https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85466
--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #5)
> I see sth like
>
> template<typename _RealType, size_t __bits,
> typename _UniformRandomNumberGenerator>
> _RealType
> generate_canonical(_UniformRandomNumberGenerator& __urng)
> {
> ...
> __ret = std::nextafter(_RealType(1), _RealType(0));
>
> instantiated as
>
> _RealType std::generate_canonical(_UniformRandomNumberGenerator&) [with
> _RealType = double; long unsigned int __bits = 53;
> _UniformRandomNumberGenerator = std::mersenne_twister_engine<long unsigned
> int, 32, 624, 397, 31, 2567483615, 11, 4294967295, 7, 2636928640, 15,
> 4022730752, 18, 1812433253>] (struct mersenne_twister_engine & __urng)
> {
> ...
> const long double __r;
> ^^^
> (but that's unused it seems)
> ...
> __ret = nextafter (1.0e+0, 0.0);
>
> and cmath containing
>
> constexpr float
> nextafter(float __x, float __y)
> { return __builtin_nextafterf(__x, __y); }
>
> constexpr long double
> nextafter(long double __x, long double __y)
> { return __builtin_nextafterl(__x, __y); }
>
>
>
> template<typename _Tp, typename _Up>
> constexpr typename __gnu_cxx::__promote_2<_Tp, _Up>::__type
> nextafter(_Tp __x, _Up __y)
> {
> typedef typename __gnu_cxx::__promote_2<_Tp, _Up>::__type __type;
> return nextafter(__type(__x), __type(__y));
> }
>
> which means std::nextafter will use the long double variant?
Ah, and in the same function:
_3 = (long double) __tmp;
_4 = _3 * 4.294967296e+9;
__tmp = (double) _4;
likely from
const long double __r = static_cast<long double>(__urng.max())
- static_cast<long double>(__urng.min()) + 1.0L;
the loop to be vectorized is
<bb 32> [1.36%]:
# n_315 = PHI <0(31), n_290(35)>
# ivtmp_313 = PHI <10000000(31), ivtmp_289(35)>
_312 = (long unsigned int) n_315;
_311 = _312 * 4;
_310 = _82 + _311;
_309 = *_310;
_308 = _309 - 5.0e-1;
_307 = _308 > 0.0;
_306 = (int) _307;
_305 = _308 < 0.0;
_304 = (int) _305;
_303 = _306 - _304;
_302 = (float) _303;
if (_302 < 0.0)
goto <bb 34>; [36.00%]
else
goto <bb 33>; [64.00%]
<bb 33> [0.87%]:
<bb 34> [1.37%]:
# _301 = PHI <&D.56316(32), &D.56315(33)>
D.56315 ={v} {CLOBBER};
D.56316 ={v} {CLOBBER};
_298 = *_301;
_297 = _298 * 6.99999988079071044921875e-1;
_296 = _297 + 1.00000001490116119384765625e-1;
_295 = pretmp_336 + _311;
*_295 = _296;
n_290 = n_315 + 1;
ivtmp_289 = ivtmp_313 - 1;
if (ivtmp_289 == 0)
goto <bb 36>; [1.01%]
else
goto <bb 35>; [98.99%]
<bb 35> [1.36%]:
goto <bb 32>; [100.00%]
which failed to if-convert, quite possibly because of the strange clobbers.
Which means the testcase is likely undefined as well.
