[Interpreter] Adds support to fetch return value on break at return.

src/debug/arm/debug-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_ARM
 
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 
 namespace v8 {
@@ skipping 63 matching lines @@
     FrameAndConstantPoolScope scope(masm, StackFrame::INTERNAL);
 
     // Load padding words on stack.
     __ mov(ip, Operand(Smi::FromInt(LiveEdit::kFramePaddingValue)));
     for (int i = 0; i < LiveEdit::kFramePaddingInitialSize; i++) {
       __ push(ip);
     }
     __ mov(ip, Operand(Smi::FromInt(LiveEdit::kFramePaddingInitialSize)));
     __ push(ip);
 
-    if (mode == SAVE_RESULT_REGISTER) __ push(r0);
-
-    __ mov(r0, Operand::Zero());  // no arguments
+    // Push arguments for DebugBreak call.
+    if (mode == SAVE_RESULT_REGISTER) {
+      // Break on return.
+      __ push(r0);
+    } else {
+      // Non-return breaks.
+      __ Push(masm->isolate()->factory()->the_hole_value());
+    }
+    __ mov(r0, Operand(1));
     __ mov(r1,
            Operand(ExternalReference(
                Runtime::FunctionForId(Runtime::kDebugBreak), masm->isolate())));
 
     CEntryStub ceb(masm->isolate(), 1);
     __ CallStub(&ceb);
 
     if (FLAG_debug_code) {
       for (int i = 0; i < kNumJSCallerSaved; i++) {
         Register reg = {JSCallerSavedCode(i)};
-        __ mov(reg, Operand(kDebugZapValue));
+        // Do not clobber r0 if mode is SAVE_RESULT_REGISTER. It will
+        // contain return value of the function.
+        if (!(reg.is(r0) && (mode == SAVE_RESULT_REGISTER))) {
+          __ mov(reg, Operand(kDebugZapValue));
+        }
       }
     }
 
-    if (mode == SAVE_RESULT_REGISTER) __ pop(r0);
-
     // Don't bother removing padding bytes pushed on the stack
     // as the frame is going to be restored right away.
 
     // Leave the internal frame.
   }
 
   // Now that the break point has been handled, resume normal execution by
   // jumping to the target address intended by the caller and that was
   // overwritten by the address of DebugBreakXXX.
   ExternalReference after_break_target =
@@ skipping 34 matching lines @@
 
 
 const bool LiveEdit::kFrameDropperSupported = true;
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM