Version 3.2.6

src/mips/virtual-frame-mips.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 12 matching lines @@
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 
 #ifndef V8_MIPS_VIRTUAL_FRAME_MIPS_H_
 #define V8_MIPS_VIRTUAL_FRAME_MIPS_H_
 
 #include "register-allocator.h"
-#include "scopes.h"
 
 namespace v8 {
 namespace internal {
 
+// This dummy class is only used to create invalid virtual frames.
+extern class InvalidVirtualFrameInitializer {}* kInvalidVirtualFrameInitializer;
+
 
 // -------------------------------------------------------------------------
 // Virtual frames
 //
 // The virtual frame is an abstraction of the physical stack frame. It
 // encapsulates the parameters, frame-allocated locals, and the expression
 // stack. It supports push/pop operations on the expression stack, as well
 // as random access to the expression stack elements, locals, and
 // parameters.
 
 class VirtualFrame : public ZoneObject {
  public:
+  class RegisterAllocationScope;
   // A utility class to introduce a scope where the virtual frame is
   // expected to remain spilled. The constructor spills the code
-  // generator's current frame, but no attempt is made to require it
-  // to stay spilled. It is intended as documentation while the code
-  // generator is being transformed.
+  // generator's current frame, and keeps it spilled.
   class SpilledScope BASE_EMBEDDED {
    public:
+    explicit SpilledScope(VirtualFrame* frame)
+      : old_is_spilled_(
+          Isolate::Current()->is_virtual_frame_in_spilled_scope()) {
+      if (frame != NULL) {
+        if (!old_is_spilled_) {
+          frame->SpillAll();
+        } else {
+          frame->AssertIsSpilled();
+        }
+      }
+      Isolate::Current()->set_is_virtual_frame_in_spilled_scope(true);
+    }
+    ~SpilledScope() {
+      Isolate::Current()->set_is_virtual_frame_in_spilled_scope(
+          old_is_spilled_);
+    }
+    static bool is_spilled() {
+      return Isolate::Current()->is_virtual_frame_in_spilled_scope();
+    }
+
+   private:
+    int old_is_spilled_;
+
     SpilledScope() {}
+
+    friend class RegisterAllocationScope;
+  };
+
+  class RegisterAllocationScope BASE_EMBEDDED {
+   public:
+    // A utility class to introduce a scope where the virtual frame
+    // is not spilled, ie. where register allocation occurs.  Eventually
+    // when RegisterAllocationScope is ubiquitous it can be removed
+    // along with the (by then unused) SpilledScope class.
+    inline explicit RegisterAllocationScope(CodeGenerator* cgen);
+    inline ~RegisterAllocationScope();
+
+   private:
+    CodeGenerator* cgen_;
+    bool old_is_spilled_;
+
+    RegisterAllocationScope() {}
   };
 
   // An illegal index into the virtual frame.
   static const int kIllegalIndex = -1;
 
   // Construct an initial virtual frame on entry to a JS function.
   inline VirtualFrame();
 
+  // Construct an invalid virtual frame, used by JumpTargets.
+  inline VirtualFrame(InvalidVirtualFrameInitializer* dummy);
+
   // Construct a virtual frame as a clone of an existing one.
   explicit inline VirtualFrame(VirtualFrame* original);
 
-  CodeGenerator* cgen() { return CodeGeneratorScope::Current(); }
-  MacroAssembler* masm() { return cgen()->masm(); }
-
-  // Create a duplicate of an existing valid frame element.
-  FrameElement CopyElementAt(int index,
-                             NumberInfo info = NumberInfo::Unknown());
+  inline CodeGenerator* cgen() const;
+  inline MacroAssembler* masm();
 
   // The number of elements on the virtual frame.
-  int element_count() { return elements_.length(); }
+  int element_count() const { return element_count_; }
 
