[OpenMP] Added the support for cache line size 256 for A64FX

[tianshilei1992]

Summary

Fugaku supercomputer is built with the Fujitsu A64FX microprocessor, whose cache line is 256. In current libomp, we only have cache line size 128 for PPC64 and otherwise 64. This patch added the support of cache line 256 for A64FX. It's worth noting that although A64FX is a variant of AArch64, this property is not shared. As a result, in light of UCX source code (https://github.com/openucx/ucx/blob/392443ab92626412605dee1572056f79c897c6c3/src/ucs/arch/aarch64/cpu.c#L17), we can only determine by checking whether the CPU is FUJITSU A64FX.

[tianshilei1992]

Fixed a typo in comments

[jdoerfert]

LGTM, at least I don't see anything obviously problematic

[Hahnfeld]

Why is it necessary to write and compile a C program just to parse /proc/cpuinfo? Can this be done directly from CMake?

[tianshilei1992]

In D93169#2484725, @Hahnfeld wrote:

Why is it necessary to write and compile a C program just to parse /proc/cpuinfo? Can this be done directly from CMake?

In D93169#2484725, @Hahnfeld wrote:

Why is it necessary to write and compile a C program just to parse /proc/cpuinfo? Can this be done directly from CMake?

Unfortunately we can't. CMAKE_SYSTEM_PROCESSOR just reports aarch64.

[tianshilei1992]

Updated to make OMPT work

[Hahnfeld]

In D93169#2485228, @tianshilei1992 wrote:

In D93169#2484725, @Hahnfeld wrote:

Why is it necessary to write and compile a C program just to parse /proc/cpuinfo? Can this be done directly from CMake?

Unfortunately we can't. CMAKE_SYSTEM_PROCESSOR just reports aarch64.

I understand that the predefined variables don't work, but we can surely parse /proc/cpuinfo with native CMake commands instead of compiling a C program, no?

[tianshilei1992]

Parse /proc/cpuinfo with CMake directly

[tianshilei1992]

Optimized string match

[tianshilei1992]

Removed useless comment

[Hahnfeld]

openmp/runtime/cmake/LibompGetArchitecture.cmake

78–81

Can you use TRUE and FALSE here? This also avoids the overly generic MATCHES "1" at call site.

[tianshilei1992]

Used TRUE/FALSE instead of 0/1 for LIBOMP_DETECT_AARCH64_A64FX

[Hahnfeld]

LGTM, thanks for the changes!

[chandlerc]

I'm going to revert this as it breaks CMake on systems which do not have /proc/cpuinfo such as macOS.

This may be a bit hard to see because the code isn't reached unless the architecture is aarch64, but on an ARM macOS system that path hits. It would also hit on other BSDs or other OSes running on AArch64 but without /proc/cpuinfo.

For your reference, here is the error message from CMake for me:

CMake Error at /Users/chandlerc/src/llvm/llvm-project/openmp/runtime/cmake/LibompGetArchitecture.cmake:74 (file):
  file failed to open for reading (No such file or directory):

    /proc/cpuinfo
Call Stack (most recent call first):
  /Users/chandlerc/src/llvm/llvm-project/openmp/runtime/CMakeLists.txt:73 (libomp_is_aarch64_a64fx)

[tianshilei1992]

In D93169#2503946, @chandlerc wrote:

I'm going to revert this as it breaks CMake on systems which do not have /proc/cpuinfo such as macOS.

This may be a bit hard to see because the code isn't reached unless the architecture is aarch64, but on an ARM macOS system that path hits. It would also hit on other BSDs or other OSes running on AArch64 but without /proc/cpuinfo.

For your reference, here is the error message from CMake for me:

CMake Error at /Users/chandlerc/src/llvm/llvm-project/openmp/runtime/cmake/LibompGetArchitecture.cmake:74 (file):
  file failed to open for reading (No such file or directory):

    /proc/cpuinfo
Call Stack (most recent call first):
  /Users/chandlerc/src/llvm/llvm-project/openmp/runtime/CMakeLists.txt:73 (libomp_is_aarch64_a64fx)

Will fix it right away.

