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

src/debug/mips/debug-mips.cc

Index: src/debug/mips/debug-mips.cc
diff --git a/src/debug/mips/debug-mips.cc b/src/debug/mips/debug-mips.cc
index 2da326c2853dcc7c74a36616da3cd607711898b8..0b628aeda08a3a0ebf8b76e0e365c7b65f4cbd2c 100644
--- a/src/debug/mips/debug-mips.cc
+++ b/src/debug/mips/debug-mips.cc
@@ -77,9 +77,15 @@ void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
     __ li(at, Operand(Smi::FromInt(LiveEdit::kFramePaddingInitialSize)));
     __ push(at);
 
-    if (mode == SAVE_RESULT_REGISTER) __ push(v0);
-
-    __ PrepareCEntryArgs(0);  // No arguments.
+    // Push arguments for DebugBreak call.
+    if (mode == SAVE_RESULT_REGISTER) {
+      // Break on return.
+      __ push(v0);
+    } else {
+      // Non-return breaks.
+      __ Push(masm->isolate()->factory()->the_hole_value());
+    }
+    __ PrepareCEntryArgs(1);
     __ PrepareCEntryFunction(ExternalReference(
         Runtime::FunctionForId(Runtime::kDebugBreak), masm->isolate()));
 
@@ -89,12 +95,14 @@ void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
     if (FLAG_debug_code) {
       for (int i = 0; i < kNumJSCallerSaved; i++) {
         Register reg = {JSCallerSavedCode(i)};
-        __ li(reg, kDebugZapValue);
+        // Do not clobber v0 if SAVE_RESULT_REGISTER is set. It will
+        // contain return value of the function returned by DebugBreak.
+        if (!(reg.is(v0) && SAVE_RESULT_REGISTER)) {
+          __ li(reg, kDebugZapValue);
+        }
       }
     }
 
-    if (mode == SAVE_RESULT_REGISTER) __ pop(v0);
-
     // Don't bother removing padding bytes pushed on the stack
     // as the frame is going to be restored right away.