CSE2410 Fall 2014 Bounce

// Copyright 2011 the V8 project authors. All rights reserved.

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#include "v8.h"

#include "codegen.h"

#include "deoptimizer.h"

#include "full-codegen.h"

#include "safepoint-table.h"

namespace v8 {

namespace internal {

int Deoptimizer::patch_size() {

  const int kCallInstructionSizeInWords = 4;

  return kCallInstructionSizeInWords * Assembler::kInstrSize;

}

void Deoptimizer::PatchCodeForDeoptimization(Isolate* isolate, Code* code) {

  Address code_start_address = code->instruction_start();

  // Invalidate the relocation information, as it will become invalid by the

  // code patching below, and is not needed any more.

  code->InvalidateRelocation();

  // For each LLazyBailout instruction insert a call to the corresponding

  // deoptimization entry.

  DeoptimizationInputData* deopt_data =

      DeoptimizationInputData::cast(code->deoptimization_data());

#ifdef DEBUG

  Address prev_call_address = NULL;

#endif

  for (int i = 0; i < deopt_data->DeoptCount(); i++) {

    if (deopt_data->Pc(i)->value() == -1) continue;

    Address call_address = code_start_address + deopt_data->Pc(i)->value();

    Address deopt_entry = GetDeoptimizationEntry(isolate, i, LAZY);

    int call_size_in_bytes = MacroAssembler::CallSize(deopt_entry,

                                                      RelocInfo::NONE32);

    int call_size_in_words = call_size_in_bytes / Assembler::kInstrSize;

    ASSERT(call_size_in_bytes % Assembler::kInstrSize == 0);

    ASSERT(call_size_in_bytes <= patch_size());

    CodePatcher patcher(call_address, call_size_in_words);

    patcher.masm()->Call(deopt_entry, RelocInfo::NONE32);

    ASSERT(prev_call_address == NULL ||

           call_address >= prev_call_address + patch_size());

    ASSERT(call_address + patch_size() <= code->instruction_end());

#ifdef DEBUG

    prev_call_address = call_address;

#endif

  }

}

void Deoptimizer::FillInputFrame(Address tos, JavaScriptFrame* frame) {

  // Set the register values. The values are not important as there are no

  // callee saved registers in JavaScript frames, so all registers are

  // spilled. Registers fp and sp are set to the correct values though.

  for (int i = 0; i < Register::kNumRegisters; i++) {

    input_->SetRegister(i, i * 4);

  }

  input_->SetRegister(sp.code(), reinterpret_cast<intptr_t>(frame->sp()));

  input_->SetRegister(fp.code(), reinterpret_cast<intptr_t>(frame->fp()));

  for (int i = 0; i < DoubleRegister::NumAllocatableRegisters(); i++) {

    input_->SetDoubleRegister(i, 0.0);

  }

  // Fill the frame content from the actual data on the frame.

  for (unsigned i = 0; i < input_->GetFrameSize(); i += kPointerSize) {

    input_->SetFrameSlot(i, Memory::uint32_at(tos + i));

  }

}

void Deoptimizer::SetPlatformCompiledStubRegisters(

    FrameDescription* output_frame, CodeStubInterfaceDescriptor* descriptor) {

  ApiFunction function(descriptor->deoptimization_handler_);

  ExternalReference xref(&function, ExternalReference::BUILTIN_CALL, isolate_);

  intptr_t handler = reinterpret_cast<intptr_t>(xref.address());

  int params = descriptor->environment_length();

  output_frame->SetRegister(s0.code(), params);

  output_frame->SetRegister(s1.code(), (params - 1) * kPointerSize);

  output_frame->SetRegister(s2.code(), handler);

}

void Deoptimizer::CopyDoubleRegisters(FrameDescription* output_frame) {

  for (int i = 0; i < DoubleRegister::kMaxNumRegisters; ++i) {

    double double_value = input_->GetDoubleRegister(i);

    output_frame->SetDoubleRegister(i, double_value);

  }

}

bool Deoptimizer::HasAlignmentPadding(JSFunction* function) {

  // There is no dynamic alignment padding on MIPS in the input frame.

  return false;

}

#define __ masm()->

// This code tries to be close to ia32 code so that any changes can be

// easily ported.

void Deoptimizer::EntryGenerator::Generate() {

  GeneratePrologue();

  // Unlike on ARM we don't save all the registers, just the useful ones.

  // For the rest, there are gaps on the stack, so the offsets remain the same.

  const int kNumberOfRegisters = Register::kNumRegisters;

  RegList restored_regs = kJSCallerSaved | kCalleeSaved;

  RegList saved_regs = restored_regs | sp.bit() | ra.bit();

  const int kDoubleRegsSize =

      kDoubleSize * FPURegister::kMaxNumAllocatableRegisters;

  // Save all FPU registers before messing with them.

