On 18/08/2021 17:23, Neill Clift via Boost-users wrote:
Hi,
In my program I am seeing my code use the slower (I assume)
subtract_unsigned_constexpr rather than subtract_unsigned with he
borrow chain handled intrinsics.
This seems to be happening because of these lines in intel_intrinsics.hpp:
#if defined(__clang__) && (__clang__ < 9)
// We appear to crash the compiler if we try to use these intrinsics?
#undef BOOST_MP_HAS_IMMINTRIN_H
#endif
__clang__ is not the version but just the value 1. I expect this
should be the major version instead:
Good catch, see https://github.com/boostorg/multiprecision/pull/356
#define __clang__ 1
#define __clang_major__ 12
#define __clang_minor__ 0
As an aside 128bit support does work in windows with clang. I have to
force it on like this:
#define __STRICT_ANSI__
#define BOOST_HAS_INT128
#define BOOST_MP_HAS_IMMINTRIN_H
#include <boost/multiprecision/cpp_int.hpp>
I'll look at that separately, thanks John.
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