[openmp][AIX]Initial changes for porting to AIX (#76841)

This PR contains initial changes for building and testing libomp on AIX. More changes will follow. - `KMP_OS_AIX` is defined for the AIX platform - `KMP_ARCH_PPC` is defined for 32-bit PPC - `KMP_ARCH_PPC_XCOFF` and `KMP_ARCH_PPC64_XCOFF` are for 32- and 64-bit XCOFF object formats respectively - Assembly file `z_AIX_asm.S` is used for AIX specific assembly code and will be added in a separate PR - The target library is disabled because AIX does not have the device support - OMPT is temporarily disabled
llvm · Jan 8, 2024 · 2edce42 · 2edce42 · brad0 · Mar 16, 2024
1 parent 0e4a380
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Showing 18 changed files with 112 additions and 33 deletions.
diff --git a/openmp/CMakeLists.txt b/openmp/CMakeLists.txt
@@ -94,7 +94,8 @@ set(ENABLE_LIBOMPTARGET ON)
 # Since the device plugins are only supported on Linux anyway,
 # there is no point in trying to compile libomptarget on other OSes.
 # 32-bit systems are not supported either.
-if (APPLE OR WIN32 OR WASM OR NOT "cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES OR NOT CMAKE_SIZEOF_VOID_P EQUAL 8)
+if (APPLE OR WIN32 OR WASM OR NOT "cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES
+    OR NOT CMAKE_SIZEOF_VOID_P EQUAL 8 OR ${CMAKE_SYSTEM_NAME} MATCHES "AIX")
   set(ENABLE_LIBOMPTARGET OFF)
 endif()
 

diff --git a/openmp/cmake/OpenMPTesting.cmake b/openmp/cmake/OpenMPTesting.cmake
@@ -55,6 +55,9 @@ if (${OPENMP_STANDALONE_BUILD})
   if (MSVC OR XCODE)
     set(DEFAULT_LIT_ARGS "${DEFAULT_LIT_ARGS} --no-progress-bar")
   endif()
+  if (${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+    set(DEFAULT_LIT_ARGS "${DEFAULT_LIT_ARGS} --time-tests --timeout=1800")
+  endif()
   set(OPENMP_LIT_ARGS "${DEFAULT_LIT_ARGS}" CACHE STRING "Options for lit.")
   separate_arguments(OPENMP_LIT_ARGS)
 else()

diff --git a/openmp/runtime/CMakeLists.txt b/openmp/runtime/CMakeLists.txt
@@ -30,7 +30,7 @@ if(${OPENMP_STANDALONE_BUILD})
   # If adding a new architecture, take a look at cmake/LibompGetArchitecture.cmake
   libomp_get_architecture(LIBOMP_DETECTED_ARCH)
   set(LIBOMP_ARCH ${LIBOMP_DETECTED_ARCH} CACHE STRING
-    "The architecture to build for (x86_64/i386/arm/ppc64/ppc64le/aarch64/mic/mips/mips64/riscv64/loongarch64/ve/s390x/wasm32).")
+    "The architecture to build for (x86_64/i386/arm/ppc/ppc64/ppc64le/aarch64/mic/mips/mips64/riscv64/loongarch64/ve/s390x/wasm32).")
   # Should assertions be enabled?  They are on by default.
   set(LIBOMP_ENABLE_ASSERTIONS TRUE CACHE BOOL
     "enable assertions?")
@@ -51,8 +51,10 @@ else() # Part of LLVM build
     set(LIBOMP_ARCH x86_64)
   elseif(LIBOMP_NATIVE_ARCH MATCHES "powerpc64le")
     set(LIBOMP_ARCH ppc64le)
-  elseif(LIBOMP_NATIVE_ARCH MATCHES "powerpc")
+  elseif(LIBOMP_NATIVE_ARCH MATCHES "powerpc64")
     set(LIBOMP_ARCH ppc64)
+  elseif(LIBOMP_NATIVE_ARCH MATCHES "powerpc")
+    set(LIBOMP_ARCH ppc)
   elseif(LIBOMP_NATIVE_ARCH MATCHES "aarch64")
     set(LIBOMP_ARCH aarch64)
   elseif(LIBOMP_NATIVE_ARCH MATCHES "arm64")
@@ -89,7 +91,7 @@ if(LIBOMP_ARCH STREQUAL "aarch64")
   endif()
 endif()
 
