() the problem disappears.
