Reverts commit r301424, r301425 and r301426

Commits were:

"Use WeakVH instead of WeakTrackingVH in AliasSetTracker's UnkownInsts"
"Add a new WeakVH value handle; NFC"
"Rename WeakVH to WeakTrackingVH; NFC"

The changes assumed pointers are 8 byte aligned on all architectures.

llvm-svn: 301429
diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index 1c2e6f6..43ab725 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -757,7 +757,7 @@
 
   // Simplify any new induction variables in the partially unrolled loop.
   if (SE && !CompletelyUnroll && Count > 1) {
-    SmallVector<WeakTrackingVH, 16> DeadInsts;
+    SmallVector<WeakVH, 16> DeadInsts;
     simplifyLoopIVs(L, SE, DT, LI, DeadInsts);
 
     // Aggressively clean up dead instructions that simplifyLoopIVs already