Refactor DexInstructionIterator

Add a way to get the dex PC for the "for each" use case.

Bug: 67104794
Test: test-art-host
Change-Id: I144c459c9a2a03ec8d56842280338d1f7ce1caf0

16 files changed, 164 insertions, 108 deletions

diff --git a/compiler/dex/inline_method_analyser.cc b/compiler/dex/inline_method_analyser.cc
index 925863ef0e..518b0ece73 100644
--- a/compiler/dex/inline_method_analyser.cc
+++ b/compiler/dex/inline_method_analyser.cc
@@ -302,7 +302,8 @@ bool DoAnalyseConstructor(const DexFile::CodeItem* code_item,
   uint16_t this_vreg = code_item->registers_size_ - code_item->ins_size_;
   uint16_t zero_vreg_mask = 0u;
 
-  for (const Instruction& instruction : code_item->Instructions()) {
+  for (const DexInstructionPcPair& pair : code_item->Instructions()) {
+    const Instruction& instruction = pair.Inst();
     if (instruction.Opcode() == Instruction::RETURN_VOID) {
       break;
     } else if (instruction.Opcode() == Instruction::INVOKE_DIRECT) {
diff --git a/compiler/dex/verified_method.cc b/compiler/dex/verified_method.cc
index 9c5b63232e..df75e07c3f 100644
--- a/compiler/dex/verified_method.cc
+++ b/compiler/dex/verified_method.cc
@@ -64,12 +64,11 @@ void VerifiedMethod::GenerateSafeCastSet(verifier::MethodVerifier* method_verifi
   if (method_verifier->HasFailures()) {
     return;
   }
-  IterationRange<DexInstructionIterator> instructions = method_verifier->CodeItem()->Instructions();
-  for (auto it = instructions.begin(); it != instructions.end(); ++it) {
-    const Instruction& inst = *it;
+  for (const DexInstructionPcPair& pair : method_verifier->CodeItem()->Instructions()) {
+    const Instruction& inst = pair.Inst();
     const Instruction::Code code = inst.Opcode();
     if (code == Instruction::CHECK_CAST) {
-      const uint32_t dex_pc = it.GetDexPC(instructions.begin());
+      const uint32_t dex_pc = pair.DexPc();
       if (!method_verifier->GetInstructionFlags(dex_pc).IsVisited()) {
         // Do not attempt to quicken this instruction, it's unreachable anyway.
         continue;
diff --git a/compiler/driver/compiler_driver.cc b/compiler/driver/compiler_driver.cc
index 135f9c7b47..ed3f0d2081 100644
--- a/compiler/driver/compiler_driver.cc
+++ b/compiler/driver/compiler_driver.cc
@@ -736,13 +736,13 @@ static void ResolveConstStrings(Handle<mirror::DexCache> dex_cache,
   }
 
