[StreamExecutor] Pass device memory by ref

[jhen]

Summary

Step 3 of getting GlobalDeviceMemory to own its handle.

Since GlobalDeviceMemory will no longer by copy-constructible, we must
pass instances by reference rather than by value.

[jhen]

• clang-format

[jlebar]

streamexecutor/include/streamexecutor/Device.h

223

I wonder if we should take by non-const reference. This "pass mutable things by pointer" idiom is kind of a Google-ism; I am not sure it will make a lot of sense to other people reading the code.

[jhen]

• Use ref instead of pointer for dst

[jhen]

streamexecutor/include/streamexecutor/Device.h

223

Yeah, you're right. It could be confusing. I've changed all the destinations to pass-by-non-const-ref now instead of pass-by-pointer.

streamexecutor/include/streamexecutor/Device.h

public:
   template <typename T>
   Error synchronousCopyD2H(GlobalDeviceMemorySlice<T> Src, T *Dst,
                            size_t ElementCount) {
     return synchronousCopyD2H(Src, llvm::MutableArrayRef<T>(Dst, ElementCount),
                               ElementCount);
   }
 
   template <typename T>
-  Error synchronousCopyD2H(GlobalDeviceMemory<T> Src,
+  Error synchronousCopyD2H(const GlobalDeviceMemory<T> &Src,
                            llvm::MutableArrayRef<T> Dst, size_t ElementCount) {
     return synchronousCopyD2H(Src.asSlice(), Dst, ElementCount);
   }
 
   template <typename T>
-  Error synchronousCopyD2H(GlobalDeviceMemory<T> Src,
+  Error synchronousCopyD2H(const GlobalDeviceMemory<T> &Src,
                            llvm::MutableArrayRef<T> Dst) {
     return synchronousCopyD2H(Src.asSlice(), Dst);
   }
 
   template <typename T>
-  Error synchronousCopyD2H(GlobalDeviceMemory<T> Src, T *Dst,
+  Error synchronousCopyD2H(const GlobalDeviceMemory<T> &Src, T *Dst,
                            size_t ElementCount) {
     return synchronousCopyD2H(Src.asSlice(), Dst, ElementCount);
   }
 
   template <typename T>
   Error synchronousCopyH2D(llvm::ArrayRef<T> Src,
                            GlobalDeviceMemorySlice<T> Dst,
                            size_t ElementCount) {
public:
   template <typename T>
   Error synchronousCopyH2D(T *Src, GlobalDeviceMemorySlice<T> Dst,
                            size_t ElementCount) {
     return synchronousCopyH2D(llvm::ArrayRef<T>(Src, ElementCount), Dst,
                               ElementCount);
   }
 
   template <typename T>
-  Error synchronousCopyH2D(llvm::ArrayRef<T> Src, GlobalDeviceMemory<T> Dst,
+  Error synchronousCopyH2D(llvm::ArrayRef<T> Src, GlobalDeviceMemory<T> &Dst,
                            size_t ElementCount) {
     return synchronousCopyH2D(Src, Dst.asSlice(), ElementCount);
   }
 
   template <typename T>
-  Error synchronousCopyH2D(llvm::ArrayRef<T> Src, GlobalDeviceMemory<T> Dst) {
+  Error synchronousCopyH2D(llvm::ArrayRef<T> Src, GlobalDeviceMemory<T> &Dst) {
     return synchronousCopyH2D(Src, Dst.asSlice());
   }
 
   template <typename T>
-  Error synchronousCopyH2D(T *Src, GlobalDeviceMemory<T> Dst,
+  Error synchronousCopyH2D(T *Src, GlobalDeviceMemory<T> &Dst,
                            size_t ElementCount) {
     return synchronousCopyH2D(Src, Dst.asSlice(), ElementCount);
   }
 
   template <typename T>
   Error synchronousCopyD2D(GlobalDeviceMemorySlice<T> Src,
                            GlobalDeviceMemorySlice<T> Dst,
                            size_t ElementCount) {
if (Src.getElementCount() != Dst.getElementCount())
           "array size mismatch for D2D, device source has element count " +
           llvm::Twine(Src.getElementCount()) +
           " but device destination has element count " +
           llvm::Twine(Dst.getElementCount()));
     return synchronousCopyD2D(Src, Dst, Src.getElementCount());
   }
 
   template <typename T>
-  Error synchronousCopyD2D(GlobalDeviceMemory<T> Src,
+  Error synchronousCopyD2D(const GlobalDeviceMemory<T> &Src,
                            GlobalDeviceMemorySlice<T> Dst,
                            size_t ElementCount) {
     return synchronousCopyD2D(Src.asSlice(), Dst, ElementCount);
   }
 