   // The height of the virtual expression stack.
-  int height() {
-    return element_count() - expression_base_index();
-  }
-
-  int register_location(int num) {
-    ASSERT(num >= 0 && num < RegisterAllocator::kNumRegisters);
-    return register_locations_[num];
-  }
-
-  int register_location(Register reg) {
-    return register_locations_[RegisterAllocator::ToNumber(reg)];
-  }
-
-  void set_register_location(Register reg, int index) {
-    register_locations_[RegisterAllocator::ToNumber(reg)] = index;
-  }
+  inline int height() const;
 
   bool is_used(int num) {
-    ASSERT(num >= 0 && num < RegisterAllocator::kNumRegisters);
-    return register_locations_[num] != kIllegalIndex;
-  }
-
-  bool is_used(Register reg) {
-    return register_locations_[RegisterAllocator::ToNumber(reg)]
-        != kIllegalIndex;
+    switch (num) {
+      case 0: {  // a0.
+        return kA0InUse[top_of_stack_state_];
+      }
+      case 1: {  // a1.
+        return kA1InUse[top_of_stack_state_];
+      }
+      case 2:
+      case 3:
+      case 4:
+      case 5:
+      case 6: {  // a2 to a3, t0 to t2.
+        ASSERT(num - kFirstAllocatedRegister < kNumberOfAllocatedRegisters);
+        ASSERT(num >= kFirstAllocatedRegister);
+        if ((register_allocation_map_ &
+             (1 << (num - kFirstAllocatedRegister))) == 0) {
+          return false;
+        } else {
+          return true;
+        }
+      }
+      default: {
+        ASSERT(num < kFirstAllocatedRegister ||
+               num >= kFirstAllocatedRegister + kNumberOfAllocatedRegisters);
+        return false;
+      }
+    }
   }
 
   // Add extra in-memory elements to the top of the frame to match an actual
   // frame (eg, the frame after an exception handler is pushed). No code is
   // emitted.
   void Adjust(int count);
 
   // Forget elements from the top of the frame to match an actual frame (eg,
-  // the frame after a runtime call). No code is emitted.
-  void Forget(int count) {
-    ASSERT(count >= 0);
-    ASSERT(stack_pointer_ == element_count() - 1);
-    stack_pointer_ -= count;
-    // On mips, all elements are in memory, so there is no extra bookkeeping
-    // (registers, copies, etc.) beyond dropping the elements.
-    elements_.Rewind(stack_pointer_ + 1);
-  }
+  // the frame after a runtime call). No code is emitted except to bring the
+  // frame to a spilled state.
+  void Forget(int count);
 
-  // Forget count elements from the top of the frame and adjust the stack
-  // pointer downward. This is used, for example, before merging frames at
-  // break, continue, and return targets.
-  void ForgetElements(int count);
 
   // Spill all values from the frame to memory.
   void SpillAll();
 
+  void AssertIsSpilled() const {
+    ASSERT(top_of_stack_state_ == NO_TOS_REGISTERS);
+    ASSERT(register_allocation_map_ == 0);
+  }
+
+  void AssertIsNotSpilled() {
+    ASSERT(!SpilledScope::is_spilled());
+  }
+
   // Spill all occurrences of a specific register from the frame.
   void Spill(Register reg) {
-    if (is_used(reg)) SpillElementAt(register_location(reg));
+    UNIMPLEMENTED();
   }
 
   // Spill all occurrences of an arbitrary register if possible. Return the
   // register spilled or no_reg if it was not possible to free any register
-  // (ie, they all have frame-external references).
+  // (ie, they all have frame-external references). Unimplemented.
   Register SpillAnyRegister();
 
