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// Copyright 2011 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include "safepoint-table.h"
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#include "deoptimizer.h"
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#include "macro-assembler.h"
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bool SafepointEntry::HasRegisters() const {
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ASSERT(IsAligned(kNumSafepointRegisters, kBitsPerByte));
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const int num_reg_bytes = kNumSafepointRegisters >> kBitsPerByteLog2;
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for (int i = 0; i < num_reg_bytes; i++) {
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if (bits_[i] != SafepointTable::kNoRegisters) return true;
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bool SafepointEntry::HasRegisterAt(int reg_index) const {
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ASSERT(reg_index >= 0 && reg_index < kNumSafepointRegisters);
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int byte_index = reg_index >> kBitsPerByteLog2;
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int bit_index = reg_index & (kBitsPerByte - 1);
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return (bits_[byte_index] & (1 << bit_index)) != 0;
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SafepointTable::SafepointTable(Code* code) {
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ASSERT(code->kind() == Code::OPTIMIZED_FUNCTION);
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Address header = code->instruction_start() + code->safepoint_table_offset();
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length_ = Memory::uint32_at(header + kLengthOffset);
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entry_size_ = Memory::uint32_at(header + kEntrySizeOffset);
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pc_and_deoptimization_indexes_ = header + kHeaderSize;
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entries_ = pc_and_deoptimization_indexes_ +
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(length_ * kPcAndDeoptimizationIndexSize);
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ASSERT(entry_size_ > 0);
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STATIC_ASSERT(SafepointEntry::DeoptimizationIndexField::kMax ==
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Safepoint::kNoDeoptimizationIndex);
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SafepointEntry SafepointTable::FindEntry(Address pc) const {
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unsigned pc_offset = static_cast<unsigned>(pc - code_->instruction_start());
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for (unsigned i = 0; i < length(); i++) {
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// TODO(kasperl): Replace the linear search with binary search.
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if (GetPcOffset(i) == pc_offset) return GetEntry(i);
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return SafepointEntry();
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void SafepointTable::PrintEntry(unsigned index) const {
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disasm::NameConverter converter;
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SafepointEntry entry = GetEntry(index);
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uint8_t* bits = entry.bits();
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// Print the stack slot bits.
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if (entry_size_ > 0) {
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ASSERT(IsAligned(kNumSafepointRegisters, kBitsPerByte));
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const int first = kNumSafepointRegisters >> kBitsPerByteLog2;
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int last = entry_size_ - 1;
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for (int i = first; i < last; i++) PrintBits(bits[i], kBitsPerByte);
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int last_bits = code_->stack_slots() - ((last - first) * kBitsPerByte);
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PrintBits(bits[last], last_bits);
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// Print the registers (if any).
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if (!entry.HasRegisters()) return;
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for (int j = 0; j < kNumSafepointRegisters; j++) {
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if (entry.HasRegisterAt(j)) {
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PrintF(" | %s", converter.NameOfCPURegister(j));
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void SafepointTable::PrintBits(uint8_t byte, int digits) {
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ASSERT(digits >= 0 && digits <= kBitsPerByte);
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for (int i = 0; i < digits; i++) {
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PrintF("%c", ((byte & (1 << i)) == 0) ? '0' : '1');
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void Safepoint::DefinePointerRegister(Register reg, Zone* zone) {
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registers_->Add(reg.code(), zone);
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Safepoint SafepointTableBuilder::DefineSafepoint(
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Assembler* assembler,
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Safepoint::Kind kind,
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Safepoint::DeoptMode deopt_mode) {
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ASSERT(arguments >= 0);
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DeoptimizationInfo info;
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info.pc = assembler->pc_offset();
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info.arguments = arguments;
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info.has_doubles = (kind & Safepoint::kWithDoubles);
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deoptimization_info_.Add(info, zone_);
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deopt_index_list_.Add(Safepoint::kNoDeoptimizationIndex, zone_);
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if (deopt_mode == Safepoint::kNoLazyDeopt) {
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last_lazy_safepoint_ = deopt_index_list_.length();
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indexes_.Add(new(zone_) ZoneList<int>(8, zone_), zone_);
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registers_.Add((kind & Safepoint::kWithRegisters)
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? new(zone_) ZoneList<int>(4, zone_)
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return Safepoint(indexes_.last(), registers_.last());
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void SafepointTableBuilder::RecordLazyDeoptimizationIndex(int index) {
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while (last_lazy_safepoint_ < deopt_index_list_.length()) {
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deopt_index_list_[last_lazy_safepoint_++] = index;
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unsigned SafepointTableBuilder::GetCodeOffset() const {
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void SafepointTableBuilder::Emit(Assembler* assembler, int bits_per_entry) {
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// For lazy deoptimization we need space to patch a call after every call.