[chandlerc]

In D93169#2503947, @tianshilei1992 wrote:

In D93169#2503946, @chandlerc wrote:

I'm going to revert this as it breaks CMake on systems which do not have /proc/cpuinfo such as macOS.

This may be a bit hard to see because the code isn't reached unless the architecture is aarch64, but on an ARM macOS system that path hits. It would also hit on other BSDs or other OSes running on AArch64 but without /proc/cpuinfo.

For your reference, here is the error message from CMake for me:

CMake Error at /Users/chandlerc/src/llvm/llvm-project/openmp/runtime/cmake/LibompGetArchitecture.cmake:74 (file):
  file failed to open for reading (No such file or directory):

    /proc/cpuinfo
Call Stack (most recent call first):
  /Users/chandlerc/src/llvm/llvm-project/openmp/runtime/CMakeLists.txt:73 (libomp_is_aarch64_a64fx)

Will fix it right away.

I didn't think my CMake fu was up to it, but I think I have a fix, WDYT: https://reviews.llvm.org/D94889

[chandlerc]

In D93169#2503960, @chandlerc wrote:

In D93169#2503947, @tianshilei1992 wrote:

In D93169#2503946, @chandlerc wrote:

I'm going to revert this as it breaks CMake on systems which do not have /proc/cpuinfo such as macOS.

This may be a bit hard to see because the code isn't reached unless the architecture is aarch64, but on an ARM macOS system that path hits. It would also hit on other BSDs or other OSes running on AArch64 but without /proc/cpuinfo.

For your reference, here is the error message from CMake for me:

CMake Error at /Users/chandlerc/src/llvm/llvm-project/openmp/runtime/cmake/LibompGetArchitecture.cmake:74 (file):
  file failed to open for reading (No such file or directory):

    /proc/cpuinfo
Call Stack (most recent call first):
  /Users/chandlerc/src/llvm/llvm-project/openmp/runtime/CMakeLists.txt:73 (libomp_is_aarch64_a64fx)

Will fix it right away.

I didn't think my CMake fu was up to it, but I think I have a fix, WDYT: https://reviews.llvm.org/D94889

And thanks to the speedy review, landed fix in: https://github.com/llvm/llvm-project/commit/f855751c1284c82c1c46b98f6d1b3ca2021d6cb9

openmp/runtime/CMakeLists.txt

else() # Part of LLVM build
   elseif(LIBOMP_NATIVE_ARCH MATCHES "riscv64")
     set(LIBOMP_ARCH riscv64)
   else()
     # last ditch effort
     libomp_get_architecture(LIBOMP_ARCH)
   endif ()
   set(LIBOMP_ENABLE_ASSERTIONS ${LLVM_ENABLE_ASSERTIONS})
 endif()
-libomp_check_variable(LIBOMP_ARCH 32e x86_64 32 i386 arm ppc64 ppc64le aarch64 mic mips mips64 riscv64)
+
+# FUJITSU A64FX is a special processor because its cache line size is 256.
+# We need to pass this information into kmp_config.h.
+if(LIBOMP_ARCH STREQUAL "aarch64")
+  libomp_is_aarch64_a64fx(LIBOMP_DETECT_AARCH64_A64FX)
+  if (LIBOMP_DETECT_AARCH64_A64FX MATCHES "1")
+    set(LIBOMP_ARCH "aarch64_a64fx")
+    set(LIBOMP_ARCH_AARCH64_A64FX TRUE)
+  endif()
+endif()
+
+libomp_check_variable(LIBOMP_ARCH 32e x86_64 32 i386 arm ppc64 ppc64le aarch64 aarch64_a64fx mic mips mips64 riscv64)
 
 set(LIBOMP_LIB_TYPE normal CACHE STRING
   "Performance,Profiling,Stubs library (normal/profile/stubs)")
 libomp_check_variable(LIBOMP_LIB_TYPE normal profile stubs)
 # Set the OpenMP Year and Month associated with version
 set(LIBOMP_OMP_YEAR_MONTH 201611)
 set(LIBOMP_MIC_ARCH knc CACHE STRING
   "Intel(R) Many Integrated Core Architecture (Intel(R) MIC Architecture) (knf/knc).  Ignored if not Intel(R) MIC Architecture build.")