-libomp_check_variable(LIBOMP_ARCH 32e x86_64 32 i386 arm ppc64 ppc64le aarch64 aarch64_a64fx mic mips mips64 riscv64 loongarch64 ve s390x wasm32)
+libomp_check_variable(LIBOMP_ARCH 32e x86_64 32 i386 arm ppc ppc64 ppc64le aarch64 aarch64_a64fx mic mips mips64 riscv64 loongarch64 ve s390x wasm32)
 
 set(LIBOMP_LIB_TYPE normal CACHE STRING
   "Performance,Profiling,Stubs library (normal/profile/stubs)")
@@ -128,8 +130,14 @@ set(LIBOMP_ASMFLAGS "" CACHE STRING
   "Appended user specified assembler flags.")
 set(LIBOMP_LDFLAGS "" CACHE STRING
   "Appended user specified linker flags.")
-set(LIBOMP_LIBFLAGS "" CACHE STRING
-  "Appended user specified linked libs flags. (e.g., -lm)")
+if("${LIBOMP_ARCH}" STREQUAL "ppc" AND ${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+  # PPC (32-bit) on AIX needs libatomic for __atomic_load_8, etc.
+  set(LIBOMP_LIBFLAGS "-latomic" CACHE STRING
+    "Appended user specified linked libs flags. (e.g., -lm)")
+else()
+  set(LIBOMP_LIBFLAGS "" CACHE STRING
+    "Appended user specified linked libs flags. (e.g., -lm)")
+endif()
 set(LIBOMP_FFLAGS "" CACHE STRING
   "Appended user specified Fortran compiler flags.  These are only used if LIBOMP_FORTRAN_MODULES==TRUE.")
 
@@ -171,12 +179,15 @@ set(LOONGARCH64 FALSE)
 set(VE FALSE)
 set(S390X FALSE)
 set(WASM FALSE)
+set(PPC FALSE)
 if("${LIBOMP_ARCH}" STREQUAL "i386" OR "${LIBOMP_ARCH}" STREQUAL "32")    # IA-32 architecture
   set(IA32 TRUE)
 elseif("${LIBOMP_ARCH}" STREQUAL "x86_64" OR "${LIBOMP_ARCH}" STREQUAL "32e") # Intel(R) 64 architecture
   set(INTEL64 TRUE)
 elseif("${LIBOMP_ARCH}" STREQUAL "arm") # ARM architecture
   set(ARM TRUE)
+elseif("${LIBOMP_ARCH}" STREQUAL "ppc") # PPC32 architecture
+  set(PPC TRUE)
 elseif("${LIBOMP_ARCH}" STREQUAL "ppc64") # PPC64BE architecture
   set(PPC64BE TRUE)
   set(PPC64 TRUE)

diff --git a/openmp/runtime/cmake/LibompGetArchitecture.cmake b/openmp/runtime/cmake/LibompGetArchitecture.cmake
@@ -41,6 +41,8 @@ function(libomp_get_architecture return_arch)
       #error ARCHITECTURE=ppc64le
     #elif defined(__powerpc64__)
       #error ARCHITECTURE=ppc64
+    #elif defined(__powerpc__) && !defined(__powerpc64__)
+      #error ARCHITECTURE=ppc
     #elif defined(__mips__) && defined(__mips64)
       #error ARCHITECTURE=mips64
     #elif defined(__mips__) && !defined(__mips64)

diff --git a/openmp/runtime/cmake/config-ix.cmake b/openmp/runtime/cmake/config-ix.cmake
@@ -333,7 +333,8 @@ else()
       (LIBOMP_ARCH STREQUAL loongarch64) OR
       (LIBOMP_ARCH STREQUAL s390x))
      AND # OS supported?
-     ((WIN32 AND LIBOMP_HAVE_PSAPI) OR APPLE OR (NOT WIN32 AND LIBOMP_HAVE_WEAK_ATTRIBUTE)))
+     ((WIN32 AND LIBOMP_HAVE_PSAPI) OR APPLE OR
+      (NOT (WIN32 OR ${CMAKE_SYSTEM_NAME} MATCHES "AIX") AND LIBOMP_HAVE_WEAK_ATTRIBUTE)))
     set(LIBOMP_HAVE_OMPT_SUPPORT TRUE)
   else()
     set(LIBOMP_HAVE_OMPT_SUPPORT FALSE)

