Update SmallVector to support move semantics if the host does.

Note that support for rvalue references does not imply support
for the full set of move-related STL operations.

I've preserved support for an odd little thing in insert() where
we're trying to support inserting a new element from an existing
one.  If we actually want to support that, there's a lot more we
need to do:  insert can call either grow or push_back, neither of
which is safe against this particular use pattern.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155979 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 0 deletions

diff --git a/include/llvm/Support/Compiler.h b/include/llvm/Support/Compiler.h
index d0b186e..0ae02e8 100644
--- a/include/llvm/Support/Compiler.h
+++ b/include/llvm/Support/Compiler.h
@@ -19,6 +19,25 @@
 # define __has_feature(x) 0
 #endif
 
+/// LLVM_HAS_RVALUE_REFERENCES - Does the compiler provide r-value references?
+/// This implies that <utility> provides the one-argument std::move;  it
+/// does not imply the existence of any other C++ library features.
+#if (__has_feature(cxx_rvalue_references)   \
+     || defined(__GXX_EXPERIMENTAL_CXX0X__) \
+     || _MSC_VER >= 1600)
+#define LLVM_USE_RVALUE_REFERENCES 1
+#else
+#define LLVM_USE_RVALUE_REFERENCES 0
+#endif
+
+/// llvm_move - Expands to ::std::move if the compiler supports
+/// r-value references; otherwise, expands to the argument.
+#if LLVM_USE_RVALUE_REFERENCES
+#define llvm_move(value) (::std::move(arg))
+#else
+#define llvm_move(value) (value)
+#endif
+
 /// LLVM_LIBRARY_VISIBILITY - If a class marked with this attribute is linked
 /// into a shared library, then the class should be private to the library and
 /// not accessible from outside it.  Can also be used to mark variables and