CSE2410 Fall 2014 Bounce

// Copyright 2012 the V8 project authors. All rights reserved.

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#include "v8.h"

#if V8_TARGET_ARCH_IA32

#include "codegen.h"

#include "deoptimizer.h"

#include "full-codegen.h"

#include "safepoint-table.h"

namespace v8 {

namespace internal {

const int Deoptimizer::table_entry_size_ = 10;

int Deoptimizer::patch_size() {

  return Assembler::kCallInstructionLength;

}

void Deoptimizer::EnsureRelocSpaceForLazyDeoptimization(Handle<Code> code) {

  Isolate* isolate = code->GetIsolate();

  HandleScope scope(isolate);

  // Compute the size of relocation information needed for the code

  // patching in Deoptimizer::DeoptimizeFunction.

  int min_reloc_size = 0;

  int prev_pc_offset = 0;

  DeoptimizationInputData* deopt_data =

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

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

    int pc_offset = deopt_data->Pc(i)->value();

    if (pc_offset == -1) continue;

    ASSERT_GE(pc_offset, prev_pc_offset);

    int pc_delta = pc_offset - prev_pc_offset;

    // We use RUNTIME_ENTRY reloc info which has a size of 2 bytes

    // if encodable with small pc delta encoding and up to 6 bytes

    // otherwise.

    if (pc_delta <= RelocInfo::kMaxSmallPCDelta) {

      min_reloc_size += 2;

    } else {

      min_reloc_size += 6;

    }

    prev_pc_offset = pc_offset;

  }

  // If the relocation information is not big enough we create a new

  // relocation info object that is padded with comments to make it

  // big enough for lazy doptimization.

  int reloc_length = code->relocation_info()->length();

  if (min_reloc_size > reloc_length) {

    int comment_reloc_size = RelocInfo::kMinRelocCommentSize;

    // Padding needed.

    int min_padding = min_reloc_size - reloc_length;

    // Number of comments needed to take up at least that much space.

    int additional_comments =

        (min_padding + comment_reloc_size - 1) / comment_reloc_size;

    // Actual padding size.

    int padding = additional_comments * comment_reloc_size;

    // Allocate new relocation info and copy old relocation to the end

    // of the new relocation info array because relocation info is

    // written and read backwards.

    Factory* factory = isolate->factory();

    Handle<ByteArray> new_reloc =

        factory->NewByteArray(reloc_length + padding, TENURED);

    OS::MemCopy(new_reloc->GetDataStartAddress() + padding,

                code->relocation_info()->GetDataStartAddress(),

                reloc_length);

    // Create a relocation writer to write the comments in the padding

    // space. Use position 0 for everything to ensure short encoding.

    RelocInfoWriter reloc_info_writer(

        new_reloc->GetDataStartAddress() + padding, 0);

    intptr_t comment_string

        = reinterpret_cast<intptr_t>(RelocInfo::kFillerCommentString);

    RelocInfo rinfo(0, RelocInfo::COMMENT, comment_string, NULL);

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

#ifdef DEBUG

      byte* pos_before = reloc_info_writer.pos();

#endif

      reloc_info_writer.Write(&rinfo);

      ASSERT(RelocInfo::kMinRelocCommentSize ==

             pos_before - reloc_info_writer.pos());

    }

    // Replace relocation information on the code object.

    code->set_relocation_info(*new_reloc);

  }

}

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

  Address code_start_address = code->instruction_start();

  // We will overwrite the code's relocation info in-place. Relocation info

  // is written backward. The relocation info is the payload of a byte

  // array.  Later on we will slide this to the start of the byte array and

  // create a filler object in the remaining space.

  ByteArray* reloc_info = code->relocation_info();

  Address reloc_end_address = reloc_info->address() + reloc_info->Size();

  RelocInfoWriter reloc_info_writer(reloc_end_address, code_start_address);

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

  // deoptimization entry.

  // Since the call is a relative encoding, write new

  // reloc info.  We do not need any of the existing reloc info because the

  // existing code will not be used again (we zap it in debug builds).

  //

  // Emit call to lazy deoptimization at all lazy deopt points.

  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;

    // Patch lazy deoptimization entry.

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

    CodePatcher patcher(call_address, patch_size());

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

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

    // We use RUNTIME_ENTRY for deoptimization bailouts.

    RelocInfo rinfo(call_address + 1,  // 1 after the call opcode.

                    RelocInfo::RUNTIME_ENTRY,

                    reinterpret_cast<intptr_t>(deopt_entry),

                    NULL);

    reloc_info_writer.Write(&rinfo);

    ASSERT_GE(reloc_info_writer.pos(),

              reloc_info->address() + ByteArray::kHeaderSize);

    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

  }

  // Move the relocation info to the beginning of the byte array.

  int new_reloc_size = reloc_end_address - reloc_info_writer.pos();

  OS::MemMove(

      code->relocation_start(), reloc_info_writer.pos(), new_reloc_size);

  // The relocation info is in place, update the size.

  reloc_info->set_length(new_reloc_size);

  // Handle the junk part after the new relocation info. We will create

  // a non-live object in the extra space at the end of the former reloc info.

