1From cf168ae0b7bceab8432d096719b331f18428fe39 Mon Sep 17 00:00:00 2001
2From: Khem Raj <raj.khem@gmail.com>
3Date: Wed, 18 Mar 2020 15:10:37 -0700
4Subject: [PATCH] cmake: Add check for atomic support
5
6Detect if libatomic should be linked in or compiler and platform can
7provide the needed atomic instrinsics, this helps build on certain
8platforms like mips or clang/i386
9
10Fixes
11
12| /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'
13| /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'
14| /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'
15| /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'
16| /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'
17| /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'
18| /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'
19
20Upstream-Status: Submitted [https://github.com/facebook/rocksdb/pull/6555]
21Signed-off-by: Khem Raj <raj.khem@gmail.com>
22---
23 CMakeLists.txt                  |  5 +++
24 cmake/modules/CheckAtomic.cmake | 69 +++++++++++++++++++++++++++++++++
25 2 files changed, 74 insertions(+)
26 create mode 100644 cmake/modules/CheckAtomic.cmake
27
28diff --git a/CMakeLists.txt b/CMakeLists.txt
29index f9c8f3346..4d604004b 100644
30--- a/CMakeLists.txt
31+++ b/CMakeLists.txt
32@@ -852,7 +852,12 @@ endif()
33 if(WIN32)
34   set(SYSTEM_LIBS ${SYSTEM_LIBS} shlwapi.lib rpcrt4.lib)
35 else()
36+  # check if linking against libatomic is necessary
37+  include(CheckAtomic)
38   set(SYSTEM_LIBS ${CMAKE_THREAD_LIBS_INIT})
39+  if(HAVE_CXX_ATOMIC_WITH_LIB OR HAVE_CXX_ATOMICS64_WITH_LIB)
40+    set(SYSTEM_LIBS ${SYSTEM_LIBS} atomic)
41+  endif()
42 endif()
43
44 add_library(${ROCKSDB_STATIC_LIB} STATIC ${SOURCES})
45diff --git a/cmake/modules/CheckAtomic.cmake b/cmake/modules/CheckAtomic.cmake
46new file mode 100644
47index 000000000..8b7dc8a37
48--- /dev/null
49+++ b/cmake/modules/CheckAtomic.cmake
50@@ -0,0 +1,69 @@
51+# Checks if atomic operations are supported natively or if linking against
52+# libatomic is needed.
53+
54+# Check inspired by LLVMs cmake/modules/CheckAtomic.cmake
55+
56+INCLUDE(CheckCXXSourceCompiles)
57+INCLUDE(CheckLibraryExists)
58+
59+function(check_working_cxx_atomics varname)
60+  set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
61+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11")
62+  CHECK_CXX_SOURCE_COMPILES("
63+#include <atomic>
64+std::atomic<int> x;
65+int main() {
66+  return x;
67+}
68+" ${varname})
69+  set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
70+endfunction(check_working_cxx_atomics)
71+
72+function(check_working_cxx_atomics64 varname)
73+  set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
74+  set(CMAKE_REQUIRED_FLAGS "-std=c++11 ${CMAKE_REQUIRED_FLAGS}")
75+  CHECK_CXX_SOURCE_COMPILES("
76+#include <atomic>
77+#include <cstdint>
78+std::atomic<uint64_t> x (0);
79+std::atomic<double> y (0);
80+int main() {
81+  uint64_t i = x.load(std::memory_order_relaxed);
82+  return int(y);
83+}
84+" ${varname})
85+  set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
86+endfunction(check_working_cxx_atomics64)
87+
88+# Check if atomics work without libatomic
89+check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITHOUT_LIB)
90+
91+if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB)
92+  check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC)
93+  if( HAVE_LIBATOMIC )
94+    list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
95+    check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITH_LIB)
96+    if (NOT HAVE_CXX_ATOMICS_WITH_LIB)
97+      message(FATAL_ERROR "Host compiler must support std::atomic!")
98+    endif()
99+  else()
100+    message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
101+  endif()
102+endif()
103+
104+# Check if 64bit atomics work without libatomic
105+check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITHOUT_LIB)
106+
107+if(NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB)
108+  check_library_exists(atomic __atomic_load_8 "" HAVE_CXX_LIBATOMICS64)
109+  if(HAVE_CXX_LIBATOMICS64)
110+    list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
111+    check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITH_LIB)
112+    if (NOT HAVE_CXX_ATOMICS64_WITH_LIB)
113+      message(FATAL_ERROR "Host compiler must support std::atomic!")
114+    endif()
115+  else()
116+    message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
117+  endif()
118+endif()
119+
120--
1212.28.0
122
123