diff --git a/openmp/runtime/src/CMakeLists.txt b/openmp/runtime/src/CMakeLists.txt
@@ -108,7 +108,11 @@ else()
     # Unix specific files
     libomp_append(LIBOMP_CXXFILES z_Linux_util.cpp)
     libomp_append(LIBOMP_CXXFILES kmp_gsupport.cpp)
-    libomp_append(LIBOMP_GNUASMFILES z_Linux_asm.S) # Unix assembly file
+    if(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+      libomp_append(LIBOMP_GNUASMFILES z_AIX_asm.S) # AIX assembly file
+    else()
+      libomp_append(LIBOMP_GNUASMFILES z_Linux_asm.S) # Unix assembly file
+    endif()
   endif()
   libomp_append(LIBOMP_CXXFILES thirdparty/ittnotify/ittnotify_static.cpp LIBOMP_USE_ITT_NOTIFY)
   libomp_append(LIBOMP_CXXFILES kmp_debugger.cpp LIBOMP_USE_DEBUGGER)

diff --git a/openmp/runtime/src/kmp.h b/openmp/runtime/src/kmp.h
@@ -1192,6 +1192,9 @@ extern void __kmp_init_target_task();
 // Minimum stack size for pthread for VE is 4MB.
 //   https://www.hpc.nec/documents/veos/en/glibc/Difference_Points_glibc.htm
 #define KMP_DEFAULT_STKSIZE ((size_t)(4 * 1024 * 1024))
+#elif KMP_OS_AIX
+// The default stack size for worker threads on AIX is 4MB.
+#define KMP_DEFAULT_STKSIZE ((size_t)(4 * 1024 * 1024))
 #else
 #define KMP_DEFAULT_STKSIZE ((size_t)(1024 * 1024))
 #endif
@@ -1354,6 +1357,10 @@ extern kmp_uint64 __kmp_now_nsec();
 /* TODO: tune for KMP_OS_WASI */
 #define KMP_INIT_WAIT 1024U /* initial number of spin-tests   */
 #define KMP_NEXT_WAIT 512U /* susequent number of spin-tests */
+#elif KMP_OS_AIX
+/* TODO: tune for KMP_OS_AIX */
+#define KMP_INIT_WAIT 1024U /* initial number of spin-tests   */
+#define KMP_NEXT_WAIT 512U /* susequent number of spin-tests */
 #endif
 
 #if KMP_ARCH_X86 || KMP_ARCH_X86_64

diff --git a/openmp/runtime/src/kmp_config.h.cmake b/openmp/runtime/src/kmp_config.h.cmake
@@ -100,7 +100,7 @@
 #define ENABLE_LIBOMPTARGET OPENMP_ENABLE_LIBOMPTARGET
 
 // Configured cache line based on architecture
-#if KMP_ARCH_PPC64
+#if KMP_ARCH_PPC64 || KMP_ARCH_PPC
 # define CACHE_LINE 128
 #elif KMP_ARCH_AARCH64_A64FX
 # define CACHE_LINE 256

diff --git a/openmp/runtime/src/kmp_ftn_entry.h b/openmp/runtime/src/kmp_ftn_entry.h
@@ -582,7 +582,7 @@ int FTN_STDCALL KMP_EXPAND_NAME(FTN_GET_THREAD_NUM)(void) {
   int gtid;
 
 #if KMP_OS_DARWIN || KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD ||    \
-    KMP_OS_OPENBSD || KMP_OS_HURD || KMP_OS_SOLARIS
+    KMP_OS_OPENBSD || KMP_OS_HURD || KMP_OS_SOLARIS || KMP_OS_AIX
   gtid = __kmp_entry_gtid();
 #elif KMP_OS_WINDOWS
   if (!__kmp_init_parallel ||

