If the __is_trivially_copyable type trait is available use it as the baseline for...

This way we can enable the POD-like class optimization for a lot more classes,
saving ~120k of code in clang/i386/Release+Asserts when selfhosting.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155761 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Support/type_traits.h b/include/llvm/Support/type_traits.h
index a3a551f851f3b626b3322e783f9e5ec0d2510f12..7b97547be52af409574587e6d3c1e9ff321e9c65 100644 (file)
--- a/include/llvm/Support/type_traits.h
+++ b/include/llvm/Support/type_traits.h
@@ -21,6 +21,11 @@
 #include <cstddef>
 #include <utility>
 
+#ifndef __has_feature
+#define LLVM_DEFINED_HAS_FEATURE
+#define __has_feature(x) 0
+#endif
+
 // This is actually the conforming implementation which works with abstract
 // classes.  However, enough compilers have trouble with it that most will use
 // the one in boost/type_traits/object_traits.hpp. This implementation actually
@@ -58,9 +63,15 @@ struct is_class
 /// type can be copied around with memcpy instead of running ctors etc.
 template <typename T>
 struct isPodLike {
+#if __has_feature(is_trivially_copyable)
+  // If the compiler supports the is_trivially_copyable trait use it, as it
+  // matches the definition of isPodLike closely.
+  static const bool value = __is_trivially_copyable(T);
+#else
   // If we don't know anything else, we can (at least) assume that all non-class
   // types are PODs.
   static const bool value = !is_class<T>::value;
+#endif
 };
 
 // std::pair's are pod-like if their elements are.
@@ -202,4 +213,8 @@ struct conditional<false, T, F> { typedef F type; };
 
 }
 
+#ifdef LLVM_DEFINED_HAS_FEATURE
+#undef __has_feature
+#endif
+
 #endif