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// Ensure there is always space for such patching, even if the code ends
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int target_offset = assembler->pc_offset() + Deoptimizer::patch_size();
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while (assembler->pc_offset() < target_offset) {
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// Make sure the safepoint table is properly aligned. Pad with nops.
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assembler->Align(kIntSize);
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assembler->RecordComment(";;; Safepoint table.");
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offset_ = assembler->pc_offset();
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// Take the register bits into account.
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bits_per_entry += kNumSafepointRegisters;
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// Compute the number of bytes per safepoint entry.
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int bytes_per_entry =
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RoundUp(bits_per_entry, kBitsPerByte) >> kBitsPerByteLog2;
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// Emit the table header.
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int length = deoptimization_info_.length();
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assembler->dd(length);
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assembler->dd(bytes_per_entry);
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// Emit sorted table of pc offsets together with deoptimization indexes.
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for (int i = 0; i < length; i++) {
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assembler->dd(deoptimization_info_[i].pc);
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assembler->dd(EncodeExceptPC(deoptimization_info_[i],
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deopt_index_list_[i]));
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// Emit table of bitmaps.
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ZoneList<uint8_t> bits(bytes_per_entry, zone_);
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for (int i = 0; i < length; i++) {
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ZoneList<int>* indexes = indexes_[i];
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ZoneList<int>* registers = registers_[i];
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bits.AddBlock(0, bytes_per_entry, zone_);
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// Run through the registers (if any).
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ASSERT(IsAligned(kNumSafepointRegisters, kBitsPerByte));
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if (registers == NULL) {
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const int num_reg_bytes = kNumSafepointRegisters >> kBitsPerByteLog2;
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for (int j = 0; j < num_reg_bytes; j++) {
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bits[j] = SafepointTable::kNoRegisters;
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for (int j = 0; j < registers->length(); j++) {
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int index = registers->at(j);
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ASSERT(index >= 0 && index < kNumSafepointRegisters);
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int byte_index = index >> kBitsPerByteLog2;
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int bit_index = index & (kBitsPerByte - 1);
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bits[byte_index] |= (1 << bit_index);
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// Run through the indexes and build a bitmap.
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for (int j = 0; j < indexes->length(); j++) {
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int index = bits_per_entry - 1 - indexes->at(j);
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int byte_index = index >> kBitsPerByteLog2;
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int bit_index = index & (kBitsPerByte - 1);
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bits[byte_index] |= (1U << bit_index);
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// Emit the bitmap for the current entry.
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for (int k = 0; k < bytes_per_entry; k++) {
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assembler->db(bits[k]);
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uint32_t SafepointTableBuilder::EncodeExceptPC(const DeoptimizationInfo& info,
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uint32_t encoding = SafepointEntry::DeoptimizationIndexField::encode(index);
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encoding |= SafepointEntry::ArgumentsField::encode(info.arguments);
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encoding |= SafepointEntry::SaveDoublesField::encode(info.has_doubles);
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} } // namespace v8::internal