diff --git a/openmp/runtime/src/kmp_global.cpp b/openmp/runtime/src/kmp_global.cpp
@@ -172,7 +172,7 @@ int __kmp_ncores = 0;
 int __kmp_chunk = 0;
 int __kmp_force_monotonic = 0;
 int __kmp_abort_delay = 0;
-#if KMP_OS_LINUX && defined(KMP_TDATA_GTID)
+#if (KMP_OS_LINUX || KMP_OS_AIX) && defined(KMP_TDATA_GTID)
 int __kmp_gtid_mode = 3; /* use __declspec(thread) TLS to store gtid */
 int __kmp_adjust_gtid_mode = FALSE;
 #elif KMP_OS_WINDOWS

diff --git a/openmp/runtime/src/kmp_gsupport.cpp b/openmp/runtime/src/kmp_gsupport.cpp
@@ -357,7 +357,8 @@ void KMP_EXPAND_NAME(KMP_API_NAME_GOMP_ORDERED_END)(void) {
 // They come in two flavors: 64-bit unsigned, and either 32-bit signed
 // (IA-32 architecture) or 64-bit signed (Intel(R) 64).
 
-#if KMP_ARCH_X86 || KMP_ARCH_ARM || KMP_ARCH_MIPS || KMP_ARCH_WASM
+#if KMP_ARCH_X86 || KMP_ARCH_ARM || KMP_ARCH_MIPS || KMP_ARCH_WASM ||          \
+    KMP_ARCH_PPC
 #define KMP_DISPATCH_INIT __kmp_aux_dispatch_init_4
 #define KMP_DISPATCH_FINI_CHUNK __kmp_aux_dispatch_fini_chunk_4
 #define KMP_DISPATCH_NEXT __kmpc_dispatch_next_4

diff --git a/openmp/runtime/src/kmp_os.h b/openmp/runtime/src/kmp_os.h
@@ -176,7 +176,8 @@ typedef unsigned long long kmp_uint64;
 #define KMP_UINT64_SPEC "llu"
 #endif /* KMP_OS_UNIX */
 
-#if KMP_ARCH_X86 || KMP_ARCH_ARM || KMP_ARCH_MIPS || KMP_ARCH_WASM
+#if KMP_ARCH_X86 || KMP_ARCH_ARM || KMP_ARCH_MIPS || KMP_ARCH_WASM ||          \
+    KMP_ARCH_PPC
 #define KMP_SIZE_T_SPEC KMP_UINT32_SPEC
 #elif KMP_ARCH_X86_64 || KMP_ARCH_PPC64 || KMP_ARCH_AARCH64 ||                 \
     KMP_ARCH_MIPS64 || KMP_ARCH_RISCV64 || KMP_ARCH_LOONGARCH64 ||             \
@@ -186,7 +187,7 @@ typedef unsigned long long kmp_uint64;
 #error "Can't determine size_t printf format specifier."
 #endif
 
-#if KMP_ARCH_X86 || KMP_ARCH_ARM || KMP_ARCH_WASM
+#if KMP_ARCH_X86 || KMP_ARCH_ARM || KMP_ARCH_WASM || KMP_ARCH_PPC
 #define KMP_SIZE_T_MAX (0xFFFFFFFF)
 #else
 #define KMP_SIZE_T_MAX (0xFFFFFFFFFFFFFFFF)
@@ -1046,7 +1047,7 @@ extern kmp_real64 __kmp_xchg_real64(volatile kmp_real64 *p, kmp_real64 v);
 
 #if KMP_ARCH_PPC64 || KMP_ARCH_ARM || KMP_ARCH_AARCH64 || KMP_ARCH_MIPS ||     \
     KMP_ARCH_MIPS64 || KMP_ARCH_RISCV64 || KMP_ARCH_LOONGARCH64 ||             \
-    KMP_ARCH_VE || KMP_ARCH_S390X
+    KMP_ARCH_VE || KMP_ARCH_S390X || KMP_ARCH_PPC
 #if KMP_OS_WINDOWS
 #undef KMP_MB
 #define KMP_MB() std::atomic_thread_fence(std::memory_order_seq_cst)
@@ -1146,7 +1147,7 @@ extern kmp_real64 __kmp_xchg_real64(volatile kmp_real64 *p, kmp_real64 v);
   KMP_COMPARE_AND_STORE_REL64((volatile kmp_int64 *)(volatile void *)&(a),     \
                               (kmp_int64)(b), (kmp_int64)(c))
 
