[liveedit] reimplement frame restarting.

src/debug/mips/debug-mips.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_MIPS
 
 #include "src/debug/debug.h"
 
 #include "src/codegen.h"
 #include "src/debug/liveedit.h"
@@ skipping 51 matching lines @@
   Instr current_instr = Assembler::instr_at(pc);
   return !Assembler::IsNop(current_instr, Assembler::DEBUG_BREAK_NOP);
 }
 
 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)));
-    __ Subu(sp, sp,
-            Operand(kPointerSize * LiveEdit::kFramePaddingInitialSize));
-    for (int i = LiveEdit::kFramePaddingInitialSize - 1; i >= 0; i--) {
-      __ sw(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.
       __ push(v0);
     } else {
       // Non-return breaks.
       __ Push(masm->isolate()->factory()->the_hole_value());
     }
     __ PrepareCEntryArgs(1);
     __ PrepareCEntryFunction(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)};
         // Do not clobber v0 if mode is SAVE_RESULT_REGISTER. It will
         // contain return value of the function returned by DebugBreak.
         if (!(reg.is(v0) && (mode == SAVE_RESULT_REGISTER))) {
           __ li(reg, kDebugZapValue);
         }
       }
     }
-
-    // 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));
-  __ lw(t9, MemOperand(t9));
-  __ Jump(t9);
+  __ MaybeDropFrames();
+
+  // Return to caller.
+  __ Ret();
 }
 
+void DebugCodegen::GenerateHandleDebuggerStatement(MacroAssembler* masm) {
+  {
+    FrameScope scope(masm, StackFrame::INTERNAL);
+    __ CallRuntime(Runtime::kHandleDebuggerStatement, 0);
+  }
+  __ MaybeDropFrames();
 
-void DebugCodegen::GenerateFrameDropperLiveEdit(MacroAssembler* masm) {
-  // We do not know our frame height, but set sp based on fp.
-  __ lw(a1, MemOperand(fp, FrameDropperFrameConstants::kFunctionOffset));
+  // Return to caller.
+  __ Ret();
+}
+
+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);
+  __ lw(a1, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
 
   // Pop return address and frame.
   __ LeaveFrame(StackFrame::INTERNAL);
 
-  ParameterCount dummy(0);
-  __ CheckDebugHook(a1, no_reg, dummy, dummy);
+  __ lw(a0, FieldMemOperand(a1, JSFunction::kSharedFunctionInfoOffset));
+  __ lw(a0,
+        FieldMemOperand(a0, SharedFunctionInfo::kFormalParameterCountOffset));
+  __ mov(a2, a0);
 
-  // Load context from the function.
-  __ lw(cp, FieldMemOperand(a1, JSFunction::kContextOffset));
-
-  // Clear new.target as a safety measure.
-  __ LoadRoot(a3, Heap::kUndefinedValueRootIndex);
-
-  // Get function code.
-  __ lw(at, FieldMemOperand(a1, JSFunction::kSharedFunctionInfoOffset));
-  __ lw(at, FieldMemOperand(at, SharedFunctionInfo::kCodeOffset));
-  __ Addu(t9, at, Operand(Code::kHeaderSize - kHeapObjectTag));
-
-  // Re-run JSFunction, a1 is function, cp is context.
-  __ Jump(t9);
+  ParameterCount dummy1(a2);
+  ParameterCount dummy2(a0);
+  __ InvokeFunction(a1, dummy1, dummy2, JUMP_FUNCTION,
+                    CheckDebugStepCallWrapper());
 }
 
 
 const bool LiveEdit::kFrameDropperSupported = true;
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS