runtime/globals.h

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef ART_RUNTIME_GLOBALS_H_
#define ART_RUNTIME_GLOBALS_H_

#include <stddef.h>
#include <stdint.h>
#include "read_barrier_c.h"

namespace art {

typedef uint8_t byte;
typedef intptr_t word;
typedef uintptr_t uword;

static constexpr size_t KB = 1024;
static constexpr size_t MB = KB * KB;
static constexpr size_t GB = KB * KB * KB;

// Runtime sizes.
static constexpr size_t kWordSize = sizeof(word);
static constexpr size_t kPointerSize = sizeof(void*);

// Architecture-specific pointer sizes
static constexpr size_t kArmPointerSize = 4;
static constexpr size_t kArm64PointerSize = 8;
static constexpr size_t kMipsPointerSize = 4;
static constexpr size_t kX86PointerSize = 4;
static constexpr size_t kX86_64PointerSize = 8;

static constexpr size_t kBitsPerByte = 8;
static constexpr size_t kBitsPerByteLog2 = 3;
static constexpr int kBitsPerWord = kWordSize * kBitsPerByte;
static constexpr size_t kWordHighBitMask = static_cast<size_t>(1) << (kBitsPerWord - 1);

// Required stack alignment
static constexpr size_t kStackAlignment = 16;

// Required object alignment
static constexpr size_t kObjectAlignment = 8;

// ARM instruction alignment. ARM processors require code to be 4-byte aligned,
// but ARM ELF requires 8..
static constexpr size_t kArmAlignment = 8;

// ARM64 instruction alignment. AArch64 require code to be 4-byte aligned.
// AArch64 ELF requires at least 4.
static constexpr size_t kArm64Alignment = 4;

// MIPS instruction alignment.  MIPS processors require code to be 4-byte aligned.
// TODO: Can this be 4?
static constexpr size_t kMipsAlignment = 8;

// X86 instruction alignment. This is the recommended alignment for maximum performance.
static constexpr size_t kX86Alignment = 16;

// System page size. We check this against sysconf(_SC_PAGE_SIZE) at runtime, but use a simple
// compile-time constant so the compiler can generate better code.
static constexpr int kPageSize = 4096;

// Whether or not this is a debug build. Useful in conditionals where NDEBUG isn't.
#if defined(NDEBUG)
static constexpr bool kIsDebugBuild = false;
#else
static constexpr bool kIsDebugBuild = true;
#endif

// Whether or not this is a target (vs host) build. Useful in conditionals where ART_TARGET isn't.
#if defined(ART_TARGET)
static constexpr bool kIsTargetBuild = true;
#else
static constexpr bool kIsTargetBuild = false;
#endif

#if defined(ART_USE_PORTABLE_COMPILER)
static constexpr bool kUsePortableCompiler = true;
#else
static constexpr bool kUsePortableCompiler = false;
#endif

// Garbage collector constants.
static constexpr bool kMovingCollector = true && !kUsePortableCompiler;
// True if we allow moving classes.
static constexpr bool kMovingClasses = true;
// True if we allow moving fields.
static constexpr bool kMovingFields = false;
// True if we allow moving methods.
static constexpr bool kMovingMethods = false;

// If true, the quick compiler embeds class pointers in the compiled
// code, if possible.
static constexpr bool kEmbedClassInCode = true;

#ifdef USE_BAKER_READ_BARRIER
static constexpr bool kUseBakerReadBarrier = true;
#else
static constexpr bool kUseBakerReadBarrier = false;
#endif

#ifdef USE_BROOKS_READ_BARRIER
static constexpr bool kUseBrooksReadBarrier = true;
#else
static constexpr bool kUseBrooksReadBarrier = false;
#endif

static constexpr bool kUseBakerOrBrooksReadBarrier = kUseBakerReadBarrier || kUseBrooksReadBarrier;

// If true, references within the heap are poisoned (negated).
static constexpr bool kPoisonHeapReferences = false;

}  // namespace art

#endif  // ART_RUNTIME_GLOBALS_H_