Some autoconf tests use module level inline asm to test compiler's handling of
.cfi_startproc. e.g. libffi:

 $ cat confopt.c 
asm (".cfi_startproc\n\t.cfi_endproc");

int main () { return 0; }

Teach MC / dwarf emission to handle these cfi directives which essentially
create an empty frame.

rdar://10017184


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@138504 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCDwarf.cpp b/lib/MC/MCDwarf.cpp
index 06ce502..b57fd9a 100644
--- a/lib/MC/MCDwarf.cpp
+++ b/lib/MC/MCDwarf.cpp
@@ -895,7 +895,7 @@
   const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
   bool verboseAsm = streamer.isVerboseAsm();
 
-  if (!MOFI->isFunctionEHFrameSymbolPrivate() && IsEH) {
+  if (IsEH && frame.Function && !MOFI->isFunctionEHFrameSymbolPrivate()) {
     MCSymbol *EHSym =
       context.GetOrCreateSymbol(frame.Function->getName() + Twine(".eh"));
     streamer.EmitEHSymAttributes(frame.Function, EHSym);