-  // Prepare this virtual frame for merging to an expected frame by
-  // performing some state changes that do not require generating
-  // code. It is guaranteed that no code will be generated.
-  void PrepareMergeTo(VirtualFrame* expected);
-
   // Make this virtual frame have a state identical to an expected virtual
   // frame. As a side effect, code may be emitted to make this frame match
   // the expected one.
-  void MergeTo(VirtualFrame* expected);
+  void MergeTo(const VirtualFrame* expected,
+               Condition cond = al,
+               Register r1 = no_reg,
+               const Operand& r2 = Operand(no_reg));
+
+  void MergeTo(VirtualFrame* expected,
+               Condition cond = al,
+               Register r1 = no_reg,
+               const Operand& r2 = Operand(no_reg));
+
+  // Checks whether this frame can be branched to by the other frame.
+  bool IsCompatibleWith(const VirtualFrame* other) const {
+    return (tos_known_smi_map_ & (~other->tos_known_smi_map_)) == 0;
+  }
+
+  inline void ForgetTypeInfo() {
+    tos_known_smi_map_ = 0;
+  }
 
   // Detach a frame from its code generator, perhaps temporarily. This
   // tells the register allocator that it is free to use frame-internal
   // registers. Used when the code generator's frame is switched from this
   // one to NULL by an unconditional jump.
   void DetachFromCodeGenerator() {
-    RegisterAllocator* cgen_allocator = cgen()->allocator();
-    for (int i = 0; i < RegisterAllocator::kNumRegisters; i++) {
-      if (is_used(i)) cgen_allocator->Unuse(i);
-    }
   }
 
   // (Re)attach a frame to its code generator. This informs the register
   // allocator that the frame-internal register references are active again.
   // Used when a code generator's frame is switched from NULL to this one by
   // binding a label.
   void AttachToCodeGenerator() {
-    RegisterAllocator* cgen_allocator = cgen()->allocator();
-    for (int i = 0; i < RegisterAllocator::kNumRegisters; i++) {
-      if (is_used(i)) cgen_allocator->Unuse(i);
-    }
   }
 
   // Emit code for the physical JS entry and exit frame sequences. After
   // calling Enter, the virtual frame is ready for use; and after calling
   // Exit it should not be used. Note that Enter does not allocate space in
   // the physical frame for storing frame-allocated locals.
   void Enter();
   void Exit();
 
-  // Prepare for returning from the frame by spilling locals and
-  // dropping all non-locals elements in the virtual frame. This
-  // avoids generating unnecessary merge code when jumping to the
-  // shared return site. Emits code for spills.
-  void PrepareForReturn();
+  // Prepare for returning from the frame by elements in the virtual frame.
+  // This avoids generating unnecessary merge code when jumping to the shared
+  // return site. No spill code emitted. Value to return should be in v0.
+  inline void PrepareForReturn();
+
+  // Number of local variables after when we use a loop for allocating.
+  static const int kLocalVarBound = 5;
 
   // Allocate and initialize the frame-allocated locals.
   void AllocateStackSlots();
 
   // The current top of the expression stack as an assembly operand.
-  MemOperand Top() { return MemOperand(sp, 0); }
+  MemOperand Top() {
+    AssertIsSpilled();
+    return MemOperand(sp, 0);
+  }
 
   // An element of the expression stack as an assembly operand.
   MemOperand ElementAt(int index) {
-    return MemOperand(sp, index * kPointerSize);
+    int adjusted_index = index - kVirtualElements[top_of_stack_state_];
+    ASSERT(adjusted_index >= 0);
+    return MemOperand(sp, adjusted_index * kPointerSize);
   }
 
-  // Random-access store to a frame-top relative frame element. The result
-  // becomes owned by the frame and is invalidated.
-  void SetElementAt(int index, Result* value);
-
-  // Set a frame element to a constant. The index is frame-top relative.
-  void SetElementAt(int index, Handle<Object> value) {
-    Result temp(value);
-    SetElementAt(index, &temp);
+  bool KnownSmiAt(int index) {
+    if (index >= kTOSKnownSmiMapSize) return false;
+    return (tos_known_smi_map_ & (1 << index)) != 0;
   }
-
-  void PushElementAt(int index) {
-    PushFrameSlotAt(element_count() - index - 1);
-  }
-
   // A frame-allocated local as an assembly operand.
-  MemOperand LocalAt(int index) {
-    ASSERT(0 <= index);
-    ASSERT(index < local_count());
-    return MemOperand(s8_fp, kLocal0Offset - index * kPointerSize);
-  }
-
-  // Push a copy of the value of a local frame slot on top of the frame.
-  void PushLocalAt(int index) {
-    PushFrameSlotAt(local0_index() + index);
-  }
-
-  // Push the value of a local frame slot on top of the frame and invalidate
-  // the local slot. The slot should be written to before trying to read
-  // from it again.
-  void TakeLocalAt(int index) {
-    TakeFrameSlotAt(local0_index() + index);
-  }
-
-  // Store the top value on the virtual frame into a local frame slot. The
-  // value is left in place on top of the frame.
-  void StoreToLocalAt(int index) {
-    StoreToFrameSlotAt(local0_index() + index);
-  }
+  inline MemOperand LocalAt(int index);
 
