diff --git a/compiler/optimizing/loop_optimization.cc b/compiler/optimizing/loop_optimization.cc
index d249313..d39bc16 100644
--- a/compiler/optimizing/loop_optimization.cc
+++ b/compiler/optimizing/loop_optimization.cc
@@ -31,6 +31,9 @@
 // Enables vectorization (SIMDization) in the loop optimizer.
 static constexpr bool kEnableVectorization = true;
 
+// All current SIMD targets want 16-byte alignment.
+static constexpr size_t kAlignedBase = 16;
+
 // Remove the instruction from the graph. A bit more elaborate than the usual
 // instruction removal, since there may be a cycle in the use structure.
 static void RemoveFromCycle(HInstruction* instruction) {
@@ -283,6 +286,9 @@
       simplified_(false),
       vector_length_(0),
       vector_refs_(nullptr),
+      vector_peeling_candidate_(nullptr),
+      vector_runtime_test_a_(nullptr),
+      vector_runtime_test_b_(nullptr),
       vector_map_(nullptr) {
 }
 
@@ -422,23 +428,6 @@
 // Optimization.
 //
 
-bool HLoopOptimization::CanRemoveCycle() {
-  for (HInstruction* i : *iset_) {
-    // We can never remove instructions that have environment
-    // uses when we compile 'debuggable'.
-    if (i->HasEnvironmentUses() && graph_->IsDebuggable()) {
-      return false;
-    }
-    // A deoptimization should never have an environment input removed.
-    for (const HUseListNode<HEnvironment*>& use : i->GetEnvUses()) {
-      if (use.GetUser()->GetHolder()->IsDeoptimize()) {
-        return false;
-      }
-    }
-  }
-  return true;
-}
-
 void HLoopOptimization::SimplifyInduction(LoopNode* node) {
   HBasicBlock* header = node->loop_info->GetHeader();
   HBasicBlock* preheader = node->loop_info->GetPreHeader();
@@ -565,7 +554,7 @@
   if (kEnableVectorization) {
     iset_->clear();  // prepare phi induction
     if (TrySetSimpleLoopHeader(header) &&
-        CanVectorize(node, body, trip_count) &&
+        ShouldVectorize(node, body, trip_count) &&
         TryAssignLastValue(node->loop_info, phi, preheader, /*collect_loop_uses*/ true)) {
       Vectorize(node, body, exit, trip_count);
       graph_->SetHasSIMD(true);  // flag SIMD usage
@@ -580,10 +569,11 @@
 // Intel Press, June, 2004 (http://www.aartbik.com/).
 //
 
-bool HLoopOptimization::CanVectorize(LoopNode* node, HBasicBlock* block, int64_t trip_count) {
+bool HLoopOptimization::ShouldVectorize(LoopNode* node, HBasicBlock* block, int64_t trip_count) {
   // Reset vector bookkeeping.
   vector_length_ = 0;
   vector_refs_->clear();
+  vector_peeling_candidate_ = nullptr;
   vector_runtime_test_a_ =
   vector_runtime_test_b_= nullptr;
 
@@ -600,12 +590,9 @@
     }
   }
 
-  // Heuristics. Does vectorization seem profitable?
-  // TODO: refine
-  if (vector_length_ == 0) {
-    return false;  // nothing found
-  } else if (0 < trip_count && trip_count < vector_length_) {
-    return false;  // insufficient iterations
+  // Does vectorization seem profitable?
+  if (!IsVectorizationProfitable(trip_count)) {
+    return false;
   }
 
   // Data dependence analysis. Find each pair of references with same type, where
@@ -645,6 +632,9 @@
     }
   }
 
+  // Consider dynamic loop peeling for alignment.
+  SetPeelingCandidate(trip_count);
+
   // Success!
   return true;
 }
@@ -657,28 +647,52 @@
   HBasicBlock* header = node->loop_info->GetHeader();
   HBasicBlock* preheader = node->loop_info->GetPreHeader();
 
-  // A cleanup is needed for any unknown trip count or for a known trip count
-  // with remainder iterations after vectorization.
-  bool needs_cleanup = trip_count == 0 || (trip_count % vector_length_) != 0;
+  // Pick a loop unrolling factor for the vector loop.
+  uint32_t unroll = GetUnrollingFactor(block, trip_count);
+  uint32_t chunk = vector_length_ * unroll;
+
+  // A cleanup loop is needed, at least, for any unknown trip count or
+  // for a known trip count with remainder iterations after vectorization.
+  bool needs_cleanup = trip_count == 0 || (trip_count % chunk) != 0;
 
   // Adjust vector bookkeeping.
   iset_->clear();  // prepare phi induction
   bool is_simple_loop_header = TrySetSimpleLoopHeader(header);  // fills iset_
   DCHECK(is_simple_loop_header);
+  vector_header_ = header;
+  vector_body_ = block;
 