   ClassLinker* const class_linker = Runtime::Current()->GetClassLinker();
-  for (const Instruction& inst : code_item->Instructions()) {
-    switch (inst.Opcode()) {
+  for (const DexInstructionPcPair& inst : code_item->Instructions()) {
+    switch (inst->Opcode()) {
       case Instruction::CONST_STRING:
       case Instruction::CONST_STRING_JUMBO: {
-        dex::StringIndex string_index((inst.Opcode() == Instruction::CONST_STRING)
-            ? inst.VRegB_21c()
-            : inst.VRegB_31c());
+        dex::StringIndex string_index((inst->Opcode() == Instruction::CONST_STRING)
+            ? inst->VRegB_21c()
+            : inst->VRegB_31c());
         mirror::String* string = class_linker->ResolveString(dex_file, string_index, dex_cache);
         CHECK(string != nullptr) << "Could not allocate a string when forcing determinism";
         break;
@@ -2416,14 +2416,14 @@ class InitializeClassVisitor : public CompilationVisitor {
     if (clinit != nullptr) {
       const DexFile::CodeItem* code_item = clinit->GetCodeItem();
       DCHECK(code_item != nullptr);
-      for (const Instruction& inst : code_item->Instructions()) {
-        if (inst.Opcode() == Instruction::CONST_STRING) {
+      for (const DexInstructionPcPair& inst : code_item->Instructions()) {
+        if (inst->Opcode() == Instruction::CONST_STRING) {
           ObjPtr<mirror::String> s = class_linker->ResolveString(
-              *dex_file, dex::StringIndex(inst.VRegB_21c()), h_dex_cache);
+              *dex_file, dex::StringIndex(inst->VRegB_21c()), h_dex_cache);
           CHECK(s != nullptr);
-        } else if (inst.Opcode() == Instruction::CONST_STRING_JUMBO) {
+        } else if (inst->Opcode() == Instruction::CONST_STRING_JUMBO) {
           ObjPtr<mirror::String> s = class_linker->ResolveString(
-              *dex_file, dex::StringIndex(inst.VRegB_31c()), h_dex_cache);
+              *dex_file, dex::StringIndex(inst->VRegB_31c()), h_dex_cache);
           CHECK(s != nullptr);
         }
       }
diff --git a/compiler/optimizing/code_generator.cc b/compiler/optimizing/code_generator.cc
index b8d1f52995..23142514f7 100644
--- a/compiler/optimizing/code_generator.cc
+++ b/compiler/optimizing/code_generator.cc
@@ -919,10 +919,9 @@ static void CheckLoopEntriesCanBeUsedForOsr(const HGraph& graph,
   }
   ArenaVector<size_t> covered(
       loop_headers.size(), 0, graph.GetAllocator()->Adapter(kArenaAllocMisc));
-  IterationRange<DexInstructionIterator> instructions = code_item.Instructions();
-  for (auto it = instructions.begin(); it != instructions.end(); ++it) {
-    const uint32_t dex_pc = it.GetDexPC(instructions.begin());
-    const Instruction& instruction = *it;
+  for (const DexInstructionPcPair& pair : code_item.Instructions()) {
+    const uint32_t dex_pc = pair.DexPc();
+    const Instruction& instruction = pair.Inst();
     if (instruction.IsBranch()) {
       uint32_t target = dex_pc + instruction.GetTargetOffset();
       CheckCovers(target, graph, code_info, loop_headers, &covered);
diff --git a/compiler/optimizing/instruction_builder.cc b/compiler/optimizing/instruction_builder.cc
index 902985e4ee..0f0be20961 100644
--- a/compiler/optimizing/instruction_builder.cc
+++ b/compiler/optimizing/instruction_builder.cc
@@ -382,16 +382,18 @@ ArenaBitVector* HInstructionBuilder::FindNativeDebugInfoLocations() {
   dex_file_->DecodeDebugPositionInfo(&code_item_, Callback::Position, locations);
   // Instruction-specific tweaks.
   IterationRange<DexInstructionIterator> instructions = code_item_.Instructions();
-  for (const Instruction& inst : instructions) {
-    switch (inst.Opcode()) {
+  for (DexInstructionIterator it = instructions.begin(); it != instructions.end(); ++it) {
+    switch (it->Opcode()) {
       case Instruction::MOVE_EXCEPTION: {
         // Stop in native debugger after the exception has been moved.
         // The compiler also expects the move at the start of basic block so
         // we do not want to interfere by inserting native-debug-info before it.
-        locations->ClearBit(inst.GetDexPc(code_item_.insns_));
-        const Instruction* next = inst.Next();
-        if (DexInstructionIterator(next) != instructions.end()) {
-          locations->SetBit(next->GetDexPc(code_item_.insns_));
+        locations->ClearBit(it.DexPc());
+        DexInstructionIterator next = it;
+        ++next;
+        DCHECK(next != it);
+        if (next != instructions.end()) {
+          locations->SetBit(next.DexPc());
         }
         break;
       }
diff --git a/dexlayout/dex_ir.cc b/dexlayout/dex_ir.cc
index 23c3a5ca93..3edb0a44f2 100644
--- a/dexlayout/dex_ir.cc
+++ b/dexlayout/dex_ir.cc
@@ -173,11 +173,11 @@ static bool GetIdsFromByteCode(Collections& collections,
     // In case the instruction goes past the end of the code item, make sure to not process it.
     SafeDexInstructionIterator next = it;
     ++next;
-    if (next.IsErrorState() || next > instructions.end()) {
+    if (next.IsErrorState()) {
       break;
     }
     has_id |= GetIdFromInstruction(collections,
-                                   it.Inst(),
+                                   &it.Inst(),
                                    type_ids,
                                    string_ids,
                                    method_ids,
diff --git a/dexlayout/dex_ir.h b/dexlayout/dex_ir.h
index 99a66f348c..179d3b96e0 100644
--- a/dexlayout/dex_ir.h
+++ b/dexlayout/dex_ir.h
@@ -952,8 +952,8 @@ class CodeItem : public Item {
   void Accept(AbstractDispatcher* dispatch) { dispatch->Dispatch(this); }
 
