Implemented missing pieces of the debugger for ARM

src/arm/codegen-arm.cc

Index: src/arm/codegen-arm.cc
===================================================================
--- src/arm/codegen-arm.cc	(revision 2877)
+++ src/arm/codegen-arm.cc	(working copy)
@@ -299,7 +299,10 @@
   }
 
   // Generate the return sequence if necessary.
-  if (frame_ != NULL || function_return_.is_linked()) {
+  if (has_valid_frame() || function_return_.is_linked()) {
+    if (!function_return_.is_linked()) {
+      CodeForReturnPosition(fun);
+    }
     // exit
     // r0: result
     // sp: stack pointer
@@ -315,12 +318,24 @@
       frame_->CallRuntime(Runtime::kTraceExit, 1);
     }
 
+    // Add a label for checking the size of the code used for returning.
+    Label check_exit_codesize;
+    masm_->bind(&check_exit_codesize);
+
     // Tear down the frame which will restore the caller's frame pointer and
     // the link register.
     frame_->Exit();
 
-    __ add(sp, sp, Operand((scope_->num_parameters() + 1) * kPointerSize));
-    __ Jump(lr);
+    // Here we use masm_-> instead of the __ macro to avoid the code coverage
+    // tool from instrumenting as we rely on the code size here.
+    masm_->add(sp, sp, Operand((scope_->num_parameters() + 1) * kPointerSize));
+    masm_->Jump(lr);
+
+    // Check that the size of the code used for returning matches what is
+    // expected by the debugger.
+    ASSERT_EQ(kJSReturnSequenceLength,
+              masm_->InstructionsGeneratedSince(&check_exit_codesize));
+
   }
 
   // Code generation state must be reset.
@@ -1111,10 +1126,10 @@
   if (FLAG_check_stack) {
     Comment cmnt(masm_, "[ check stack");
     __ LoadRoot(ip, Heap::kStackLimitRootIndex);
-    // Put the lr setup instruction in the delay slot.  The 'sizeof(Instr)' is
-    // added to the implicit 8 byte offset that always applies to operations
-    // with pc and gives a return address 12 bytes down.
-    masm_->add(lr, pc, Operand(sizeof(Instr)));
+    // Put the lr setup instruction in the delay slot.  kInstrSize is added to
+    // the implicit 8 byte offset that always applies to operations with pc and
+    // gives a return address 12 bytes down.
+    masm_->add(lr, pc, Operand(Assembler::kInstrSize));
     masm_->cmp(sp, Operand(ip));
     StackCheckStub stub;
     // Call the stub if lower.
@@ -1380,16 +1395,12 @@
   VirtualFrame::SpilledScope spilled_scope;
   Comment cmnt(masm_, "[ ReturnStatement");
 
+  CodeForStatementPosition(node);
+  LoadAndSpill(node->expression());
   if (function_return_is_shadowed_) {
-    CodeForStatementPosition(node);
-    LoadAndSpill(node->expression());
     frame_->EmitPop(r0);
     function_return_.Jump();
   } else {
-    // Load the returned value.
-    CodeForStatementPosition(node);
-    LoadAndSpill(node->expression());
-
     // Pop the result from the frame and prepare the frame for
     // returning thus making it easier to merge.
     frame_->EmitPop(r0);