Fix llvm::is_trivially_copyable portability issues

llvm::is_trivially_copyable portability is verified at compile time using
std::is_trivially_copyable as the reference implementation.

Unfortunately, the latter is not available on all platforms, so introduce
a proper configure check to detect if it is available on the target platform.

In a similar manner, std::is_copy_assignable is not fully supported for gcc4.9.
Provide a portable (?) implementation instead.

Differential Revision: https://reviews.llvm.org/D57018

llvm-svn: 351820

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/cmake/config-ix.cmake b/llvm/cmake/config-ix.cmake
index 30ee2b9cbb6..9e9e28f0673 100644
--- a/llvm/cmake/config-ix.cmake
+++ b/llvm/cmake/config-ix.cmake
@@ -325,6 +325,15 @@ else()
   unset(HAVE_FFI_CALL CACHE)
 endif( LLVM_ENABLE_FFI )
 
+# Whether we can use std::is_trivially_copyable to verify llvm::is_trivially_copyable.
+CHECK_CXX_SOURCE_COMPILES("
+#include <type_traits>
+struct T { int val; };
+static_assert(std::is_trivially_copyable<T>::value, \"ok\");
+int main() { return 0;}
+" HAVE_STD_IS_TRIVIALLY_COPYABLE)
+
+
 # Define LLVM_HAS_ATOMICS if gcc or MSVC atomic builtins are supported.
 include(CheckAtomic)