-  // Generate preheader:
+  // Generate dynamic loop peeling trip count, if needed:
+  // ptc = <peeling-needed-for-candidate>
+  HInstruction* ptc = nullptr;
+  if (vector_peeling_candidate_ != nullptr) {
+    DCHECK_LT(vector_length_, trip_count) << "dynamic peeling currently requires known trip count";
+    //
+    // TODO: Implement this. Compute address of first access memory location and
+    //       compute peeling factor to obtain kAlignedBase alignment.
+    //
+    needs_cleanup = true;
+  }
+
+  // Generate loop control:
   // stc = <trip-count>;
-  // vtc = stc - stc % VL;
+  // vtc = stc - (stc - ptc) % chunk;
+  // i = 0;
   HInstruction* stc = induction_range_.GenerateTripCount(node->loop_info, graph_, preheader);
   HInstruction* vtc = stc;
   if (needs_cleanup) {
-    DCHECK(IsPowerOfTwo(vector_length_));
+    DCHECK(IsPowerOfTwo(chunk));
+    HInstruction* diff = stc;
+    if (ptc != nullptr) {
+      diff = Insert(preheader, new (global_allocator_) HSub(induc_type, stc, ptc));
+    }
     HInstruction* rem = Insert(
         preheader, new (global_allocator_) HAnd(induc_type,
-                                                stc,
-                                                graph_->GetIntConstant(vector_length_ - 1)));
+                                                diff,
+                                                graph_->GetIntConstant(chunk - 1)));
     vtc = Insert(preheader, new (global_allocator_) HSub(induc_type, stc, rem));
   }
+  vector_index_ = graph_->GetIntConstant(0);
 
   // Generate runtime disambiguation test:
   // vtc = a != b ? vtc : 0;
@@ -691,16 +705,31 @@
     needs_cleanup = true;
   }
 
-  // Generate vector loop:
-  // for (i = 0; i < vtc; i += VL)
+  // Generate dynamic peeling loop for alignment, if needed:
+  // for ( ; i < ptc; i += 1)
+  //    <loop-body>
+  if (ptc != nullptr) {
+    vector_mode_ = kSequential;
+    GenerateNewLoop(node,
+                    block,
+                    graph_->TransformLoopForVectorization(vector_header_, vector_body_, exit),
+                    vector_index_,
+                    ptc,
+                    graph_->GetIntConstant(1),
+                    /*unroll*/ 1);
+  }
+
+  // Generate vector loop, possibly further unrolled:
+  // for ( ; i < vtc; i += chunk)
   //    <vectorized-loop-body>
   vector_mode_ = kVector;
   GenerateNewLoop(node,
                   block,
-                  graph_->TransformLoopForVectorization(header, block, exit),
-                  graph_->GetIntConstant(0),
+                  graph_->TransformLoopForVectorization(vector_header_, vector_body_, exit),
+                  vector_index_,
                   vtc,
-                  graph_->GetIntConstant(vector_length_));
+                  graph_->GetIntConstant(vector_length_),  // increment per unroll
+                  unroll);
   HLoopInformation* vloop = vector_header_->GetLoopInformation();
 
   // Generate cleanup loop, if needed:
@@ -711,9 +740,10 @@
     GenerateNewLoop(node,
                     block,
                     graph_->TransformLoopForVectorization(vector_header_, vector_body_, exit),
-                    vector_phi_,
+                    vector_index_,
                     stc,
-                    graph_->GetIntConstant(1));
+                    graph_->GetIntConstant(1),
+                    /*unroll*/ 1);
   }
 