   // Push the address of the receiver slot on the frame.
   void PushReceiverSlotAddress();
 
   // The function frame slot.
-  MemOperand Function() { return MemOperand(s8_fp, kFunctionOffset); }
-
-  // Push the function on top of the frame.
-  void PushFunction() { PushFrameSlotAt(function_index()); }
+  MemOperand Function() { return MemOperand(fp, kFunctionOffset); }
 
   // The context frame slot.
-  MemOperand Context() { return MemOperand(s8_fp, kContextOffset); }
-
-  // Save the value of the cp register to the context frame slot.
-  void SaveContextRegister();
-
-  // Restore the cp register from the value of the context frame
-  // slot.
-  void RestoreContextRegister();
+  MemOperand Context() { return MemOperand(fp, kContextOffset); }
 
   // A parameter as an assembly operand.
-  MemOperand ParameterAt(int index) {
-    // Index -1 corresponds to the receiver.
-    ASSERT(-1 <= index);  // -1 is the receiver.
-    ASSERT(index <= parameter_count());
-    uint16_t a = 0;   // Number of argument slots.
-    return MemOperand(s8_fp, (1 + parameter_count() + a - index) *kPointerSize);
-  }
-
-  // Push a copy of the value of a parameter frame slot on top of the frame.
-  void PushParameterAt(int index) {
-    PushFrameSlotAt(param0_index() + index);
-  }
-
-  // Push the value of a paramter frame slot on top of the frame and
-  // invalidate the parameter slot. The slot should be written to before
-  // trying to read from it again.
-  void TakeParameterAt(int index) {
-    TakeFrameSlotAt(param0_index() + index);
-  }
-
-  // Store the top value on the virtual frame into a parameter frame slot.
-  // The value is left in place on top of the frame.
-  void StoreToParameterAt(int index) {
-    StoreToFrameSlotAt(param0_index() + index);
-  }
+  inline MemOperand ParameterAt(int index);
 
   // The receiver frame slot.
-  MemOperand Receiver() { return ParameterAt(-1); }
+  inline MemOperand Receiver();
 
   // Push a try-catch or try-finally handler on top of the virtual frame.
   void PushTryHandler(HandlerType type);
 
   // Call stub given the number of arguments it expects on (and
   // removes from) the stack.
-  void CallStub(CodeStub* stub, int arg_count) {
-    PrepareForCall(arg_count, arg_count);
-    RawCallStub(stub);
-  }
+  inline void CallStub(CodeStub* stub, int arg_count);
 
-  void CallStub(CodeStub* stub, Result* arg);
-
-  void CallStub(CodeStub* stub, Result* arg0, Result* arg1);
+  // Call JS function from top of the stack with arguments
+  // taken from the stack.
+  void CallJSFunction(int arg_count);
 
   // Call runtime given the number of arguments expected on (and
   // removed from) the stack.
-  void CallRuntime(Runtime::Function* f, int arg_count);
+  void CallRuntime(const Runtime::Function* f, int arg_count);
   void CallRuntime(Runtime::FunctionId id, int arg_count);
 
