Add the -ffixed-r9 flag for ARM.

This patch adds the -ffixed-r9 flag to clang to instruct llvm to
globally preserve the contents of r9. The flag is added to the newly
created ARM specific group.

While at it, also place marm / mno-thumb in that group.

Patch by Jeroen Hofstee.

llvm-svn: 189174

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 25be6b48b66..71cbcb292f7 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -795,6 +795,14 @@ void Clang::AddARMTargetArgs(const ArgList &Args,
                     options::OPT_mno_implicit_float,
                     true))
     CmdArgs.push_back("-no-implicit-float");
+
+    // llvm does not support reserving registers in general. There is support
+    // for reserving r9 on ARM though (defined as a platform-specific register
+    // in ARM EABI).
+    if (Args.hasArg(options::OPT_ffixed_r9)) {
+      CmdArgs.push_back("-backend-option");
+      CmdArgs.push_back("-arm-reserve-r9");
+    }
 }
 
 // Translate MIPS CPU name alias option to CPU name.