 # Currently don't record any timestamps
 set(LIBOMP_BUILD_DATE "No_Timestamp")
 
 # Architecture
 set(IA32 FALSE)
 set(INTEL64 FALSE)
 set(ARM FALSE)
 set(AARCH64 FALSE)
+set(AARCH64_A64FX FALSE)
 set(PPC64BE FALSE)
 set(PPC64LE FALSE)
 set(PPC64 FALSE)
 set(MIC FALSE)
 set(MIPS64 FALSE)
 set(MIPS FALSE)
 set(RISCV64 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 "ppc64") # PPC64BE architecture
   set(PPC64BE TRUE)
   set(PPC64 TRUE)
 elseif("${LIBOMP_ARCH}" STREQUAL "ppc64le") # PPC64LE architecture
   set(PPC64LE TRUE)
   set(PPC64 TRUE)
 elseif("${LIBOMP_ARCH}" STREQUAL "aarch64") # AARCH64 architecture
   set(AARCH64 TRUE)
+elseif("${LIBOMP_ARCH}" STREQUAL "aarch64_a64fx") # AARCH64_A64FX architecture
+  set(AARCH64_A64FX TRUE)
 elseif("${LIBOMP_ARCH}" STREQUAL "mic") # Intel(R) Many Integrated Core Architecture
   set(MIC TRUE)
 elseif("${LIBOMP_ARCH}" STREQUAL "mips") # MIPS architecture
     set(MIPS TRUE)
 elseif("${LIBOMP_ARCH}" STREQUAL "mips64") # MIPS64 architecture
     set(MIPS64 TRUE)
   elseif("${LIBOMP_ARCH}" STREQUAL "riscv64") # RISCV64 architecture
     set(RISCV64 TRUE)

openmp/runtime/cmake/LibompGetArchitecture.cmake

function(libomp_get_architecture return_arch)
   string(REPLACE "ARCHITECTURE=" "" local_architecture "${local_architecture}")
 
   # set the return value to the architecture detected (e.g., 32e, 32, arm, ppc64, etc.)
   set(${return_arch} "${local_architecture}" PARENT_SCOPE)
 
   # Remove ${detect_arch_src_txt} from cmake/ subdirectory
   file(REMOVE "${CMAKE_CURRENT_BINARY_DIR}/libomp_detect_arch.c")
 endfunction()
+
+function(libomp_is_aarch64_a64fx return_is_aarch64_a64fx)
+  set(detect_aarch64_a64fx_src_txt "
+    #include <stdio.h>
+
+    typedef struct aarch64_cpuid {
+      int implementer\;
+      int architecture\;
+      int variant\;
+      int partno\;
+      int revision\;
+    } aarch64_cpuid_t\;
+
+    int main(int argc, char *argv[]) {
+      char buf[256]\;
+      int value\;
+      FILE *f\;
+
+      aarch64_cpuid_t cpuid\;
+
+      cpuid.implementer = -1\;
+      cpuid.architecture = -1\;
+      cpuid.variant = -1\;
+      cpuid.partno = -1\;
+      cpuid.revision = -1\;
+
+      f = fopen(\"/proc/cpuinfo\", \"r\")\;
+      if (!f) {
+        printf(\"0\\n\")\;
+        return 0\;
+      }
+
+      while (fgets(buf, sizeof(buf), f)) {
+        if (sscanf(buf, \"CPU implementer : 0x%x\", &value) == 1) {
+          cpuid.implementer = value\;
+        } else if (sscanf(buf, \"CPU architecture : %d\", &value) == 1) {
+          cpuid.architecture = value\;
+        } else if (sscanf(buf, \"CPU variant : 0x%x\", &value) == 1) {
+          cpuid.variant = value\;
+        } else if (sscanf(buf, \"CPU part : 0x%x\", &value) == 1) {
+          cpuid.partno = value\;
+        } else if (sscanf(buf, \"CPU revision : %d\", &value) == 1) {
+          cpuid.revision = value\;
+        }
+
+        if ((cpuid.implementer != -1) && (cpuid.architecture != -1) &&
+            (cpuid.variant != -1) && (cpuid.partno != -1) &&
+            (cpuid.revision != -1)) {
+          break\;
+        }
+      }
+
+      fclose(f)\;
+
+      if (cpuid.implementer == 0x46 && cpuid.architecture == 8) {
+        printf(\"1\\n\")\;
+      } else {
+        printf(\"0\\n\")\;
+      }
+
+      return 0\;
+    }
+  ")
+
+  # Write out ${detect_a64fx_src_txt} to a file within the cmake/ subdirectory
+  file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/libomp_detect_aarch64_a64fx.c" ${detect_aarch64_a64fx_src_txt})
+
+  # Compile using the C Compiler.  It will always error out with an #error directive, so store error output to ${is_aarch64_a64fx}
+  try_run(run_dummy compile_dummy "${CMAKE_CURRENT_BINARY_DIR}" "${CMAKE_CURRENT_BINARY_DIR}/libomp_detect_aarch64_a64fx.c" RUN_OUTPUT_VARIABLE is_aarch64_a64fx)
+
+  set(${return_is_aarch64_a64fx} "${is_aarch64_a64fx}" PARENT_SCOPE)
+
+  # Remove ${detect_aarch64_a64fx_src_txt} from cmake/ subdirectory
+  file(REMOVE "${CMAKE_CURRENT_BINARY_DIR}/libomp_detect_aarch64_a64fx.c")
+endfunction(libomp_is_aarch64_a64fx)

