Refactor: Simplify boolean conditional return statements in llvm/lib/DebugInfo/DWARF

Use clang-tidy to simplify boolean conditional return statements. Patch by
Richard Thomson <legalize@xmission.com>!

Differential Revision: http://reviews.llvm.org/D9972

llvm-svn: 238132
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
index 63a9985..348476d 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -79,10 +79,7 @@
     return false;
 
   Abbrevs = Abbrev->getAbbreviationDeclarationSet(AbbrOffset);
-  if (Abbrevs == nullptr)
-    return false;
-
-  return true;
+  return Abbrevs != nullptr;
 }
 
 bool DWARFUnit::extract(DataExtractor debug_info, uint32_t *offset_ptr) {