   template <typename T>
-  Error synchronousCopyD2D(GlobalDeviceMemory<T> Src,
+  Error synchronousCopyD2D(const GlobalDeviceMemory<T> &Src,
                            GlobalDeviceMemorySlice<T> Dst) {
     return synchronousCopyD2D(Src.asSlice(), Dst);
   }
 
   template <typename T>
   Error synchronousCopyD2D(GlobalDeviceMemorySlice<T> Src,
-                           GlobalDeviceMemory<T> Dst, size_t ElementCount) {
+                           GlobalDeviceMemory<T> &Dst, size_t ElementCount) {
     return synchronousCopyD2D(Src, Dst.asSlice(), ElementCount);
   }
 
   template <typename T>
   Error synchronousCopyD2D(GlobalDeviceMemorySlice<T> Src,
-                           GlobalDeviceMemory<T> Dst) {
+                           GlobalDeviceMemory<T> &Dst) {
     return synchronousCopyD2D(Src, Dst.asSlice());
   }
 
   template <typename T>
-  Error synchronousCopyD2D(GlobalDeviceMemory<T> Src, GlobalDeviceMemory<T> Dst,
-                           size_t ElementCount) {
+  Error synchronousCopyD2D(const GlobalDeviceMemory<T> &Src,
+                           GlobalDeviceMemory<T> &Dst, size_t ElementCount) {
     return synchronousCopyD2D(Src.asSlice(), Dst.asSlice(), ElementCount);
   }
 
   template <typename T>
-  Error synchronousCopyD2D(GlobalDeviceMemory<T> Src,
-                           GlobalDeviceMemory<T> Dst) {
+  Error synchronousCopyD2D(const GlobalDeviceMemory<T> &Src,
+                           GlobalDeviceMemory<T> &Dst) {
     return synchronousCopyD2D(Src.asSlice(), Dst.asSlice());
   }
 
   ///@} End host-synchronous device memory copying functions
 
 private:
   PlatformDevice *PDevice;
 };
 
 } // namespace streamexecutor
 
 #endif // STREAMEXECUTOR_DEVICE_H

streamexecutor/include/streamexecutor/DeviceMemory.h

public:
   /// Copy-assignable like a pointer.
   GlobalDeviceMemory &operator=(const GlobalDeviceMemory &) = default;
 
   /// Returns the number of elements of type ElemT that constitute this
   /// allocation.
   size_t getElementCount() const { return getByteCount() / sizeof(ElemT); }
 
   /// Converts this memory object into a slice.
-  GlobalDeviceMemorySlice<ElemT> asSlice() {
+  GlobalDeviceMemorySlice<ElemT> asSlice() const {
     return GlobalDeviceMemorySlice<ElemT>(*this);
   }
 
 private:
   /// Constructs a GlobalDeviceMemory instance from an opaque handle and an
   /// element count.
   ///
   /// This constructor is not public because there is a potential for confusion

streamexecutor/include/streamexecutor/Stream.h

public:
   template <typename T>
   Stream &thenCopyD2H(GlobalDeviceMemorySlice<T> Src, T *Dst,
                       size_t ElementCount) {
     thenCopyD2H(Src, llvm::MutableArrayRef<T>(Dst, ElementCount), ElementCount);
     return *this;
   }
 
   template <typename T>
-  Stream &thenCopyD2H(GlobalDeviceMemory<T> Src, llvm::MutableArrayRef<T> Dst,
-                      size_t ElementCount) {
+  Stream &thenCopyD2H(const GlobalDeviceMemory<T> &Src,
+                      llvm::MutableArrayRef<T> Dst, size_t ElementCount) {
     thenCopyD2H(Src.asSlice(), Dst, ElementCount);
     return *this;
   }
 
   template <typename T>
-  Stream &thenCopyD2H(GlobalDeviceMemory<T> Src, llvm::MutableArrayRef<T> Dst) {
+  Stream &thenCopyD2H(const GlobalDeviceMemory<T> &Src,
+                      llvm::MutableArrayRef<T> Dst) {
     thenCopyD2H(Src.asSlice(), Dst);
     return *this;
   }
 
   template <typename T>
-  Stream &thenCopyD2H(GlobalDeviceMemory<T> Src, T *Dst, size_t ElementCount) {
+  Stream &thenCopyD2H(const GlobalDeviceMemory<T> &Src, T *Dst,
+                      size_t ElementCount) {
     thenCopyD2H(Src.asSlice(), Dst, ElementCount);
     return *this;
   }
 
