external: import cpu_features library

Taken from https://github.com/google/cpu_features at revision
26133d3b620c2c27f31d571efd27371100f891e9

external/cpu_features/cmake/CpuFeaturesConfig.cmake.in

@@ -0,0 +1,3 @@
+# CpuFeatures CMake configuration file
+
+include("${CMAKE_CURRENT_LIST_DIR}/CpuFeaturesTargets.cmake")

external/cpu_features/cmake/README.md

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+# CMake build instructions
+
+## Recommended usage : Incorporating cpu_features into a CMake project
+
+  For API / ABI compatibility reasons, it is recommended to build and use
+  cpu_features in a subdirectory of your project or as an embedded dependency.
+
+  This is similar to the recommended usage of the googletest framework
+  ( https://github.com/google/googletest/blob/master/googletest/README.md )
+
+  Build and use step-by-step
+
+
+  1- Download cpu_features and copy it in a sub-directory in your project.
+      or add cpu_features as a git-submodule in your project
+
+  2- You can then use the cmake command `add_subdirectory()` to include
+     cpu_features directly and use the `cpu_features` target in your project.
+
+  3- Add the `cpu_features` target to the `target_link_libraries()` section of
+     your executable or of your library.
+
+## Enabling tests
+
+  CMake default options for cpu_features is Release built type with tests
+  disabled. To enable testing set cmake `BUILD_TESTING` variable to `ON`,
+  [.travis.yml](../.travis.yml) and [appveyor.yml](../appveyor.yml) have up to
+  date examples.

external/cpu_features/cmake/googletest.CMakeLists.txt.in

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+cmake_minimum_required(VERSION 2.8.2)
+
+project(googletest-download NONE)
+
+include(ExternalProject)
+ExternalProject_Add(googletest
+  GIT_REPOSITORY    https://github.com/google/googletest.git
+  GIT_TAG           master
+  SOURCE_DIR        "${CMAKE_BINARY_DIR}/googletest-src"
+  BINARY_DIR        "${CMAKE_BINARY_DIR}/googletest-build"
+  CONFIGURE_COMMAND ""
+  BUILD_COMMAND     ""
+  INSTALL_COMMAND   ""
+  TEST_COMMAND      ""
+)

external/cpu_features/cmake/mips32-linux-gcc.cmake

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+set(CMAKE_SYSTEM_NAME "Linux")
+set(CMAKE_SYSTEM_PROCESSOR "mips32")
+
+if (ENABLE_DSPR2 AND ENABLE_MSA)
+  message(FATAL_ERROR "ENABLE_DSPR2 and ENABLE_MSA cannot be combined.")
+endif ()
+
+if (ENABLE_DSPR2)
+  set(HAVE_DSPR2            1 CACHE BOOL "" FORCE)
+  set(MIPS_CFLAGS           "-mdspr2")
+  set(MIPS_CXXFLAGS         "-mdspr2")
+elseif (ENABLE_MSA)
+  set(HAVE_MSA 1 CACHE BOOL "" FORCE)
+  set(MIPS_CFLAGS           "-mmsa")
+  set(MIPS_CXXFLAGS         "-mmsa")
+endif ()
+
+if ("${MIPS_CPU}" STREQUAL "")
+  set(MIPS_CFLAGS           "${MIPS_CFLAGS} -mips32r2")
+  set(MIPS_CXXFLAGS         "${MIPS_CXXFLAGS} -mips32r2")
+elseif ("${MIPS_CPU}" STREQUAL "p5600")
+  set(P56_FLAGS             "-mips32r5 -mload-store-pairs -msched-weight -mhard-float -mfp64")
+  set(MIPS_CFLAGS           "${MIPS_CFLAGS} ${P56_FLAGS}")
+  set(MIPS_CXXFLAGS         "${MIPS_CXXFLAGS} ${P56_FLAGS}")
+  set(CMAKE_EXE_LINKER_FLAGS  "-mfp64 ${CMAKE_EXE_LINKER_FLAGS}")
+endif ()
+
+set(CMAKE_C_COMPILER        ${CROSS}gcc)
+set(CMAKE_CXX_COMPILER      ${CROSS}g++)
+set(AS_EXECUTABLE           ${CROSS}as)
+set(CMAKE_C_COMPILER_ARG1   "-EL ${MIPS_CFLAGS}")
+set(CMAKE_CXX_COMPILER_ARG1 "-EL ${MIPS_CXXFLAGS}")
+
+set(THREADS_PTHREAD_ARG "2" CACHE STRING "Forcibly set by CMakeLists.txt." FORCE)