Generate the segmented stack prologue for fastcc too.
Patch by Brian Anderson.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147958 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp
index fba4788..4386762 100644
--- a/lib/Target/X86/X86FrameLowering.cpp
+++ b/lib/Target/X86/X86FrameLowering.cpp
@@ -1306,7 +1306,8 @@
     CallingConv::ID CallingConvention = MF.getFunction()->getCallingConv();
     bool IsNested = HasNestArgument(&MF);
 
-    if (CallingConvention == CallingConv::X86_FastCall) {
+    if (CallingConvention == CallingConv::X86_FastCall ||
+        CallingConvention == CallingConv::Fast) {
       if (IsNested) {
         report_fatal_error("Segmented stacks does not support fastcall with "
                            "nested function.");