Move iterator to where it's used and update comments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185498 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 24e04f4..70b9df4 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -443,7 +443,7 @@
   if (Ranges.empty())
     return 0;
 
-  SmallVector<InsnRange, 4>::const_iterator RI = Ranges.begin();
+  // If we have multiple ranges, emit them into the range section.
   if (Ranges.size() > 1) {
     // .debug_range section has not been laid out yet. Emit offset in
     // .debug_range as a uint, size 4, for now. emitDIE will handle
@@ -463,6 +463,8 @@
     return ScopeDIE;
   }
 
+  // Construct the address range for this DIE.
+  SmallVector<InsnRange, 4>::const_iterator RI = Ranges.begin();
   MCSymbol *Start = getLabelBeforeInsn(RI->first);
   MCSymbol *End = getLabelAfterInsn(RI->second);