312 lines
13 KiB
C++
312 lines
13 KiB
C++
/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "verified_method.h"
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#include <algorithm>
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#include <memory>
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#include <vector>
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#include "base/logging.h"
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#include "base/stl_util.h"
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#include "dex_file.h"
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#include "dex_instruction.h"
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#include "dex_instruction-inl.h"
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#include "base/mutex.h"
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#include "base/mutex-inl.h"
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#include "mirror/art_method.h"
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#include "mirror/art_method-inl.h"
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#include "mirror/class.h"
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#include "mirror/class-inl.h"
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#include "mirror/dex_cache.h"
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#include "mirror/dex_cache-inl.h"
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#include "mirror/object.h"
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#include "mirror/object-inl.h"
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#include "verifier/dex_gc_map.h"
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#include "verifier/method_verifier.h"
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#include "verifier/method_verifier-inl.h"
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#include "verifier/register_line.h"
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#include "verifier/register_line-inl.h"
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namespace art {
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const VerifiedMethod* VerifiedMethod::Create(verifier::MethodVerifier* method_verifier,
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bool compile) {
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std::unique_ptr<VerifiedMethod> verified_method(new VerifiedMethod);
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if (compile) {
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/* Generate a register map. */
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if (!verified_method->GenerateGcMap(method_verifier)) {
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return nullptr; // Not a real failure, but a failure to encode.
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}
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if (kIsDebugBuild) {
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VerifyGcMap(method_verifier, verified_method->dex_gc_map_);
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}
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// TODO: move this out when DEX-to-DEX supports devirtualization.
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if (method_verifier->HasVirtualOrInterfaceInvokes()) {
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verified_method->GenerateDevirtMap(method_verifier);
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}
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}
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if (method_verifier->HasCheckCasts()) {
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verified_method->GenerateSafeCastSet(method_verifier);
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}
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return verified_method.release();
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}
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const MethodReference* VerifiedMethod::GetDevirtTarget(uint32_t dex_pc) const {
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auto it = devirt_map_.find(dex_pc);
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return (it != devirt_map_.end()) ? &it->second : nullptr;
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}
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bool VerifiedMethod::IsSafeCast(uint32_t pc) const {
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return std::binary_search(safe_cast_set_.begin(), safe_cast_set_.end(), pc);
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}
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bool VerifiedMethod::GenerateGcMap(verifier::MethodVerifier* method_verifier) {
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DCHECK(dex_gc_map_.empty());
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size_t num_entries, ref_bitmap_bits, pc_bits;
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ComputeGcMapSizes(method_verifier, &num_entries, &ref_bitmap_bits, &pc_bits);
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// There's a single byte to encode the size of each bitmap.
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if (ref_bitmap_bits >= (8 /* bits per byte */ * 8192 /* 13-bit size */ )) {
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LOG(WARNING) << "Cannot encode GC map for method with " << ref_bitmap_bits << " registers: "
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<< PrettyMethod(method_verifier->GetMethodReference().dex_method_index,
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*method_verifier->GetMethodReference().dex_file);
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return false;
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}
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size_t ref_bitmap_bytes = (ref_bitmap_bits + 7) / 8;
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// There are 2 bytes to encode the number of entries.
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if (num_entries >= 65536) {
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LOG(WARNING) << "Cannot encode GC map for method with " << num_entries << " entries: "
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<< PrettyMethod(method_verifier->GetMethodReference().dex_method_index,
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*method_verifier->GetMethodReference().dex_file);
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return false;
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}
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size_t pc_bytes;
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verifier::RegisterMapFormat format;
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if (pc_bits <= 8) {
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format = verifier::kRegMapFormatCompact8;
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pc_bytes = 1;
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} else if (pc_bits <= 16) {
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format = verifier::kRegMapFormatCompact16;
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pc_bytes = 2;
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} else {
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LOG(WARNING) << "Cannot encode GC map for method with "
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<< (1 << pc_bits) << " instructions (number is rounded up to nearest power of 2): "
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<< PrettyMethod(method_verifier->GetMethodReference().dex_method_index,
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*method_verifier->GetMethodReference().dex_file);
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return false;
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}
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size_t table_size = ((pc_bytes + ref_bitmap_bytes) * num_entries) + 4;
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dex_gc_map_.reserve(table_size);
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// Write table header.
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dex_gc_map_.push_back(format | ((ref_bitmap_bytes & ~0xFF) >> 5));
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dex_gc_map_.push_back(ref_bitmap_bytes & 0xFF);
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dex_gc_map_.push_back(num_entries & 0xFF);
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dex_gc_map_.push_back((num_entries >> 8) & 0xFF);
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// Write table data.
