enable openmp for ios.zh - nihui/ncnn GitHub Wiki
目前，最新版本的 Xcode-8.2.1 携带的 clang 编译器不具有 openmp 特性，Apple 方面比较推 GCD 技术，网络上能找到的大多是教你如何把 openmp 代码改用 GCD 实现，而关于如何真正用 openmp，这是第一篇吧
这篇文章记录 up 主在 Linux 上用 clang 编译器和交叉编译方式实现 ios 的 openmp 加速
系统：fedora 25
工具链：llvm 3.8.1，clang 3.8.0，fuse 2.9.7
从 Apple 官网上下载 Xcode_7.3.1.dmg，因为 cctools-port 还没有支持最新版的 Xcode https://developer.apple.com/download/more/
安装 Xcode dmg 挂载工具 https://github.com/darlinghq/darling-dmg
$ mkdir xcode
$ ./darling-dmg/build/darling-dmg Xcode_7.3.1.dmg xcode
Skipping partition of type Primary GPT Header
Skipping partition of type Primary GPT Table
Skipping partition of type Apple_Free
Skipping partition of type C12A7328-F81F-11D2-BA4B-00A0C93EC93B
Using partition #4 of type Apple_HFS
Everything looks OK, disk mounted
提取 ios sdk，卸载 dmg
$ mkdir -p iPhoneSDK/iPhoneOS9.3.sdk
$ cp -r xcode/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/* iPhoneSDK/iPhoneOS9.3.sdk
$ cp -r xcode/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/* iPhoneSDK/iPhoneOS9.3.sdk/usr/include/c++
$ fusermount -u xcode # unmount the image
打包 ios sdk
$ cd iPhoneSDK
$ tar -cf - iPhoneOS9.3.sdk | xz -9 -c - > iPhoneOS9.3.sdk.tar.xz
安装 cctools 移植版本，感谢 cjacker 和 tpoechtrager 的辛勤付出！ https://github.com/tpoechtrager/cctools-port
$ cd cctools-port/usage_examples/ios_toolchain
$ ./build.sh iPhoneOS9.3.sdk.tar.xz armv7
交叉编译的工具链在 cctools-port/usage_examples/ios_toolchain/target/bin 目录下
下载 llvm 官网上的 openmp 运行时
svn co http://llvm.org/svn/llvm-project/openmp/trunk openmp
准备好 ios 交叉编译的 cmake toolchain，文件名 iosxc.toolchain.cmake，放在 openmp 目录中
# standard settings
set (CMAKE_SYSTEM_NAME Darwin)
set (CMAKE_SYSTEM_VERSION 1)
set (UNIX True)
set (APPLE True)
set (IOS True)
set(CMAKE_C_COMPILER arm-apple-darwin11-clang)
set(CMAKE_CXX_COMPILER arm-apple-darwin11-clang++)
set(_CMAKE_TOOLCHAIN_PREFIX arm-apple-darwin11-)
# 这里指定交叉编译工具链中的 sdk 目录
set(CMAKE_IOS_SDK_ROOT "/home/nihui/osd/cctools-port/usage_examples/ios_toolchain/target/SDK/")
# set the sysroot default to the most recent SDK
set(CMAKE_OSX_SYSROOT ${CMAKE_IOS_SDK_ROOT} CACHE PATH "Sysroot used for iOS support")
# set the architecture for iOS 双架构
set(IOS_ARCH armv7;arm64)
set(CMAKE_OSX_ARCHITECTURES ${IOS_ARCH} CACHE string "Build architecture for iOS")
# set the find root to the iOS developer roots and to user defined paths
set(CMAKE_FIND_ROOT_PATH ${CMAKE_IOS_DEVELOPER_ROOT} ${CMAKE_IOS_SDK_ROOT} ${CMAKE_PREFIX_PATH} CACHE string "iOS find search path root")
# searching for frameworks only
set(CMAKE_FIND_FRAMEWORK FIRST)
# set up the default search directories for frameworks
set(CMAKE_SYSTEM_FRAMEWORK_PATH
${CMAKE_IOS_SDK_ROOT}/System/Library/Frameworks
)
直接编译的话会失败，所以 up 主自己弄了下面三个补丁，放在附件里可以下载 编译补丁A，ios sdk 没有 crt_externs.h 头文件，改为经典声明
diff --git a/runtime/src/kmp_environment.cpp b/runtime/src/kmp_environment.cpp
index d4d95df..c8c2970 100644
--- a/runtime/src/kmp_environment.cpp
+++ b/runtime/src/kmp_environment.cpp
@@ -64,12 +64,12 @@
#if KMP_OS_UNIX
#include <stdlib.h> // getenv, setenv, unsetenv.
#include <string.h> // strlen, strcpy.
