Enable support for __float128 in Clang and enable it on pertinent platforms

This patch corresponds to reviews:
http://reviews.llvm.org/D15120
http://reviews.llvm.org/D19125

It adds support for the __float128 keyword, literals and target feature to
enable it. Based on the latter of the two aforementioned reviews, this feature
is enabled on Linux on i386/X86 as well as SystemZ.
This is also the second attempt in commiting this feature. The first attempt
did not enable it on required platforms which caused failures when compiling
type_traits with -std=gnu++11.

If you see failures with compiling this header on your platform after this
commit, it is likely that your platform needs to have this feature enabled.

llvm-svn: 268898

1 files changed, 6 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index a98df93a042..a63f5582cd9 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -528,7 +528,13 @@ llvm::DIType *CGDebugInfo::CreateType(const BuiltinType *BT) {
   case BuiltinType::Half:
   case BuiltinType::Float:
   case BuiltinType::LongDouble:
+  case BuiltinType::Float128:
   case BuiltinType::Double:
+    // FIXME: For targets where long double and __float128 have the same size,
+    // they are currently indistinguishable in the debugger without some
+    // special treatment. However, there is currently no consensus on encoding
+    // and this should be updated once a DWARF encoding exists for distinct
+    // floating point types of the same size.
     Encoding = llvm::dwarf::DW_ATE_float;
     break;
   }