openmp/runtime/cmake/LibompUtils.cmake

function(libomp_get_legal_arch return_arch_string)
   elseif(${ARM})
     set(${return_arch_string} "ARM" PARENT_SCOPE)
   elseif(${PPC64BE})
     set(${return_arch_string} "PPC64BE" PARENT_SCOPE)
   elseif(${PPC64LE})
     set(${return_arch_string} "PPC64LE" PARENT_SCOPE)
   elseif(${AARCH64})
     set(${return_arch_string} "AARCH64" PARENT_SCOPE)
+  elseif(${AARCH64_A64FX})
+    set(${return_arch_string} "AARCH64_A64FX" PARENT_SCOPE)
   elseif(${MIPS})
     set(${return_arch_string} "MIPS" PARENT_SCOPE)
   elseif(${MIPS64})
     set(${return_arch_string} "MIPS64" PARENT_SCOPE)
   elseif(${RISCV64})
     set(${return_arch_string} "RISCV64" PARENT_SCOPE)
   else()
     set(${return_arch_string} "${LIBOMP_ARCH}" PARENT_SCOPE)

openmp/runtime/src/kmp_config.h.cmake

 #cmakedefine01 LIBOMP_HAVE_IMMINTRIN_H
 #define KMP_HAVE_IMMINTRIN_H LIBOMP_HAVE_IMMINTRIN_H
 #cmakedefine01 LIBOMP_HAVE_INTRIN_H
 #define KMP_HAVE_INTRIN_H LIBOMP_HAVE_INTRIN_H
 #cmakedefine01 LIBOMP_HAVE_ATTRIBUTE_WAITPKG
 #define KMP_HAVE_ATTRIBUTE_WAITPKG LIBOMP_HAVE_ATTRIBUTE_WAITPKG
 #cmakedefine01 LIBOMP_HAVE_ATTRIBUTE_RTM
 #define KMP_HAVE_ATTRIBUTE_RTM LIBOMP_HAVE_ATTRIBUTE_RTM
+#cmakedefine01 LIBOMP_ARCH_AARCH64_A64FX
+#define KMP_ARCH_AARCH64_A64FX LIBOMP_ARCH_AARCH64_A64FX
 
 // Configured cache line based on architecture
 #if KMP_ARCH_PPC64
 # define CACHE_LINE 128
+#elif KMP_ARCH_AARCH64_A64FX
+# define CACHE_LINE 256
 #else
 # define CACHE_LINE 64
 #endif
 
 #if ! KMP_32_BIT_ARCH
 # define BUILD_I8 1
 #endif