build: bump to TensorFlow 2.4.0

Update to build X10 against TensorFlow 2.4.0.

CMakeLists.txt

@@ -167,7 +167,7 @@ if(NOT X10_FOUND AND NOT USE_BUNDLED_X10)
     GIT_REPOSITORY
       git://github.com/tensorflow/tensorflow
     GIT_TAG
-      r2.3
+      r2.4
     UPDATE_DISCONNECTED
       TRUE
     CONFIGURE_COMMAND

Sources/TensorFlow/Core/StringTensor.swift

@@ -47,72 +47,23 @@ extension StringTensor {
     // utf8CString is null-terminated. TF APIs want the strings without null-terminators.
     let cStrings = scalars.map { $0.utf8CString.dropLast() }
 
-    // Note: `TENSORFLOW_MASTER` changes below are necessary for the new TensorFlow ABI-stable
-    // unified string tensor design.
-    #if TENSORFLOW_MASTER
-      let byteCount = scalars.count * MemoryLayout<TF_TString>.stride
-
-      let handle = TensorHandle<String>(
-        shape: shape.dimensions,
-        byteCount: byteCount,
-        bufferInitializer: { tensorBuffer in
-          var dataAddr =
-            tensorBuffer.bindMemory(to: TF_TString.self, capacity: scalars.count)
-          for cString in cStrings {
-            TF_TString_Init(dataAddr)
-            cString.withUnsafeBufferPointer { buffer in
-              TF_TString_Copy(dataAddr, buffer.baseAddress, buffer.count)
-            }
-            dataAddr = dataAddr.advanced(by: 1)
-          }
-        })
-      self.init(handle: handle)
-    #else
-      let tfEncodedSizes = cStrings.map { TF_StringEncodedSize($0.count) }
-
-      // Format information copied from tensorflow/c/c_api.h:
-      // The format for TF_STRING tensors is:
-      //   start_offset: array[uint64]
-      //   data:         byte[...]
-      //
-      //   The string length (as a varint), followed by the contents of the string is encoded at
-      //   data[start_offset[i]]].
-      // The size of the "start_offset" region.
-      let startOffsetsByteCount = scalars.count * MemoryLayout<UInt64>.stride
-
-      // The size of the "data" region.
-      let dataByteCount = tfEncodedSizes.reduce(0, +) * MemoryLayout<UInt8>.stride
-
-      let handle = TensorHandle<String>(
-        shape: shape.dimensions,
-        byteCount: startOffsetsByteCount + dataByteCount,
-        bufferInitializer: { tensorBuffer in
-          // Initialize the "start_offset" region.
-          var startOffset: UInt64 = 0
-          var startOffsetAddr =
-            tensorBuffer.bindMemory(to: UInt64.self, capacity: scalars.count)
-          for tfEncodedSize in tfEncodedSizes {
-            startOffsetAddr.initialize(to: startOffset)
-            startOffsetAddr = startOffsetAddr.advanced(by: 1)
-            startOffset = startOffset + UInt64(tfEncodedSize)
-          }
-
-          // Initialize the "data" region.
-          var dataAddr = tensorBuffer.advanced(by: startOffsetsByteCount)
-            .bindMemory(to: Int8.self, capacity: dataByteCount)
-          let status = TF_NewStatus()
-          for (cString, tfEncodedSize) in zip(cStrings, tfEncodedSizes) {
-            _ = cString.withUnsafeBufferPointer { buffer in
-              TF_StringEncode(
-                buffer.baseAddress, buffer.count, dataAddr, tfEncodedSize, status)
-            }
-            checkOk(status)
-            dataAddr = dataAddr.advanced(by: tfEncodedSize)
+    let byteCount = scalars.count * MemoryLayout<TF_TString>.stride
+
+    let handle = TensorHandle<String>(
+      shape: shape.dimensions,
+      byteCount: byteCount,
+      bufferInitializer: { tensorBuffer in
+        var dataAddr =
+          tensorBuffer.bindMemory(to: TF_TString.self, capacity: scalars.count)
+        for cString in cStrings {
+          TF_TString_Init(dataAddr)
+          cString.withUnsafeBufferPointer { buffer in
+            TF_TString_Copy(dataAddr, buffer.baseAddress, buffer.count)
           }
-          TF_DeleteStatus(status)
-        })
-      self.init(handle: handle)
-    #endif
+          dataAddr = dataAddr.advanced(by: 1)
+        }
+      })
+    self.init(handle: handle)
   }
 
   /// Creates a 0-D `StringTensor` from a scalar value.