Add fallback AVX2 swizzle constant mask

Author: AntoinePrv

include/xsimd/arch/xsimd_avx2.hpp

@@ -1142,6 +1142,39 @@ namespace xsimd
         }
 
         // swizzle (constant mask)
+        template <
+            class A, typename T,
+            uint8_t V0, uint8_t V1, uint8_t V2, uint8_t V3, uint8_t V4, uint8_t V5, uint8_t V6, uint8_t V7,
+            uint8_t V8, uint8_t V9, uint8_t V10, uint8_t V11, uint8_t V12, uint8_t V13, uint8_t V14, uint8_t V15,
+            uint8_t V16, uint8_t V17, uint8_t V18, uint8_t V19, uint8_t V20, uint8_t V21, uint8_t V22, uint8_t V23,
+            uint8_t V24, uint8_t V25, uint8_t V26, uint8_t V27, uint8_t V28, uint8_t V29, uint8_t V30, uint8_t V31,
+            detail::enable_sized_t<T, 1> = 0>
+        XSIMD_INLINE batch<T, A> swizzle(
+            batch<T, A> const& self,
+            batch_constant<
+                uint8_t, A,
+                V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15,
+                V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30, V31>
+                mask,
+            requires_arch<avx2> req) noexcept
+        {
+            return swizzle(self, mask.as_batch(), req);
+        }
+
+        template <
+            class A, typename T,
+            uint16_t V0, uint16_t V1, uint16_t V2, uint16_t V3, uint16_t V4, uint16_t V5, uint16_t V6, uint16_t V7,
+            uint16_t V8, uint16_t V9, uint16_t V10, uint16_t V11, uint16_t V12, uint16_t V13, uint16_t V14, uint16_t V15,
+            detail::enable_sized_t<T, 2> = 0>
+        XSIMD_INLINE batch<T, A> swizzle(
+            batch<T, A> const& self,
+            batch_constant<uint16_t, A, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15>
+                mask,
+            requires_arch<avx2> req) noexcept
+        {
+            return swizzle(self, mask.as_batch(), req);
+        }
+
         template <class A, uint32_t V0, uint32_t V1, uint32_t V2, uint32_t V3, uint32_t V4, uint32_t V5, uint32_t V6, uint32_t V7>
         XSIMD_INLINE batch<float, A> swizzle(batch<float, A> const& self, batch_constant<uint32_t, A, V0, V1, V2, V3, V4, V5, V6, V7> mask, requires_arch<avx2>) noexcept
         {