Refactor DynamicDispatch for auto static dispatch

Author: AntoinePrv

cpp/src/arrow/util/bpacking.cc

@@ -56,7 +56,7 @@ void unpack(const uint8_t* in, Uint* out, const UnpackOptions& opts) {
   return bpacking::unpack_neon(in, out, opts);
 #else
   static DynamicDispatch<UnpackDynamicFunction<Uint> > dispatch;
-  return dispatch.func(in, out, opts);
+  return dispatch(in, out, opts);
 #endif
 }
 

cpp/src/arrow/util/byte_stream_split_internal.cc

@@ -24,6 +24,7 @@ namespace arrow::util::internal {
 
 using ::arrow::internal::DispatchLevel;
 using ::arrow::internal::DynamicDispatch;
+using ::arrow::internal::DynamicDispatchTarget;
 
 /************************
  *  Decode dispatching  *
@@ -32,28 +33,16 @@ using ::arrow::internal::DynamicDispatch;
 template <int kNumStreams>
 struct ByteStreamSplitDecodeDynamic {
   using FunctionType = decltype(&ByteStreamSplitDecodeScalar<kNumStreams>);
-  using Implementation = std::pair<DispatchLevel, FunctionType>;
 
   constexpr static auto implementations() {
     return std::array{
-        Implementation{
-            DispatchLevel::NONE,
-#if defined(ARROW_HAVE_NEON)
-            // We always expect Neon to be available on Arm64
-            &ByteStreamSplitDecodeSimd<xsimd::neon64, kNumStreams>,
-#elif defined(ARROW_HAVE_SSE4_2)
-            // We always expect SSE4.2 to be available on x86_64
-            &ByteStreamSplitDecodeSimd<xsimd::sse4_2, kNumStreams>,
-#else
-            &ByteStreamSplitDecodeScalar<kNumStreams>,
-#endif
-        },
-#if defined(ARROW_HAVE_RUNTIME_AVX2)
-        Implementation{
-            DispatchLevel::AVX2,
-            &ByteStreamSplitDecodeSimd<xsimd::avx2, kNumStreams>,
-        },
-#endif
+        ARROW_DISPATCH_TARGET_NONE(&ByteStreamSplitDecodeScalar<kNumStreams>)  //
+        ARROW_DISPATCH_TARGET_NEON(
+            (&ByteStreamSplitDecodeSimd<xsimd::neon64, kNumStreams>))  //
+        ARROW_DISPATCH_TARGET_SSE4_2(
+            (&ByteStreamSplitDecodeSimd<xsimd::sse4_2, kNumStreams>))  //
+        ARROW_DISPATCH_TARGET_AVX2(
+            (&ByteStreamSplitDecodeSimd<xsimd::avx2, kNumStreams>))  //
     };
   }
 };
@@ -62,7 +51,7 @@ template <int kNumStreams>
 void ByteStreamSplitDecodeSimdDispatch(const uint8_t* data, int width, int64_t num_values,
                                        int64_t stride, uint8_t* out) {
   static const DynamicDispatch<ByteStreamSplitDecodeDynamic<kNumStreams>> dispatch;
-  return dispatch.func(data, width, num_values, stride, out);
+  return dispatch(data, width, num_values, stride, out);
 }
 
 template void ByteStreamSplitDecodeSimdDispatch<2>(const uint8_t*, int, int64_t, int64_t,
@@ -79,25 +68,15 @@ template void ByteStreamSplitDecodeSimdDispatch<8>(const uint8_t*, int, int64_t,
 template <int kNumStreams>
 struct ByteStreamSplitEncodeDynamic {
   using FunctionType = decltype(&ByteStreamSplitEncodeScalar<kNumStreams>);
-  using Implementation = std::pair<DispatchLevel, FunctionType>;
 
   constexpr static auto implementations() {
     return std::array{
-        Implementation{
-            DispatchLevel::NONE,
-#if defined(ARROW_HAVE_NEON)
-            // We always expect Neon to be available on Arm64
-            &ByteStreamSplitEncodeSimd<xsimd::neon64, kNumStreams>,
-#elif defined(ARROW_HAVE_SSE4_2)
-            // We always expect SSE4.2 to be available on x86_64
-            &ByteStreamSplitEncodeSimd<xsimd::sse4_2, kNumStreams>,
-#else
-            &ByteStreamSplitEncodeScalar<kNumStreams>,
-#endif
-        },
-#if defined(ARROW_HAVE_RUNTIME_AVX2)
-        Implementation{DispatchLevel::AVX2, &ByteStreamSplitEncodeAvx2<kNumStreams>},
-#endif
+        ARROW_DISPATCH_TARGET_NONE(&ByteStreamSplitEncodeScalar<kNumStreams>)  //
+        ARROW_DISPATCH_TARGET_NEON(                                            //
+            (&ByteStreamSplitEncodeSimd<xsimd::neon64, kNumStreams>))          //
+        ARROW_DISPATCH_TARGET_SSE4_2(                                          //
+            (&ByteStreamSplitEncodeSimd<xsimd::sse4_2, kNumStreams>))          //
+        ARROW_DISPATCH_TARGET_AVX2((&ByteStreamSplitEncodeAvx2<kNumStreams>))  //
     };
   }
 };
@@ -107,7 +86,7 @@ void ByteStreamSplitEncodeSimdDispatch(const uint8_t* raw_values, int width,
                                        const int64_t num_values,
                                        uint8_t* output_buffer_raw) {
   static const DynamicDispatch<ByteStreamSplitEncodeDynamic<kNumStreams>> dispatch;
-  return dispatch.func(raw_values, width, num_values, output_buffer_raw);
+  return dispatch(raw_values, width, num_values, output_buffer_raw);
 }
 
 template void ByteStreamSplitEncodeSimdDispatch<2>(const uint8_t*, int, const int64_t,