  __ Subu(sp, sp, Operand(kDoubleRegsSize));

  for (int i = 0; i < FPURegister::kMaxNumAllocatableRegisters; ++i) {

    FPURegister fpu_reg = FPURegister::FromAllocationIndex(i);

    int offset = i * kDoubleSize;

    __ sdc1(fpu_reg, MemOperand(sp, offset));

  }

  // Push saved_regs (needed to populate FrameDescription::registers_).

  // Leave gaps for other registers.

  __ Subu(sp, sp, kNumberOfRegisters * kPointerSize);

  for (int16_t i = kNumberOfRegisters - 1; i >= 0; i--) {

    if ((saved_regs & (1 << i)) != 0) {

      __ sw(ToRegister(i), MemOperand(sp, kPointerSize * i));

    }

  }

  const int kSavedRegistersAreaSize =

      (kNumberOfRegisters * kPointerSize) + kDoubleRegsSize;

  // Get the bailout id from the stack.

  __ lw(a2, MemOperand(sp, kSavedRegistersAreaSize));

  // Get the address of the location in the code object (a3) (return

  // address for lazy deoptimization) and compute the fp-to-sp delta in

  // register t0.

  __ mov(a3, ra);

  // Correct one word for bailout id.

  __ Addu(t0, sp, Operand(kSavedRegistersAreaSize + (1 * kPointerSize)));

  __ Subu(t0, fp, t0);

  // Allocate a new deoptimizer object.

  // Pass four arguments in a0 to a3 and fifth & sixth arguments on stack.

  __ PrepareCallCFunction(6, t1);

  __ lw(a0, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));

  __ li(a1, Operand(type()));  // bailout type,

  // a2: bailout id already loaded.

  // a3: code address or 0 already loaded.

  __ sw(t0, CFunctionArgumentOperand(5));  // Fp-to-sp delta.

  __ li(t1, Operand(ExternalReference::isolate_address(isolate())));

  __ sw(t1, CFunctionArgumentOperand(6));  // Isolate.

  // Call Deoptimizer::New().

  {

    AllowExternalCallThatCantCauseGC scope(masm());

    __ CallCFunction(ExternalReference::new_deoptimizer_function(isolate()), 6);

  }

  // Preserve "deoptimizer" object in register v0 and get the input

  // frame descriptor pointer to a1 (deoptimizer->input_);

  // Move deopt-obj to a0 for call to Deoptimizer::ComputeOutputFrames() below.

  __ mov(a0, v0);

  __ lw(a1, MemOperand(v0, Deoptimizer::input_offset()));

  // Copy core registers into FrameDescription::registers_[kNumRegisters].

  ASSERT(Register::kNumRegisters == kNumberOfRegisters);

  for (int i = 0; i < kNumberOfRegisters; i++) {

    int offset = (i * kPointerSize) + FrameDescription::registers_offset();

    if ((saved_regs & (1 << i)) != 0) {

      __ lw(a2, MemOperand(sp, i * kPointerSize));

      __ sw(a2, MemOperand(a1, offset));

    } else if (FLAG_debug_code) {

      __ li(a2, kDebugZapValue);

      __ sw(a2, MemOperand(a1, offset));

    }

  }

  int double_regs_offset = FrameDescription::double_registers_offset();

  // Copy FPU registers to

  // double_registers_[DoubleRegister::kNumAllocatableRegisters]

  for (int i = 0; i < FPURegister::NumAllocatableRegisters(); ++i) {

    int dst_offset = i * kDoubleSize + double_regs_offset;

    int src_offset = i * kDoubleSize + kNumberOfRegisters * kPointerSize;

    __ ldc1(f0, MemOperand(sp, src_offset));

    __ sdc1(f0, MemOperand(a1, dst_offset));

  }

  // Remove the bailout id and the saved registers from the stack.

  __ Addu(sp, sp, Operand(kSavedRegistersAreaSize + (1 * kPointerSize)));

  // Compute a pointer to the unwinding limit in register a2; that is

  // the first stack slot not part of the input frame.

  __ lw(a2, MemOperand(a1, FrameDescription::frame_size_offset()));

  __ Addu(a2, a2, sp);

  // Unwind the stack down to - but not including - the unwinding

  // limit and copy the contents of the activation frame to the input

  // frame description.

  __ Addu(a3, a1, Operand(FrameDescription::frame_content_offset()));

  Label pop_loop;

  Label pop_loop_header;

  __ Branch(&pop_loop_header);

  __ bind(&pop_loop);

  __ pop(t0);

  __ sw(t0, MemOperand(a3, 0));

  __ addiu(a3, a3, sizeof(uint32_t));

  __ bind(&pop_loop_header);

  __ Branch(&pop_loop, ne, a2, Operand(sp));

  // Compute the output frame in the deoptimizer.

  __ push(a0);  // Preserve deoptimizer object across call.

  // a0: deoptimizer object; a1: scratch.

  __ PrepareCallCFunction(1, a1);

  // Call Deoptimizer::ComputeOutputFrames().

