[llvm-commits] [llvm] r155761 - /llvm/trunk/include/llvm/Support/type_traits.h

[Benjamin Kramer]

Author: d0k
Date: Sat Apr 28 11:22:31 2012
New Revision: 155761

URL: http://llvm.org/viewvc/llvm-project?rev=155761&view=rev
Log:
If the __is_trivially_copyable type trait is available use it as the baseline for isPodLike.

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.

Modified:
    llvm/trunk/include/llvm/Support/type_traits.h

Modified: llvm/trunk/include/llvm/Support/type_traits.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/type_traits.h?rev=155761&r1=155760&r2=155761&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/type_traits.h (original)
+++ llvm/trunk/include/llvm/Support/type_traits.h Sat Apr 28 11:22:31 2012
@@ -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 @@
 /// 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 @@
 
 }
 
+#ifdef LLVM_DEFINED_HAS_FEATURE
+#undef __has_feature
+#endif
+
 #endif