[Offload] Add support for riscv64 to host plugin (llvm#115773)

This adds support for the riscv64 architecture to the offload host
plugin. The check to define FFI_DEFAULT_ABI is intentionally not guarded
by __riscv_xlen as the value is the same for riscv32 and riscv64
(support for OpenMP on riscv32 is still under review).

Author: aurel32

offload/CMakeLists.txt

@@ -199,6 +199,8 @@ set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} nvptx64-nvidia-cuda-L
 set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} nvptx64-nvidia-cuda-JIT-LTO")
 set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} s390x-ibm-linux-gnu")
 set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} s390x-ibm-linux-gnu-LTO")
+set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} riscv64-unknown-linux-gnu")
+set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} riscv64-unknown-linux-gnu-LTO")
 
 # Once the plugins for the different targets are validated, they will be added to
 # the list of supported targets in the current system.

offload/plugins-nextgen/common/src/Utils/ELF.cpp

@@ -45,6 +45,8 @@ uint16_t utils::elf::getTargetMachine() {
   return EM_AARCH64;
 #elif defined(__powerpc64__)
   return EM_PPC64;
+#elif defined(__riscv)
+  return EM_RISCV;
 #else
 #warning "Unknown ELF compilation target architecture"
   return EM_NONE;

offload/plugins-nextgen/host/CMakeLists.txt

@@ -1,4 +1,4 @@
-set(supported_targets x86_64 aarch64 ppc64 ppc64le s390x)
+set(supported_targets x86_64 aarch64 ppc64 ppc64le riscv64 s390x)
 if(NOT ${CMAKE_SYSTEM_PROCESSOR} IN_LIST supported_targets)
   message(STATUS "Not building ${machine} NextGen offloading plugin")
   return()
@@ -59,4 +59,8 @@ elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "s390x$")
   list(APPEND LIBOMPTARGET_SYSTEM_TARGETS
        "s390x-ibm-linux-gnu" "s390x-ibm-linux-gnu-LTO")
   set(LIBOMPTARGET_SYSTEM_TARGETS "${LIBOMPTARGET_SYSTEM_TARGETS}" PARENT_SCOPE)
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "riscv64$")
+  list(APPEND LIBOMPTARGET_SYSTEM_TARGETS
+       "riscv64-unknown-linux-gnu" "riscv64-unknown-linux-gnu-LTO")
+  set(LIBOMPTARGET_SYSTEM_TARGETS "${LIBOMPTARGET_SYSTEM_TARGETS}" PARENT_SCOPE)
 endif()

offload/plugins-nextgen/host/dynamic_ffi/ffi.h

@@ -43,7 +43,8 @@ typedef enum {
 typedef enum ffi_abi {
 #if (defined(_M_X64) || defined(__x86_64__))
   FFI_DEFAULT_ABI = 2, // FFI_UNIX64.
-#elif defined(__aarch64__) || defined(__arm64__) || defined(_M_ARM64)
+#elif defined(__aarch64__) || defined(__arm64__) || defined(_M_ARM64) ||       \
+    defined(__riscv)
   FFI_DEFAULT_ABI = 1, // FFI_SYSV.
 #elif defined(__powerpc64__)
   FFI_DEFAULT_ABI = 8, // FFI_LINUX.

offload/plugins-nextgen/host/src/rtl.cpp

@@ -440,6 +440,8 @@ struct GenELF64PluginTy final : public GenericPluginTy {
 #else
     return llvm::Triple::ppc64;
 #endif
+#elif defined(__riscv) && (__riscv_xlen == 64)
+    return llvm::Triple::riscv64;
 #else
     return llvm::Triple::UnknownArch;
 #endif