-  // Call runtime with sp aligned to 8 bytes.
-  void CallAlignedRuntime(Runtime::Function* f, int arg_count);
-  void CallAlignedRuntime(Runtime::FunctionId id, int arg_count);
+#ifdef ENABLE_DEBUGGER_SUPPORT
+  void DebugBreak();
+#endif
 
   // Invoke builtin given the number of arguments it expects on (and
   // removes from) the stack.
   void InvokeBuiltin(Builtins::JavaScript id,
                      InvokeJSFlags flag,
-                     Result* arg_count_register,
                      int arg_count);
 
+  // Call load IC. Receiver is on the stack and is consumed. Result is returned
+  // in v0.
+  void CallLoadIC(Handle<String> name, RelocInfo::Mode mode);
+
+  // Call store IC. If the load is contextual, value is found on top of the
+  // frame. If not, value and receiver are on the frame. Both are consumed.
+  // Result is returned in v0.
+  void CallStoreIC(Handle<String> name, bool is_contextual);
+
+  // Call keyed load IC. Key and receiver are on the stack. Both are consumed.
+  // Result is returned in v0.
+  void CallKeyedLoadIC();
+
+  // Call keyed store IC. Value, key and receiver are on the stack. All three
+  // are consumed. Result is returned in v0 (and a0).
+  void CallKeyedStoreIC();
+
   // Call into an IC stub given the number of arguments it removes
-  // from the stack. Register arguments are passed as results and
-  // consumed by the call.
+  // from the stack. Register arguments to the IC stub are implicit,
+  // and depend on the type of IC stub.
   void CallCodeObject(Handle<Code> ic,
                       RelocInfo::Mode rmode,
                       int dropped_args);
-  void CallCodeObject(Handle<Code> ic,
-                      RelocInfo::Mode rmode,
-                      Result* arg,
-                      int dropped_args);
-  void CallCodeObject(Handle<Code> ic,
-                      RelocInfo::Mode rmode,
-                      Result* arg0,
-                      Result* arg1,
-                      int dropped_args,
-                      bool set_auto_args_slots = false);
 
   // Drop a number of elements from the top of the expression stack. May
   // emit code to affect the physical frame. Does not clobber any registers
   // excepting possibly the stack pointer.
   void Drop(int count);
-  // Similar to VirtualFrame::Drop but we don't modify the actual stack.
-  // This is because we need to manually restore sp to the correct position.
-  void DropFromVFrameOnly(int count);
 
   // Drop one element.
   void Drop() { Drop(1); }
-  void DropFromVFrameOnly() { DropFromVFrameOnly(1); }
 
-  // Duplicate the top element of the frame.
-  void Dup() { PushFrameSlotAt(element_count() - 1); }
+  // Pop an element from the top of the expression stack. Discards
+  // the result.
+  void Pop();
 
-  // Pop an element from the top of the expression stack. Returns a
-  // Result, which may be a constant or a register.
-  Result Pop();
+  // Pop an element from the top of the expression stack.  The register
+  // will be one normally used for the top of stack register allocation
+  // so you can't hold on to it if you push on the stack.
+  Register PopToRegister(Register but_not_to_this_one = no_reg);
+
+  // Look at the top of the stack.  The register returned is aliased and
+  // must be copied to a scratch register before modification.
+  Register Peek();
+
+  // Look at the value beneath the top of the stack. The register returned is
+  // aliased and must be copied to a scratch register before modification.
+  Register Peek2();
+
+  // Duplicate the top of stack.
+  void Dup();
+
+  // Duplicate the two elements on top of stack.
+  void Dup2();
+
+  // Flushes all registers, but it puts a copy of the top-of-stack in a0.
+  void SpillAllButCopyTOSToA0();
+
+  // Flushes all registers, but it puts a copy of the top-of-stack in a1.
+  void SpillAllButCopyTOSToA1();
+
+  // Flushes all registers, but it puts a copy of the top-of-stack in a1
+  // and the next value on the stack in a0.
+  void SpillAllButCopyTOSToA1A0();
 