  Address junk_address = reloc_info->address() + reloc_info->Size();

  ASSERT(junk_address <= reloc_end_address);

  isolate->heap()->CreateFillerObjectAt(junk_address,

                                        reloc_end_address - junk_address);

}

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 ebp and esp are set to the correct values though.

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

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

  }

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

  input_->SetRegister(ebp.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) {

  intptr_t handler =

      reinterpret_cast<intptr_t>(descriptor->deoptimization_handler_);

  int params = descriptor->environment_length();

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

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

}

void Deoptimizer::CopyDoubleRegisters(FrameDescription* output_frame) {

  if (!CpuFeatures::IsSupported(SSE2)) return;

  for (int i = 0; i < XMMRegister::kNumAllocatableRegisters; ++i) {

    double double_value = input_->GetDoubleRegister(i);

    output_frame->SetDoubleRegister(i, double_value);

  }

}

bool Deoptimizer::HasAlignmentPadding(JSFunction* function) {

  int parameter_count = function->shared()->formal_parameter_count() + 1;

  unsigned input_frame_size = input_->GetFrameSize();

  unsigned alignment_state_offset =

      input_frame_size - parameter_count * kPointerSize -

      StandardFrameConstants::kFixedFrameSize -

      kPointerSize;

  ASSERT(JavaScriptFrameConstants::kDynamicAlignmentStateOffset ==

      JavaScriptFrameConstants::kLocal0Offset);

  int32_t alignment_state = input_->GetFrameSlot(alignment_state_offset);

  return (alignment_state == kAlignmentPaddingPushed);

}

#define __ masm()->

void Deoptimizer::EntryGenerator::Generate() {

  GeneratePrologue();

  // Save all general purpose registers before messing with them.

  const int kNumberOfRegisters = Register::kNumRegisters;

  const int kDoubleRegsSize = kDoubleSize *

                              XMMRegister::kNumAllocatableRegisters;

  __ sub(esp, Immediate(kDoubleRegsSize));

  if (CpuFeatures::IsSupported(SSE2)) {

    CpuFeatureScope scope(masm(), SSE2);

    for (int i = 0; i < XMMRegister::kNumAllocatableRegisters; ++i) {

      XMMRegister xmm_reg = XMMRegister::FromAllocationIndex(i);

      int offset = i * kDoubleSize;

      __ movsd(Operand(esp, offset), xmm_reg);

    }

  }

  __ pushad();

  const int kSavedRegistersAreaSize = kNumberOfRegisters * kPointerSize +

                                      kDoubleRegsSize;

  // Get the bailout id from the stack.

  __ mov(ebx, Operand(esp, kSavedRegistersAreaSize));

  // Get the address of the location in the code object

  // and compute the fp-to-sp delta in register edx.

  __ mov(ecx, Operand(esp, kSavedRegistersAreaSize + 1 * kPointerSize));

  __ lea(edx, Operand(esp, kSavedRegistersAreaSize + 2 * kPointerSize));

  __ sub(edx, ebp);

  __ neg(edx);

  // Allocate a new deoptimizer object.

  __ PrepareCallCFunction(6, eax);

  __ mov(eax, Operand(ebp, JavaScriptFrameConstants::kFunctionOffset));

  __ mov(Operand(esp, 0 * kPointerSize), eax);  // Function.

  __ mov(Operand(esp, 1 * kPointerSize), Immediate(type()));  // Bailout type.

  __ mov(Operand(esp, 2 * kPointerSize), ebx);  // Bailout id.

  __ mov(Operand(esp, 3 * kPointerSize), ecx);  // Code address or 0.

  __ mov(Operand(esp, 4 * kPointerSize), edx);  // Fp-to-sp delta.

  __ mov(Operand(esp, 5 * kPointerSize),

         Immediate(ExternalReference::isolate_address(isolate())));

  {

    AllowExternalCallThatCantCauseGC scope(masm());

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

  }

  // Preserve deoptimizer object in register eax and get the input

  // frame descriptor pointer.

  __ mov(ebx, Operand(eax, Deoptimizer::input_offset()));

  // Fill in the input registers.

