Support the Nodebug emission kind for DICompileUnits.

Sample-based profiling and optimization remarks currently remove
DICompileUnits from llvm.dbg.cu to suppress the emission of debug info
from them. This is somewhat of a hack and only borderline legal IR.

This patch uses the recently introduced NoDebug emission kind in
DICompileUnit to achieve the same result without breaking the Verifier.
A nice side-effect of this change is that it is now possible to combine
NoDebug and regular compile units under LTO.

http://reviews.llvm.org/D18808
<rdar://problem/25427165>

llvm-svn: 265861

llvm/lib/IR/Module.cpp

@@ -19,6 +19,7 @@
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/GVMaterializer.h"
 #include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/LLVMContext.h"
@@ -380,6 +381,19 @@ void Module::setDataLayout(const DataLayout &Other) { DL = Other; }
 
 const DataLayout &Module::getDataLayout() const { return DL; }
 
+DICompileUnit *Module::debug_compile_units_iterator::operator*() const {
+  return cast<DICompileUnit>(CUs->getOperand(Idx));
+}
+DICompileUnit *Module::debug_compile_units_iterator::operator->() const {
+  return cast<DICompileUnit>(CUs->getOperand(Idx));
+}
+
+void Module::debug_compile_units_iterator::SkipNoDebugCUs() {
+  while (CUs && (Idx < CUs->getNumOperands()) &&
+         ((*this)->getEmissionKind() == DICompileUnit::NoDebug))
+    ++Idx;
+}
+
 //===----------------------------------------------------------------------===//
 // Methods to control the materialization of GlobalValues in the Module.
 //