Fix a bug in DebugInfo lib, extend a comment for one of the methods

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159707 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/DebugInfo/DWARFCompileUnit.cpp b/lib/DebugInfo/DWARFCompileUnit.cpp
index 2683990..6d4c7df 100644
--- a/lib/DebugInfo/DWARFCompileUnit.cpp
+++ b/lib/DebugInfo/DWARFCompileUnit.cpp
@@ -239,8 +239,8 @@
 
 const DWARFDebugInfoEntryMinimal*
 DWARFCompileUnit::getFunctionDIEForAddress(int64_t address) {
-  size_t n = extractDIEsIfNeeded(false);
-  for (size_t i = 0; i != n; i++) {
+  extractDIEsIfNeeded(false);
+  for (size_t i = 0, n = DieArray.size(); i != n; i++) {
     if (DieArray[i].addressRangeContainsAddress(this, address))
       return &DieArray[i];
   }