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

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

    __ pop(Operand(ebx, offset));

  }

  int double_regs_offset = FrameDescription::double_registers_offset();

  if (CpuFeatures::IsSupported(SSE2)) {

    CpuFeatureScope scope(masm(), SSE2);

    // Fill in the double input registers.

    for (int i = 0; i < XMMRegister::kNumAllocatableRegisters; ++i) {

      int dst_offset = i * kDoubleSize + double_regs_offset;

      int src_offset = i * kDoubleSize;

      __ movsd(xmm0, Operand(esp, src_offset));

      __ movsd(Operand(ebx, dst_offset), xmm0);

    }

  }

  // Clear FPU all exceptions.

  // TODO(ulan): Find out why the TOP register is not zero here in some cases,

  // and check that the generated code never deoptimizes with unbalanced stack.

  __ fnclex();

  // Remove the bailout id, return address and the double registers.

  __ add(esp, Immediate(kDoubleRegsSize + 2 * kPointerSize));

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

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

  __ mov(ecx, Operand(ebx, FrameDescription::frame_size_offset()));

  __ add(ecx, esp);

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

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

  // frame description.

  __ lea(edx, Operand(ebx, FrameDescription::frame_content_offset()));

  Label pop_loop_header;

  __ jmp(&pop_loop_header);

  Label pop_loop;

  __ bind(&pop_loop);

  __ pop(Operand(edx, 0));

  __ add(edx, Immediate(sizeof(uint32_t)));

  __ bind(&pop_loop_header);

  __ cmp(ecx, esp);

  __ j(not_equal, &pop_loop);

  // Compute the output frame in the deoptimizer.

  __ push(eax);

  __ PrepareCallCFunction(1, ebx);

  __ mov(Operand(esp, 0 * kPointerSize), eax);

  {

    AllowExternalCallThatCantCauseGC scope(masm());

    __ CallCFunction(

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

  }

  __ pop(eax);

  // If frame was dynamically aligned, pop padding.

  Label no_padding;

  __ cmp(Operand(eax, Deoptimizer::has_alignment_padding_offset()),

         Immediate(0));

  __ j(equal, &no_padding);

  __ pop(ecx);

  if (FLAG_debug_code) {

    __ cmp(ecx, Immediate(kAlignmentZapValue));

    __ Assert(equal, kAlignmentMarkerExpected);

  }

  __ bind(&no_padding);

  // Replace the current frame with the output frames.

  Label outer_push_loop, inner_push_loop,

      outer_loop_header, inner_loop_header;

  // Outer loop state: eax = current FrameDescription**, edx = one past the

  // last FrameDescription**.

  __ mov(edx, Operand(eax, Deoptimizer::output_count_offset()));

  __ mov(eax, Operand(eax, Deoptimizer::output_offset()));

  __ lea(edx, Operand(eax, edx, times_4, 0));

  __ jmp(&outer_loop_header);

  __ bind(&outer_push_loop);

  // Inner loop state: ebx = current FrameDescription*, ecx = loop index.

  __ mov(ebx, Operand(eax, 0));

  __ mov(ecx, Operand(ebx, FrameDescription::frame_size_offset()));

  __ jmp(&inner_loop_header);

  __ bind(&inner_push_loop);

  __ sub(ecx, Immediate(sizeof(uint32_t)));

  __ push(Operand(ebx, ecx, times_1, FrameDescription::frame_content_offset()));

  __ bind(&inner_loop_header);

  __ test(ecx, ecx);

  __ j(not_zero, &inner_push_loop);

  __ add(eax, Immediate(kPointerSize));

  __ bind(&outer_loop_header);

  __ cmp(eax, edx);

  __ j(below, &outer_push_loop);

  // In case of a failed STUB, we have to restore the XMM registers.

  if (CpuFeatures::IsSupported(SSE2)) {

    CpuFeatureScope scope(masm(), SSE2);

    for (int i = 0; i < XMMRegister::kNumAllocatableRegisters; ++i) {

      XMMRegister xmm_reg = XMMRegister::FromAllocationIndex(i);

      int src_offset = i * kDoubleSize + double_regs_offset;

      __ movsd(xmm_reg, Operand(ebx, src_offset));

    }

  }

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

  __ push(Operand(ebx, FrameDescription::state_offset()));

  __ push(Operand(ebx, FrameDescription::pc_offset()));

  __ push(Operand(ebx, FrameDescription::continuation_offset()));

  // Push the registers from the last output frame.

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

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

    __ push(Operand(ebx, offset));

  }

  // Restore the registers from the stack.

  __ popad();

  // Return to the continuation point.

  __ ret(0);

}

void Deoptimizer::TableEntryGenerator::GeneratePrologue() {

  // Create a sequence of deoptimization entries.

  Label done;

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

    int start = masm()->pc_offset();

    USE(start);

    __ push_imm32(i);

    __ jmp(&done);

    ASSERT(masm()->pc_offset() - start == table_entry_size_);

  }

  __ bind(&done);

}

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

#endif  // V8_TARGET_ARCH_IA32