Add support for .cfi_signal_frame. Fixes pr11762.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148733 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCStreamer.cpp b/lib/MC/MCStreamer.cpp
index 7bbb379..1690eea 100644
--- a/lib/MC/MCStreamer.cpp
+++ b/lib/MC/MCStreamer.cpp
@@ -439,6 +439,12 @@
   CurFrame->Instructions.push_back(Instruction);
 }
 
+void MCStreamer::EmitCFISignalFrame() {
+  EnsureValidFrame();
+  MCDwarfFrameInfo *CurFrame = getCurrentFrameInfo();
+  CurFrame->IsSignalFrame = true;
+}
+
 void MCStreamer::setCurrentW64UnwindInfo(MCWin64EHUnwindInfo *Frame) {
   W64UnwindInfos.push_back(Frame);
   CurrentW64UnwindInfo = W64UnwindInfos.back();