X86: Emit _fltused instead of __fltused on Windows x64.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117205 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86AsmPrinter.cpp b/lib/Target/X86/X86AsmPrinter.cpp
index f7cb9e7..5cb73be 100644
--- a/lib/Target/X86/X86AsmPrinter.cpp
+++ b/lib/Target/X86/X86AsmPrinter.cpp
@@ -583,7 +583,8 @@
   if (Subtarget->isTargetWindows()
    && !Subtarget->isTargetCygMing()
    && MMI->callsExternalVAFunctionWithFloatingPointArguments()) {
-    MCSymbol *S = MMI->getContext().GetOrCreateSymbol(StringRef("__fltused"));
+    StringRef SymbolName = Subtarget->is64Bit() ? "_fltused" : "__fltused";
+    MCSymbol *S = MMI->getContext().GetOrCreateSymbol(SymbolName);
     OutStreamer.EmitSymbolAttribute(S, MCSA_Global);
   }