   // Remove the original loop by disconnecting the body block
@@ -722,8 +752,9 @@
   while (!header->GetFirstInstruction()->IsGoto()) {
     header->RemoveInstruction(header->GetFirstInstruction());
   }
-  // Update loop hierarchy: the old header now resides in the
-  // same outer loop as the old preheader.
+  // Update loop hierarchy: the old header now resides in the same outer loop
+  // as the old preheader. Note that we don't bother putting sequential
+  // loops back in the hierarchy at this point.
   header->SetLoopInformation(preheader->GetLoopInformation());  // outward
   node->loop_info = vloop;
 }
@@ -733,44 +764,64 @@
                                         HBasicBlock* new_preheader,
                                         HInstruction* lo,
                                         HInstruction* hi,
-                                        HInstruction* step) {
+                                        HInstruction* step,
+                                        uint32_t unroll) {
+  DCHECK(unroll == 1 || vector_mode_ == kVector);
   Primitive::Type induc_type = Primitive::kPrimInt;
   // Prepare new loop.
-  vector_map_->clear();
   vector_preheader_ = new_preheader,
   vector_header_ = vector_preheader_->GetSingleSuccessor();
   vector_body_ = vector_header_->GetSuccessors()[1];
-  vector_phi_ = new (global_allocator_) HPhi(global_allocator_,
-                                             kNoRegNumber,
-                                             0,
-                                             HPhi::ToPhiType(induc_type));
+  HPhi* phi = new (global_allocator_) HPhi(global_allocator_,
+                                           kNoRegNumber,
+                                           0,
+                                           HPhi::ToPhiType(induc_type));
   // Generate header and prepare body.
   // for (i = lo; i < hi; i += step)
   //    <loop-body>
-  HInstruction* cond = new (global_allocator_) HAboveOrEqual(vector_phi_, hi);
-  vector_header_->AddPhi(vector_phi_);
+  HInstruction* cond = new (global_allocator_) HAboveOrEqual(phi, hi);
+  vector_header_->AddPhi(phi);
   vector_header_->AddInstruction(cond);
   vector_header_->AddInstruction(new (global_allocator_) HIf(cond));
-  for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) {
-    bool vectorized_def = VectorizeDef(node, it.Current(), /*generate_code*/ true);
-    DCHECK(vectorized_def);
-  }
-  // Generate body from the instruction map, but in original program order.
-  HEnvironment* env = vector_header_->GetFirstInstruction()->GetEnvironment();
-  for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) {
-    auto i = vector_map_->find(it.Current());
-    if (i != vector_map_->end() && !i->second->IsInBlock()) {
-      Insert(vector_body_, i->second);
-      // Deal with instructions that need an environment, such as the scalar intrinsics.
-      if (i->second->NeedsEnvironment()) {
-        i->second->CopyEnvironmentFromWithLoopPhiAdjustment(env, vector_header_);
+  vector_index_ = phi;
+  for (uint32_t u = 0; u < unroll; u++) {
+    // Clear map, leaving loop invariants setup during unrolling.
+    if (u == 0) {
+      vector_map_->clear();
+    } else {
+      for (auto i = vector_map_->begin(); i != vector_map_->end(); ) {
+        if (i->second->IsVecReplicateScalar()) {
+          DCHECK(node->loop_info->IsDefinedOutOfTheLoop(i->first));
+          ++i;
+        } else {
+          i = vector_map_->erase(i);
+        }
       }
     }
+    // Generate instruction map.
+    for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) {
+      bool vectorized_def = VectorizeDef(node, it.Current(), /*generate_code*/ true);
+      DCHECK(vectorized_def);
+    }
+    // Generate body from the instruction map, but in original program order.
+    HEnvironment* env = vector_header_->GetFirstInstruction()->GetEnvironment();
+    for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) {
+      auto i = vector_map_->find(it.Current());
+      if (i != vector_map_->end() && !i->second->IsInBlock()) {
+        Insert(vector_body_, i->second);
+        // Deal with instructions that need an environment, such as the scalar intrinsics.
+        if (i->second->NeedsEnvironment()) {
+          i->second->CopyEnvironmentFromWithLoopPhiAdjustment(env, vector_header_);
+        }
+      }
+    }
+    vector_index_ = new (global_allocator_) HAdd(induc_type, vector_index_, step);
+    Insert(vector_body_, vector_index_);
   }
-  // Finalize increment and phi.
-  HInstruction* inc = new (global_allocator_) HAdd(induc_type, vector_phi_, step);
-  vector_phi_->AddInput(lo);
-  vector_phi_->AddInput(Insert(vector_body_, inc));
+  // Finalize phi for the loop index.
+  phi->AddInput(lo);
+  phi->AddInput(vector_index_);
+  vector_index_ = phi;
 }
 
 // TODO: accept reductions at left-hand-side, mixed-type store idioms, etc.
@@ -795,7 +846,7 @@
         VectorizeUse(node, value, generate_code, type, restrictions)) {
       if (generate_code) {
         GenerateVecSub(index, offset);
-        GenerateVecMem(instruction, vector_map_->Get(index), vector_map_->Get(value), type);
+        GenerateVecMem(instruction, vector_map_->Get(index), vector_map_->Get(value), offset, type);
       } else {
         vector_refs_->insert(ArrayReference(base, offset, type, /*lhs*/ true));
       }
@@ -852,7 +903,7 @@
         induction_range_.IsUnitStride(instruction, index, &offset)) {
       if (generate_code) {
         GenerateVecSub(index, offset);
-        GenerateVecMem(instruction, vector_map_->Get(index), nullptr, type);
+        GenerateVecMem(instruction, vector_map_->Get(index), nullptr, offset, type);
       } else {
         vector_refs_->insert(ArrayReference(base, offset, type, /*lhs*/ false));
       }
@@ -1164,7 +1215,7 @@
 
