[Driver] Make -moutline-atomics default for aarch64-fuchsia targets

This makes Fuchsia consistent with Linux on AArch64.

Reviewed By: abrachet

Differential Revision: https://reviews.llvm.org/D122613

Author: frobtech

clang/lib/Driver/ToolChains/Fuchsia.h

@@ -75,24 +75,27 @@ class LLVM_LIBRARY_VISIBILITY Fuchsia : public ToolChain {
 
   RuntimeLibType
   GetRuntimeLibType(const llvm::opt::ArgList &Args) const override;
-  CXXStdlibType
-  GetCXXStdlibType(const llvm::opt::ArgList &Args) const override;
+  CXXStdlibType GetCXXStdlibType(const llvm::opt::ArgList &Args) const override;
+
+  bool IsAArch64OutlineAtomicsDefault(
+      const llvm::opt::ArgList &Args) const override {
+    return true;
+  }
 
-  void addClangTargetOptions(const llvm::opt::ArgList &DriverArgs,
-                             llvm::opt::ArgStringList &CC1Args,
-                             Action::OffloadKind DeviceOffloadKind) const override;
+  void
+  addClangTargetOptions(const llvm::opt::ArgList &DriverArgs,
+                        llvm::opt::ArgStringList &CC1Args,
+                        Action::OffloadKind DeviceOffloadKind) const override;
   void
   AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                             llvm::opt::ArgStringList &CC1Args) const override;
-  void
-  AddClangCXXStdlibIncludeArgs(const llvm::opt::ArgList &DriverArgs,
-                               llvm::opt::ArgStringList &CC1Args) const override;
+  void AddClangCXXStdlibIncludeArgs(
+      const llvm::opt::ArgList &DriverArgs,
+      llvm::opt::ArgStringList &CC1Args) const override;
   void AddCXXStdlibLibArgs(const llvm::opt::ArgList &Args,
                            llvm::opt::ArgStringList &CmdArgs) const override;
 
-  const char *getDefaultLinker() const override {
-    return "ld.lld";
-  }
+  const char *getDefaultLinker() const override { return "ld.lld"; }
 
 protected:
   Tool *buildLinker() const override;

clang/test/Driver/fuchsia.c

@@ -34,6 +34,7 @@
 // CHECK-AARCH64: "-fsanitize=shadow-call-stack"
 // CHECK-X86_64: "-fsanitize=safe-stack"
 // CHECK: "-stack-protector" "2"
+// CHECK-AARCH64: "-target-feature" "+outline-atomics"
 // CHECK-NOT: "-fcommon"
 // CHECK: {{.*}}ld.lld{{.*}}" "-z" "max-page-size=4096" "-z" "now" "-z" "rodynamic" "-z" "separate-loadable-segments" "-z" "rel" "--pack-dyn-relocs=relr"
 // CHECK: "--sysroot=[[SYSROOT]]"