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const DexFile::CodeItem* code_item = method_verifier->CodeItem();
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for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
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if (method_verifier->GetInstructionFlags(i).IsCompileTimeInfoPoint()) {
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dex_gc_map_.push_back(i & 0xFF);
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if (pc_bytes == 2) {
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dex_gc_map_.push_back((i >> 8) & 0xFF);
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}
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verifier::RegisterLine* line = method_verifier->GetRegLine(i);
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line->WriteReferenceBitMap(dex_gc_map_, ref_bitmap_bytes);
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}
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}
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DCHECK_EQ(dex_gc_map_.size(), table_size);
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return true;
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}
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void VerifiedMethod::VerifyGcMap(verifier::MethodVerifier* method_verifier,
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const std::vector<uint8_t>& data) {
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// Check that for every GC point there is a map entry, there aren't entries for non-GC points,
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// that the table data is well formed and all references are marked (or not) in the bitmap.
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verifier::DexPcToReferenceMap map(&data[0]);
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DCHECK_EQ(data.size(), map.RawSize());
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size_t map_index = 0;
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const DexFile::CodeItem* code_item = method_verifier->CodeItem();
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for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
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const uint8_t* reg_bitmap = map.FindBitMap(i, false);
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if (method_verifier->GetInstructionFlags(i).IsCompileTimeInfoPoint()) {
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DCHECK_LT(map_index, map.NumEntries());
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DCHECK_EQ(map.GetDexPc(map_index), i);
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DCHECK_EQ(map.GetBitMap(map_index), reg_bitmap);
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map_index++;
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verifier::RegisterLine* line = method_verifier->GetRegLine(i);
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for (size_t j = 0; j < code_item->registers_size_; j++) {
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if (line->GetRegisterType(j).IsNonZeroReferenceTypes()) {
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DCHECK_LT(j / 8, map.RegWidth());
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DCHECK_EQ((reg_bitmap[j / 8] >> (j % 8)) & 1, 1);
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} else if ((j / 8) < map.RegWidth()) {
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DCHECK_EQ((reg_bitmap[j / 8] >> (j % 8)) & 1, 0);
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} else {
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// If a register doesn't contain a reference then the bitmap may be shorter than the line.
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}
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}
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} else {
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DCHECK(i >= 65536 || reg_bitmap == NULL);
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}
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}
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}
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void VerifiedMethod::ComputeGcMapSizes(verifier::MethodVerifier* method_verifier,
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size_t* gc_points, size_t* ref_bitmap_bits,
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size_t* log2_max_gc_pc) {
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size_t local_gc_points = 0;
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size_t max_insn = 0;
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size_t max_ref_reg = -1;
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const DexFile::CodeItem* code_item = method_verifier->CodeItem();
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for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
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if (method_verifier->GetInstructionFlags(i).IsCompileTimeInfoPoint()) {
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local_gc_points++;
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max_insn = i;
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verifier::RegisterLine* line = method_verifier->GetRegLine(i);
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max_ref_reg = line->GetMaxNonZeroReferenceReg(max_ref_reg);
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}
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}
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*gc_points = local_gc_points;
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*ref_bitmap_bits = max_ref_reg + 1; // If max register is 0 we need 1 bit to encode (ie +1).
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size_t i = 0;
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while ((1U << i) <= max_insn) {
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i++;
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}
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*log2_max_gc_pc = i;
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}
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void VerifiedMethod::GenerateDevirtMap(verifier::MethodVerifier* method_verifier) {
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// It is risky to rely on reg_types for sharpening in cases of soft
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// verification, we might end up sharpening to a wrong implementation. Just abort.
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if (method_verifier->HasFailures()) {
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return;
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}
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const DexFile::CodeItem* code_item = method_verifier->CodeItem();
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const uint16_t* insns = code_item->insns_;
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const Instruction* inst = Instruction::At(insns);
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const Instruction* end = Instruction::At(insns + code_item->insns_size_in_code_units_);
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for (; inst < end; inst = inst->Next()) {
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bool is_virtual = (inst->Opcode() == Instruction::INVOKE_VIRTUAL) ||
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(inst->Opcode() == Instruction::INVOKE_VIRTUAL_RANGE);
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bool is_interface = (inst->Opcode() == Instruction::INVOKE_INTERFACE) ||
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(inst->Opcode() == Instruction::INVOKE_INTERFACE_RANGE);
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if (!is_interface && !is_virtual) {
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continue;
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}
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// Get reg type for register holding the reference to the object that will be dispatched upon.
