Revert "[CodeGenPrepare][NFC] Update the dominator tree instead of rebuilding it"

This reverts commit 0b1d1cd. It causes a clang crash. Details will be posted to D153638.

Author: rupprecht

llvm/include/llvm/Transforms/Utils/BypassSlowDivision.h

@@ -25,8 +25,6 @@
 namespace llvm {
 
 class BasicBlock;
-class DomTreeUpdater;
-class LoopInfo;
 class Value;
 
 struct DivRemMapKey {
@@ -68,9 +66,8 @@ template <> struct DenseMapInfo<DivRemMapKey> {
 ///
 /// This optimization may add basic blocks immediately after BB; for obvious
 /// reasons, you shouldn't pass those blocks to bypassSlowDivision.
-bool bypassSlowDivision(BasicBlock *BB,
-                        const DenseMap<unsigned int, unsigned int> &BypassWidth,
-                        DomTreeUpdater *DTU = nullptr, LoopInfo *LI = nullptr);
+bool bypassSlowDivision(
+    BasicBlock *BB, const DenseMap<unsigned int, unsigned int> &BypassWidth);
 
 } // end namespace llvm