src/debug/mips64/debug-mips64.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_MIPS64

#include "src/debug/debug.h"

#include "src/codegen.h"
#include "src/debug/liveedit.h"

namespace v8 {
namespace internal {

#define __ ACCESS_MASM(masm)

void EmitDebugBreakSlot(MacroAssembler* masm) {
  Label check_size;
  __ bind(&check_size);
  for (int i = 0; i < Assembler::kDebugBreakSlotInstructions; i++) {
    __ nop(MacroAssembler::DEBUG_BREAK_NOP);
  }
  DCHECK_EQ(Assembler::kDebugBreakSlotInstructions,
            masm->InstructionsGeneratedSince(&check_size));
}


void DebugCodegen::GenerateSlot(MacroAssembler* masm, RelocInfo::Mode mode) {
  // Generate enough nop's to make space for a call instruction. Avoid emitting
  // the trampoline pool in the debug break slot code.
  Assembler::BlockTrampolinePoolScope block_pool(masm);
  masm->RecordDebugBreakSlot(mode);
  EmitDebugBreakSlot(masm);
}


void DebugCodegen::ClearDebugBreakSlot(Isolate* isolate, Address pc) {
  CodePatcher patcher(isolate, pc, Assembler::kDebugBreakSlotInstructions);
  EmitDebugBreakSlot(patcher.masm());
}


void DebugCodegen::PatchDebugBreakSlot(Isolate* isolate, Address pc,
                                       Handle<Code> code) {
  DCHECK(code->is_debug_stub());
  CodePatcher patcher(isolate, pc, Assembler::kDebugBreakSlotInstructions);
  // Patch the code changing the debug break slot code from:
  //   nop(DEBUG_BREAK_NOP) - nop(1) is sll(zero_reg, zero_reg, 1)
  //   nop(DEBUG_BREAK_NOP)
  //   nop(DEBUG_BREAK_NOP)
  //   nop(DEBUG_BREAK_NOP)
  //   nop(DEBUG_BREAK_NOP)
  //   nop(DEBUG_BREAK_NOP)
  // to a call to the debug break slot code.
  //   li t9, address   (4-instruction sequence on mips64)
  //   call t9          (jalr t9 / nop instruction pair)
  patcher.masm()->li(v8::internal::t9,
                     Operand(reinterpret_cast<int64_t>(code->entry())),
                     ADDRESS_LOAD);
  patcher.masm()->Call(v8::internal::t9);
}

bool DebugCodegen::DebugBreakSlotIsPatched(Address pc) {
  Instr current_instr = Assembler::instr_at(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);

    // 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);
        }
      }
    }

    // Leave the internal frame.
  }

  __ MaybeDropFrames();

  // 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);
  __ Ld(a1, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));

  // Pop return address and frame.
  __ LeaveFrame(StackFrame::INTERNAL);

  __ Ld(a0, FieldMemOperand(a1, JSFunction::kSharedFunctionInfoOffset));
  __ Lw(a0,
        FieldMemOperand(a0, SharedFunctionInfo::kFormalParameterCountOffset));
  __ mov(a2, a0);

  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_MIPS64