- #if KMP_OS_DARWIN
- #include <crt_externs.h>
- #define environ (*_NSGetEnviron())
- #else
+// #if KMP_OS_DARWIN
+// #include <crt_externs.h>
+// #define environ (*_NSGetEnviron())
+// #else
extern char * * environ;
- #endif
+// #endif
#elif KMP_OS_WINDOWS
#include <windows.h> // GetEnvironmentVariable, SetEnvironmentVariable, GetLastError.
#else
$ patch -p1 -i openmp-ios-classic-environ.patch
编译补丁B，clang 不支持 .size 的语法，删除，并为符号名字前补上额外下划线，不然会链接失败
diff --git a/runtime/src/z_Linux_asm.s b/runtime/src/z_Linux_asm.s
index d6e1c0b..69f94ef 100644
--- a/runtime/src/z_Linux_asm.s
+++ b/runtime/src/z_Linux_asm.s
@@ -1781,10 +1781,10 @@ __kmp_invoke_microtask:
.comm .gomp_critical_user_,32,8
.data
.align 4
- .global __kmp_unnamed_critical_addr
-__kmp_unnamed_critical_addr:
+ .global ___kmp_unnamed_critical_addr
+___kmp_unnamed_critical_addr:
.4byte .gomp_critical_user_
- .size __kmp_unnamed_critical_addr,4
+// .size __kmp_unnamed_critical_addr,4
#endif /* KMP_ARCH_ARM */
#if KMP_ARCH_PPC64 || KMP_ARCH_AARCH64 || KMP_ARCH_MIPS64
@@ -1792,10 +1792,10 @@ __kmp_unnamed_critical_addr:
.comm .gomp_critical_user_,32,8
.data
.align 8
- .global __kmp_unnamed_critical_addr
-__kmp_unnamed_critical_addr:
+ .global ___kmp_unnamed_critical_addr
+___kmp_unnamed_critical_addr:
.8byte .gomp_critical_user_
- .size __kmp_unnamed_critical_addr,8
+// .size __kmp_unnamed_critical_addr,8
#endif /* KMP_ARCH_PPC64 || KMP_ARCH_AARCH64 */
#if KMP_OS_LINUX
$ patch -p1 -i openmp-kmp_unnamed_critical_addr-clang-arm-build-fix.patch
编译补丁C，交叉编译的工具链会把 complex 类型的除法放在 compiler-rt builtin library 实现，但是 ios sdk 本身没有，为了免去麻烦就直接删掉了。这个补丁也许在正常的 macos 下不需要，不过 up 主不用 macos 也就不管了
diff --git a/runtime/src/kmp_atomic.cpp b/runtime/src/kmp_atomic.cpp
index 3831165..b969175 100644
--- a/runtime/src/kmp_atomic.cpp
+++ b/runtime/src/kmp_atomic.cpp
@@ -1139,23 +1139,23 @@ ATOMIC_CRITICAL( float16, div, QUAD_LEGACY, /, 16r, 1 ) // __km
ATOMIC_CMPXCHG_WORKAROUND( cmplx4, add, kmp_cmplx32, 64, +, 8c, 7, 1 ) // __kmpc_atomic_cmplx4_add
ATOMIC_CMPXCHG_WORKAROUND( cmplx4, sub, kmp_cmplx32, 64, -, 8c, 7, 1 ) // __kmpc_atomic_cmplx4_sub
ATOMIC_CMPXCHG_WORKAROUND( cmplx4, mul, kmp_cmplx32, 64, *, 8c, 7, 1 ) // __kmpc_atomic_cmplx4_mul
-ATOMIC_CMPXCHG_WORKAROUND( cmplx4, div, kmp_cmplx32, 64, /, 8c, 7, 1 ) // __kmpc_atomic_cmplx4_div
+// ATOMIC_CMPXCHG_WORKAROUND( cmplx4, div, kmp_cmplx32, 64, /, 8c, 7, 1 ) // __kmpc_atomic_cmplx4_div
// end of the workaround for C78287
#else
ATOMIC_CRITICAL( cmplx4, add, kmp_cmplx32, +, 8c, 1 ) // __kmpc_atomic_cmplx4_add
ATOMIC_CRITICAL( cmplx4, sub, kmp_cmplx32, -, 8c, 1 ) // __kmpc_atomic_cmplx4_sub
ATOMIC_CRITICAL( cmplx4, mul, kmp_cmplx32, *, 8c, 1 ) // __kmpc_atomic_cmplx4_mul
-ATOMIC_CRITICAL( cmplx4, div, kmp_cmplx32, /, 8c, 1 ) // __kmpc_atomic_cmplx4_div
