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

src/debug/x87/debug-x87.cc

Index: src/debug/x87/debug-x87.cc
diff --git a/src/debug/x87/debug-x87.cc b/src/debug/x87/debug-x87.cc
index 28b635b3266ac7ed8c48aaba6a94a9b678f4489e..b4dbfc9bb9f65562f5db3c7f854817a6c3e0ab0b 100644
--- a/src/debug/x87/debug-x87.cc
+++ b/src/debug/x87/debug-x87.cc
@@ -68,9 +68,15 @@ void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
     }
     __ push(Immediate(Smi::FromInt(LiveEdit::kFramePaddingInitialSize)));
 
-    if (mode == SAVE_RESULT_REGISTER) __ push(eax);
-
-    __ Move(eax, Immediate(0));  // No arguments.
+    // Push arguments for DebugBreak call.
+    if (mode == SAVE_RESULT_REGISTER) {
+      // Break on return.
+      __ push(eax);
+    } else {
+      // Non-return breaks.
+      __ Push(masm->isolate()->factory()->the_hole_value());
+    }
+    __ Move(eax, Immediate(1));
     __ mov(ebx,
            Immediate(ExternalReference(
                Runtime::FunctionForId(Runtime::kDebugBreak), masm->isolate())));
@@ -81,12 +87,14 @@ void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
     if (FLAG_debug_code) {
       for (int i = 0; i < kNumJSCallerSaved; ++i) {
         Register reg = {JSCallerSavedCode(i)};
-        __ Move(reg, Immediate(kDebugZapValue));
+        // Do not clobber eax if SAVE_RESULT_REGISTER is set. It will
+        // contain return value of the function.
+        if (!(reg.is(eax) && SAVE_RESULT_REGISTER)) {
+          __ Move(reg, Immediate(kDebugZapValue));
+        }
       }
     }
 
-    if (mode == SAVE_RESULT_REGISTER) __ pop(eax);
-
     __ pop(ebx);
     // We divide stored value by 2 (untagging) and multiply it by word's size.
     STATIC_ASSERT(kSmiTagSize == 1 && kSmiShiftSize == 0);