Add -foutline option to enable the MachineOutliner in AArch64

Since we've been working on productizing the MachineOutliner in AArch64, it
makes sense to provide a more user-friendly way to enable it.

This allows users of AArch64 to enable the outliner using -foutline instead
of -mllvm -enable-machine-outliner. Other, less mature implementations (e.g,
x86-64) can still enable the pass using the -mllvm option.

Also add a test to make sure it works.

llvm-svn: 331370

clang/include/clang/Driver/Options.td

@@ -1317,6 +1317,8 @@ def fno_exceptions : Flag<["-"], "fno-exceptions">, Group<f_Group>;
 def fno_gnu_keywords : Flag<["-"], "fno-gnu-keywords">, Group<f_Group>, Flags<[CC1Option]>;
 def fno_inline_functions : Flag<["-"], "fno-inline-functions">, Group<f_clang_Group>, Flags<[CC1Option]>;
 def fno_inline : Flag<["-"], "fno-inline">, Group<f_clang_Group>, Flags<[CC1Option]>;
+def foutline : Flag<["-"], "foutline">, Group<f_clang_Group>, Flags<[CC1Option]>,
+    HelpText<"Enable function outlining (AArch64 only)">;
 def fno_experimental_isel : Flag<["-"], "fno-experimental-isel">, Group<f_clang_Group>,
   HelpText<"Disables the experimental global instruction selector">;
 def fno_experimental_new_pass_manager : Flag<["-"], "fno-experimental-new-pass-manager">,

clang/lib/Driver/ToolChains/Clang.cpp

@@ -1484,6 +1484,11 @@ void Clang::AddAArch64TargetArgs(const ArgList &Args,
     else
       CmdArgs.push_back("-aarch64-enable-global-merge=true");
   }
+
+  if (Arg *A = Args.getLastArg(options::OPT_foutline)) {
+    CmdArgs.push_back("-mllvm");
+    CmdArgs.push_back("-enable-machine-outliner");
+  }
 }
 
 void Clang::AddMIPSTargetArgs(const ArgList &Args,

clang/test/Driver/aarch64-outliner.c

@@ -0,0 +1,4 @@
+// REQUIRES: aarch64-registered-target
+
+// RUN: %clang -target aarch64 -foutline -S %s -### 2>&1 | FileCheck %s
+// CHECK: "-mllvm" "-enable-machine-outliner"