[liveedit] reimplement frame restarting.

src/debug/mips64/debug-mips64.cc

Index: src/debug/mips64/debug-mips64.cc
diff --git a/src/debug/mips64/debug-mips64.cc b/src/debug/mips64/debug-mips64.cc
index 0230f13145745a2829ce9ad1d2cb04a43859570f..b8dbbfb45ee033e10f834b5488292e95018865ef 100644
--- a/src/debug/mips64/debug-mips64.cc
+++ b/src/debug/mips64/debug-mips64.cc
@@ -65,22 +65,23 @@ bool DebugCodegen::DebugBreakSlotIsPatched(Address pc) {
   return !Assembler::IsNop(current_instr, Assembler::DEBUG_BREAK_NOP);
 }
 
+void DebugCodegen::GenerateHandleDebuggerStatement(MacroAssembler* masm) {
+  {
+    FrameScope scope(masm, StackFrame::INTERNAL);
+    __ CallRuntime(Runtime::kHandleDebuggerStatement, 0);
+  }
+  __ MaybeDropFrames();
+
+  // Return to caller.
+  __ Ret();
+}
+
 void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
                                           DebugBreakCallHelperMode mode) {
   __ RecordComment("Debug break");
   {
     FrameScope scope(masm, StackFrame::INTERNAL);
 
-    // Load padding words on stack.
-    __ li(at, Operand(Smi::FromInt(LiveEdit::kFramePaddingValue)));
-    __ Dsubu(sp, sp,
-            Operand(kPointerSize * LiveEdit::kFramePaddingInitialSize));
-    for (int i = LiveEdit::kFramePaddingInitialSize - 1; i >= 0; i--) {
-      __ sd(at, MemOperand(sp, kPointerSize * i));
-    }
-    __ li(at, Operand(Smi::FromInt(LiveEdit::kFramePaddingInitialSize)));
-    __ push(at);
-
     // Push arguments for DebugBreak call.
     if (mode == SAVE_RESULT_REGISTER) {
       // Break on return.
@@ -107,46 +108,36 @@ void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
       }
     }
 
-    // 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 =
-      ExternalReference::debug_after_break_target_address(masm->isolate());
-  __ li(t9, Operand(after_break_target));
-  __ ld(t9, MemOperand(t9));
-  __ Jump(t9);
-}
+  __ MaybeDropFrames();
 
+  // Return to caller.
+  __ Ret();
+}
 
-void DebugCodegen::GenerateFrameDropperLiveEdit(MacroAssembler* masm) {
-  // We do not know our frame height, but set sp based on fp.
-  __ ld(a1, MemOperand(fp, FrameDropperFrameConstants::kFunctionOffset));
+void DebugCodegen::GenerateFrameDropperTrampoline(MacroAssembler* masm) {
+  // Frame is being dropped:
+  // - Drop to the target frame specified by a1.
+  // - Look up current function on the frame.
+  // - Leave the frame.
+  // - Restart the frame by calling the function.
+  __ mov(fp, a1);
+  __ ld(a1, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
 
   // Pop return address and frame.
   __ LeaveFrame(StackFrame::INTERNAL);
 
-  ParameterCount dummy(0);
-  __ CheckDebugHook(a1, no_reg, dummy, dummy);
-
-  // Load context from the function.
-  __ ld(cp, FieldMemOperand(a1, JSFunction::kContextOffset));
-
-  // Clear new.target as a safety measure.
-  __ LoadRoot(a3, Heap::kUndefinedValueRootIndex);
-
-  // Get function code.
-  __ ld(at, FieldMemOperand(a1, JSFunction::kSharedFunctionInfoOffset));
-  __ ld(at, FieldMemOperand(at, SharedFunctionInfo::kCodeOffset));
-  __ Daddu(t9, at, Operand(Code::kHeaderSize - kHeapObjectTag));
+  __ ld(a0, FieldMemOperand(a1, JSFunction::kSharedFunctionInfoOffset));
+  __ ld(a0,
+        FieldMemOperand(a0, SharedFunctionInfo::kFormalParameterCountOffset));
+  __ mov(a2, a0);
 
-  // Re-run JSFunction, a1 is function, cp is context.
-  __ Jump(t9);
+  ParameterCount dummy1(a2);
+  ParameterCount dummy2(a0);
+  __ InvokeFunction(a1, dummy1, dummy2, JUMP_FUNCTION,
+                    CheckDebugStepCallWrapper());
 }