   IterationRange<DexInstructionIterator> Instructions() const {
-    return MakeIterationRange(DexInstructionIterator(Insns()),
-                              DexInstructionIterator(Insns() + InsnsSize()));
+    return MakeIterationRange(DexInstructionIterator(Insns(), 0u),
+                              DexInstructionIterator(Insns(), InsnsSize()));
   }
 
  private:
diff --git a/dexlayout/dexlayout.cc b/dexlayout/dexlayout.cc
index 9a2ab665ba..dd2e809a92 100644
--- a/dexlayout/dexlayout.cc
+++ b/dexlayout/dexlayout.cc
@@ -1054,15 +1054,13 @@ void DexLayout::DumpBytecodes(uint32_t idx, const dex_ir::CodeItem* code, uint32
           code_offset, code_offset, dot.c_str(), name, type_descriptor.c_str());
 
   // Iterate over all instructions.
-  IterationRange<DexInstructionIterator> instructions = code->Instructions();
-  for (auto inst = instructions.begin(); inst != instructions.end(); ++inst) {
-    const uint32_t dex_pc = inst.GetDexPC(instructions.begin());
+  for (const DexInstructionPcPair& inst : code->Instructions()) {
     const uint32_t insn_width = inst->SizeInCodeUnits();
     if (insn_width == 0) {
-      fprintf(stderr, "GLITCH: zero-width instruction at idx=0x%04x\n", dex_pc);
+      fprintf(stderr, "GLITCH: zero-width instruction at idx=0x%04x\n", inst.DexPc());
       break;
     }
-    DumpInstruction(code, code_offset, dex_pc, insn_width, &*inst);
+    DumpInstruction(code, code_offset, inst.DexPc(), insn_width, &inst.Inst());
   }  // for
 }
 
diff --git a/dexlayout/dexlayout_test.cc b/dexlayout/dexlayout_test.cc
index 38d3c6ec07..08673056d9 100644
--- a/dexlayout/dexlayout_test.cc
+++ b/dexlayout/dexlayout_test.cc
@@ -724,7 +724,7 @@ TEST_F(DexLayoutTest, CodeItemOverrun) {
             }
             if (last_instruction->SizeInCodeUnits() == 1) {
               // Set the opcode to something that will go past the end of the code item.
-              const_cast<Instruction*>(last_instruction.Inst())->SetOpcode(
+              const_cast<Instruction&>(last_instruction.Inst()).SetOpcode(
                   Instruction::CONST_STRING_JUMBO);
               mutated_successfully = true;
               // Test that the safe iterator doesn't go past the end.
diff --git a/oatdump/oatdump.cc b/oatdump/oatdump.cc
index 7064fa3a9b..40efafc05f 100644
--- a/oatdump/oatdump.cc
+++ b/oatdump/oatdump.cc
@@ -1000,16 +1000,16 @@ class OatDumper {
         dex_code_bytes_ += code_item->insns_size_in_code_units_ * sizeof(code_ptr[0]);
       }
 
-      for (const Instruction& inst : code_item->Instructions()) {
-        switch (inst.Opcode()) {
+      for (const DexInstructionPcPair& inst : code_item->Instructions()) {
+        switch (inst->Opcode()) {
           case Instruction::CONST_STRING: {
-            const dex::StringIndex string_index(inst.VRegB_21c());
+            const dex::StringIndex string_index(inst->VRegB_21c());
             unique_string_ids_from_code_.insert(StringReference(&dex_file, string_index));
             ++num_string_ids_from_code_;
             break;
           }
           case Instruction::CONST_STRING_JUMBO: {
-            const dex::StringIndex string_index(inst.VRegB_31c());
+            const dex::StringIndex string_index(inst->VRegB_31c());
             unique_string_ids_from_code_.insert(StringReference(&dex_file, string_index));
             ++num_string_ids_from_code_;
             break;
@@ -1624,11 +1624,9 @@ class OatDumper {
 
