Implement .cfi_escape. Patch by Brian Anderson!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147352 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCStreamer.cpp b/lib/MC/MCStreamer.cpp
index 74c3e39..23d8c1c 100644
--- a/lib/MC/MCStreamer.cpp
+++ b/lib/MC/MCStreamer.cpp
@@ -408,6 +408,15 @@
   CurFrame->Instructions.push_back(Instruction);
 }
 
+void MCStreamer::EmitCFIEscape(StringRef Values) {
+  EnsureValidFrame();
+  MCDwarfFrameInfo *CurFrame = getCurrentFrameInfo();
+  MCSymbol *Label = getContext().CreateTempSymbol();
+  EmitLabel(Label);
+  MCCFIInstruction Instruction(MCCFIInstruction::Escape, Label, Values);
+  CurFrame->Instructions.push_back(Instruction);
+}
+
 void MCStreamer::setCurrentW64UnwindInfo(MCWin64EHUnwindInfo *Frame) {
   W64UnwindInfos.push_back(Frame);
   CurrentW64UnwindInfo = W64UnwindInfos.back();