-#if KMP_ARCH_X86 || KMP_ARCH_MIPS || KMP_ARCH_WASM
+#if KMP_ARCH_X86 || KMP_ARCH_MIPS || KMP_ARCH_WASM || KMP_ARCH_PPC
 // What about ARM?
 #define TCR_PTR(a) ((void *)TCR_4(a))
 #define TCW_PTR(a, b) TCW_4((a), (b))

diff --git a/openmp/runtime/src/kmp_platform.h b/openmp/runtime/src/kmp_platform.h
@@ -82,15 +82,20 @@
 #define KMP_OS_WASI 1
 #endif
 
+#if (defined _AIX)
+#undef KMP_OS_AIX
+#define KMP_OS_AIX 1
+#endif
+
 #if (1 != KMP_OS_LINUX + KMP_OS_DRAGONFLY + KMP_OS_FREEBSD + KMP_OS_NETBSD +   \
               KMP_OS_OPENBSD + KMP_OS_DARWIN + KMP_OS_WINDOWS + KMP_OS_HURD +  \
-              KMP_OS_SOLARIS + KMP_OS_WASI)
+              KMP_OS_SOLARIS + KMP_OS_WASI + KMP_OS_AIX)
 #error Unknown OS
 #endif
 
 #if KMP_OS_LINUX || KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD ||     \
     KMP_OS_OPENBSD || KMP_OS_DARWIN || KMP_OS_HURD || KMP_OS_SOLARIS ||        \
-    KMP_OS_WASI
+    KMP_OS_WASI || KMP_OS_AIX
 #undef KMP_OS_UNIX
 #define KMP_OS_UNIX 1
 #endif
@@ -102,7 +107,8 @@
 #define KMP_ARCH_AARCH64 0
 #define KMP_ARCH_PPC64_ELFv1 0
 #define KMP_ARCH_PPC64_ELFv2 0
-#define KMP_ARCH_PPC64 (KMP_ARCH_PPC64_ELFv2 || KMP_ARCH_PPC64_ELFv1)
+#define KMP_ARCH_PPC64_XCOFF 0
+#define KMP_ARCH_PPC_XCOFF 0
 #define KMP_ARCH_MIPS 0
 #define KMP_ARCH_MIPS64 0
 #define KMP_ARCH_RISCV64 0
@@ -134,13 +140,23 @@
 #undef KMP_ARCH_X86
 #define KMP_ARCH_X86 1
 #elif defined __powerpc64__
-#if defined(_CALL_ELF) && _CALL_ELF == 2
+#if defined(_CALL_ELF)
+#if _CALL_ELF == 2
 #undef KMP_ARCH_PPC64_ELFv2
 #define KMP_ARCH_PPC64_ELFv2 1
 #else
 #undef KMP_ARCH_PPC64_ELFv1
 #define KMP_ARCH_PPC64_ELFv1 1
 #endif
+#elif defined KMP_OS_AIX
+#undef KMP_ARCH_PPC64_XCOFF
+#define KMP_ARCH_PPC64_XCOFF 1
+#endif
+#elif defined(__powerpc__) && defined(KMP_OS_AIX)
+#undef KMP_ARCH_PPC_XCOFF
+#define KMP_ARCH_PPC_XCOFF 1
+#undef KMP_ARCH_PPC
+#define KMP_ARCH_PPC 1
 #elif defined __aarch64__
 #undef KMP_ARCH_AARCH64
 #define KMP_ARCH_AARCH64 1
@@ -207,6 +223,9 @@
 #define KMP_ARCH_WASM 1
 #endif
 
+#define KMP_ARCH_PPC64                                                         \
+  (KMP_ARCH_PPC64_ELFv2 || KMP_ARCH_PPC64_ELFv1 || KMP_ARCH_PPC64_XCOFF)
+
 #if defined(__MIC__) || defined(__MIC2__)
 #define KMP_MIC 1
 #if __MIC2__ || __KNC__
@@ -224,7 +243,8 @@
 
 /* Specify 32 bit architectures here */
 #define KMP_32_BIT_ARCH                                                        \
-  (KMP_ARCH_X86 || KMP_ARCH_ARM || KMP_ARCH_MIPS || KMP_ARCH_WASM)
+  (KMP_ARCH_X86 || KMP_ARCH_ARM || KMP_ARCH_MIPS || KMP_ARCH_WASM ||           \
+   KMP_ARCH_PPC)
 