  {

    AllowExternalCallThatCantCauseGC scope(masm());

    __ CallCFunction(

        ExternalReference::compute_output_frames_function(isolate()), 1);

  }

  __ pop(a0);  // Restore deoptimizer object (class Deoptimizer).

  // Replace the current (input) frame with the output frames.

  Label outer_push_loop, inner_push_loop,

      outer_loop_header, inner_loop_header;

  // Outer loop state: t0 = current "FrameDescription** output_",

  // a1 = one past the last FrameDescription**.

  __ lw(a1, MemOperand(a0, Deoptimizer::output_count_offset()));

  __ lw(t0, MemOperand(a0, Deoptimizer::output_offset()));  // t0 is output_.

  __ sll(a1, a1, kPointerSizeLog2);  // Count to offset.

  __ addu(a1, t0, a1);  // a1 = one past the last FrameDescription**.

  __ jmp(&outer_loop_header);

  __ bind(&outer_push_loop);

  // Inner loop state: a2 = current FrameDescription*, a3 = loop index.

  __ lw(a2, MemOperand(t0, 0));  // output_[ix]

  __ lw(a3, MemOperand(a2, FrameDescription::frame_size_offset()));

  __ jmp(&inner_loop_header);

  __ bind(&inner_push_loop);

  __ Subu(a3, a3, Operand(sizeof(uint32_t)));

  __ Addu(t2, a2, Operand(a3));

  __ lw(t3, MemOperand(t2, FrameDescription::frame_content_offset()));

  __ push(t3);

  __ bind(&inner_loop_header);

  __ Branch(&inner_push_loop, ne, a3, Operand(zero_reg));

  __ Addu(t0, t0, Operand(kPointerSize));

  __ bind(&outer_loop_header);

  __ Branch(&outer_push_loop, lt, t0, Operand(a1));

  __ lw(a1, MemOperand(a0, Deoptimizer::input_offset()));

  for (int i = 0; i < FPURegister::kMaxNumAllocatableRegisters; ++i) {

    const FPURegister fpu_reg = FPURegister::FromAllocationIndex(i);

    int src_offset = i * kDoubleSize + double_regs_offset;

    __ ldc1(fpu_reg, MemOperand(a1, src_offset));

  }

  // Push state, pc, and continuation from the last output frame.

  __ lw(t2, MemOperand(a2, FrameDescription::state_offset()));

  __ push(t2);

  __ lw(t2, MemOperand(a2, FrameDescription::pc_offset()));

  __ push(t2);

  __ lw(t2, MemOperand(a2, FrameDescription::continuation_offset()));

  __ push(t2);

  // Technically restoring 'at' should work unless zero_reg is also restored

  // but it's safer to check for this.

  ASSERT(!(at.bit() & restored_regs));

  // Restore the registers from the last output frame.

  __ mov(at, a2);

  for (int i = kNumberOfRegisters - 1; i >= 0; i--) {

    int offset = (i * kPointerSize) + FrameDescription::registers_offset();

    if ((restored_regs & (1 << i)) != 0) {

      __ lw(ToRegister(i), MemOperand(at, offset));

    }

  }

  __ InitializeRootRegister();

  __ pop(at);  // Get continuation, leave pc on stack.

  __ pop(ra);

  __ Jump(at);

  __ stop("Unreachable.");

}

// Maximum size of a table entry generated below.

const int Deoptimizer::table_entry_size_ = 7 * Assembler::kInstrSize;

void Deoptimizer::TableEntryGenerator::GeneratePrologue() {

  Assembler::BlockTrampolinePoolScope block_trampoline_pool(masm());

  // Create a sequence of deoptimization entries.

  // Note that registers are still live when jumping to an entry.

  Label table_start;

  __ bind(&table_start);

  for (int i = 0; i < count(); i++) {

    Label start;

    __ bind(&start);

    __ addiu(sp, sp, -1 * kPointerSize);

    // Jump over the remaining deopt entries (including this one).

    // This code is always reached by calling Jump, which puts the target (label

    // start) into t9.

    const int remaining_entries = (count() - i) * table_entry_size_;

    __ Addu(t9, t9, remaining_entries);

    // 'at' was clobbered so we can only load the current entry value here.

    __ li(at, i);

    __ jr(t9);  // Expose delay slot.

    __ sw(at, MemOperand(sp, 0 * kPointerSize));  // In the delay slot.

    // Pad the rest of the code.

    while (table_entry_size_ > (masm()->SizeOfCodeGeneratedSince(&start))) {

      __ nop();

    }

    ASSERT_EQ(table_entry_size_, masm()->SizeOfCodeGeneratedSince(&start));

  }

  ASSERT_EQ(masm()->SizeOfCodeGeneratedSince(&table_start),

      count() * table_entry_size_);

}

void FrameDescription::SetCallerPc(unsigned offset, intptr_t value) {

  SetFrameSlot(offset, value);

}

void FrameDescription::SetCallerFp(unsigned offset, intptr_t value) {

  SetFrameSlot(offset, value);

}

#undef __

} }  // namespace v8::internal