X86-Windows: Emit an undefined global __fltused symbol when targeting Windows
if any floating point arguments are passed to an external function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116665 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86AsmPrinter.cpp b/lib/Target/X86/X86AsmPrinter.cpp
index 85441b1..c4fd729 100644
--- a/lib/Target/X86/X86AsmPrinter.cpp
+++ b/lib/Target/X86/X86AsmPrinter.cpp
@@ -580,6 +580,13 @@
     OutStreamer.EmitAssemblerFlag(MCAF_SubsectionsViaSymbols);
   }
 
+  if (Subtarget->isTargetWindows()
+   && !Subtarget->isTargetCygMing()
+   && MMI->callsExternalFunctionWithFloatingPointArguments()) {
+    MCSymbol *S = MMI->getContext().GetOrCreateSymbol(StringRef("__fltused"));
+    OutStreamer.EmitSymbolAttribute(S, MCSA_Global);
+  }
+
   if (Subtarget->isTargetCOFF()) {
     X86COFFMachineModuleInfo &COFFMMI =
       MMI->getObjFileInfo<X86COFFMachineModuleInfo>();