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/IR/Value.cpp b/llvm/lib/IR/Value.cpp
index 18e44dc..d83bdf2 100644
--- a/llvm/lib/IR/Value.cpp
+++ b/llvm/lib/IR/Value.cpp
@@ -826,9 +826,7 @@
       Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
       break;
     case Weak:
-    case WeakTracking:
-      // WeakTracking and Weak just go to null, which unlinks them
-      // from the list.
+      // Weak just goes to null, which will unlink it from the list.
       Entry->operator=(nullptr);
       break;
     case Callback:
@@ -876,20 +874,17 @@
 
     switch (Entry->getKind()) {
     case Assert:
-    case Weak:
-      // Asserting and Weak handles do not follow RAUW implicitly.
+      // Asserting handle does not follow RAUW implicitly.
       break;
     case Tracking:
-      // Tracking goes to new value like a WeakTrackingVH. Note that this may
-      // make it something incompatible with its templated type. We don't want
-      // to have a virtual (or inline) interface to handle this though, so
-      // instead we make the TrackingVH accessors guarantee that a client never
-      // sees this value.
+      // Tracking goes to new value like a WeakVH. Note that this may make it
+      // something incompatible with its templated type. We don't want to have a
+      // virtual (or inline) interface to handle this though, so instead we make
+      // the TrackingVH accessors guarantee that a client never sees this value.
 
       LLVM_FALLTHROUGH;
-    case WeakTracking:
-      // WeakTracking goes to the new value, which will unlink it from Old's
-      // list.
+    case Weak:
+      // Weak goes to the new value, which will unlink it from Old's list.
       Entry->operator=(New);
       break;
     case Callback:
@@ -906,7 +901,7 @@
     for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
       switch (Entry->getKind()) {
       case Tracking:
-      case WeakTracking:
+      case Weak:
         dbgs() << "After RAUW from " << *Old->getType() << " %"
                << Old->getName() << " to " << *New->getType() << " %"
                << New->getName() << "\n";