1495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin/* 2495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * Copyright (C) 2017 The Android Open Source Project 3495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * 4495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * Licensed under the Apache License, Version 2.0 (the "License"); 5495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * you may not use this file except in compliance with the License. 6495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * You may obtain a copy of the License at 7495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * 8495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * http://www.apache.org/licenses/LICENSE-2.0 9495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * 10495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * Unless required by applicable law or agreed to in writing, software 11495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * distributed under the License is distributed on an "AS IS" BASIS, 12495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * See the License for the specific language governing permissions and 14495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * limitations under the License. 15495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin */ 16495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin 17495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin#ifndef ART_RUNTIME_SUBTYPE_CHECK_BITS_AND_STATUS_H_ 18495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin#define ART_RUNTIME_SUBTYPE_CHECK_BITS_AND_STATUS_H_ 19495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin 20495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin#include "base/bit_struct.h" 21495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin#include "base/bit_utils.h" 22dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko#include "base/casts.h" 23495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin#include "class_status.h" 24495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin#include "subtype_check_bits.h" 25495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin 26495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkinnamespace art { 27495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin 28495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin/* 29495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * Enables a highly efficient O(1) subtype comparison by storing extra data 30495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * in the unused padding bytes of ClassStatus. 31495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin */ 32495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin 33495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin// TODO: Update BitSizeOf with this version. 34495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkintemplate <typename T> 35495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkinstatic constexpr size_t NonNumericBitSizeOf() { 36495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin return kBitsPerByte * sizeof(T); 37495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin} 38495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin 39495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin/** 40dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * MSB (most significant bit) LSB 41dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * +---------------+---------------------------------------------------+ 42dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * | | | 43dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * | ClassStatus | SubtypeCheckBits | 44dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * | | | 45dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * +---------------+---------------------------------------------------+ 46dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * <-- 4 bits --> <----- 28 bits -----> 47495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * 48495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * Invariants: 49495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * 50495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * AddressOf(ClassStatus) == AddressOf(SubtypeCheckBitsAndStatus) 51495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * BitSizeOf(SubtypeCheckBitsAndStatus) == 32 52495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * 53495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * Note that with this representation the "Path To Root" in the MSB of this 32-bit word: 54495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * This enables a highly efficient path comparison between any two labels: 55495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * 56495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * src <: target := 57dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * (src & mask) == (target & mask) where mask := (1u << len(path-to-root(target)) - 1u 58495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * 59dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * In the above example, the `len()` (and thus `mask`) is a function of the depth. 60dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * Since the target is known at compile time, it becomes 61dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * (src & #imm_mask) == #imm 62dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * or 63dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * ((src - #imm) << #imm_shift_to_remove_high_bits) == 0 64dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko * or a similar expression chosen for the best performance or code size. 65495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * 66495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin * (This requires that path-to-root in `target` is not truncated, i.e. it is in the Assigned state). 67495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin */ 68dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Markostatic constexpr size_t kClassStatusBitSize = MinimumBitsToStore(enum_cast<>(ClassStatus::kLast)); 69dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Markostatic_assert(kClassStatusBitSize == 4u, "ClassStatus should need 4 bits."); 70495e783c9180c3fc033ce459ee0a783e633f7754Igor MurashkinBITSTRUCT_DEFINE_START(SubtypeCheckBitsAndStatus, BitSizeOf<BitString::StorageType>()) 71dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko BitStructField<SubtypeCheckBits, /*lsb*/ 0> subtype_check_info_; 72dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko BitStructField<ClassStatus, 73dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko /*lsb*/ SubtypeCheckBits::BitStructSizeOf(), 74dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko /*width*/ kClassStatusBitSize> status_; 75dc682aa9d0eae1a851af059434adb6f6cf8f06f8Vladimir Marko BitStructInt</*lsb*/ 0, /*width*/ BitSizeOf<BitString::StorageType>()> int32_alias_; 76495e783c9180c3fc033ce459ee0a783e633f7754Igor MurashkinBITSTRUCT_DEFINE_END(SubtypeCheckBitsAndStatus); 77495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin 78495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin// Use the spare alignment from "ClassStatus" to store all the new SubtypeCheckInfo data. 79495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkinstatic_assert(sizeof(SubtypeCheckBitsAndStatus) == sizeof(uint32_t), 80495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin "All of SubtypeCheckInfo+ClassStatus should fit into 4 bytes"); 81495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin} // namespace art 82495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin 83495e783c9180c3fc033ce459ee0a783e633f7754Igor Murashkin#endif // ART_RUNTIME_SUBTYPE_CHECK_BITS_AND_STATUS_H_ 84