[clang] Add clang support for Machine Function Splitting on AArch64

On x86 targets, -fsplit-machine-functions enables splitting of machine
functions using profile information. This patch rolls out the flag for
AArch64 targets.

Depends on D158647

Differential Revision: https://reviews.llvm.org/D157157

clang/lib/Driver/ToolChains/Clang.cpp

@@ -5878,8 +5878,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (Arg *A = Args.getLastArg(options::OPT_fsplit_machine_functions,
                                options::OPT_fno_split_machine_functions)) {
     if (!A->getOption().matches(options::OPT_fno_split_machine_functions)) {
-      // This codegen pass is only available on x86-elf targets.
-      if (Triple.isX86() && Triple.isOSBinFormatELF())
+      // This codegen pass is only available on x86 and AArch64 ELF targets.
+      if ((Triple.isX86() || Triple.isAArch64()) && Triple.isOSBinFormatELF())
         A->render(Args, CmdArgs);
       else
         D.Diag(diag::err_drv_unsupported_opt_for_target)

clang/test/Driver/fsplit-machine-functions.c

@@ -1,4 +1,5 @@
 // RUN: %clang -### --target=x86_64 -fprofile-use=default.profdata -fsplit-machine-functions %s 2>&1 | FileCheck %s --check-prefixes=CHECK,LTO-NEG
+// RUN: %clang -### --target=aarch64 -fprofile-use=default.profdata -fsplit-machine-functions %s 2>&1 | FileCheck %s --check-prefixes=CHECK,LTO-NEG
 // RUN: %clang -### --target=x86_64 -fprofile-use=default.profdata -fsplit-machine-functions -fno-split-machine-functions %s -c 2>&1 | FileCheck -check-prefix=NEG %s
 
 // CHECK:      "-fsplit-machine-functions"