diff --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/clang/lib/Basic/TargetInfo.cpp
@@ -300,8 +300,11 @@
     if (ExplicitType == FloatModeKind::Ibm128)
       return hasIbm128Type() ? FloatModeKind::Ibm128
                              : FloatModeKind::NoFloat;
-    if (ExplicitType == FloatModeKind::LongDouble)
-      return ExplicitType;
+    if (&getLongDoubleFormat() == &llvm::APFloat::PPCDoubleDouble() ||
+        &getLongDoubleFormat() == &llvm::APFloat::IEEEquad())
+      return FloatModeKind::LongDouble;
+    if (hasFloat128Type())
+      return FloatModeKind::Float128;
     break;
   }
 
diff --git a/clang/test/CodeGenCXX/complex128.cpp b/clang/test/CodeGenCXX/complex128.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGenCXX/complex128.cpp
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -emit-llvm -triple x86_64-unknown-linux-gnu %s -o - | FileCheck %s
+
+// Define __complex128 type corresponding to __float128 (as in GCC headers).
+typedef _Complex float __attribute__((mode(TC))) __complex128;
+
+void check() {
+  // CHECK: alloca { fp128, fp128 }
+  __complex128 tmp;
+}