AsmPrinter: Don't emit empty .debug_loc entries

If we don't know how to represent a .debug_loc entry, skip the entry
entirely rather than emitting an empty one.  Similarly, if a .debug_loc
list has no entries, don't create the list.

We still want to create the variables, just in an optimized-out form
that doesn't have a DW_AT_location.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240244 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/AsmPrinter/DebugLocStream.cpp

@@ -0,0 +1,46 @@
+//===- DebugLocStream.cpp - DWARF debug_loc stream --------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DebugLocStream.h"
+#include "DwarfDebug.h"
+#include "llvm/CodeGen/AsmPrinter.h"
+
+using namespace llvm;
+
+bool DebugLocStream::finalizeList(AsmPrinter &Asm) {
+  if (Lists.back().EntryOffset == Entries.size()) {
+    // Empty list.  Delete it.
+    Lists.pop_back();
+    return false;
+  }
+
+  // Real list.  Generate a label for it.
+  Lists.back().Label = Asm.createTempSymbol("debug_loc");
+  return true;
+}
+
+void DebugLocStream::finalizeEntry() {
+  if (Entries.back().ByteOffset != DWARFBytes.size())
+    return;
+
+  // The last entry was empty.  Delete it.
+  Comments.erase(Comments.begin() + Entries.back().CommentOffset,
+                 Comments.end());
+  Entries.pop_back();
+
+  assert(Lists.back().EntryOffset <= Entries.size() &&
+         "Popped off more entries than are in the list");
+}
+
+DebugLocStream::ListBuilder::~ListBuilder() {
+  if (!Locs.finalizeList(Asm))
+    return;
+  V.initializeDbgValue(&MI);
+  V.setDebugLocListIndex(ListIndex);
+}