+// ATOMIC_CRITICAL( cmplx4, div, kmp_cmplx32, /, 8c, 1 ) // __kmpc_atomic_cmplx4_div
#endif // USE_CMPXCHG_FIX
ATOMIC_CRITICAL( cmplx8, add, kmp_cmplx64, +, 16c, 1 ) // __kmpc_atomic_cmplx8_add
ATOMIC_CRITICAL( cmplx8, sub, kmp_cmplx64, -, 16c, 1 ) // __kmpc_atomic_cmplx8_sub
ATOMIC_CRITICAL( cmplx8, mul, kmp_cmplx64, *, 16c, 1 ) // __kmpc_atomic_cmplx8_mul
-ATOMIC_CRITICAL( cmplx8, div, kmp_cmplx64, /, 16c, 1 ) // __kmpc_atomic_cmplx8_div
+// ATOMIC_CRITICAL( cmplx8, div, kmp_cmplx64, /, 16c, 1 ) // __kmpc_atomic_cmplx8_div
ATOMIC_CRITICAL( cmplx10, add, kmp_cmplx80, +, 20c, 1 ) // __kmpc_atomic_cmplx10_add
ATOMIC_CRITICAL( cmplx10, sub, kmp_cmplx80, -, 20c, 1 ) // __kmpc_atomic_cmplx10_sub
ATOMIC_CRITICAL( cmplx10, mul, kmp_cmplx80, *, 20c, 1 ) // __kmpc_atomic_cmplx10_mul
-ATOMIC_CRITICAL( cmplx10, div, kmp_cmplx80, /, 20c, 1 ) // __kmpc_atomic_cmplx10_div
+// ATOMIC_CRITICAL( cmplx10, div, kmp_cmplx80, /, 20c, 1 ) // __kmpc_atomic_cmplx10_div
#if KMP_HAVE_QUAD
ATOMIC_CRITICAL( cmplx16, add, CPLX128_LEG, +, 32c, 1 ) // __kmpc_atomic_cmplx16_add
ATOMIC_CRITICAL( cmplx16, sub, CPLX128_LEG, -, 32c, 1 ) // __kmpc_atomic_cmplx16_sub
@@ -1541,7 +1541,7 @@ ATOMIC_BEGIN_MIX(TYPE_ID,TYPE,OP_ID,RTYPE_ID,RTYPE)
ATOMIC_CMPXCHG_CMPLX( cmplx4, kmp_cmplx32, add, 64, +, cmplx8, kmp_cmplx64, 8c, 7, KMP_ARCH_X86 ) // __kmpc_atomic_cmplx4_add_cmplx8
ATOMIC_CMPXCHG_CMPLX( cmplx4, kmp_cmplx32, sub, 64, -, cmplx8, kmp_cmplx64, 8c, 7, KMP_ARCH_X86 ) // __kmpc_atomic_cmplx4_sub_cmplx8
ATOMIC_CMPXCHG_CMPLX( cmplx4, kmp_cmplx32, mul, 64, *, cmplx8, kmp_cmplx64, 8c, 7, KMP_ARCH_X86 ) // __kmpc_atomic_cmplx4_mul_cmplx8
-ATOMIC_CMPXCHG_CMPLX( cmplx4, kmp_cmplx32, div, 64, /, cmplx8, kmp_cmplx64, 8c, 7, KMP_ARCH_X86 ) // __kmpc_atomic_cmplx4_div_cmplx8
+// ATOMIC_CMPXCHG_CMPLX( cmplx4, kmp_cmplx32, div, 64, /, cmplx8, kmp_cmplx64, 8c, 7, KMP_ARCH_X86 ) // __kmpc_atomic_cmplx4_div_cmplx8
// READ, WRITE, CAPTURE are supported only on IA-32 architecture and Intel(R) 64
#if KMP_ARCH_X86 || KMP_ARCH_X86_64
diff --git a/runtime/src/kmp_atomic.h b/runtime/src/kmp_atomic.h
index 7a98de6..d3d37c2 100644
--- a/runtime/src/kmp_atomic.h
+++ b/runtime/src/kmp_atomic.h
@@ -573,15 +573,15 @@ void __kmpc_atomic_float16_div( ident_t *id_ref, int gtid, QUAD_LEGACY * lhs, QU
void __kmpc_atomic_cmplx4_add( ident_t *id_ref, int gtid, kmp_cmplx32 * lhs, kmp_cmplx32 rhs );
void __kmpc_atomic_cmplx4_sub( ident_t *id_ref, int gtid, kmp_cmplx32 * lhs, kmp_cmplx32 rhs );
void __kmpc_atomic_cmplx4_mul( ident_t *id_ref, int gtid, kmp_cmplx32 * lhs, kmp_cmplx32 rhs );
-void __kmpc_atomic_cmplx4_div( ident_t *id_ref, int gtid, kmp_cmplx32 * lhs, kmp_cmplx32 rhs );
+// void __kmpc_atomic_cmplx4_div( ident_t *id_ref, int gtid, kmp_cmplx32 * lhs, kmp_cmplx32 rhs );
