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.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@227062 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Driver/Options.td b/include/clang/Driver/Options.td
index f96da515631c72e1314077cc1638d73e0d166999..3d1b5bf68be6bfbb87bc2fb2bb84484a6fdc01ef 100644 (file)
--- a/include/clang/Driver/Options.td
+++ b/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/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 1f0d4f09f815e7236b4387377290f3f63e47c0ba..21c8580e320c1f61449096845872313d1507fd52 100644 (file)
--- a/lib/Driver/Tools.cpp
+++ b/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/test/Driver/aarch64-fixed-x18.c b/test/Driver/aarch64-fixed-x18.c
new file mode 100644 (file)
index 0000000..35d0caf
--- /dev/null
+++ b/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"