Support: Stop stringifying DW_TAG_{lo,hi}_user

`dwarf::TagString()` shouldn't stringify `DW_TAG_lo_user` or
`DW_TAG_hi_user`.  These aren't actual tags; they're markers for the
edge of vendor-specific tag regions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228029 91177308-0d34-0410-b5e6-96231b3b80d8

unittests/Support/DwarfTest.cpp

@@ -0,0 +1,29 @@
+//===- unittest/Support/DwarfTest.cpp - Dwarf support tests ---------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Dwarf.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+using namespace llvm::dwarf;
+
+namespace {
+
+TEST(DwarfTest, TagStringOnInvalid) {
+  // This is invalid, so it shouldn't be stringified.
+  EXPECT_EQ(nullptr, TagString(DW_TAG_invalid));
+
+  // These aren't really tags: they describe ranges within tags.  They
+  // shouldn't be stringified either.
+  EXPECT_EQ(nullptr, TagString(DW_TAG_lo_user));
+  EXPECT_EQ(nullptr, TagString(DW_TAG_hi_user));
+  EXPECT_EQ(nullptr, TagString(DW_TAG_user_base));
+}
+
+} // end namespace