ARM: Fix jumptargets to actually merge virtual frames....

src/arm/virtual-frame-arm.h

 // Copyright 2009 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 211 matching lines @@
   void AllocateStackSlots();
 
   // The current top of the expression stack as an assembly operand.
   MemOperand Top() {
     AssertIsSpilled();
     return MemOperand(sp, 0);
   }
 
   // An element of the expression stack as an assembly operand.
   MemOperand ElementAt(int index) {
-    AssertIsSpilled();
-    return MemOperand(sp, index * kPointerSize);
+    int adjusted_index = index - kVirtualElements[top_of_stack_state_];
+    ASSERT(adjusted_index >= 0);

[Søren Thygesen Gjesse, 2010/05/11 13:46:12]

You don't want to spill to the point where this always is possible?

[Erik Corry, 2010/05/12 09:00:32]

I think I want to keep that explicit since we want to try to avoid spilling.

+    return MemOperand(sp, adjusted_index * kPointerSize);
   }
 
   // A frame-allocated local as an assembly operand.
   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(fp, kFunctionOffset); }
@@ skipping 104 matching lines @@
   // Takes the top element and puts it in r0.
   void PopToR0();
 
   // Push an element on top of the expression stack and emit a
   // corresponding push instruction.
   void EmitPush(Register reg);
   void EmitPush(Operand operand);
   void EmitPush(MemOperand operand);
   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 mov, otherwise an str.  Afterwards
+  // you can still use the register even if it is a register that can be
+  // used for TOS (r0 or r1).
+  void OverwriteStackPosition(Register reg, int this_far_down);

[Søren Thygesen Gjesse, 2010/05/11 13:46:12]

Why is this not called SetElementAt?

[Erik Corry, 2010/05/12 09:00:32]

Done.

+
   // Get a register which is free and which must be immediately used to
   // push on the top of the stack.
   Register GetTOSRegister();
 
   // Push multiple registers on the stack and the virtual frame
   // Register are selected by setting bit in src_regs and
   // are pushed in decreasing order: r15 .. r0.
   void EmitPushMultiple(int count, int src_regs);
 
   static Register scratch0() { return r7; }
@@ skipping 84 matching lines @@
   // 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);
 
   // If all top-of-stack registers are in use then the lowest one is pushed
   // onto the physical stack and made free.
   void EnsureOneFreeTOSRegister();
 
+  // Emit instructions to get the top of stack state from where we are to where
+  // we want to be.
+  void MergeTOSTo(TopOfStack expected_state);
+
   inline bool Equals(VirtualFrame* other);
 
   friend class JumpTarget;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM_VIRTUAL_FRAME_ARM_H_