text: // Copyright 2017 The Abseil Authors.
  //
  // 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
  //
  //      https://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 ABSL_RANDOM_INTERNAL_PLATFORM_H_
  #define ABSL_RANDOM_INTERNAL_PLATFORM_H_
  
  // HERMETIC NOTE: The randen_hwaes target must not introduce duplicate
  // symbols from arbitrary system and other headers, since it may be built
  // with different flags from other targets, using different levels of
  // optimization, potentially introducing ODR violations.
  
  // -----------------------------------------------------------------------------
  // Platform Feature Checks
  // -----------------------------------------------------------------------------
  
  // Currently supported operating systems and associated preprocessor
  // symbols:
  //
  //   Linux and Linux-derived           __linux__
  //   Android                           __ANDROID__ (implies __linux__)
  //   Linux (non-Android)               __linux__ && !__ANDROID__
  //   Darwin (Mac OS X and iOS)         __APPLE__
  //   Akaros (http://akaros.org)        __ros__
  //   Windows                           _WIN32
  //   NaCL                              __native_client__
  //   AsmJS                             __asmjs__
  //   WebAssembly                       __wasm__
  //   Fuchsia                           __Fuchsia__
  //
  // Note that since Android defines both __ANDROID__ and __linux__, one
  // may probe for either Linux or Android by simply testing for __linux__.
  //
  // NOTE: For __APPLE__ platforms, we use #include <TargetConditionals.h>
  // to distinguish os variants.
  //
  // http://nadeausoftware.com/articles/2012/01/c_c_tip_how_use_compiler_predefined_macros_detect_operating_system
  
  #if defined(__APPLE__)
  #include <TargetConditionals.h>
  #endif
  
  // -----------------------------------------------------------------------------
  // Architecture Checks
  // -----------------------------------------------------------------------------
  
  // These preprocessor directives are trying to determine CPU architecture,
  // including necessary headers to support hardware AES.
  //
  // ABSL_ARCH_{X86/PPC/ARM} macros determine the platform.
  #if defined(__x86_64__) || defined(__x86_64) || defined(_M_AMD64) || \
      defined(_M_X64)
  #define ABSL_ARCH_X86_64
  #elif defined(__i386) || defined(_M_IX86)
  #define ABSL_ARCH_X86_32
  #elif defined(__aarch64__) || defined(__arm64__) || defined(_M_ARM64)
  #define ABSL_ARCH_AARCH64
  #elif defined(__arm__) || defined(__ARMEL__) || defined(_M_ARM)
  #define ABSL_ARCH_ARM
  #elif defined(__powerpc64__) || defined(__PPC64__) || defined(__powerpc__) || \
      defined(__ppc__) || defined(__PPC__)
  #define ABSL_ARCH_PPC
  #else
  // Unsupported architecture.
  //  * https://sourceforge.net/p/predef/wiki/Architectures/
  //  * https://msdn.microsoft.com/en-us/library/b0084kay.aspx
  //  * for gcc, clang: "echo | gcc -E -dM -"
  #endif
  
  // -----------------------------------------------------------------------------
  // Attribute Checks
  // -----------------------------------------------------------------------------
  
  // ABSL_RANDOM_INTERNAL_RESTRICT annotates whether pointers may be considered
  // to be unaliased.
  #if defined(__clang__) || defined(__GNUC__)
  #define ABSL_RANDOM_INTERNAL_RESTRICT __restrict__
  #elif defined(_MSC_VER)
  #define ABSL_RANDOM_INTERNAL_RESTRICT __restrict
  #else
  #define ABSL_RANDOM_INTERNAL_RESTRICT
  #endif
  
  // ABSL_HAVE_ACCELERATED_AES indicates whether the currently active compiler
  // flags (e.g. -maes) allow using hardware accelerated AES instructions, which
  // implies us assuming that the target platform supports them.
  #define ABSL_HAVE_ACCELERATED_AES 0
  
  #if defined(ABSL_ARCH_X86_64)
  
  #if defined(__AES__) || defined(__AVX__)
  #undef ABSL_HAVE_ACCELERATED_AES
  #define ABSL_HAVE_ACCELERATED_AES 1
  #endif
  
  #elif defined(ABSL_ARCH_PPC)
  
  // Rely on VSX and CRYPTO extensions for vcipher on PowerPC.
  #if (defined(__VEC__) || defined(__ALTIVEC__)) && defined(__VSX__) && \
      defined(__CRYPTO__)
  #undef ABSL_HAVE_ACCELERATED_AES
  #define ABSL_HAVE_ACCELERATED_AES 1
  #endif
  
  #elif defined(ABSL_ARCH_ARM) || defined(ABSL_ARCH_AARCH64)
  
  // http://infocenter.arm.com/help/topic/com.arm.doc.ihi0053c/IHI0053C_acle_2_0.pdf
  // Rely on NEON+CRYPTO extensions for ARM.
  #if defined(__ARM_NEON) && defined(__ARM_FEATURE_CRYPTO)
  #undef ABSL_HAVE_ACCELERATED_AES
  #define ABSL_HAVE_ACCELERATED_AES 1
  #endif
  
  #endif
  
  // NaCl does not allow AES.
  #if defined(__native_client__)
  #undef ABSL_HAVE_ACCELERATED_AES
  #define ABSL_HAVE_ACCELERATED_AES 0
  #endif
  
  // ABSL_RANDOM_INTERNAL_AES_DISPATCH indicates whether the currently active
  // platform has, or should use run-time dispatch for selecting the
  // acclerated Randen implementation.
  #define ABSL_RANDOM_INTERNAL_AES_DISPATCH 0
  
  #if defined(ABSL_ARCH_X86_64)
  // Dispatch is available on x86_64
  #undef ABSL_RANDOM_INTERNAL_AES_DISPATCH
  #define ABSL_RANDOM_INTERNAL_AES_DISPATCH 1
  #elif defined(__linux__) && defined(ABSL_ARCH_PPC)
  // Or when running linux PPC
  #undef ABSL_RANDOM_INTERNAL_AES_DISPATCH
  #define ABSL_RANDOM_INTERNAL_AES_DISPATCH 1
  #elif defined(__linux__) && defined(ABSL_ARCH_AARCH64)
  // Or when running linux AArch64
  #undef ABSL_RANDOM_INTERNAL_AES_DISPATCH
  #define ABSL_RANDOM_INTERNAL_AES_DISPATCH 1
  #elif defined(__linux__) && defined(ABSL_ARCH_ARM) && (__ARM_ARCH >= 8)
  // Or when running linux ARM v8 or higher.
  // (This captures a lot of Android configurations.)
  #undef ABSL_RANDOM_INTERNAL_AES_DISPATCH
  #define ABSL_RANDOM_INTERNAL_AES_DISPATCH 1
  #endif
  
  // NaCl does not allow dispatch.
  #if defined(__native_client__)
  #undef ABSL_RANDOM_INTERNAL_AES_DISPATCH
  #define ABSL_RANDOM_INTERNAL_AES_DISPATCH 0
  #endif
  
  // iOS does not support dispatch, even on x86, since applications
  // should be bundled as fat binaries, with a different build tailored for
  // each specific supported platform/architecture.
  #if defined(__APPLE__) && (TARGET_OS_IPHONE || TARGET_OS_IPHONE_SIMULATOR)
  #undef ABSL_RANDOM_INTERNAL_AES_DISPATCH
  #define ABSL_RANDOM_INTERNAL_AES_DISPATCH 0
  #endif
  
  #endif  // ABSL_RANDOM_INTERNAL_PLATFORM_H_
  