   void DumpDexCode(std::ostream& os, const DexFile& dex_file, const DexFile::CodeItem* code_item) {
     if (code_item != nullptr) {
-      IterationRange<DexInstructionIterator> instructions = code_item->Instructions();
-      for (auto it = instructions.begin(); it != instructions.end(); ++it) {
-        const size_t dex_pc = it.GetDexPC(instructions.begin());
-        os << StringPrintf("0x%04zx: ", dex_pc) << it->DumpHexLE(5)
-           << StringPrintf("\t| %s\n", it->DumpString(&dex_file).c_str());
+      for (const DexInstructionPcPair& inst : code_item->Instructions()) {
+        os << StringPrintf("0x%04x: ", inst.DexPc()) << inst->DumpHexLE(5)
+           << StringPrintf("\t| %s\n", inst->DumpString(&dex_file).c_str());
       }
     }
   }
diff --git a/runtime/dex_file.h b/runtime/dex_file.h
index c895e0d1da..c0e0fbcf8f 100644
--- a/runtime/dex_file.h
+++ b/runtime/dex_file.h
@@ -305,8 +305,8 @@ class DexFile {
   // Raw code_item.
   struct CodeItem {
     IterationRange<DexInstructionIterator> Instructions() const {
-      return { DexInstructionIterator(insns_),
-               DexInstructionIterator(insns_ + insns_size_in_code_units_)};
+      return { DexInstructionIterator(insns_, 0u),
+               DexInstructionIterator(insns_, insns_size_in_code_units_) };
     }
 
     const Instruction& InstructionAt(uint32_t dex_pc) const {
diff --git a/runtime/dex_instruction_iterator.h b/runtime/dex_instruction_iterator.h
index 9e4dea34bb..f77908cffc 100644
--- a/runtime/dex_instruction_iterator.h
+++ b/runtime/dex_instruction_iterator.h
@@ -24,33 +24,69 @@
 
 namespace art {
 
+class DexInstructionPcPair {
+ public:
+  ALWAYS_INLINE const Instruction& Inst() const {
+    return *Instruction::At(instructions_ + DexPc());
+  }
+
+  ALWAYS_INLINE const Instruction* operator->() const {
+    return &Inst();
+  }
+
+  ALWAYS_INLINE uint32_t DexPc() const {
+    return dex_pc_;
+  }
+
+  ALWAYS_INLINE const uint16_t* Instructions() const {
+    return instructions_;
+  }
+
+ protected:
+  explicit DexInstructionPcPair(const uint16_t* instructions, uint32_t dex_pc)
+      : instructions_(instructions), dex_pc_(dex_pc) {}
+
+  const uint16_t* instructions_ = nullptr;
+  uint32_t dex_pc_ = 0;
+
+  friend class DexInstructionIteratorBase;
+  friend class DexInstructionIterator;
+  friend class SafeDexInstructionIterator;
+};
+
 // Base helper class to prevent duplicated comparators.
-class DexInstructionIteratorBase : public std::iterator<std::forward_iterator_tag, Instruction> {
+class DexInstructionIteratorBase : public
+        std::iterator<std::forward_iterator_tag, DexInstructionPcPair> {
  public:
-  using value_type = std::iterator<std::forward_iterator_tag, Instruction>::value_type;
+  using value_type = std::iterator<std::forward_iterator_tag, DexInstructionPcPair>::value_type;
   using difference_type = std::iterator<std::forward_iterator_tag, value_type>::difference_type;
 
   DexInstructionIteratorBase() = default;
-  explicit DexInstructionIteratorBase(const value_type* inst) : inst_(inst) {}
+  explicit DexInstructionIteratorBase(const Instruction* inst, uint32_t dex_pc)
+      : data_(reinterpret_cast<const uint16_t*>(inst), dex_pc) {}
 
-  const value_type* Inst() const {
-    return inst_;
+  const Instruction& Inst() const {
+    return data_.Inst();
   }
 