void __kmpc_atomic_cmplx8_add( ident_t *id_ref, int gtid, kmp_cmplx64 * lhs, kmp_cmplx64 rhs );
void __kmpc_atomic_cmplx8_sub( ident_t *id_ref, int gtid, kmp_cmplx64 * lhs, kmp_cmplx64 rhs );
void __kmpc_atomic_cmplx8_mul( ident_t *id_ref, int gtid, kmp_cmplx64 * lhs, kmp_cmplx64 rhs );
-void __kmpc_atomic_cmplx8_div( ident_t *id_ref, int gtid, kmp_cmplx64 * lhs, kmp_cmplx64 rhs );
+// void __kmpc_atomic_cmplx8_div( ident_t *id_ref, int gtid, kmp_cmplx64 * lhs, kmp_cmplx64 rhs );
void __kmpc_atomic_cmplx10_add( ident_t *id_ref, int gtid, kmp_cmplx80 * lhs, kmp_cmplx80 rhs );
void __kmpc_atomic_cmplx10_sub( ident_t *id_ref, int gtid, kmp_cmplx80 * lhs, kmp_cmplx80 rhs );
void __kmpc_atomic_cmplx10_mul( ident_t *id_ref, int gtid, kmp_cmplx80 * lhs, kmp_cmplx80 rhs );
-void __kmpc_atomic_cmplx10_div( ident_t *id_ref, int gtid, kmp_cmplx80 * lhs, kmp_cmplx80 rhs );
+// void __kmpc_atomic_cmplx10_div( ident_t *id_ref, int gtid, kmp_cmplx80 * lhs, kmp_cmplx80 rhs );
#if KMP_HAVE_QUAD
void __kmpc_atomic_cmplx16_add( ident_t *id_ref, int gtid, CPLX128_LEG * lhs, CPLX128_LEG rhs );
void __kmpc_atomic_cmplx16_sub( ident_t *id_ref, int gtid, CPLX128_LEG * lhs, CPLX128_LEG rhs );
@@ -753,7 +753,7 @@ void __kmpc_atomic_float10_div_rev_fp( ident_t *id_ref, int gtid, long double *
void __kmpc_atomic_cmplx4_add_cmplx8( ident_t *id_ref, int gtid, kmp_cmplx32 * lhs, kmp_cmplx64 rhs );
void __kmpc_atomic_cmplx4_sub_cmplx8( ident_t *id_ref, int gtid, kmp_cmplx32 * lhs, kmp_cmplx64 rhs );
void __kmpc_atomic_cmplx4_mul_cmplx8( ident_t *id_ref, int gtid, kmp_cmplx32 * lhs, kmp_cmplx64 rhs );
-void __kmpc_atomic_cmplx4_div_cmplx8( ident_t *id_ref, int gtid, kmp_cmplx32 * lhs, kmp_cmplx64 rhs );
+// void __kmpc_atomic_cmplx4_div_cmplx8( ident_t *id_ref, int gtid, kmp_cmplx32 * lhs, kmp_cmplx64 rhs );
// generic atomic routines
void __kmpc_atomic_1( ident_t *id_ref, int gtid, void* lhs, void* rhs, void (*f)( void *, void *, void * ) );
$ patch -p1 -i openmp-atomic-drop-complex-div.patch
编译 libomp 静态库
$ mkdir build-ios
$ cd build-ios
$ cmake -DCMAKE_TOOLCHAIN_FILE=../iosxc.toolchain.cmake -DLIBOMP_ENABLE_SHARED=off ..
$ make
编译完成后，libomp.a 和 omp.h 在 openmp/build-ios/runtime/src 目录里 把这两个文件分别放在 cctools-port/usage_examples/ios_toolchain/target/SDK/usr/lib 和 cctools-port/usage_examples/ios_toolchain/target/SDK/usr/include 里面，成为 sdk 的一部分
#include <stdio.h>
#include "omp.h"
int main()
{
#pragma omp parallel for
for (int i=0; i<20; i++)
{
fprintf(stderr, "%d\n", i);
}
}
编译方法，增加 -fopenmp 参数
$ cctools-port/usage_examples/ios_toolchain/target/bin/arm-apple-darwin11-clang -fopenmp testomp.c -o testomp
找一台双核cpu的越狱设备，比如这个 ipad2，把程序上传后运行，乱许输出表明 openmp 是可用的了
Chengjiede-iPad:~ root# ./testomp
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