Lax conversions

include/xvec/detail/mask.hpp

@@ -91,6 +91,13 @@ class basic_mask
   constexpr basic_mask& operator=(const basic_mask&) = default;
   constexpr basic_mask& operator=(basic_mask&&) noexcept = default;
 
+  /// Allow a mask to be constructed from the compiler's own representation. The
+  /// compiler may use multiple or partial target registers in its
+  /// representation. This constructor allows a mask to be built from the output
+  /// of an overloaded operator, a builtin, and so on.
+  /// @ingroup simd_constructor
+  constexpr basic_mask(const builtin_type& m) noexcept : mask(m) {}
+
   /// @brief Build a mask from a boolean value.
   /// @param b The boolean value to broadcast to all mask elements.
   constexpr explicit basic_mask(std::same_as<value_type> auto b) noexcept :
@@ -183,7 +190,7 @@ class basic_mask
   /// be a type which can be used for a standard constructor (e.g.,
   /// integral-like) so the `from_builtin` ensures that the desired effect is
   /// achieved directly.
-  static constexpr basic_mask from_builtin(const auto& m) { basic_mask bm; bm.mask = traits::truncate_to_size(m); return bm; }
+  static constexpr basic_mask from_builtin(const builtin_type& m) { basic_mask bm; bm.mask = traits::truncate_to_size(m); return bm; }
 
   /// Convert the mask into a register which can be passed to an intrinsic.
   constexpr auto to_register() const noexcept { return traits::to_register(mask); }

include/xvec/detail/operators.hpp

@@ -63,7 +63,7 @@ constexpr auto builtin_operator(generic_tag, _Vp lhs, _Vp rhs, _Op op) {
   r = op(lhsd, rhsd);
 #endif
 
-  if constexpr (mask_operator<_Op>) return _Vp::mask_type::from_builtin(r);
+  if constexpr (mask_operator<_Op>) return typename _Vp::mask_type(typename _Vp::mask_type::builtin_type(r));
   else return _Vp::from_builtin(r);
 }
 

include/xvec/generic/generic_impl.hpp

@@ -1144,16 +1144,19 @@ constexpr basic_vec<_Tp, _Abi> mask_to_vec(generic_tag, const basic_mask<_Bytes,
   static_assert(_Value == 1 || _Value == -1, "Only some values are permitted for mask to vec output");
   static_assert(_Bytes == sizeof(_Tp), "Invalid mask or destination - differing sizes");
 
+  using _To = basic_vec<_Tp, _Abi>;
+  using _B = typename _To::builtin_type;
+
   if constexpr (std::integral<_Tp> && _Value == -1)
     // The mask is already entirely 0 or 1 bits, so nothing more to do
-    return basic_vec<_Tp, _Abi>(mask.to_builtin());
+    return _To(_B(mask.to_builtin()));
   else if constexpr (std::integral<_Tp> && _Value == 1)
     // The mask is entirely 0 or 1 bits so a logical shift will convert the MSB into an LSB.
-    return basic_vec<_Tp, _Abi>(mask.to_builtin() >> (sizeof(_Tp) * 8 - 1));
+    return _To(_B(mask.to_builtin() >> (sizeof(_Tp) * 8 - 1)));
   else
   {
-    constexpr auto _vs = basic_vec<_Tp, _Abi>(_Tp(_Value));
-    return select(mask, _vs, basic_vec<_Tp, _Abi>());
+    constexpr auto _vs = _To(_Tp(_Value));
+    return select(mask, _vs, _To());
   }
 }
 
@@ -1359,7 +1362,7 @@ constexpr auto get_n_bit_mask(compact_mask_tag, const _M&, simd_size_type _n)
   if constexpr (_M::size <= 64)
   {
     const auto clamped = std::min(_M::size(), _n);
-    return _M::from_builtin(clamped == 64 ? ~0ULL : (1ULL << clamped) - 1);
+    return _M::from_builtin(typename _M::builtin_type(clamped == 64 ? ~0ULL : (1ULL << clamped) - 1));
   }
   else
     return _M::from_builtin(_M(true).to_builtin() >> (_M::size - std::min(_n, _M::size())));

include/xvec/x86/permute.hpp

@@ -129,8 +129,8 @@ _mm512_permutex2var_epi8_emulated(__m512i v_data_0,
   // for that permutation comes from the upper 5-bits of the incoming index (i.e., discard the LSB). The permute
   // instruction masks the index bits itself, so we only need to put the upper 5-bits of the index
   // into the correct location.
-  __v32hi evenPerm = _mm512_permutex2var_epi16(v_data_0, v_shuf_idxs >> 1, v_data_1);
-  __v32hi oddPerm = _mm512_permutex2var_epi16(v_data_0, v_shuf_idxs >> 9, v_data_1);
+  auto evenPerm = _mm512_permutex2var_epi16(v_data_0, v_shuf_idxs >> 1, v_data_1);
+  auto oddPerm = _mm512_permutex2var_epi16(v_data_0, v_shuf_idxs >> 9, v_data_1);
 
   // evenPerm and oddPerm now contain pairs of bytes. We need to select which byte of each pair to use,
   // and that selection is driven by the LSB of each index (i.e., LSB == 0 means use the lower byte of the

test/CMakeLists.txt

@@ -250,7 +250,6 @@ elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     xvec_test_common
     INTERFACE
       -Wno-unknown-pragmas
-      -flax-vector-conversions
   )
 endif()