   // Return the dex pc for an iterator compared to the code item begin.
-  uint32_t GetDexPC(const DexInstructionIteratorBase& code_item_begin) {
-    return reinterpret_cast<const uint16_t*>(inst_) -
-        reinterpret_cast<const uint16_t*>(code_item_begin.inst_);
+  ALWAYS_INLINE uint32_t DexPc() const {
+    return data_.DexPc();
+  }
+
+  // Instructions from the start of the code item.
+  ALWAYS_INLINE const uint16_t* Instructions() const {
+    return data_.Instructions();
   }
 
  protected:
-  const value_type* inst_ = nullptr;
+  DexInstructionPcPair data_;
 };
 
-
 static ALWAYS_INLINE inline bool operator==(const DexInstructionIteratorBase& lhs,
                                             const DexInstructionIteratorBase& rhs) {
-  return lhs.Inst() == rhs.Inst();
+  DCHECK_EQ(lhs.Instructions(), rhs.Instructions()) << "Comparing different code items.";
+  return lhs.DexPc() == rhs.DexPc();
 }
 
 static inline bool operator!=(const DexInstructionIteratorBase& lhs,
@@ -60,7 +96,8 @@ static inline bool operator!=(const DexInstructionIteratorBase& lhs,
 
 static inline bool operator<(const DexInstructionIteratorBase& lhs,
                              const DexInstructionIteratorBase& rhs) {
-  return lhs.Inst() < rhs.Inst();
+  DCHECK_EQ(lhs.Instructions(), rhs.Instructions()) << "Comparing different code items.";
+  return lhs.DexPc() < rhs.DexPc();
 }
 
 static inline bool operator>(const DexInstructionIteratorBase& lhs,
@@ -78,18 +115,17 @@ static inline bool operator>=(const DexInstructionIteratorBase& lhs,
   return !(lhs < rhs);
 }
 
+// A helper class for a code_item's instructions using range based for loop syntax.
 class DexInstructionIterator : public DexInstructionIteratorBase {
  public:
-  using value_type = std::iterator<std::forward_iterator_tag, Instruction>::value_type;
-  using difference_type = std::iterator<std::forward_iterator_tag, value_type>::difference_type;
   using DexInstructionIteratorBase::DexInstructionIteratorBase;
 
-  explicit DexInstructionIterator(const uint16_t* inst)
-      : DexInstructionIteratorBase(value_type::At(inst)) {}
+  explicit DexInstructionIterator(const uint16_t* inst, uint32_t dex_pc)
+      : DexInstructionIteratorBase(Instruction::At(inst), dex_pc) {}
 
   // Value after modification.
   DexInstructionIterator& operator++() {
-    inst_ = inst_->Next();
+    data_.dex_pc_ += Inst().SizeInCodeUnits();
     return *this;
   }
 
@@ -101,38 +137,47 @@ class DexInstructionIterator : public DexInstructionIteratorBase {
   }
 
   const value_type& operator*() const {
-    return *inst_;
+    return data_;
   }
 
-  const value_type* operator->() const {
-    return &**this;
+  const Instruction* operator->() const {
+    return &data_.Inst();
+  }
+
+  // Return the dex pc for the iterator.
+  ALWAYS_INLINE uint32_t DexPc() const {
+    return data_.DexPc();
   }
 };
 
+// A safe version of DexInstructionIterator that is guaranteed to not go past the end of the code
+// item.
 class SafeDexInstructionIterator : public DexInstructionIteratorBase {
  public:
   explicit SafeDexInstructionIterator(const DexInstructionIteratorBase& start,
                                       const DexInstructionIteratorBase& end)
-      : DexInstructionIteratorBase(start.Inst())
-      , end_(end.Inst()) {}
+      : DexInstructionIteratorBase(&start.Inst(), start.DexPc())
+      , num_code_units_(end.DexPc()) {
+    DCHECK_EQ(start.Instructions(), end.Instructions())
+        << "start and end must be in the same code item.";
+  }
 
