portability_macros.h

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 * All rights reserved.
 *
 * This source code is licensed under both the BSD-style license (found in the
 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
 * in the COPYING file in the root directory of this source tree).
 * You may select, at your option, one of the above-listed licenses.
 */

#ifndef ZSTD_PORTABILITY_MACROS_H
#define ZSTD_PORTABILITY_MACROS_H

/**
 * This header file contains macro definitions to support portability.
 * This header is shared between C and ASM code, so it MUST only
 * contain macro definitions. It MUST not contain any C code.
 *
 * This header ONLY defines macros to detect platforms/feature support.
 *
 */


/* compat. with non-clang compilers */
#ifndef __has_attribute
  #define __has_attribute(x) 0
#endif

/* compat. with non-clang compilers */
#ifndef __has_builtin
#  define __has_builtin(x) 0
#endif

/* compat. with non-clang compilers */
#ifndef __has_feature
#  define __has_feature(x) 0
#endif

/* detects whether we are being compiled under msan */
#ifndef ZSTD_MEMORY_SANITIZER
#  if __has_feature(memory_sanitizer)
#    define ZSTD_MEMORY_SANITIZER 1
#  else
#    define ZSTD_MEMORY_SANITIZER 0
#  endif
#endif

/* detects whether we are being compiled under asan */
#ifndef ZSTD_ADDRESS_SANITIZER
#  if __has_feature(address_sanitizer)
#    define ZSTD_ADDRESS_SANITIZER 1
#  elif defined(__SANITIZE_ADDRESS__)
#    define ZSTD_ADDRESS_SANITIZER 1
#  else
#    define ZSTD_ADDRESS_SANITIZER 0
#  endif
#endif

/* detects whether we are being compiled under dfsan */
#ifndef ZSTD_DATAFLOW_SANITIZER
# if __has_feature(dataflow_sanitizer)
#  define ZSTD_DATAFLOW_SANITIZER 1
# else
#  define ZSTD_DATAFLOW_SANITIZER 0
# endif
#endif

/* Mark the internal assembly functions as hidden  */
#ifdef __ELF__
# define ZSTD_HIDE_ASM_FUNCTION(func) .hidden func
#else
# define ZSTD_HIDE_ASM_FUNCTION(func)
#endif

/* Enable runtime BMI2 dispatch based on the CPU.
 * Enabled for clang & gcc >=4.8 on x86 when BMI2 isn't enabled by default.
 */
#ifndef DYNAMIC_BMI2
  #if ((defined(__clang__) && __has_attribute(__target__)) \
      || (defined(__GNUC__) \
          && (__GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)))) \
      && (defined(__x86_64__) || defined(_M_X64)) \
      && !defined(__BMI2__)
  #  define DYNAMIC_BMI2 1
  #else
  #  define DYNAMIC_BMI2 0
  #endif
#endif

/**
 * Only enable assembly for GNUC compatible compilers,
 * because other platforms may not support GAS assembly syntax.
 *
 * Only enable assembly for Linux / MacOS, other platforms may
 * work, but they haven't been tested. This could likely be
 * extended to BSD systems.
 *
 * Disable assembly when MSAN is enabled, because MSAN requires
 * 100% of code to be instrumented to work.
 */
#if defined(__GNUC__)
#  if defined(__linux__) || defined(__linux) || defined(__APPLE__)
#    if ZSTD_MEMORY_SANITIZER
#      define ZSTD_ASM_SUPPORTED 0
#    elif ZSTD_DATAFLOW_SANITIZER
#      define ZSTD_ASM_SUPPORTED 0
#    else
#      define ZSTD_ASM_SUPPORTED 1
#    endif
#  else
#    define ZSTD_ASM_SUPPORTED 0
#  endif
#else
#  define ZSTD_ASM_SUPPORTED 0
#endif

/**
 * Determines whether we should enable assembly for x86-64
 * with BMI2.
 *
 * Enable if all of the following conditions hold:
 * - ASM hasn't been explicitly disabled by defining ZSTD_DISABLE_ASM
 * - Assembly is supported
 * - We are compiling for x86-64 and either:
 *   - DYNAMIC_BMI2 is enabled
 *   - BMI2 is supported at compile time
 */
#if !defined(ZSTD_DISABLE_ASM) &&                                 \
    ZSTD_ASM_SUPPORTED &&                                         \
    defined(__x86_64__) &&                                        \
    (DYNAMIC_BMI2 || defined(__BMI2__))
# define ZSTD_ENABLE_ASM_X86_64_BMI2 1
#else
# define ZSTD_ENABLE_ASM_X86_64_BMI2 0
#endif

/*
 * For x86 ELF targets, add .note.gnu.property section for Intel CET in
 * assembly sources when CET is enabled.
 *
 * Additionally, any function that may be called indirectly must begin
 * with ZSTD_CET_ENDBRANCH.
 */
#if defined(__ELF__) && (defined(__x86_64__) || defined(__i386__)) \
    && defined(__has_include)
# if __has_include(<cet.h>)
#  include <cet.h>
#  define ZSTD_CET_ENDBRANCH _CET_ENDBR
# endif
#endif

#ifndef ZSTD_CET_ENDBRANCH
# define ZSTD_CET_ENDBRANCH
#endif

#endif /* ZSTD_PORTABILITY_MACROS_H */