   template <typename T>
   Stream &thenCopyH2D(llvm::ArrayRef<T> Src, GlobalDeviceMemorySlice<T> Dst,
                       size_t ElementCount) {
     if (ElementCount > Src.size())
public:
   template <typename T>
   Stream &thenCopyH2D(T *Src, GlobalDeviceMemorySlice<T> Dst,
                       size_t ElementCount) {
     thenCopyH2D(llvm::ArrayRef<T>(Src, ElementCount), Dst, ElementCount);
     return *this;
   }
 
   template <typename T>
-  Stream &thenCopyH2D(llvm::ArrayRef<T> Src, GlobalDeviceMemory<T> Dst,
+  Stream &thenCopyH2D(llvm::ArrayRef<T> Src, GlobalDeviceMemory<T> &Dst,
                       size_t ElementCount) {
     thenCopyH2D(Src, Dst.asSlice(), ElementCount);
     return *this;
   }
 
   template <typename T>
-  Stream &thenCopyH2D(llvm::ArrayRef<T> Src, GlobalDeviceMemory<T> Dst) {
+  Stream &thenCopyH2D(llvm::ArrayRef<T> Src, GlobalDeviceMemory<T> &Dst) {
     thenCopyH2D(Src, Dst.asSlice());
     return *this;
   }
 
   template <typename T>
-  Stream &thenCopyH2D(T *Src, GlobalDeviceMemory<T> Dst, size_t ElementCount) {
+  Stream &thenCopyH2D(T *Src, GlobalDeviceMemory<T> &Dst, size_t ElementCount) {
     thenCopyH2D(Src, Dst.asSlice(), ElementCount);
     return *this;
   }
 
   template <typename T>
   Stream &thenCopyD2D(GlobalDeviceMemorySlice<T> Src,
                       GlobalDeviceMemorySlice<T> Dst, size_t ElementCount) {
     if (ElementCount > Src.getElementCount())
if (Src.getElementCount() != Dst.getElementCount())
                " but device destination has element count " +
                llvm::Twine(Dst.getElementCount()));
     else
       thenCopyD2D(Src, Dst, Src.getElementCount());
     return *this;
   }
 
   template <typename T>
-  Stream &thenCopyD2D(GlobalDeviceMemory<T> Src, GlobalDeviceMemorySlice<T> Dst,
-                      size_t ElementCount) {
+  Stream &thenCopyD2D(const GlobalDeviceMemory<T> &Src,
+                      GlobalDeviceMemorySlice<T> Dst, size_t ElementCount) {
     thenCopyD2D(Src.asSlice(), Dst, ElementCount);
     return *this;
   }
 
   template <typename T>
-  Stream &thenCopyD2D(GlobalDeviceMemory<T> Src,
+  Stream &thenCopyD2D(const GlobalDeviceMemory<T> &Src,
                       GlobalDeviceMemorySlice<T> Dst) {
     thenCopyD2D(Src.asSlice(), Dst);
     return *this;
   }
 
   template <typename T>
-  Stream &thenCopyD2D(GlobalDeviceMemorySlice<T> Src, GlobalDeviceMemory<T> Dst,
-                      size_t ElementCount) {
+  Stream &thenCopyD2D(GlobalDeviceMemorySlice<T> Src,
+                      GlobalDeviceMemory<T> &Dst, size_t ElementCount) {
     thenCopyD2D(Src, Dst.asSlice(), ElementCount);
     return *this;
   }
 
   template <typename T>
   Stream &thenCopyD2D(GlobalDeviceMemorySlice<T> Src,
-                      GlobalDeviceMemory<T> Dst) {
+                      GlobalDeviceMemory<T> &Dst) {
     thenCopyD2D(Src, Dst.asSlice());
     return *this;
   }
 
   template <typename T>
-  Stream &thenCopyD2D(GlobalDeviceMemory<T> Src, GlobalDeviceMemory<T> Dst,
-                      size_t ElementCount) {
+  Stream &thenCopyD2D(const GlobalDeviceMemory<T> &Src,
+                      GlobalDeviceMemory<T> &Dst, size_t ElementCount) {
     thenCopyD2D(Src.asSlice(), Dst.asSlice(), ElementCount);
     return *this;
   }
 
   template <typename T>
-  Stream &thenCopyD2D(GlobalDeviceMemory<T> Src, GlobalDeviceMemory<T> Dst) {
+  Stream &thenCopyD2D(const GlobalDeviceMemory<T> &Src,
+                      GlobalDeviceMemory<T> &Dst) {
     thenCopyD2D(Src.asSlice(), Dst.asSlice());
     return *this;
   }
 
   ///@} End device memory copying functions
 
 private:
   /// Sets the error state from an Error object.