From cf168ae0b7bceab8432d096719b331f18428fe39 Mon Sep 17 00:00:00 2001
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From: Khem Raj <raj.khem@gmail.com>
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Date: Wed, 18 Mar 2020 15:10:37 -0700
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Subject: [PATCH] cmake: Add check for atomic support
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Detect if libatomic should be linked in or compiler and platform can
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provide the needed atomic instrinsics, this helps build on certain
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platforms like mips or clang/i386
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Fixes
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| /mnt/b/yoe/build/tmp/work/mips32r2-yoe-linux/rocksdb/6.6.4-r0/recipe-sysroot-native/usr/bin/mips-yoe-linux/mips-yoe-linux-ld: librocksdb.so.6.6.4: undefined reference to `__atomic_exchange_8'
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| /mnt/b/yoe/build/tmp/work/mips32r2-yoe-linux/rocksdb/6.6.4-r0/recipe-sysroot-native/usr/bin/mips-yoe-linux/mips-yoe-linux-ld: librocksdb.so.6.6.4: undefined reference to `__atomic_fetch_or_8'
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| /mnt/b/yoe/build/tmp/work/mips32r2-yoe-linux/rocksdb/6.6.4-r0/recipe-sysroot-native/usr/bin/mips-yoe-linux/mips-yoe-linux-ld: librocksdb.so.6.6.4: undefined reference to `__atomic_compare_exchange_8'
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| /mnt/b/yoe/build/tmp/work/mips32r2-yoe-linux/rocksdb/6.6.4-r0/recipe-sysroot-native/usr/bin/mips-yoe-linux/mips-yoe-linux-ld: librocksdb.so.6.6.4: undefined reference to `__atomic_fetch_sub_8'
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| /mnt/b/yoe/build/tmp/work/mips32r2-yoe-linux/rocksdb/6.6.4-r0/recipe-sysroot-native/usr/bin/mips-yoe-linux/mips-yoe-linux-ld: librocksdb.so.6.6.4: undefined reference to `__atomic_load_8'
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| /mnt/b/yoe/build/tmp/work/mips32r2-yoe-linux/rocksdb/6.6.4-r0/recipe-sysroot-native/usr/bin/mips-yoe-linux/mips-yoe-linux-ld: librocksdb.so.6.6.4: undefined reference to `__atomic_store_8'
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| /mnt/b/yoe/build/tmp/work/mips32r2-yoe-linux/rocksdb/6.6.4-r0/recipe-sysroot-native/usr/bin/mips-yoe-linux/mips-yoe-linux-ld: librocksdb.so.6.6.4: undefined reference to `__atomic_fetch_add_8'
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Upstream-Status: Submitted [https://github.com/facebook/rocksdb/pull/6555]
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Signed-off-by: Khem Raj <raj.khem@gmail.com>
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---
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CMakeLists.txt | 5 +++
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cmake/modules/CheckAtomic.cmake | 69 +++++++++++++++++++++++++++++++++
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2 files changed, 74 insertions(+)
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create mode 100644 cmake/modules/CheckAtomic.cmake
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--- a/CMakeLists.txt
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+++ b/CMakeLists.txt
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@@ -935,7 +935,12 @@ endif()
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if(WIN32)
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set(SYSTEM_LIBS ${SYSTEM_LIBS} shlwapi.lib rpcrt4.lib)
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else()
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+ # check if linking against libatomic is necessary
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+ include(CheckAtomic)
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set(SYSTEM_LIBS ${CMAKE_THREAD_LIBS_INIT})
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+ if(HAVE_CXX_ATOMIC_WITH_LIB OR HAVE_CXX_ATOMICS64_WITH_LIB)
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+ set(SYSTEM_LIBS ${SYSTEM_LIBS} atomic)
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+ endif()
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endif()
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add_library(${ROCKSDB_STATIC_LIB} STATIC ${SOURCES} ${BUILD_VERSION_CC})
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--- /dev/null
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+++ b/cmake/modules/CheckAtomic.cmake
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@@ -0,0 +1,69 @@
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+# Checks if atomic operations are supported natively or if linking against
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+# libatomic is needed.
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+
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+# Check inspired by LLVMs cmake/modules/CheckAtomic.cmake
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+
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+INCLUDE(CheckCXXSourceCompiles)
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+INCLUDE(CheckLibraryExists)
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+
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+function(check_working_cxx_atomics varname)
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+ set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
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+ set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11")
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+ CHECK_CXX_SOURCE_COMPILES("
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+#include <atomic>
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+std::atomic<int> x;
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+int main() {
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+ return x;
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+}
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+" ${varname})
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+ set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
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+endfunction(check_working_cxx_atomics)
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+
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+function(check_working_cxx_atomics64 varname)
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+ set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
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+ set(CMAKE_REQUIRED_FLAGS "-std=c++11 ${CMAKE_REQUIRED_FLAGS}")
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+ CHECK_CXX_SOURCE_COMPILES("
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+#include <atomic>
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+#include <cstdint>
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+std::atomic<uint64_t> x (0);
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+std::atomic<double> y (0);
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+int main() {
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+ uint64_t i = x.load(std::memory_order_relaxed);
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+ return int(y);
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+}
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+" ${varname})
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+ set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
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+endfunction(check_working_cxx_atomics64)
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+
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+# Check if atomics work without libatomic
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+check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITHOUT_LIB)
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+
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+if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB)
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+ check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC)
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+ if( HAVE_LIBATOMIC )
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+ list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
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+ check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITH_LIB)
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+ if (NOT HAVE_CXX_ATOMICS_WITH_LIB)
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+ message(FATAL_ERROR "Host compiler must support std::atomic!")
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+ endif()
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+ else()
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+ message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
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+ endif()
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+endif()
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+
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+# Check if 64bit atomics work without libatomic
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+check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITHOUT_LIB)
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+
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+if(NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB)
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+ check_library_exists(atomic __atomic_load_8 "" HAVE_CXX_LIBATOMICS64)
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+ if(HAVE_CXX_LIBATOMICS64)
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+ list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
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+ check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITH_LIB)
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+ if (NOT HAVE_CXX_ATOMICS64_WITH_LIB)
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+ message(FATAL_ERROR "Host compiler must support std::atomic!")
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+ endif()
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+ else()
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+ message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
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+ endif()
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+endif()
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+
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