CSE2410 Fall 2014 Bounce

// Copyright 2012 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 {

const int Deoptimizer::table_entry_size_ = 12;

int Deoptimizer::patch_size() {

  const int kCallInstructionSizeInWords = 3;

  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);

    // We need calls to have a predictable size in the unoptimized code, but

    // this is optimized code, so we don't have to have a predictable size.

    int call_size_in_bytes =

        MacroAssembler::CallSizeNotPredictableCodeSize(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(r0.code(), params);

  output_frame->SetRegister(r1.code(), handler);

}

void Deoptimizer::CopyDoubleRegisters(FrameDescription* output_frame) {

  for (int i = 0; i < DwVfpRegister::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 ARM 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();

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

  const int kNumberOfRegisters = Register::kNumRegisters;

  // Everything but pc, lr and ip which will be saved but not restored.

  RegList restored_regs = kJSCallerSaved | kCalleeSaved | ip.bit();

  const int kDoubleRegsSize =

      kDoubleSize * DwVfpRegister::kMaxNumAllocatableRegisters;

  // Save all allocatable VFP registers before messing with them.

  ASSERT(kDoubleRegZero.code() == 14);

  ASSERT(kScratchDoubleReg.code() == 15);

  // Check CPU flags for number of registers, setting the Z condition flag.

  __ CheckFor32DRegs(ip);

  // Push registers d0-d13, and possibly d16-d31, on the stack.

  // If d16-d31 are not pushed, decrease the stack pointer instead.

  __ vstm(db_w, sp, d16, d31, ne);

  __ sub(sp, sp, Operand(16 * kDoubleSize), LeaveCC, eq);

  __ vstm(db_w, sp, d0, d13);

  // Push all 16 registers (needed to populate FrameDescription::registers_).

  // TODO(1588) Note that using pc with stm is deprecated, so we should perhaps

  // handle this a bit differently.

  __ stm(db_w, sp, restored_regs  | sp.bit() | lr.bit() | pc.bit());

  const int kSavedRegistersAreaSize =

      (kNumberOfRegisters * kPointerSize) + kDoubleRegsSize;

  // Get the bailout id from the stack.

  __ ldr(r2, MemOperand(sp, kSavedRegistersAreaSize));

  // Get the address of the location in the code object (r3) (return

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

  // register r4.

  __ mov(r3, lr);

  // Correct one word for bailout id.

  __ add(r4, sp, Operand(kSavedRegistersAreaSize + (1 * kPointerSize)));

  __ sub(r4, fp, r4);

  // Allocate a new deoptimizer object.

  // Pass four arguments in r0 to r3 and fifth argument on stack.

  __ PrepareCallCFunction(6, r5);

  __ ldr(r0, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));

  __ mov(r1, Operand(type()));  // bailout type,

  // r2: bailout id already loaded.

  // r3: code address or 0 already loaded.

  __ str(r4, MemOperand(sp, 0 * kPointerSize));  // Fp-to-sp delta.

  __ mov(r5, Operand(ExternalReference::isolate_address(isolate())));

  __ str(r5, MemOperand(sp, 1 * kPointerSize));  // Isolate.

  // Call Deoptimizer::New().

  {

    AllowExternalCallThatCantCauseGC scope(masm());

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

  }

  // Preserve "deoptimizer" object in register r0 and get the input

  // frame descriptor pointer to r1 (deoptimizer->input_);

  __ ldr(r1, MemOperand(r0, 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();

    __ ldr(r2, MemOperand(sp, i * kPointerSize));

    __ str(r2, MemOperand(r1, offset));

  }

  // Copy VFP registers to

  // double_registers_[DoubleRegister::kMaxNumAllocatableRegisters]

  int double_regs_offset = FrameDescription::double_registers_offset();

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

    int dst_offset = i * kDoubleSize + double_regs_offset;

    int src_offset = i * kDoubleSize + kNumberOfRegisters * kPointerSize;

