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/Scalar/LoopIdiomRecognize.cpp b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
index 0f4a1b4..5042fc1 100644
--- a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -499,7 +499,7 @@
     Instruction *Inst = &*I++;
     // Look for memset instructions, which may be optimized to a larger memset.
     if (MemSetInst *MSI = dyn_cast<MemSetInst>(Inst)) {
-      WeakTrackingVH InstPtr(&*I);
+      WeakVH InstPtr(&*I);
       if (!processLoopMemSet(MSI, BECount))
         continue;
       MadeChange = true;