   // Value after modification, does not read past the end of the allowed region. May increment past
   // the end of the code item though.
   SafeDexInstructionIterator& operator++() {
     AssertValid();
-    const size_t size_code_units = Inst()->CodeUnitsRequiredForSizeComputation();
-    const size_t available = reinterpret_cast<const uint16_t*>(end_) -
-        reinterpret_cast<const uint16_t*>(Inst());
+    const size_t size_code_units = Inst().CodeUnitsRequiredForSizeComputation();
+    const size_t available = NumCodeUnits() - DexPc();
     if (UNLIKELY(size_code_units > available)) {
       error_state_ = true;
       return *this;
     }
-    const size_t instruction_size = inst_->SizeInCodeUnits();
-    if (UNLIKELY(instruction_size > available)) {
+    const size_t instruction_code_units = Inst().SizeInCodeUnits();
+    if (UNLIKELY(instruction_code_units > available)) {
       error_state_ = true;
       return *this;
     }
-    inst_ = inst_->RelativeAt(instruction_size);
+    data_.dex_pc_ += instruction_code_units;
     return *this;
   }
 
@@ -145,12 +190,21 @@ class SafeDexInstructionIterator : public DexInstructionIteratorBase {
 
   const value_type& operator*() const {
     AssertValid();
-    return *inst_;
+    return data_;
   }
 
-  const value_type* operator->() const {
+  const Instruction* operator->() const {
     AssertValid();
-    return &**this;
+    return &data_.Inst();
+  }
+
+  // Return the current instruction of the iterator.
+  ALWAYS_INLINE const Instruction& Inst() const {
+    return data_.Inst();
+  }
+
+  const uint16_t* Instructions() const {
+    return data_.Instructions();
   }
 
   // Returns true if the iterator is in an error state. This occurs when an instruction couldn't
@@ -162,10 +216,14 @@ class SafeDexInstructionIterator : public DexInstructionIteratorBase {
  private:
   ALWAYS_INLINE void AssertValid() const {
     DCHECK(!IsErrorState());
-    DCHECK_LT(Inst(), end_);
+    DCHECK_LT(DexPc(), NumCodeUnits());
+  }
+
+  ALWAYS_INLINE uint32_t NumCodeUnits() const {
+    return num_code_units_;
   }
 
-  const value_type* end_ = nullptr;
+  const uint32_t num_code_units_ = 0;
   bool error_state_ = false;
 };
 
diff --git a/runtime/dex_instruction_test.cc b/runtime/dex_instruction_test.cc
index 48ed027882..c944085b9e 100644
--- a/runtime/dex_instruction_test.cc
+++ b/runtime/dex_instruction_test.cc
@@ -74,7 +74,7 @@ TEST(Instruction, PropertiesOf45cc) {
   Build45cc(4u /* num_vregs */, 16u /* method_idx */, 32u /* proto_idx */,
             0xcafe /* arg_regs */, instruction);
 
-  DexInstructionIterator ins(instruction);
+  DexInstructionIterator ins(instruction, /*dex_pc*/ 0u);
   ASSERT_EQ(4u, ins->SizeInCodeUnits());
 
   ASSERT_TRUE(ins->HasVRegA());
@@ -109,7 +109,7 @@ TEST(Instruction, PropertiesOf4rcc) {
   Build4rcc(4u /* num_vregs */, 16u /* method_idx */, 32u /* proto_idx */,
             0xcafe /* arg_regs */, instruction);
 
-  DexInstructionIterator ins(instruction);
+  DexInstructionIterator ins(instruction, /*dex_pc*/ 0u);
   ASSERT_EQ(4u, ins->SizeInCodeUnits());
 
   ASSERT_TRUE(ins->HasVRegA());
@@ -155,7 +155,7 @@ static std::string DumpInst35c(Instruction::Code code,
                                std::vector<uint16_t> args) {
   uint16_t inst[6] = {};
   Build35c(inst, code, method_idx, args);
-  return DexInstructionIterator(inst)->DumpString(nullptr);
+  return Instruction::At(inst)->DumpString(nullptr);
 }
 
 TEST(Instruction, DumpString) {
diff --git a/runtime/interpreter/unstarted_runtime_test.cc b/runtime/interpreter/unstarted_runtime_test.cc
index fb378251ad..9db5f88dab 100644
--- a/runtime/interpreter/unstarted_runtime_test.cc
+++ b/runtime/interpreter/unstarted_runtime_test.cc
@@ -393,7 +393,6 @@ TEST_F(UnstartedRuntimeTest, StringInit) {
 
   // create instruction data for invoke-direct {v0, v1} of method with fake index
   uint16_t inst_data[3] = { 0x2070, 0x0000, 0x0010 };
-  DexInstructionIterator inst(inst_data);
 
