[libomptarget] Add AArch64 support

[pawosm01]

Summary

This adds AArch64 support to recently added part of the runtime responsible for offloading to target. This piece of code allows offloading-to-self on AArch64 machines.

[grokos]

LGTM. Thanks for submitting!

libomptarget/CMakeLists.txt

 include(LibomptargetGetDependencies)
 
 # This is a list of all the targets that are supported/tested right now.
+set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} aarch64-unknown-linux-gnu")
 set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} powerpc64le-ibm-linux-gnu")
 set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} powerpc64-ibm-linux-gnu")
 set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} x86_64-pc-linux-gnu")

libomptarget/README.txt

 * Intel(R) 64 architecture
 * IBM(R) Power architecture (big endian)
 * IBM(R) Power architecture (little endian)
+* ARM(R) AArch64 architecture (little endian)
 
 The currently supported offloading device architectures are:
 * Intel(R) 64 architecture (generic 64-bit plugin - mostly for testing purposes)
 * IBM(R) Power architecture (big endian) (generic 64-bit plugin - mostly for testing purposes)
 * IBM(R) Power architecture (little endian) (generic 64-bit plugin - mostly for testing purposes)
+* ARM(R) AArch64 architecture (little endian) (generic 64-bit plugin - mostly for testing purposes)
 * CUDA(R) enabled 64-bit NVIDIA(R) GPU architectures
 
 Supported RTL Build Configurations

libomptarget/plugins/CMakeLists.txt

 endif()
 endmacro()
 
+add_subdirectory(aarch64)
 add_subdirectory(cuda)
 add_subdirectory(ppc64)
 add_subdirectory(ppc64le)

libomptarget/plugins/aarch64/CMakeLists.txt

+##===----------------------------------------------------------------------===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is dual licensed under the MIT and the University of Illinois Open
+# Source Licenses. See LICENSE.txt for details.
+#
+##===----------------------------------------------------------------------===##
+#
+# Build a plugin for an aarch64 machine if available.
+#
+##===----------------------------------------------------------------------===##
+
+if(CMAKE_SYSTEM_NAME MATCHES "Linux")
+  build_generic_elf64("aarch64" "aarch64" "aarch64" "aarch64-unknown-linux-gnu" "183")
+else()
+ libomptarget_say("Not building aarch64 offloading plugin: machine not found in the system.")
+endif()

libomptarget/src/omptarget.cpp

 static const char *RTLNames[] = {
     /* PowerPC target */ "libomptarget.rtl.ppc64.so",
     /* x86_64 target  */ "libomptarget.rtl.x86_64.so",
-    /* CUDA target    */ "libomptarget.rtl.cuda.so"};
+    /* CUDA target    */ "libomptarget.rtl.cuda.so",
+    /* AArch64 target */ "libomptarget.rtl.aarch64.so"};
 
 // forward declarations
 struct RTLInfoTy;

libomptarget/test/offloading/offloading_success.c

+// RUN: %libomptarget-compile-run-and-check-aarch64-unknown-linux-gnu
 // RUN: %libomptarget-compile-run-and-check-powerpc64-ibm-linux-gnu
 // RUN: %libomptarget-compile-run-and-check-powerpc64le-ibm-linux-gnu
 // RUN: %libomptarget-compile-run-and-check-x86_64-pc-linux-gnu

libomptarget/test/offloading/offloading_success.cpp

+// RUN: %libomptarget-compilexx-run-and-check-aarch64-unknown-linux-gnu
 // RUN: %libomptarget-compilexx-run-and-check-powerpc64-ibm-linux-gnu
 // RUN: %libomptarget-compilexx-run-and-check-powerpc64le-ibm-linux-gnu
 // RUN: %libomptarget-compilexx-run-and-check-x86_64-pc-linux-gnu