src/x87/deoptimizer-x87.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_X87

#include "src/codegen.h"
#include "src/deoptimizer.h"
#include "src/full-codegen/full-codegen.h"
#include "src/register-configuration.h"
#include "src/safepoint-table.h"
#include "src/x87/frames-x87.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::PatchCodeForDeoptimization below.
  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;
    DCHECK_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);
    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(isolate, 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);
      DCHECK(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();

  if (FLAG_zap_code_space) {
    // Fail hard and early if we enter this code object again.
    byte* pointer = code->FindCodeAgeSequence();
    if (pointer != NULL) {
      pointer += kNoCodeAgeSequenceLength;
    } else {
      pointer = code->instruction_start();
    }
    CodePatcher patcher(isolate, pointer, 1);
    patcher.masm()->int3();

    DeoptimizationInputData* data =
        DeoptimizationInputData::cast(code->deoptimization_data());
    int osr_offset = data->OsrPcOffset()->value();
    if (osr_offset > 0) {
      CodePatcher osr_patcher(isolate, code->instruction_start() + osr_offset,
                              1);
      osr_patcher.masm()->int3();
    }
  }

  // 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);

  // 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 each LLazyBailout instruction insert a call to the corresponding
  // deoptimization entry.
  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(isolate, 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(isolate, call_address + 1,  // 1 after the call opcode.
                    RelocInfo::RUNTIME_ENTRY,
                    reinterpret_cast<intptr_t>(deopt_entry), NULL);
    reloc_info_writer.Write(&rinfo);
    DCHECK_GE(reloc_info_writer.pos(),
              reloc_info->address() + ByteArray::kHeaderSize);
    DCHECK(prev_call_address == NULL ||
           call_address >= prev_call_address + patch_size());
    DCHECK(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.
  const int new_reloc_length = reloc_end_address - reloc_info_writer.pos();
  MemMove(code->relocation_start(), reloc_info_writer.pos(), new_reloc_length);

  // Right trim the relocation info to free up remaining space.
  const int delta = reloc_info->length() - new_reloc_length;
  if (delta > 0) {
    isolate->heap()->RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>(
        reloc_info, delta);
  }
}


void Deoptimizer::SetPlatformCompiledStubRegisters(
    FrameDescription* output_frame, CodeStubDescriptor* descriptor) {
  intptr_t handler =
      reinterpret_cast<intptr_t>(descriptor->deoptimization_handler());
  int params = descriptor->GetHandlerParameterCount();
  output_frame->SetRegister(eax.code(), params);
  output_frame->SetRegister(ebx.code(), handler);
}


void Deoptimizer::CopyDoubleRegisters(FrameDescription* output_frame) {
  for (int i = 0; i < X87Register::kMaxNumRegisters; ++i) {
    double double_value = input_->GetDoubleRegister(i);
    output_frame->SetDoubleRegister(i, double_value);
  }
}

#define __ masm()->

void Deoptimizer::TableEntryGenerator::Generate() {
  GeneratePrologue();

  // Save all general purpose registers before messing with them.
  const int kNumberOfRegisters = Register::kNumRegisters;

  const int kDoubleRegsSize = kDoubleSize * X87Register::kMaxNumRegisters;

  // Reserve space for x87 fp registers.
  __ sub(esp, Immediate(kDoubleRegsSize));

  __ pushad();

  ExternalReference c_entry_fp_address(Isolate::kCEntryFPAddress, isolate());
  __ mov(Operand::StaticVariable(c_entry_fp_address), ebp);

  // GP registers are safe to use now.
  // Save used x87 fp registers in correct position of previous reserve space.
  Label loop, done;
  // Get the layout of x87 stack.
  __ sub(esp, Immediate(kPointerSize));
  __ fistp_s(MemOperand(esp, 0));
  __ pop(eax);
  // Preserve stack layout in edi
  __ mov(edi, eax);
  // Get the x87 stack depth, the first 3 bits.
  __ mov(ecx, eax);
  __ and_(ecx, 0x7);
  __ j(zero, &done, Label::kNear);

  __ bind(&loop);
  __ shr(eax, 0x3);
  __ mov(ebx, eax);
  __ and_(ebx, 0x7);  // Extract the st_x index into ebx.
  // Pop TOS to the correct position. The disp(0x20) is due to pushad.
  // The st_i should be saved to (esp + ebx * kDoubleSize + 0x20).
  __ fstp_d(Operand(esp, ebx, times_8, 0x20));
  __ dec(ecx);  // Decrease stack depth.
  __ j(not_zero, &loop, Label::kNear);
  __ bind(&done);

  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);

  __ push(edi);
  // Allocate a new deoptimizer object.
  __ PrepareCallCFunction(6, eax);
  __ mov(eax, Immediate(0));
  Label context_check;
  __ mov(edi, Operand(ebp, CommonFrameConstants::kContextOrFrameTypeOffset));
  __ JumpIfSmi(edi, &context_check);
  __ mov(eax, Operand(ebp, JavaScriptFrameConstants::kFunctionOffset));
  __ bind(&context_check);
  __ 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);
  }

  __ pop(edi);

  // 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();
  const RegisterConfiguration* config =
      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT);
  // Fill in the double input registers.
  for (int i = 0; i < X87Register::kMaxNumAllocatableRegisters; ++i) {
    int code = config->GetAllocatableDoubleCode(i);
    int dst_offset = code * kDoubleSize + double_regs_offset;
    int src_offset = code * kDoubleSize;
    __ fld_d(Operand(esp, src_offset));
    __ fstp_d(Operand(ebx, dst_offset));
  }

  // 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(edi);
  __ push(eax);
  __ PrepareCallCFunction(1, ebx);
  __ mov(Operand(esp, 0 * kPointerSize), eax);
  {
    AllowExternalCallThatCantCauseGC scope(masm());
    __ CallCFunction(
        ExternalReference::compute_output_frames_function(isolate()), 1);
  }
  __ pop(eax);
  __ pop(edi);
  __ mov(esp, Operand(eax, Deoptimizer::caller_frame_top_offset()));

  // 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: 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 x87 stack.
  // x87 stack layout is in edi.
  Label loop2, done2;
  // Get the x87 stack depth, the first 3 bits.
  __ mov(ecx, edi);
  __ and_(ecx, 0x7);
  __ j(zero, &done2, Label::kNear);

  __ lea(ecx, Operand(ecx, ecx, times_2, 0));
  __ bind(&loop2);
  __ mov(eax, edi);
  __ shr_cl(eax);
  __ and_(eax, 0x7);
  __ fld_d(Operand(ebx, eax, times_8, double_regs_offset));
  __ sub(ecx, Immediate(0x3));
  __ j(not_zero, &loop2, Label::kNear);
  __ bind(&done2);

  // 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);
    DCHECK(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);
}


void FrameDescription::SetCallerConstantPool(unsigned offset, intptr_t value) {
  // No embedded constant pool support.
  UNREACHABLE();
}


#undef __


}  // namespace internal
}  // namespace v8

#endif  // V8_TARGET_ARCH_X87