[PATCH] [asan-asm-instrumentation] CFI directives are generated for .S files.

[Rafael Ávila de Espíndola]

LGTM with a nit.

================
Comment at: lib/Target/X86/AsmParser/X86AsmInstrumentation.cpp:868
@@ +867,3 @@
+
+  if (InitialFrameReg != X86::NoRegister) {
+    // FrameReg is set explicitly, we're instrumenting a MachineFunction.
----------------
The X86::NoRegister in here is the 0 in CurrentCfaRegister(0), no? I would probably be cleaner no just use 0 everywhere.

This could also be an assert now, no? The initial instructions should always be setting the initial frame register.

http://reviews.llvm.org/D5520