    __ vldr(d0, sp, src_offset);

    __ vstr(d0, r1, dst_offset);

  }

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

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

  // Compute a pointer to the unwinding limit in register r2; that is

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

  __ ldr(r2, MemOperand(r1, FrameDescription::frame_size_offset()));

  __ add(r2, r2, 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.

  __ add(r3,  r1, Operand(FrameDescription::frame_content_offset()));

  Label pop_loop;

  Label pop_loop_header;

  __ b(&pop_loop_header);

  __ bind(&pop_loop);

  __ pop(r4);

  __ str(r4, MemOperand(r3, 0));

  __ add(r3, r3, Operand(sizeof(uint32_t)));

  __ bind(&pop_loop_header);

  __ cmp(r2, sp);

  __ b(ne, &pop_loop);

  // Compute the output frame in the deoptimizer.

  __ push(r0);  // Preserve deoptimizer object across call.

  // r0: deoptimizer object; r1: scratch.

  __ PrepareCallCFunction(1, r1);

  // Call Deoptimizer::ComputeOutputFrames().

  {

    AllowExternalCallThatCantCauseGC scope(masm());

    __ CallCFunction(

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

  }

  __ pop(r0);  // 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: r4 = current "FrameDescription** output_",

  // r1 = one past the last FrameDescription**.

  __ ldr(r1, MemOperand(r0, Deoptimizer::output_count_offset()));

  __ ldr(r4, MemOperand(r0, Deoptimizer::output_offset()));  // r4 is output_.

  __ add(r1, r4, Operand(r1, LSL, 2));

  __ jmp(&outer_loop_header);

  __ bind(&outer_push_loop);

  // Inner loop state: r2 = current FrameDescription*, r3 = loop index.

  __ ldr(r2, MemOperand(r4, 0));  // output_[ix]

  __ ldr(r3, MemOperand(r2, FrameDescription::frame_size_offset()));

  __ jmp(&inner_loop_header);

  __ bind(&inner_push_loop);

  __ sub(r3, r3, Operand(sizeof(uint32_t)));

  __ add(r6, r2, Operand(r3));

  __ ldr(r6, MemOperand(r6, FrameDescription::frame_content_offset()));

  __ push(r6);

  __ bind(&inner_loop_header);

  __ cmp(r3, Operand::Zero());

  __ b(ne, &inner_push_loop);  // test for gt?

  __ add(r4, r4, Operand(kPointerSize));

  __ bind(&outer_loop_header);

  __ cmp(r4, r1);

  __ b(lt, &outer_push_loop);

  // Check CPU flags for number of registers, setting the Z condition flag.

  __ CheckFor32DRegs(ip);

  __ ldr(r1, MemOperand(r0, Deoptimizer::input_offset()));

  int src_offset = FrameDescription::double_registers_offset();

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

    if (i == kDoubleRegZero.code()) continue;

    if (i == kScratchDoubleReg.code()) continue;

    const DwVfpRegister reg = DwVfpRegister::from_code(i);

    __ vldr(reg, r1, src_offset, i < 16 ? al : ne);

    src_offset += kDoubleSize;

  }

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

  __ ldr(r6, MemOperand(r2, FrameDescription::state_offset()));

  __ push(r6);

  __ ldr(r6, MemOperand(r2, FrameDescription::pc_offset()));

  __ push(r6);

  __ ldr(r6, MemOperand(r2, FrameDescription::continuation_offset()));

  __ push(r6);

  // Push the registers from the last output frame.

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

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

    __ ldr(r6, MemOperand(r2, offset));

    __ push(r6);

  }

  // Restore the registers from the stack.

  __ ldm(ia_w, sp, restored_regs);  // all but pc registers.

  __ pop(ip);  // remove sp

  __ pop(ip);  // remove lr

  __ InitializeRootRegister();

  __ pop(ip);  // remove pc

  __ pop(ip);  // get continuation, leave pc on stack

  __ pop(lr);

  __ Jump(ip);

  __ stop("Unreachable.");

}

void Deoptimizer::TableEntryGenerator::GeneratePrologue() {

  // Create a sequence of deoptimization entries.

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

  Label done;

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

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

    USE(start);

    __ mov(ip, Operand(i));

    __ push(ip);

    __ b(&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