Rename WeakVH to WeakTrackingVH; NFC

Summary:
I plan to use WeakVH to mean "nulls itself out on deletion, but does
not track RAUW" in a subsequent commit.

Reviewers: dblaikie, davide

Reviewed By: davide

Subscribers: arsenm, mehdi_amini, mcrosier, mzolotukhin, jfb, llvm-commits, nhaehnle

Differential Revision: https://reviews.llvm.org/D32266

llvm-svn: 301424
diff --git a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
index 8fa806a..dbec0c0 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -1231,11 +1231,11 @@
   LoopProcessWorklist.push_back(NewLoop);
   redoLoop = true;
 
-  // Keep a WeakVH holding onto LIC.  If the first call to RewriteLoopBody
-  // deletes the instruction (for example by simplifying a PHI that feeds into
-  // the condition that we're unswitching on), we don't rewrite the second
-  // iteration.
-  WeakVH LICHandle(LIC);
+  // Keep a WeakTrackingVH holding onto LIC.  If the first call to
+  // RewriteLoopBody deletes the instruction (for example by simplifying a PHI
+  // that feeds into the condition that we're unswitching on), we don't rewrite
+  // the second iteration.
+  WeakTrackingVH LICHandle(LIC);
 
   // Now we rewrite the original code to know that the condition is true and the
   // new code to know that the condition is false.