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uint32_t dex_pc = inst->GetDexPc(insns);
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verifier::RegisterLine* line = method_verifier->GetRegLine(dex_pc);
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bool is_range = (inst->Opcode() == Instruction::INVOKE_VIRTUAL_RANGE) ||
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(inst->Opcode() == Instruction::INVOKE_INTERFACE_RANGE);
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verifier::RegType&
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reg_type(line->GetRegisterType(is_range ? inst->VRegC_3rc() : inst->VRegC_35c()));
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if (!reg_type.HasClass()) {
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// We will compute devirtualization information only when we know the Class of the reg type.
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continue;
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}
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mirror::Class* reg_class = reg_type.GetClass();
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if (reg_class->IsInterface()) {
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// We can't devirtualize when the known type of the register is an interface.
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continue;
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}
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if (reg_class->IsAbstract() && !reg_class->IsArrayClass()) {
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// We can't devirtualize abstract classes except on arrays of abstract classes.
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continue;
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}
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mirror::ArtMethod* abstract_method = method_verifier->GetDexCache()->GetResolvedMethod(
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is_range ? inst->VRegB_3rc() : inst->VRegB_35c());
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if (abstract_method == NULL) {
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// If the method is not found in the cache this means that it was never found
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// by ResolveMethodAndCheckAccess() called when verifying invoke_*.
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continue;
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}
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// Find the concrete method.
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mirror::ArtMethod* concrete_method = NULL;
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if (is_interface) {
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concrete_method = reg_type.GetClass()->FindVirtualMethodForInterface(abstract_method);
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}
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if (is_virtual) {
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concrete_method = reg_type.GetClass()->FindVirtualMethodForVirtual(abstract_method);
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}
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if (concrete_method == NULL || concrete_method->IsAbstract()) {
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// In cases where concrete_method is not found, or is abstract, continue to the next invoke.
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continue;
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}
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if (reg_type.IsPreciseReference() || concrete_method->IsFinal() ||
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concrete_method->GetDeclaringClass()->IsFinal()) {
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// If we knew exactly the class being dispatched upon, or if the target method cannot be
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// overridden record the target to be used in the compiler driver.
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MethodReference concrete_ref(
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concrete_method->GetDeclaringClass()->GetDexCache()->GetDexFile(),
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concrete_method->GetDexMethodIndex());
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devirt_map_.Put(dex_pc, concrete_ref);
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}
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}
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}
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void VerifiedMethod::GenerateSafeCastSet(verifier::MethodVerifier* method_verifier) {
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/*
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* Walks over the method code and adds any cast instructions in which
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* the type cast is implicit to a set, which is used in the code generation
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* to elide these casts.
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*/
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if (method_verifier->HasFailures()) {
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return;
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}
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const DexFile::CodeItem* code_item = method_verifier->CodeItem();
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const Instruction* inst = Instruction::At(code_item->insns_);
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const Instruction* end = Instruction::At(code_item->insns_ +
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code_item->insns_size_in_code_units_);
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for (; inst < end; inst = inst->Next()) {
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Instruction::Code code = inst->Opcode();
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if ((code == Instruction::CHECK_CAST) || (code == Instruction::APUT_OBJECT)) {
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uint32_t dex_pc = inst->GetDexPc(code_item->insns_);
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const verifier::RegisterLine* line = method_verifier->GetRegLine(dex_pc);
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bool is_safe_cast = false;
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if (code == Instruction::CHECK_CAST) {
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verifier::RegType& reg_type(line->GetRegisterType(inst->VRegA_21c()));
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verifier::RegType& cast_type =
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method_verifier->ResolveCheckedClass(inst->VRegB_21c());
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is_safe_cast = cast_type.IsStrictlyAssignableFrom(reg_type);
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} else {
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verifier::RegType& array_type(line->GetRegisterType(inst->VRegB_23x()));
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// We only know its safe to assign to an array if the array type is precise. For example,
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// an Object[] can have any type of object stored in it, but it may also be assigned a
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// String[] in which case the stores need to be of Strings.
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if (array_type.IsPreciseReference()) {
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verifier::RegType& value_type(line->GetRegisterType(inst->VRegA_23x()));
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verifier::RegType& component_type = method_verifier->GetRegTypeCache()
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->GetComponentType(array_type, method_verifier->GetClassLoader());
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is_safe_cast = component_type.IsStrictlyAssignableFrom(value_type);
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}
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}
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if (is_safe_cast) {
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// Verify ordering for push_back() to the sorted vector.
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DCHECK(safe_cast_set_.empty() || safe_cast_set_.back() < dex_pc);
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safe_cast_set_.push_back(dex_pc);
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}
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}
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}
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}
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} // namespace art
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