[SimplifyCFG] Drop unused LockstepReverseIterator class (NFC)

Unmaintained code has been removed.

Author: antoniofrighetto

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

@@ -1774,77 +1774,6 @@ static bool isSafeCheapLoadStore(const Instruction *I,
          getLoadStoreAlignment(I) < Value::MaximumAlignment;
 }
 
-namespace {
-
-// LockstepReverseIterator - Iterates through instructions
-// in a set of blocks in reverse order from the first non-terminator.
-// For example (assume all blocks have size n):
-//   LockstepReverseIterator I([B1, B2, B3]);
-//   *I-- = [B1[n], B2[n], B3[n]];
-//   *I-- = [B1[n-1], B2[n-1], B3[n-1]];
-//   *I-- = [B1[n-2], B2[n-2], B3[n-2]];
-//   ...
-class LockstepReverseIterator {
-  ArrayRef<BasicBlock *> Blocks;
-  SmallVector<Instruction *, 4> Insts;
-  bool Fail;
-
-public:
-  LockstepReverseIterator(ArrayRef<BasicBlock *> Blocks) : Blocks(Blocks) {
-    reset();
-  }
-
-  void reset() {
-    Fail = false;
-    Insts.clear();
-    for (auto *BB : Blocks) {
-      Instruction *Inst = BB->getTerminator();
-      for (Inst = Inst->getPrevNode(); Inst && isa<DbgInfoIntrinsic>(Inst);)
-        Inst = Inst->getPrevNode();
-      if (!Inst) {
-        // Block wasn't big enough.
-        Fail = true;
-        return;
-      }
-      Insts.push_back(Inst);
-    }
-  }
-
-  bool isValid() const { return !Fail; }
-
-  void operator--() {
-    if (Fail)
-      return;
-    for (auto *&Inst : Insts) {
-      for (Inst = Inst->getPrevNode(); Inst && isa<DbgInfoIntrinsic>(Inst);)
-        Inst = Inst->getPrevNode();
-      // Already at beginning of block.
-      if (!Inst) {
-        Fail = true;
-        return;
-      }
-    }
-  }
-
-  void operator++() {
-    if (Fail)
-      return;
-    for (auto *&Inst : Insts) {
-      for (Inst = Inst->getNextNode(); Inst && isa<DbgInfoIntrinsic>(Inst);)
-        Inst = Inst->getNextNode();
-      // Already at end of block.
-      if (!Inst) {
-        Fail = true;
-        return;
-      }
-    }
-  }
-
-  ArrayRef<Instruction *> operator*() const { return Insts; }
-};
-
-} // end anonymous namespace
-
 /// Hoist any common code in the successor blocks up into the block. This
 /// function guarantees that BB dominates all successors. If AllInstsEqOnly is
 /// given, only perform hoisting in case all successors blocks contain matching
@@ -1896,7 +1825,7 @@ bool SimplifyCFGOpt::hoistCommonCodeFromSuccessors(Instruction *TI,
     if (!AllSame)
       return false;
     if (AllSame) {
-      LockstepReverseIterator LRI(Succs);
+      LockstepReverseIterator<true> LRI(Succs);
       while (LRI.isValid()) {
         Instruction *I0 = (*LRI)[0];
         if (any_of(*LRI, [I0](Instruction *I) {