The attached 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.
Andrew
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td (revision 226573)
+++ include/clang/Driver/Options.td (working copy)
@@ -1214,6 +1214,8 @@ def mfix_cortex_a53_835769 : Flag<["-"], "mfix-cor
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>;
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp (revision 226573)
+++ lib/Driver/Tools.cpp (working copy)
@@ -958,6 +958,11 @@ void Clang::AddAArch64TargetArgs(const ArgList &Ar
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
Index: test/Driver/aarch64-fixed-x18.c
===================================================================
--- test/Driver/aarch64-fixed-x18.c (revision 0)
+++ test/Driver/aarch64-fixed-x18.c (working copy)
@@ -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"
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