   JValue result;
   ShadowFrame* shadow_frame = ShadowFrame::CreateDeoptimizedFrame(10, nullptr, method, 0);
@@ -403,7 +402,12 @@ TEST_F(UnstartedRuntimeTest, StringInit) {
   shadow_frame->SetVRegReference(0, reference_empty_string);
   shadow_frame->SetVRegReference(1, string_arg);
 
-  interpreter::DoCall<false, false>(method, self, *shadow_frame, &*inst, inst_data[0], &result);
+  interpreter::DoCall<false, false>(method,
+                                    self,
+                                    *shadow_frame,
+                                    Instruction::At(inst_data),
+                                    inst_data[0],
+                                    &result);
   mirror::String* string_result = reinterpret_cast<mirror::String*>(result.GetL());
   EXPECT_EQ(string_arg->GetLength(), string_result->GetLength());
 
@@ -1027,12 +1031,16 @@ TEST_F(UnstartedRuntimeTest, FloatConversion) {
 
   // create instruction data for invoke-direct {v0, v1} of method with fake index
   uint16_t inst_data[3] = { 0x2070, 0x0000, 0x0010 };
-  DexInstructionIterator inst(inst_data);
 
   JValue result;
   ShadowFrame* shadow_frame = ShadowFrame::CreateDeoptimizedFrame(10, nullptr, method, 0);
   shadow_frame->SetVRegDouble(0, 1.23);
-  interpreter::DoCall<false, false>(method, self, *shadow_frame, &*inst, inst_data[0], &result);
+  interpreter::DoCall<false, false>(method,
+                                    self,
+                                    *shadow_frame,
+                                    Instruction::At(inst_data),
+                                    inst_data[0],
+                                    &result);
   ObjPtr<mirror::String> string_result = reinterpret_cast<mirror::String*>(result.GetL());
   ASSERT_TRUE(string_result != nullptr);
 
@@ -1187,12 +1195,11 @@ class UnstartedClassForNameTest : public UnstartedRuntimeTest {
 
       // create instruction data for invoke-direct {v0} of method with fake index
       uint16_t inst_data[3] = { 0x1070, 0x0000, 0x0010 };
-      DexInstructionIterator inst(inst_data);
 
       interpreter::DoCall<false, false>(boot_cp_init,
                                         self,
                                         *shadow_frame,
-                                        &*inst,
+                                        Instruction::At(inst_data),
                                         inst_data[0],
                                         &result);
       CHECK(!self->IsExceptionPending());
diff --git a/runtime/jit/profiling_info.cc b/runtime/jit/profiling_info.cc
index ad013244c3..1344ca05b4 100644
--- a/runtime/jit/profiling_info.cc
+++ b/runtime/jit/profiling_info.cc
@@ -45,9 +45,7 @@ bool ProfilingInfo::Create(Thread* self, ArtMethod* method, bool retry_allocatio
 
   std::vector<uint32_t> entries;
 
-  IterationRange<DexInstructionIterator> instructions = method->GetCodeItem()->Instructions();
-  for (auto inst = instructions.begin(); inst != instructions.end(); ++inst) {
-    const uint32_t dex_pc = inst.GetDexPC(instructions.begin());
+  for (const DexInstructionPcPair& inst : method->GetCodeItem()->Instructions()) {
     switch (inst->Opcode()) {
       case Instruction::INVOKE_VIRTUAL:
       case Instruction::INVOKE_VIRTUAL_RANGE:
@@ -55,7 +53,7 @@ bool ProfilingInfo::Create(Thread* self, ArtMethod* method, bool retry_allocatio
       case Instruction::INVOKE_VIRTUAL_RANGE_QUICK:
       case Instruction::INVOKE_INTERFACE:
       case Instruction::INVOKE_INTERFACE_RANGE:
-        entries.push_back(dex_pc);
+        entries.push_back(inst.DexPc());
         break;
 
       default:
diff --git a/runtime/verifier/method_verifier.cc b/runtime/verifier/method_verifier.cc
index 6555e14358..e7adcbc503 100644
--- a/runtime/verifier/method_verifier.cc
+++ b/runtime/verifier/method_verifier.cc
@@ -617,8 +617,8 @@ void MethodVerifier::FindLocksAtDexPc(ArtMethod* m, uint32_t dex_pc,
 }
 
