Index: include/llvm/Support/Compiler.h
===================================================================
--- include/llvm/Support/Compiler.h
+++ include/llvm/Support/Compiler.h
@@ -293,6 +293,15 @@
 # define LLVM_ALIGNAS(x) alignas(x)
 #endif
 
+/// \macro LLVM_PACKED
+/// \brief Used to specify a packed structure.
+///
+#ifdef _MSC_VER
+# define LLVM_PACKED(d) __pragma(pack(push, 1)) d __pragma(pack(pop))
+#else
+# define LLVM_PACKED(d) d __attribute__((packed))
+#endif
+
 /// \macro LLVM_PTR_SIZE
 /// \brief A constant integer equivalent to the value of sizeof(void*).
 /// Generally used in combination with LLVM_ALIGNAS or when doing computation in