 void HLoopOptimization::GenerateVecSub(HInstruction* org, HInstruction* offset) {
   if (vector_map_->find(org) == vector_map_->end()) {
-    HInstruction* subscript = vector_phi_;
+    HInstruction* subscript = vector_index_;
     if (offset != nullptr) {
       subscript = new (global_allocator_) HAdd(Primitive::kPrimInt, subscript, offset);
       if (org->IsPhi()) {
@@ -1178,17 +1229,27 @@
 void HLoopOptimization::GenerateVecMem(HInstruction* org,
                                        HInstruction* opa,
                                        HInstruction* opb,
+                                       HInstruction* offset,
                                        Primitive::Type type) {
   HInstruction* vector = nullptr;
   if (vector_mode_ == kVector) {
     // Vector store or load.
+    HInstruction* base = org->InputAt(0);
     if (opb != nullptr) {
       vector = new (global_allocator_) HVecStore(
-          global_allocator_, org->InputAt(0), opa, opb, type, vector_length_);
+          global_allocator_, base, opa, opb, type, vector_length_);
     } else  {
       bool is_string_char_at = org->AsArrayGet()->IsStringCharAt();
       vector = new (global_allocator_) HVecLoad(
-          global_allocator_, org->InputAt(0), opa, type, vector_length_, is_string_char_at);
+          global_allocator_, base, opa, type, vector_length_, is_string_char_at);
+    }
+    // Known dynamically enforced alignment?
+    // TODO: detect offset + constant differences.
+    // TODO: long run, static alignment analysis?
+    if (vector_peeling_candidate_ != nullptr &&
+        vector_peeling_candidate_->base == base &&
+        vector_peeling_candidate_->offset == offset) {
+      vector->AsVecMemoryOperation()->SetAlignment(Alignment(kAlignedBase, 0));
     }
   } else {
     // Scalar store or load.
@@ -1444,6 +1505,47 @@
 }
 
 //
+// Vectorization heuristics.
+//
+
+bool HLoopOptimization::IsVectorizationProfitable(int64_t trip_count) {
+  // Current heuristic: non-empty body with sufficient number
+  // of iterations (if known).
+  // TODO: refine by looking at e.g. operation count, alignment, etc.
+  if (vector_length_ == 0) {
+    return false;  // nothing found
+  } else if (0 < trip_count && trip_count < vector_length_) {
+    return false;  // insufficient iterations
+  }
+  return true;
+}
+
+void HLoopOptimization::SetPeelingCandidate(int64_t trip_count ATTRIBUTE_UNUSED) {
+  // Current heuristic: none.
+  // TODO: implement
+}
+
+uint32_t HLoopOptimization::GetUnrollingFactor(HBasicBlock* block, int64_t trip_count) {
+  // Current heuristic: unroll by 2 on ARM64/X86 for large known trip
+  // counts and small loop bodies.
+  // TODO: refine with operation count, remaining iterations, etc.
+  //       Artem had some really cool ideas for this already.
+  switch (compiler_driver_->GetInstructionSet()) {
+    case kArm64:
+    case kX86:
+    case kX86_64: {
+      size_t num_instructions = block->GetInstructions().CountSize();
+      if (num_instructions <= 10 && trip_count >= 4 * vector_length_) {
+        return 2;
+      }
+      return 1;
+    }
+    default:
+      return 1;
+  }
+}
+
+//
 // Helpers.
 //
 
@@ -1576,8 +1678,8 @@
       size_t index = it->GetIndex();
       ++it;  // increment before replacing
       if (iset_->find(user->GetHolder()) == iset_->end()) {  // not excluded?
-        HLoopInformation* other_loop_info = user->GetHolder()->GetBlock()->GetLoopInformation();
         // Only update environment uses after the loop.
+        HLoopInformation* other_loop_info = user->GetHolder()->GetBlock()->GetLoopInformation();
         if (other_loop_info == nullptr || !other_loop_info->IsIn(*loop_info)) {
           user->RemoveAsUserOfInput(index);
           user->SetRawEnvAt(index, replacement);
@@ -1614,4 +1716,21 @@
   }
 }
 
+bool HLoopOptimization::CanRemoveCycle() {
+  for (HInstruction* i : *iset_) {
+    // We can never remove instructions that have environment
+    // uses when we compile 'debuggable'.
+    if (i->HasEnvironmentUses() && graph_->IsDebuggable()) {
+      return false;
+    }
+    // A deoptimization should never have an environment input removed.
+    for (const HUseListNode<HEnvironment*>& use : i->GetEnvUses()) {
+      if (use.GetUser()->GetHolder()->IsDeoptimize()) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
 }  // namespace art