 static bool HasMonitorEnterInstructions(const DexFile::CodeItem* const code_item) {
-  for (const Instruction& inst : code_item->Instructions()) {
-    if (inst.Opcode() == Instruction::MONITOR_ENTER) {
+  for (const DexInstructionPcPair& inst : code_item->Instructions()) {
+    if (inst->Opcode() == Instruction::MONITOR_ENTER) {
       return true;
     }
   }
@@ -1018,14 +1018,13 @@ bool MethodVerifier::ComputeWidthsAndCountOps() {
       default:
         break;
     }
-    GetInstructionFlags(it.GetDexPC(instructions.begin())).SetIsOpcode();
+    GetInstructionFlags(it.DexPc()).SetIsOpcode();
   }
 
   if (it != instructions.end()) {
     const size_t insns_size = code_item_->insns_size_in_code_units_;
     Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "code did not end where expected ("
-                                      << it.GetDexPC(instructions.begin()) << " vs. "
-                                      << insns_size << ")";
+                                      << it.DexPc() << " vs. " << insns_size << ")";
     return false;
   }
 
@@ -1106,10 +1105,9 @@ bool MethodVerifier::VerifyInstructions() {
   /* Flag the start of the method as a branch target, and a GC point due to stack overflow errors */
   GetInstructionFlags(0).SetBranchTarget();
   GetInstructionFlags(0).SetCompileTimeInfoPoint();
-  IterationRange<DexInstructionIterator> instructions = code_item_->Instructions();
-  for (auto inst = instructions.begin(); inst != instructions.end(); ++inst) {
-    const uint32_t dex_pc = inst.GetDexPC(instructions.begin());
-    if (!VerifyInstruction<kAllowRuntimeOnlyInstructions>(&*inst, dex_pc)) {
+  for (const DexInstructionPcPair& inst : code_item_->Instructions()) {
+    const uint32_t dex_pc = inst.DexPc();
+    if (!VerifyInstruction<kAllowRuntimeOnlyInstructions>(&inst.Inst(), dex_pc)) {
       DCHECK_NE(failures_.size(), 0U);
       return false;
     }
@@ -1695,9 +1693,8 @@ void MethodVerifier::Dump(VariableIndentationOutputStream* vios) {
   vios->Stream() << "Dumping instructions and register lines:\n";
   ScopedIndentation indent1(vios);
 
-  IterationRange<DexInstructionIterator> instructions = code_item_->Instructions();
-  for (auto inst = instructions.begin(); inst != instructions.end(); ++inst) {
-    const size_t dex_pc = inst.GetDexPC(instructions.begin());
+  for (const DexInstructionPcPair& inst : code_item_->Instructions()) {
+    const size_t dex_pc = inst.DexPc();
     RegisterLine* reg_line = reg_table_.GetLine(dex_pc);
     if (reg_line != nullptr) {
       vios->Stream() << reg_line->Dump(this) << "\n";
@@ -1963,9 +1960,8 @@ bool MethodVerifier::CodeFlowVerifyMethod() {
      */
     int dead_start = -1;
 
-    IterationRange<DexInstructionIterator> instructions = code_item_->Instructions();
-    for (auto inst = instructions.begin(); inst != instructions.end(); ++inst) {
-      const uint32_t insn_idx = inst.GetDexPC(instructions.begin());
+    for (const DexInstructionPcPair& inst : code_item_->Instructions()) {
+      const uint32_t insn_idx = inst.DexPc();
       /*
        * Switch-statement data doesn't get "visited" by scanner. It
        * may or may not be preceded by a padding NOP (for alignment).
@@ -1993,7 +1989,7 @@ bool MethodVerifier::CodeFlowVerifyMethod() {
     if (dead_start >= 0) {
       LogVerifyInfo()
           << "dead code " << reinterpret_cast<void*>(dead_start)
-          << "-" << reinterpret_cast<void*>(instructions.end().GetDexPC(instructions.begin()) - 1);
+          << "-" << reinterpret_cast<void*>(code_item_->insns_size_in_code_units_ - 1);
     }
     // To dump the state of the verify after a method, do something like:
     // if (dex_file_->PrettyMethod(dex_method_idx_) ==