 // Platforms which support Intel(R) Many Integrated Core Architecture
 #define KMP_MIC_SUPPORTED                                                      \
@@ -234,7 +254,7 @@
 #if (1 != KMP_ARCH_X86 + KMP_ARCH_X86_64 + KMP_ARCH_ARM + KMP_ARCH_PPC64 +     \
               KMP_ARCH_AARCH64 + KMP_ARCH_MIPS + KMP_ARCH_MIPS64 +             \
               KMP_ARCH_RISCV64 + KMP_ARCH_LOONGARCH64 + KMP_ARCH_VE +          \
-              KMP_ARCH_S390X + KMP_ARCH_WASM)
+              KMP_ARCH_S390X + KMP_ARCH_WASM + KMP_ARCH_PPC)
 #error Unknown or unsupported architecture
 #endif
 

diff --git a/openmp/runtime/src/kmp_runtime.cpp b/openmp/runtime/src/kmp_runtime.cpp
@@ -8901,7 +8901,7 @@ __kmp_determine_reduction_method(
 
 #if KMP_OS_LINUX || KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD ||     \
     KMP_OS_OPENBSD || KMP_OS_WINDOWS || KMP_OS_DARWIN || KMP_OS_HURD ||        \
-    KMP_OS_SOLARIS || KMP_OS_WASI
+    KMP_OS_SOLARIS || KMP_OS_WASI || KMP_OS_AIX
 
     int teamsize_cutoff = 4;
 
@@ -8926,14 +8926,14 @@ __kmp_determine_reduction_method(
 #error "Unknown or unsupported OS"
 #endif // KMP_OS_LINUX || KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD ||
        // KMP_OS_OPENBSD || KMP_OS_WINDOWS || KMP_OS_DARWIN || KMP_OS_HURD ||
-       // KMP_OS_SOLARIS || KMP_OS_WASI
+       // KMP_OS_SOLARIS || KMP_OS_WASI || KMP_OS_AIX
 
 #elif KMP_ARCH_X86 || KMP_ARCH_ARM || KMP_ARCH_AARCH || KMP_ARCH_MIPS ||       \
-    KMP_ARCH_WASM
+    KMP_ARCH_WASM || KMP_ARCH_PPC
 
 #if KMP_OS_LINUX || KMP_OS_DRAGONFLY || KMP_OS_FREEBSD || KMP_OS_NETBSD ||     \
     KMP_OS_OPENBSD || KMP_OS_WINDOWS || KMP_OS_HURD || KMP_OS_SOLARIS ||       \
-    KMP_OS_WASI
+    KMP_OS_WASI || KMP_OS_AIX
 
     // basic tuning
 

diff --git a/openmp/runtime/src/kmp_settings.cpp b/openmp/runtime/src/kmp_settings.cpp
@@ -6171,9 +6171,9 @@ void __kmp_env_initialize(char const *string) {
     // specifier, even as substrings.
     //
     // I can't find a case-insensitive version of strstr on Windows* OS.
-    // Use the case-sensitive version for now.
+    // Use the case-sensitive version for now. AIX does the same.
 
-#if KMP_OS_WINDOWS
+#if KMP_OS_WINDOWS || KMP_OS_AIX
 #define FIND strstr
 #else
 #define FIND strcasestr

diff --git a/openmp/runtime/src/kmp_wrapper_getpid.h b/openmp/runtime/src/kmp_wrapper_getpid.h
@@ -17,7 +17,9 @@
 
 // On Unix-like systems (Linux* OS and OS X*) getpid() is declared in standard
 // headers.
+#if !defined(KMP_OS_AIX)
 #include <sys/syscall.h>
+#endif
 #include <sys/types.h>
 #include <unistd.h>
 #if KMP_OS_DARWIN
@@ -31,6 +33,9 @@
 #define __kmp_gettid() _lwp_self()
 #elif KMP_OS_OPENBSD
 #define __kmp_gettid() getthrid()
+#elif KMP_OS_AIX
+#include <pthread.h>
+#define __kmp_gettid() pthread_self()
 #elif defined(SYS_gettid)
 // Hopefully other Unix systems define SYS_gettid syscall for getting os thread
 // id