Allows Clang to use LLVM's fixes-x18 option

This patch allows clang to have llvm reserve the x18
platform register on AArch64. FreeBSD will use this in the kernel for
per-cpu data but has no need to reserve this register in userland so
will need this flag to reserve it.

This uses llvm r226664 to allow this register to be reserved.

Patch by Andrew Turner.

llvm-svn: 227062

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index f96da51..3d1b5bf 100644 (file)
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1218,6 +1218,8 @@ def mfix_cortex_a53_835769 : Flag<["-"], "mfix-cortex-a53-835769">,
 def mno_fix_cortex_a53_835769 : Flag<["-"], "mno-fix-cortex-a53-835769">,
   Group<m_aarch64_Features_Group>,
   HelpText<"Don't workaround Cortex-A53 erratum 835769 (AArch64 only)">;
+def ffixed_x18 : Flag<["-"], "ffixed-x18">, Group<m_aarch64_Features_Group>,
+  HelpText<"Reserve the x18 register (AArch64 only)">;
 
 def mvsx : Flag<["-"], "mvsx">, Group<m_ppc_Features_Group>;
 def mno_vsx : Flag<["-"], "mno-vsx">, Group<m_ppc_Features_Group>;

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 1f0d4f0..21c8580 100644 (file)
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -958,6 +958,11 @@ void Clang::AddAArch64TargetArgs(const ArgList &Args,
     if (A->getOption().matches(options::OPT_mno_global_merge))
       CmdArgs.push_back("-mno-global-merge");
   }
+
+  if (Args.hasArg(options::OPT_ffixed_x18)) {
+    CmdArgs.push_back("-backend-option");
+    CmdArgs.push_back("-aarch64-reserve-x18");
+  }
 }
 
 // Get CPU and ABI names. They are not independent

diff --git a/clang/test/Driver/aarch64-fixed-x18.c b/clang/test/Driver/aarch64-fixed-x18.c
new file mode 100644 (file)
index 0000000..35d0caf
--- /dev/null
+++ b/clang/test/Driver/aarch64-fixed-x18.c
@@ -0,0 +1,4 @@
+// RUN: %clang -target aarch64-none-gnu -ffixed-x18 -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-FIXED-X18 < %t %s
+
+// CHECK-FIXED-X18: "-backend-option" "-aarch64-reserve-x18"