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

src/arm/virtual-frame-arm.h

Index: src/arm/virtual-frame-arm.h
===================================================================
--- src/arm/virtual-frame-arm.h	(revision 4640)
+++ src/arm/virtual-frame-arm.h	(working copy)
@@ -229,8 +229,9 @@
 
   // 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.
@@ -355,6 +356,12 @@
   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();
@@ -459,6 +466,10 @@
   // 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;