   // Pop and save an element from the top of the expression stack and
   // emit a corresponding pop instruction.
   void EmitPop(Register reg);
   // Same but for multiple registers
   void EmitMultiPop(RegList regs);
   void EmitMultiPopReversed(RegList regs);
 
+
+  // Takes the top two elements and puts them in a0 (top element) and a1
+  // (second element).
+  void PopToA1A0();
+
+  // Takes the top element and puts it in a1.
+  void PopToA1();
+
+  // Takes the top element and puts it in a0.
+  void PopToA0();
+
   // Push an element on top of the expression stack and emit a
   // corresponding push instruction.
-  void EmitPush(Register reg);
+  void EmitPush(Register reg, TypeInfo type_info = TypeInfo::Unknown());
+  void EmitPush(Operand operand, TypeInfo type_info = TypeInfo::Unknown());
+  void EmitPush(MemOperand operand, TypeInfo type_info = TypeInfo::Unknown());
+  void EmitPushRoot(Heap::RootListIndex index);
+
+  // Overwrite the nth thing on the stack.  If the nth position is in a
+  // register then this turns into a Move, otherwise an sw.  Afterwards
+  // you can still use the register even if it is a register that can be
+  // used for TOS (a0 or a1).
+  void SetElementAt(Register reg, int this_far_down);
+
+  // Get a register which is free and which must be immediately used to
+  // push on the top of the stack.
+  Register GetTOSRegister();
+
   // Same but for multiple registers.
   void EmitMultiPush(RegList regs);
   void EmitMultiPushReversed(RegList regs);
 
-  // Push an element on the virtual frame.
-  inline void Push(Register reg, NumberInfo info = NumberInfo::Unknown());
-  inline void Push(Handle<Object> value);
-  inline void Push(Smi* value);
-
-  // Pushing a result invalidates it (its contents become owned by the frame).
-  void Push(Result* result) {
-    if (result->is_register()) {
-      Push(result->reg());
-    } else {
-      ASSERT(result->is_constant());
-      Push(result->handle());
-    }
-    result->Unuse();
-  }
-
-  // Nip removes zero or more elements from immediately below the top
-  // of the frame, leaving the previous top-of-frame value on top of
-  // the frame. Nip(k) is equivalent to x = Pop(), Drop(k), Push(x).
-  inline void Nip(int num_dropped);
-
-  // This pushes 4 arguments slots on the stack and saves asked 'a' registers
-  // 'a' registers are arguments register a0 to a3.
-  void EmitArgumentSlots(RegList reglist);
-
-  inline void SetTypeForLocalAt(int index, NumberInfo info);
-  inline void SetTypeForParamAt(int index, NumberInfo info);
+  static Register scratch0() { return t4; }
+  static Register scratch1() { return t5; }
+  static Register scratch2() { return t6; }
 
  private:
   static const int kLocal0Offset = JavaScriptFrameConstants::kLocal0Offset;
   static const int kFunctionOffset = JavaScriptFrameConstants::kFunctionOffset;
   static const int kContextOffset = StandardFrameConstants::kContextOffset;
 
   static const int kHandlerSize = StackHandlerConstants::kSize / kPointerSize;
   static const int kPreallocatedElements = 5 + 8;  // 8 expression stack slots.
 
-  ZoneList<FrameElement> elements_;
+  // 5 states for the top of stack, which can be in memory or in a0 and a1.
+  enum TopOfStack { NO_TOS_REGISTERS, A0_TOS, A1_TOS, A1_A0_TOS, A0_A1_TOS,
+                    TOS_STATES};
+  static const int kMaxTOSRegisters = 2;
+
+  static const bool kA0InUse[TOS_STATES];
+  static const bool kA1InUse[TOS_STATES];
+  static const int kVirtualElements[TOS_STATES];
+  static const TopOfStack kStateAfterPop[TOS_STATES];
+  static const TopOfStack kStateAfterPush[TOS_STATES];
+  static const Register kTopRegister[TOS_STATES];
+  static const Register kBottomRegister[TOS_STATES];
+
+  // We allocate up to 5 locals in registers.
+  static const int kNumberOfAllocatedRegisters = 5;
+  // r2 to r6 are allocated to locals.
+  static const int kFirstAllocatedRegister = 2;
+
+  static const Register kAllocatedRegisters[kNumberOfAllocatedRegisters];
+
+  static Register AllocatedRegister(int r) {
+    ASSERT(r >= 0 && r < kNumberOfAllocatedRegisters);
+    return kAllocatedRegisters[r];
+  }
+
+  // The number of elements on the stack frame.
+  int element_count_;
+  TopOfStack top_of_stack_state_:3;
+  int register_allocation_map_:kNumberOfAllocatedRegisters;
+  static const int kTOSKnownSmiMapSize = 4;
+  unsigned tos_known_smi_map_:kTOSKnownSmiMapSize;
 
