Index: lib/Basic/Targets/OSTargets.h
===================================================================
--- lib/Basic/Targets/OSTargets.h
+++ lib/Basic/Targets/OSTargets.h
@@ -257,6 +257,10 @@
     Builder.defineMacro("__HAIKU__");
     Builder.defineMacro("__ELF__");
     DefineStd(Builder, "unix", Opts);
+    if (this->HasFloat128) {
+      Builder.defineMacro("__FLOAT128__");
+      Builder.defineMacro("_GLIBCXX_USE_FLOAT128");
+    }
   }
 
 public:
@@ -267,6 +271,14 @@
     this->PtrDiffType = TargetInfo::SignedLong;
     this->ProcessIDType = TargetInfo::SignedLong;
     this->TLSSupported = false;
+    switch (Triple.getArch()) {
+    default:
+      break;
+    case llvm::Triple::x86:
+    case llvm::Triple::x86_64:
+      this->HasFloat128 = true;
+      break;
+    }
   }
 };
 
Index: test/CodeGenCXX/float128-declarations.cpp
===================================================================
--- test/CodeGenCXX/float128-declarations.cpp
+++ test/CodeGenCXX/float128-declarations.cpp
@@ -16,6 +16,10 @@
 // RUN:   %s -o - | FileCheck %s -check-prefix=CHECK-X86
 // RUN: %clang_cc1 -emit-llvm -triple x86_64-pc-solaris2.11 -std=c++11 \
 // RUN:   %s -o - | FileCheck %s -check-prefix=CHECK-X86
+// RUN: %clang_cc1 -emit-llvm -triple i586-pc-haiku -std=c++11 \
+// RUN:   %s -o - | FileCheck %s -check-prefix=CHECK-X86
+// RUN: %clang_cc1 -emit-llvm -triple x86_64-unknown-haiku -std=c++11 \
+// RUN:   %s -o - | FileCheck %s -check-prefix=CHECK-X86
 //
 /*  Various contexts where type __float128 can appear. The different check
     prefixes are due to different mangling on X86 and different calling