   // The index of the element that is at the processor's stack pointer
-  // (the sp register).
-  int stack_pointer_;
-
-  // The index of the register frame element using each register, or
-  // kIllegalIndex if a register is not on the frame.
-  int register_locations_[RegisterAllocator::kNumRegisters];
+  // (the sp register).  For now since everything is in memory it is given
+  // by the number of elements on the not-very-virtual stack frame.
+  int stack_pointer() { return element_count_ - 1; }
 
   // The number of frame-allocated locals and parameters respectively.
-  int parameter_count() { return cgen()->scope()->num_parameters(); }
-  int local_count() { return cgen()->scope()->num_stack_slots(); }
+  inline int parameter_count() const;
+  inline int local_count() const;
 
   // The index of the element that is at the processor's frame pointer
   // (the fp register). The parameters, receiver, function, and context
   // are below the frame pointer.
-  int frame_pointer() { return parameter_count() + 3; }
+  inline int frame_pointer() const;
 
   // The index of the first parameter. The receiver lies below the first
   // parameter.
   int param0_index() { return 1; }
 
   // The index of the context slot in the frame. It is immediately
   // below the frame pointer.
-  int context_index() { return frame_pointer() - 1; }
+  inline int context_index();
 
   // The index of the function slot in the frame. It is below the frame
   // pointer and context slot.
-  int function_index() { return frame_pointer() - 2; }
+  inline int function_index();
 
   // The index of the first local. Between the frame pointer and the
   // locals lies the return address.
-  int local0_index() { return frame_pointer() + 2; }
+  inline int local0_index() const;
 
   // The index of the base of the expression stack.
-  int expression_base_index() { return local0_index() + local_count(); }
+  inline int expression_base_index() const;
 
   // Convert a frame index into a frame pointer relative offset into the
   // actual stack.
-  int fp_relative(int index) {
-    ASSERT(index < element_count());
-    ASSERT(frame_pointer() < element_count());  // FP is on the frame.
-    return (frame_pointer() - index) * kPointerSize;
-  }
-
-  // Record an occurrence of a register in the virtual frame. This has the
-  // effect of incrementing the register's external reference count and
-  // of updating the index of the register's location in the frame.
-  void Use(Register reg, int index) {
-    ASSERT(!is_used(reg));
-    set_register_location(reg, index);
-    cgen()->allocator()->Use(reg);
-  }
-
-  // Record that a register reference has been dropped from the frame. This
-  // decrements the register's external reference count and invalidates the
-  // index of the register's location in the frame.
-  void Unuse(Register reg) {
-    ASSERT(is_used(reg));
-    set_register_location(reg, kIllegalIndex);
-    cgen()->allocator()->Unuse(reg);
-  }
-
-  // Spill the element at a particular index---write it to memory if
-  // necessary, free any associated register, and forget its value if
-  // constant.
-  void SpillElementAt(int index);
-
-  // Sync the element at a particular index. If it is a register or
-  // constant that disagrees with the value on the stack, write it to memory.
-  // Keep the element type as register or constant, and clear the dirty bit.
-  void SyncElementAt(int index);
-
-  // Sync the range of elements in [begin, end] with memory.
-  void SyncRange(int begin, int end);
-
-  // Sync a single unsynced element that lies beneath or at the stack pointer.
-  void SyncElementBelowStackPointer(int index);
-
-  // Sync a single unsynced element that lies just above the stack pointer.
-  void SyncElementByPushing(int index);
-
-  // Push a copy of a frame slot (typically a local or parameter) on top of
-  // the frame.
-  inline void PushFrameSlotAt(int index);
-
-  // Push a the value of a frame slot (typically a local or parameter) on
-  // top of the frame and invalidate the slot.
-  void TakeFrameSlotAt(int index);
-
-  // Store the value on top of the frame to a frame slot (typically a local
-  // or parameter).
-  void StoreToFrameSlotAt(int index);
+  inline int fp_relative(int index);
 
   // Spill all elements in registers. Spill the top spilled_args elements
   // on the frame. Sync all other frame elements.
   // Then drop dropped_args elements from the virtual frame, to match
   // the effect of an upcoming call that will drop them from the stack.
   void PrepareForCall(int spilled_args, int dropped_args);
 
-  // Move frame elements currently in registers or constants, that
-  // should be in memory in the expected frame, to memory.
-  void MergeMoveRegistersToMemory(VirtualFrame* expected);
+  // If all top-of-stack registers are in use then the lowest one is pushed
+  // onto the physical stack and made free.
+  void EnsureOneFreeTOSRegister();
 
-  // Make the register-to-register moves necessary to
-  // merge this frame with the expected frame.
-  // Register to memory moves must already have been made,
-  // and memory to register moves must follow this call.
-  // This is because some new memory-to-register moves are
-  // created in order to break cycles of register moves.
-  // Used in the implementation of MergeTo().
-  void MergeMoveRegistersToRegisters(VirtualFrame* expected);
+  // Emit instructions to get the top of stack state from where we are to where
+  // we want to be.
+  void MergeTOSTo(TopOfStack expected_state,
+                  Condition cond = al,
+                  Register r1 = no_reg,
+                  const Operand& r2 = Operand(no_reg));
 
-  // Make the memory-to-register and constant-to-register moves
-  // needed to make this frame equal the expected frame.
-  // Called after all register-to-memory and register-to-register
-  // moves have been made. After this function returns, the frames
-  // should be equal.
-  void MergeMoveMemoryToRegisters(VirtualFrame* expected);
+  inline bool Equals(const VirtualFrame* other);
 
-  // Invalidates a frame slot (puts an invalid frame element in it).
-  // Copies on the frame are correctly handled, and if this slot was
-  // the backing store of copies, the index of the new backing store
-  // is returned. Otherwise, returns kIllegalIndex.
-  // Register counts are correctly updated.
-  int InvalidateFrameSlotAt(int index);
+  inline void LowerHeight(int count) {
+    element_count_ -= count;
+    if (count >= kTOSKnownSmiMapSize) {
+      tos_known_smi_map_ = 0;
+    } else {
+      tos_known_smi_map_ >>= count;
+    }
+  }
 
-  // Call a code stub that has already been prepared for calling (via
-  // PrepareForCall).
-  void RawCallStub(CodeStub* stub);
-
-  // Calls a code object which has already been prepared for calling
-  // (via PrepareForCall).
-  void RawCallCodeObject(Handle<Code> code, RelocInfo::Mode rmode);
-
-  inline bool Equals(VirtualFrame* other);
-
-  // Classes that need raw access to the elements_ array.
-  friend class DeferredCode;
+  inline void RaiseHeight(int count, unsigned known_smi_map = 0) {
+    ASSERT(known_smi_map < (1u << count));
+    element_count_ += count;
+    if (count >= kTOSKnownSmiMapSize) {
+      tos_known_smi_map_ = known_smi_map;
+    } else {
+      tos_known_smi_map_ = ((tos_known_smi_map_ << count) | known_smi_map);
+    }
+  }
   friend class JumpTarget;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_MIPS_VIRTUAL_FRAME_MIPS_H_